In previous posts, I reviewed some of the evidence suggesting that human evolution has accelerated rapidly since the development of agriculture (and to some degree, before it). Europeans (and other lineages with a long history of agriculture) carry known genetic adaptations to the Neolithic diet, and there are probably many adaptations that have not yet been identified. In my final post in this series, I'll argue that although we've adapted, the adaptation is probably not complete, and we're left in a sort of genetic limbo between the Paleolithic and Neolithic state.
Recent Genetic Adaptations are Often Crude
It may at first seem strange, but many genes responsible for common genetic disorders show evidence of positive selection. In other words, the genes that cause these disorders were favored by evolution at some point because they presumably provided a survival advantage. For example, the sickle cell anemia gene protects against malaria, but if you inherit two copies of it, you end up with a serious and life-threatening disorder (1). The cystic fibrosis gene may have been selected to protect against one or more infectious diseases, but again if you get two copies of it, quality of life and lifespan are greatly curtailed (2, 3). Familial Mediterranean fever is a very common disorder in Mediterranean populations, involving painful inflammatory attacks of the digestive tract, and sometimes a deadly condition called amyloidosis. It shows evidence of positive selection and probably protected against intestinal disease due to the heightened inflammatory state it confers to the digestive tract (4, 5). Celiac disease, a severe autoimmune reaction to gluten found in some grains, may be a by-product of selection for protection against bacterial infection (6). Phenylketonuria also shows evidence of positive selection (7), and the list goes on. It's clear that a lot of our recent evolution was in response to new disease pressures, likely from increased population density, sendentism, and contact with domestic animals.
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Showing posts with label phytic acid. Show all posts
Showing posts with label phytic acid. Show all posts
Dr. Mellanby's Tooth Decay Reversal Diet
I have a lot of admiration for Drs. Edward and May Mellanby. A husband-and-wife team, they discovered vitamin D, and determined that rickets is caused by poor calcium (or phosphorus) status, typically due to vitamin D deficiency. They believed that an ideal diet is omnivorous, based on whole foods, and offers an adequate supply of fat-soluble vitamins and easily absorbed minerals. They also felt that grain intake should be modest, as their research showed that unsoaked whole grains antagonize the effect of vitamins D and A.
Not only did the Mellanbys discover vitamin D and end the rickets epidemic that was devastating Western cities at the time, they also discovered a cure for early-stage tooth decay that has been gathering dust in medical libraries throughout the world since 1924.
It was in that year that Dr. May Mellanby published a summary of the results of the Mellanby tooth decay reversal studies in the British Medical Journal, titled "Remarks on the Influence of a Cereal-free Diet Rich in Vitamin D and Calcium on Dental Caries in Children". Last year, I had to specially request this article from the basement of the University of Washington medical library (1). Thanks to the magic of the internet, the full version of the paper is now freely available online (2).
You don't need my help to read the study, but in this post I offer a little background, a summary and my interpretation.
In previous studies, the Mellanbys used dogs to define the dietary factors that influence tooth development and repair. They identified three, which together made the difference between excellent and poor dental health (from Nutrition and Disease):
I'll start with diet 1. Children on this diet ate the typical fare, plus extra oatmeal. Oatmeal is typically eaten as an unsoaked whole grain (and soaking it isn't very effective in any case), and so it is high in phytic acid, which effectively inhibits the absorption of a number of minerals including calcium. These children formed 5.8 cavities each and healed virtually none-- not good!
Diet number 2 was similar to diet 1, except there was no extra oatmeal and the children received a large supplemental dose of vitamin D. Over 28 weeks, only 1 cavity per child developed or worsened, while 3.9 healed. Thus, simply adding vitamin D to a reasonable diet allowed most of their cavities to heal.
Diet number 3 was the most effective. This was a grain-free diet plus supplemental vitamin D. Over 26 weeks, children in this group saw an average of only 0.4 cavities form or worsen, while 4.7 healed. The Mellanbys considered that they had essentially found a cure for this disorder in its early stages.
What exactly was this diet? Here's how it was described in the paper (note: cereals = grains):
Here are two sample meals provided in Dr. Mellanby's paper. I believe the word "dinner" refers to the noon meal, and "supper" refers to the evening meal:
This diet is capable of reversing early stage tooth decay. It will not reverse advanced decay, which requires professional dental treatment as soon as possible. It is not a substitute for dental care in general, and if you try using diet to reverse your own tooth decay, please do it under the supervision of a dentist. And while you're there, tell her about Edward and May Mellanby!
Preventing Tooth Decay
Reversing Tooth Decay
Images of Tooth Decay Healing due to an Improved Diet
Dental Anecdotes
Not only did the Mellanbys discover vitamin D and end the rickets epidemic that was devastating Western cities at the time, they also discovered a cure for early-stage tooth decay that has been gathering dust in medical libraries throughout the world since 1924.
It was in that year that Dr. May Mellanby published a summary of the results of the Mellanby tooth decay reversal studies in the British Medical Journal, titled "Remarks on the Influence of a Cereal-free Diet Rich in Vitamin D and Calcium on Dental Caries in Children". Last year, I had to specially request this article from the basement of the University of Washington medical library (1). Thanks to the magic of the internet, the full version of the paper is now freely available online (2).
You don't need my help to read the study, but in this post I offer a little background, a summary and my interpretation.
In previous studies, the Mellanbys used dogs to define the dietary factors that influence tooth development and repair. They identified three, which together made the difference between excellent and poor dental health (from Nutrition and Disease):
- The diet's mineral content, particularly calcium and phosphorus
- The diet's fat-soluble vitamin content, chiefly vitamin D
- The diet's content of inhibitors of mineral absorption, primarily phytic acid
I'll start with diet 1. Children on this diet ate the typical fare, plus extra oatmeal. Oatmeal is typically eaten as an unsoaked whole grain (and soaking it isn't very effective in any case), and so it is high in phytic acid, which effectively inhibits the absorption of a number of minerals including calcium. These children formed 5.8 cavities each and healed virtually none-- not good!Diet number 2 was similar to diet 1, except there was no extra oatmeal and the children received a large supplemental dose of vitamin D. Over 28 weeks, only 1 cavity per child developed or worsened, while 3.9 healed. Thus, simply adding vitamin D to a reasonable diet allowed most of their cavities to heal.
Diet number 3 was the most effective. This was a grain-free diet plus supplemental vitamin D. Over 26 weeks, children in this group saw an average of only 0.4 cavities form or worsen, while 4.7 healed. The Mellanbys considered that they had essentially found a cure for this disorder in its early stages.
What exactly was this diet? Here's how it was described in the paper (note: cereals = grains):
...instead of cereals- for example, bread, oatmeal, rice, and tapioca- an increased allowance of potatoes and other vegetables, milk, fat, meat, and eggs was given. The total sugar, jam, and syrup intake was the same as before. Vitamin D was present in abundance in either cod-liver oil or irradiated ergosterol, and in egg yolk, butter, milk, etc. The diet of these children was thus rich in those factors, especially vitamin D and calcium, which experimental evidence has shown to assist calcification, and was devoid of those factors- namely, cereals- which interfere with the process.Carbohydrate intake was reduced by almost half. Bread and oatmeal were replaced by potatoes, milk, meat, fish, eggs, butter and vegetables. The diet is reminiscent of what Dr. Weston Price used to reverse tooth decay in his dental clinic in Cleveland, although Price's diet did include rolls made from freshly ground whole wheat. Price also identified the fat-soluble vitamin K2 MK-4 as another important factor in tooth decay reversal, which would have been abundant in Mellanby's studies due to the dairy. The Mellanbys and Price were contemporaries and had parallel and complementary findings. The Mellanbys did not understand the role of vitamin K2 in mineral metabolism, and Price did not seem to appreciate the role of phytic acid from unsoaked whole grains in preventing mineral absorption.
Here are two sample meals provided in Dr. Mellanby's paper. I believe the word "dinner" refers to the noon meal, and "supper" refers to the evening meal:
Breakfast- Omelette, cocoa, with milk.In addition, children received vitamin D daily. Here's Dr. Mellanby's summary of their findings:
Lunch- Milk.
Dinner- Potatoes, steamed minced meat, carrots, stewed fruit, milk.
Tea- Fresh fruit salad, cocoa made with milk.
Supper- Fish and potatoes fried in dripping, milk.
Breakfast- Scrambled egg, milk, fresh salad.
Dinner- Irish stew, potatoes, cabbage, stewed fruit, milk.
Tea- Minced meat warmed with bovril, green salad, milk.
Supper- Thick potato soup made with milk.
The tests do not indicate that in order to prevent dental caries children must live on a cereal-free diet, but in association with the results of the other investigations on animals and children they do indicate that the amount of cereal eaten should be reduced, particularly during infancy and in the earlier years of life, and should be replaced by an increased consumption of milk, eggs, butter, potatoes, and other vegetables. They also indicate that a sufficiency of vitamin D and calcium should be given from birth, and before birth, by supplying a suitable diet to the pregnant mother. The teeth of the children would be well formed and more resistant to dental caries instead of being hypoplastic and badly calcified, as were those in this investigation.If I could add something to this program, I would recommend daily tooth brushing and flossing, avoiding sugar, and rinsing the mouth with water after each meal.
This diet is capable of reversing early stage tooth decay. It will not reverse advanced decay, which requires professional dental treatment as soon as possible. It is not a substitute for dental care in general, and if you try using diet to reverse your own tooth decay, please do it under the supervision of a dentist. And while you're there, tell her about Edward and May Mellanby!
Preventing Tooth Decay
Reversing Tooth Decay
Images of Tooth Decay Healing due to an Improved Diet
Dental Anecdotes
Traditional Preparation Methods Improve Grains' Nutritive Value
Soaking or Germinating Grains
The most basic method of preparing grains is prolonged soaking in water, followed by cooking. This combination reduces the level of water-soluble and heat-sensitive toxins and anti-nutrients such as tannins, saponins, digestive enzyme inhibitors and lectins, as well as flatulence factors. It also partially degrades phytic acid, which is a potent inhibitor of mineral absorption, an inhibitor of the digestive enzyme trypsin and an enemy of dental health (1). This improves the digestibility and nutritional value of grains as well as legumes.
I prefer to soak all grains and legumes for at least 12 hours in a warm location, preferably 24. This includes foods that most people don't soak, such as lentils. Soaking does not reduce phytic acid at all in grains that have been heat-treated, such as oats and kasha (technically not a grain), because they no longer contain the phytic acid-degrading enzyme phytase. Cooking without soaking first also does not have much effect on phytic acid.
The next level of grain preparation is germination. After soaking, rinse the grains twice per day for an additional day or two. This activates the grains' sprouting program and further increases their digestibility and vitamin content. When combined with cooking, it reduces phytic acid, although modestly. Therefore, most of the minerals in sprouted whole grains will continue to be inaccessible. Many raw sprouted grains and legumes are edible, but I wouldn't use them as a staple food because they retain most of their phytic acid as well as some heat-sensitive anti-nutrients (2).
Grinding and Fermenting Grains
Many cultures around the world have independently discovered fermentation as a way to greatly improve the digestibility and nutritive value of grains (3). Typically, grains are soaked, ground, and allowed to sour ferment for times ranging from 12 hours to several days. In some cases, a portion of the bran is removed before or after grinding.
In addition to the reduction in toxins and anti-nutrients afforded by soaking and cooking, grinding and fermentation goes much further. Grinding greatly increases the surface area of the grains and breaks up their cellular structure, releasing enzymes which are important for the transformation to come. Under the right conditions, which are easy to achieve, lactic acid bacteria rapidly acidify the batter. These bacteria are naturally present on grains, but adding a starter makes the process more efficient and reliable.
Due to some quirk of nature, grain phytase is maximally active at a pH of between 4.5 and 5.5, which is mildly acidic. This is why the Weston Price foundation recommends soaking grains in an acidic medium before cooking. The combination of grinding and sour fermentation causes grains to efficiently degrade their own phytic acid (as long as they haven't been heat treated first), making minerals much more available for absorption (4, 5, 6, 7). This transforms whole grains from a poor source of minerals into a good source.
The degree of phytic acid degradation depends on the starting amount of phytase in the grain. Corn, rice, oats and millet don't contain much phytase activity, so they require either a longer fermentation time, or the addition of high-phytase grains to the batter (8). Whole raw buckwheat, wheat, and particularly rye contain a large amount of phytase (9), although I feel wheat is problematic for other reasons.
As fermentation proceeds, bacteria secrete enzymes that begin digesting the protein, starch and other substances in the batter. Fermentation reduces lectin levels substantially, which are reduced further by cooking (10). Lectins are toxins that can interfere with digestion and may be involved in autoimmune disease, an idea championed by Dr. Loren Cordain. Grain lectins are generally heat-sensitive, but one notable exception is the nasty lectin wheat germ agglutinin (WGA). As its name suggests, WGA is found in wheat germ, and thus is mostly absent in white flour. WGA may have been another reason why DART participants who increased their wheat fiber intake had significantly more heart attacks than those who didn't. I don't know if fermentation degrades WGA.
One of the problems with grains is their poor protein quality. Besides containing a fairly low concentration of protein to begin with, they also don't contain a good balance of essential amino acids. This prevents their efficient use by the body, unless a separate source of certain amino acids is eaten along with them. The main limiting amino acid in grains is lysine. Legumes are rich in lysine, which is why cultures around the world pair them with grains. Bacterial fermentation produces lysine, often increasing its concentration by many fold and making grains nearly a "complete protein", i.e. one that contains the ideal balance of essential amino acids as do animal proteins (11, scroll down to see graph). Not very many plant foods can make that claim. Fermentation also increases the concentration of the amino acid methionine and certain vitamins.
Another problem with grain protein is it's poorly digested relative to animal protein. This means that a portion of it escapes digestion, leading to a lower nutritive value and a higher risk of allergy due to undigested protein hanging around in the digestive tract. Fermentation followed by cooking increases the digestibility of grain protein, bringing it nearly to the same level as meat (12, 13, 14, 15). This may relate to the destruction of protease inhibitors (trypsin inhibitors, phytic acid) and the partial pre-digestion of grain proteins by bacteria.
Once you delve into the research on traditional grain preparation methods, you begin to see why grain-eating cultures throughout the world have favored certain techniques. Proper grain processing transforms them from toxic to nutritious, from health-degrading to health-giving. Modern industrial grain processing has largely eschewed these time-honored techniques, replacing them with low-extraction milling, extrusion and quick-rise yeast strains.
Many people will not be willing to go through the trouble of grinding and fermentation to prepare grains. I can sympathize, although if you have the right tools, once you establish a routine it really isn't that much work. It just requires a bit of organization. In fact, it can even be downright convenient. I often keep a bowl of fermented dosa or buckwheat batter in the fridge, ready to make a tasty "pancake" at a moment's notice. In the next post, I'll describe a few recipes from different parts of the world.
Further reading:
How to Eat Grains
A Few Thoughts on Minerals, Milling, Grains and Tubers
Dietary Fiber and Mineral Availability
A New Way to Soak Brown Rice
The most basic method of preparing grains is prolonged soaking in water, followed by cooking. This combination reduces the level of water-soluble and heat-sensitive toxins and anti-nutrients such as tannins, saponins, digestive enzyme inhibitors and lectins, as well as flatulence factors. It also partially degrades phytic acid, which is a potent inhibitor of mineral absorption, an inhibitor of the digestive enzyme trypsin and an enemy of dental health (1). This improves the digestibility and nutritional value of grains as well as legumes.
I prefer to soak all grains and legumes for at least 12 hours in a warm location, preferably 24. This includes foods that most people don't soak, such as lentils. Soaking does not reduce phytic acid at all in grains that have been heat-treated, such as oats and kasha (technically not a grain), because they no longer contain the phytic acid-degrading enzyme phytase. Cooking without soaking first also does not have much effect on phytic acid.
The next level of grain preparation is germination. After soaking, rinse the grains twice per day for an additional day or two. This activates the grains' sprouting program and further increases their digestibility and vitamin content. When combined with cooking, it reduces phytic acid, although modestly. Therefore, most of the minerals in sprouted whole grains will continue to be inaccessible. Many raw sprouted grains and legumes are edible, but I wouldn't use them as a staple food because they retain most of their phytic acid as well as some heat-sensitive anti-nutrients (2).
Grinding and Fermenting Grains
Many cultures around the world have independently discovered fermentation as a way to greatly improve the digestibility and nutritive value of grains (3). Typically, grains are soaked, ground, and allowed to sour ferment for times ranging from 12 hours to several days. In some cases, a portion of the bran is removed before or after grinding.
In addition to the reduction in toxins and anti-nutrients afforded by soaking and cooking, grinding and fermentation goes much further. Grinding greatly increases the surface area of the grains and breaks up their cellular structure, releasing enzymes which are important for the transformation to come. Under the right conditions, which are easy to achieve, lactic acid bacteria rapidly acidify the batter. These bacteria are naturally present on grains, but adding a starter makes the process more efficient and reliable.
Due to some quirk of nature, grain phytase is maximally active at a pH of between 4.5 and 5.5, which is mildly acidic. This is why the Weston Price foundation recommends soaking grains in an acidic medium before cooking. The combination of grinding and sour fermentation causes grains to efficiently degrade their own phytic acid (as long as they haven't been heat treated first), making minerals much more available for absorption (4, 5, 6, 7). This transforms whole grains from a poor source of minerals into a good source.
The degree of phytic acid degradation depends on the starting amount of phytase in the grain. Corn, rice, oats and millet don't contain much phytase activity, so they require either a longer fermentation time, or the addition of high-phytase grains to the batter (8). Whole raw buckwheat, wheat, and particularly rye contain a large amount of phytase (9), although I feel wheat is problematic for other reasons.
As fermentation proceeds, bacteria secrete enzymes that begin digesting the protein, starch and other substances in the batter. Fermentation reduces lectin levels substantially, which are reduced further by cooking (10). Lectins are toxins that can interfere with digestion and may be involved in autoimmune disease, an idea championed by Dr. Loren Cordain. Grain lectins are generally heat-sensitive, but one notable exception is the nasty lectin wheat germ agglutinin (WGA). As its name suggests, WGA is found in wheat germ, and thus is mostly absent in white flour. WGA may have been another reason why DART participants who increased their wheat fiber intake had significantly more heart attacks than those who didn't. I don't know if fermentation degrades WGA.
One of the problems with grains is their poor protein quality. Besides containing a fairly low concentration of protein to begin with, they also don't contain a good balance of essential amino acids. This prevents their efficient use by the body, unless a separate source of certain amino acids is eaten along with them. The main limiting amino acid in grains is lysine. Legumes are rich in lysine, which is why cultures around the world pair them with grains. Bacterial fermentation produces lysine, often increasing its concentration by many fold and making grains nearly a "complete protein", i.e. one that contains the ideal balance of essential amino acids as do animal proteins (11, scroll down to see graph). Not very many plant foods can make that claim. Fermentation also increases the concentration of the amino acid methionine and certain vitamins.
Another problem with grain protein is it's poorly digested relative to animal protein. This means that a portion of it escapes digestion, leading to a lower nutritive value and a higher risk of allergy due to undigested protein hanging around in the digestive tract. Fermentation followed by cooking increases the digestibility of grain protein, bringing it nearly to the same level as meat (12, 13, 14, 15). This may relate to the destruction of protease inhibitors (trypsin inhibitors, phytic acid) and the partial pre-digestion of grain proteins by bacteria.
Once you delve into the research on traditional grain preparation methods, you begin to see why grain-eating cultures throughout the world have favored certain techniques. Proper grain processing transforms them from toxic to nutritious, from health-degrading to health-giving. Modern industrial grain processing has largely eschewed these time-honored techniques, replacing them with low-extraction milling, extrusion and quick-rise yeast strains.
Many people will not be willing to go through the trouble of grinding and fermentation to prepare grains. I can sympathize, although if you have the right tools, once you establish a routine it really isn't that much work. It just requires a bit of organization. In fact, it can even be downright convenient. I often keep a bowl of fermented dosa or buckwheat batter in the fridge, ready to make a tasty "pancake" at a moment's notice. In the next post, I'll describe a few recipes from different parts of the world.
Further reading:
How to Eat Grains
A Few Thoughts on Minerals, Milling, Grains and Tubers
Dietary Fiber and Mineral Availability
A New Way to Soak Brown Rice
Grains as Food: an Update
Improperly Prepared Grain Fiber can be Harmful
Last year, I published a post on the Diet and Reinfarction trial (DART), a controlled trial that increased grain fiber intake using whole wheat bread and wheat bran supplements, and reported long-term health outcomes in people who had previously suffered a heart attack (1). The initial paper found a trend toward increased heart attacks and deaths in the grain fiber-supplemented group at two years, which was not statistically significant.
What I didn't know at the time is that a follow-up study has been published. After mathematically "adjusting" for preexisting conditions and medication use, the result reached statistical significance: people who increased their grain fiber intake had more heart attacks than people who didn't during the two years of the controlled trial. Overall mortality was higher as well, but that didn't reach statistical significance. You have to get past the abstract of the paper to realize this, but fortunately it's free access (2).
Here's a description of what not to eat if you're a Westerner with established heart disease:
The term 'fiber' can refer to many different things. Dietary fiber is simply defined as an edible substance that doesn't get digested by the human body. It doesn't even necessarily come from plants. If you eat a shrimp with the shell on, and the shell comes out the other end (which it will), it was fiber.
Grain fiber is a particular class of dietary fiber that has specific characteristics. It's mostly cellulose (like wood; although some grains are rich in soluble fiber as well), and it contains a number of defensive substances and storage molecules that make it more difficult to eat. These may include phytic acid, protease inhibitors, amylase inhibitors, lectins, tannins, saponins, and goitrogens (3). Grain fiber is also a rich source of vitamins and minerals, although the minerals are mostly inaccessible due to grains' high phytic acid content (4, 5, 6).
Every plant food (and some animal foods) has its chemical defense strategy, and grains are no different*. It's just that grains are particularly good at it, and also happen to be one of our staple foods in the modern world. If you don't think grains are naturally inedible for humans, try eating a heaping bowl full of dry, raw whole wheat berries.
Human Ingenuity to the Rescue
Humans are clever creatures, and we've found ways to use grains as a food source, despite not being naturally adapted to eating them**. The most important is our ability to cook. Cooking deactivates many of the harmful substances found in grains and other plant foods. However, some are not deactivated by cooking. These require other strategies to remove or deactivate.
Healthy grain-based cultures don't prepare their grains haphazardly. Throughout the world, using a number of different grains, many have arrived at similar strategies for making grains edible and nutritious. The most common approach involves most or all of these steps:
In the next post, I'll explain why these processing steps greatly improve the nutritional value of grains, and I'll describe recipes from around the world to illustrate the point.
* Including tubers. For example, sweet potatoes contain goitrogens, oxalic acid, and protease inhibitors. Potatoes contain toxic glycoalkaloids. Taro contains oxalic acid and protease inhibitors. Cassava contains highly toxic cyanogens. Some of these substances are deactivated by cooking, others are not. Each food has an associated preparation method that minimizes its toxic qualities. Potatoes are peeled, removing the majority of the glycoalkaloids. Cassava is grated and dried or fermented to inactivate cyanogens. Some cultures ferment taro.
** As opposed to mice, for example, which can survive on raw whole grains.
Last year, I published a post on the Diet and Reinfarction trial (DART), a controlled trial that increased grain fiber intake using whole wheat bread and wheat bran supplements, and reported long-term health outcomes in people who had previously suffered a heart attack (1). The initial paper found a trend toward increased heart attacks and deaths in the grain fiber-supplemented group at two years, which was not statistically significant.
What I didn't know at the time is that a follow-up study has been published. After mathematically "adjusting" for preexisting conditions and medication use, the result reached statistical significance: people who increased their grain fiber intake had more heart attacks than people who didn't during the two years of the controlled trial. Overall mortality was higher as well, but that didn't reach statistical significance. You have to get past the abstract of the paper to realize this, but fortunately it's free access (2).
Here's a description of what not to eat if you're a Westerner with established heart disease:
Those randomised to fibre advice were encouraged to eat at least six slices of wholemeal bread per day, or an equivalent amount of cereal fibre from a mixture of wholemeal bread, high-fibre breakfast cereals and wheat bran.Characteristics of Grain Fiber
The term 'fiber' can refer to many different things. Dietary fiber is simply defined as an edible substance that doesn't get digested by the human body. It doesn't even necessarily come from plants. If you eat a shrimp with the shell on, and the shell comes out the other end (which it will), it was fiber.
Grain fiber is a particular class of dietary fiber that has specific characteristics. It's mostly cellulose (like wood; although some grains are rich in soluble fiber as well), and it contains a number of defensive substances and storage molecules that make it more difficult to eat. These may include phytic acid, protease inhibitors, amylase inhibitors, lectins, tannins, saponins, and goitrogens (3). Grain fiber is also a rich source of vitamins and minerals, although the minerals are mostly inaccessible due to grains' high phytic acid content (4, 5, 6).
Every plant food (and some animal foods) has its chemical defense strategy, and grains are no different*. It's just that grains are particularly good at it, and also happen to be one of our staple foods in the modern world. If you don't think grains are naturally inedible for humans, try eating a heaping bowl full of dry, raw whole wheat berries.
Human Ingenuity to the Rescue
Humans are clever creatures, and we've found ways to use grains as a food source, despite not being naturally adapted to eating them**. The most important is our ability to cook. Cooking deactivates many of the harmful substances found in grains and other plant foods. However, some are not deactivated by cooking. These require other strategies to remove or deactivate.
Healthy grain-based cultures don't prepare their grains haphazardly. Throughout the world, using a number of different grains, many have arrived at similar strategies for making grains edible and nutritious. The most common approach involves most or all of these steps:
- Soaking
- Grinding
- Removing 50-75% of the bran
- Sour fermentation
- Cooking
In the next post, I'll explain why these processing steps greatly improve the nutritional value of grains, and I'll describe recipes from around the world to illustrate the point.
* Including tubers. For example, sweet potatoes contain goitrogens, oxalic acid, and protease inhibitors. Potatoes contain toxic glycoalkaloids. Taro contains oxalic acid and protease inhibitors. Cassava contains highly toxic cyanogens. Some of these substances are deactivated by cooking, others are not. Each food has an associated preparation method that minimizes its toxic qualities. Potatoes are peeled, removing the majority of the glycoalkaloids. Cassava is grated and dried or fermented to inactivate cyanogens. Some cultures ferment taro.
** As opposed to mice, for example, which can survive on raw whole grains.
Magnesium and Insulin Sensitivity
From a paper based on US NHANES nutrition and health survey data (1):
Magnesium status is associated with insulin sensitivity (2, 3), and a low magnesium intake predicts the development of type II diabetes in most studies (4, 5) but not all (6). Magnesium supplements largely prevent diabetes in a rat model* (7). Interestingly, excess blood glucose and insulin themselves seem to reduce magnesium status, possibly creating a vicious cycle.
In a 1993 trial, a low-magnesium diet reduced insulin sensitivity in healthy volunteers by 25% in just four weeks (8). It also increased urinary thromboxane concentration, a potential concern for cardiovascular health**.
At least three trials have shown that magnesium supplementation increases insulin sensitivity in insulin-resistant diabetics and non-diabetics (9, 10, 11). In some cases, the results were remarkable. In type II diabetics, 16 weeks of magnesium supplementation improved fasting glucose, calculated insulin sensitivity and HbA1c*** (12). HbA1c dropped by 22 percent.
In insulin resistant volunteers with low blood magnesium, magnesium supplementation for four months reduced estimated insulin resistance by 43 percent and decreased fasting insulin by 32 percent (13). This suggests to me that magnesium deficiency was probably one of the main reasons they were insulin resistant in the first place. But the study had another very interesting finding: magnesium improved the subjects' blood lipid profile remarkably. Total cholesterol decreased, LDL decreased, HDL increased and triglycerides decreased by a whopping 39 percent. The same thing had been reported in the medical literature decades earlier when doctors used magnesium injections to treat heart disease, and also in animals treated with magnesium. Magnesium supplementation also suppresses atherosclerosis (thickening and hardening of the arteries) in animal models, a fact that I may discuss in more detail at some point (14, 15).
In the previous study, participants were given 2.5 g magnesium chloride (MgCl2) per day. That's a bit more than the USDA recommended daily allowance (MgCl2 is mostly chloride by weight), in addition to what they were already getting from their diet. Most of a person's magnesium is in their bones, so correcting a deficiency by eating a nutritious diet may take a while.
Speaking of nutritious diets, how does one get magnesium? Good sources include halibut, leafy greens, chocolate and nuts. Bone broths are also an excellent source of highly absorbable magnesium. Whole grains and beans are also fairly good sources, while refined grains lack most of the magnesium in the whole grain. Organic foods, particularly artisanally produced foods from a farmer's market, are richer in magnesium because they grow on better soil and often use older varieties that are more nutritious.
The problem with seeds such as grains, beans and nuts is that they also contain phytic acid which prevents the absorption of magnesium and other minerals (16). Healthy non-industrial societies that relied on grains took great care in their preparation: they soaked them, often fermented them, and also frequently removed a portion of the bran before cooking (17). These steps all served to reduce the level of phytic acid and other anti-nutrients. I've posted a method for effectively reducing the amount of phytic acid in brown rice (18). Beans should ideally be soaked for 24 hours before cooking, preferably in warm water.
Industrial agriculture has systematically depleted our soil of many minerals, due to high-yield crop varieties and the fact that synthetic fertilizers only replace a few minerals. The mineral content of foods in the US, including magnesium, has dropped sharply in the last 50 years. The reason we need to use fertilizers in the first place is that we've broken the natural nutrient cycle in which minerals always return to the soil in the same place they were removed. In 21st century America, minerals are removed from the soil, pass through our toilets, and end up in the landfill or in waste water. This will continue until we find an acceptable way to return human feces and urine to agricultural soil, as many cultures do to this day****.
I believe that an adequate magnesium intake is critical for proper insulin sensitivity and overall health.
* Zucker rats that lack leptin signaling
** Thromboxane A2 is an omega-6 derived eicosanoid that potently constricts blood vessels and promotes blood clotting. It's interesting that magnesium has such a strong effect on it. It indicates that fatty acid balance is not the only major influence on eicosanoid production.
*** Glycated hemoglobin. A measure of the average blood glucose level over the past few weeks.
**** Anyone interested in further reading on this should look up The Humanure Handbook
During 1999–2000, the diet of a large proportion of the U.S. population did not contain adequate magnesium... Furthermore, racial or ethnic differences in magnesium persist and may contribute to some health disparities.... Because magnesium intake is low among many people in the United States and inadequate magnesium status is associated with increased risk of acute and chronic conditions, an urgent need exists to perform a current survey to assess the physiologic status of magnesium in the U.S. population.Magnesium is an essential mineral that's slowly disappearing from the modern diet, as industrial agriculture and industrial food processing increasingly dominate our food choices. One of the many things it's necessary for in mammals is proper insulin sensitivity and glucose control. A loss of glucose control due to insulin resistance can eventually lead to diabetes and all its complications.
Magnesium status is associated with insulin sensitivity (2, 3), and a low magnesium intake predicts the development of type II diabetes in most studies (4, 5) but not all (6). Magnesium supplements largely prevent diabetes in a rat model* (7). Interestingly, excess blood glucose and insulin themselves seem to reduce magnesium status, possibly creating a vicious cycle.
In a 1993 trial, a low-magnesium diet reduced insulin sensitivity in healthy volunteers by 25% in just four weeks (8). It also increased urinary thromboxane concentration, a potential concern for cardiovascular health**.
At least three trials have shown that magnesium supplementation increases insulin sensitivity in insulin-resistant diabetics and non-diabetics (9, 10, 11). In some cases, the results were remarkable. In type II diabetics, 16 weeks of magnesium supplementation improved fasting glucose, calculated insulin sensitivity and HbA1c*** (12). HbA1c dropped by 22 percent.
In insulin resistant volunteers with low blood magnesium, magnesium supplementation for four months reduced estimated insulin resistance by 43 percent and decreased fasting insulin by 32 percent (13). This suggests to me that magnesium deficiency was probably one of the main reasons they were insulin resistant in the first place. But the study had another very interesting finding: magnesium improved the subjects' blood lipid profile remarkably. Total cholesterol decreased, LDL decreased, HDL increased and triglycerides decreased by a whopping 39 percent. The same thing had been reported in the medical literature decades earlier when doctors used magnesium injections to treat heart disease, and also in animals treated with magnesium. Magnesium supplementation also suppresses atherosclerosis (thickening and hardening of the arteries) in animal models, a fact that I may discuss in more detail at some point (14, 15).
In the previous study, participants were given 2.5 g magnesium chloride (MgCl2) per day. That's a bit more than the USDA recommended daily allowance (MgCl2 is mostly chloride by weight), in addition to what they were already getting from their diet. Most of a person's magnesium is in their bones, so correcting a deficiency by eating a nutritious diet may take a while.
Speaking of nutritious diets, how does one get magnesium? Good sources include halibut, leafy greens, chocolate and nuts. Bone broths are also an excellent source of highly absorbable magnesium. Whole grains and beans are also fairly good sources, while refined grains lack most of the magnesium in the whole grain. Organic foods, particularly artisanally produced foods from a farmer's market, are richer in magnesium because they grow on better soil and often use older varieties that are more nutritious.
The problem with seeds such as grains, beans and nuts is that they also contain phytic acid which prevents the absorption of magnesium and other minerals (16). Healthy non-industrial societies that relied on grains took great care in their preparation: they soaked them, often fermented them, and also frequently removed a portion of the bran before cooking (17). These steps all served to reduce the level of phytic acid and other anti-nutrients. I've posted a method for effectively reducing the amount of phytic acid in brown rice (18). Beans should ideally be soaked for 24 hours before cooking, preferably in warm water.
Industrial agriculture has systematically depleted our soil of many minerals, due to high-yield crop varieties and the fact that synthetic fertilizers only replace a few minerals. The mineral content of foods in the US, including magnesium, has dropped sharply in the last 50 years. The reason we need to use fertilizers in the first place is that we've broken the natural nutrient cycle in which minerals always return to the soil in the same place they were removed. In 21st century America, minerals are removed from the soil, pass through our toilets, and end up in the landfill or in waste water. This will continue until we find an acceptable way to return human feces and urine to agricultural soil, as many cultures do to this day****.
I believe that an adequate magnesium intake is critical for proper insulin sensitivity and overall health.
* Zucker rats that lack leptin signaling
** Thromboxane A2 is an omega-6 derived eicosanoid that potently constricts blood vessels and promotes blood clotting. It's interesting that magnesium has such a strong effect on it. It indicates that fatty acid balance is not the only major influence on eicosanoid production.
*** Glycated hemoglobin. A measure of the average blood glucose level over the past few weeks.
**** Anyone interested in further reading on this should look up The Humanure Handbook
Images of Tooth Decay Healing due to an Improved Diet
This one's for the skeptics out there. As I mentioned in my previous post, Drs. Edward and May Mellanby and Dr. Weston Price reported that under the right circumstances, tooth decay can be reversed by proper nutrition. Here are images taken from the book Nutrition and Disease, by Dr. Mellanby, showing the re-calcification of decayed human teeth due to the growth of tertiary dentin (formerly known as secondary dentin). These are sections (slices) of teeth that have been treated with a chemical that darkens decayed areas. They represent four different teeth at different stages of decay reversal. Click on the image for a larger view:
Here's the text that accompanies the figure:
In the book Nutrition and Physical Degeneration, Dr. Price provides X-rays showing the re-calcification of a mouth full of cavities using a similar diet.
Here's the text that accompanies the figure:The hardening of carious areas that takes place in the teeth of children fed on diets of high calcifying value indicates the arrest of the active process and may result in “healing” of the infected area. As might be surmised, this phenomenon is accompanied by a laying down of a thick barrier of well-formed secondary denture. Illustrations of this healing process can be seen in Figs. 21 (b), (c) and (d). Summing up these results it will be clear that the clinical deductions made on the basis of the animal experiments have been justified, and that it is now known how to diminish the spread of caries and even to stop the active carious process in many affected teeth.The following reference contains a summary of Dr. May Mellanby's experiments on healing tooth decay in children using diet: Mellanby, M. et al. British Medical Journal. Issue 1, page 507. 1932. The diet they used was typically a combination of some source of vitamin D (cod liver oil or irradiated ergosterol), plus liberal full-fat dairy, meats, eggs, vegetables, potatoes and grains low in phytic acid such as white bread. The most effective version of his diet, however, did not include grains.
In the book Nutrition and Physical Degeneration, Dr. Price provides X-rays showing the re-calcification of a mouth full of cavities using a similar diet.
A New Way to Soak Brown Rice
I've been looking for a way to prepare whole brown rice that increases its mineral availability without changing its texture. I've been re-reading some of the papers I've accumulated on grain processing and mineral availability, and I've found a simple way to do it.
In the 2008 paper "Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice", Dr. Robert J. Hamer's group found that soaking alone didn't have much of an effect on phytic acid in brown rice. However, fermentation was highly effective at degrading it. What I didn't realize the first time I read the paper is that they fermented intact brown rice rather than grinding it. This wasn't clear from the description in the methods section but I confirmed it by e-mail with the lead author Dr. Jianfen Liang. He added that the procedure comes from a traditional Chinese recipe for rice noodles. The method they used is very simple:
You can probably use the same liquid to soak other grains and beans.
In the 2008 paper "Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice", Dr. Robert J. Hamer's group found that soaking alone didn't have much of an effect on phytic acid in brown rice. However, fermentation was highly effective at degrading it. What I didn't realize the first time I read the paper is that they fermented intact brown rice rather than grinding it. This wasn't clear from the description in the methods section but I confirmed it by e-mail with the lead author Dr. Jianfen Liang. He added that the procedure comes from a traditional Chinese recipe for rice noodles. The method they used is very simple:
- Soak brown rice in dechlorinated water for 24 hours at room temperature without changing the water. Reserve 10% of the soaking liquid (should keep for a long time in the fridge). Discard the rest of the soaking liquid; cook the rice in fresh water.
- The next time you make brown rice, use the same procedure as above, but add the soaking liquid you reserved from the last batch to the rest of the soaking water.
- Repeat the cycle. The process will gradually improve until 96% or more of the phytic acid is degraded at 24 hours.
You can probably use the same liquid to soak other grains and beans.
Reversing Tooth Decay
In the last post, I discussed the research of Drs. Edward and May Mellanby on the nutritional factors affecting tooth formation. Dr. Mellanby is the man who discovered vitamin D and identified the cause of rickets. Nutrition has a profound effect on tooth structure, and well-formed teeth are inherently resistant to decay. But is there anything you can do if your teeth are already formed?
Teeth are able to heal themselves. That's how traditional cultures such as the Inuit can wear their teeth down to the pulp due to chewing leather and sand-covered dried fish, yet still have an exceptionally low rate of tooth decay. It's also how the African Wakamba tribe can file their front teeth into sharp points without causing decay. Both cultures lost their resistance to tooth decay after adopting nutrient-poor Western foods such as white flour and sugar.
Teeth are made of four layers. Enamel is the hardest, most mineralized outer shell. Dentin is another protective mineralized layer that's below the enamel. Below the dentin is the pulp, which contains blood vessels and nerves. The roots are coated with cementum, another mineralized tissue.
When enamel is poorly formed and the diet isn't adequate, enamel dissolves and decay sets in. Tooth decay is an opportunistic infection that takes advantage of poorly built or maintained teeth. If the diet remains inadequate, the tooth has to be filled or removed, or the person risks more serious complications.
Fortunately, a decaying or broken tooth has the ability to heal itself. Pulp contains cells called odontoblasts, which form new dentin if the diet is good. Here's what Dr. Edward Mellanby had to say about his wife's research on the subject. This is taken from Nutrition and Disease:
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In group 1, oatmeal prevented healing and encouraged new cavities, presumably due to its ability to prevent mineral absorption. In group 2, simply adding vitamin D to the diet caused most cavities to heal and fewer to form. The most striking effect was in group 3, the group eating a grain-free diet plus vitamin D, in which nearly all cavities healed and very few new cavities developed. Grains are the main source of phytic acid in the modern diet, although we can't rule out the possibility that grains were promoting tooth decay through another mechanism as well.
Dr. Mellanby was quick to point out that diet 3 contained some carbohydrate (~45% reduction) and was not low in sugar: "Although [diet 3] contained no bread, porridge or other cereals, it included a moderate amount of carbohydrates, for plenty of milk, jam, sugar, potatoes and vegetables were eaten by this group of children." This study was published in the British Medical Journal (1) and the British Dental journal. Here's Dr. Edward Mellanby again:
Dr. Weston Price also had success curing tooth decay using a similar diet. He fed underprivileged children one very nutritious meal a day and monitored their dental health. From Nutrition and Physical Degeneration (p. 290):
Price's diet was not grain-free, but used rolls made from freshly ground whole wheat. Freshly ground whole wheat has a high phytase (the enzyme that degrades phytic acid) activity, thus in conjunction with the long yeast rises common in Price's time, it would have broken down nearly all of its own phytic acid. This would have made it a source of minerals rather than a sink for them. He also used high-vitamin pastured butter in conjunction with cod liver oil. We now know that the vitamin K2 in pastured butter is important for bone and tooth development and maintenance. This was something that Dr. Mellanby did not understand at the time, but modern science has corroborated Price's finding that K2 is synergistic with vitamin D in promoting skeletal and dental health.
If I were to design the ultimate dietary program to heal cavities that incorporates the successes of both doctors, it would look something like this:
Teeth are able to heal themselves. That's how traditional cultures such as the Inuit can wear their teeth down to the pulp due to chewing leather and sand-covered dried fish, yet still have an exceptionally low rate of tooth decay. It's also how the African Wakamba tribe can file their front teeth into sharp points without causing decay. Both cultures lost their resistance to tooth decay after adopting nutrient-poor Western foods such as white flour and sugar.
Teeth are made of four layers. Enamel is the hardest, most mineralized outer shell. Dentin is another protective mineralized layer that's below the enamel. Below the dentin is the pulp, which contains blood vessels and nerves. The roots are coated with cementum, another mineralized tissue.
When enamel is poorly formed and the diet isn't adequate, enamel dissolves and decay sets in. Tooth decay is an opportunistic infection that takes advantage of poorly built or maintained teeth. If the diet remains inadequate, the tooth has to be filled or removed, or the person risks more serious complications.Fortunately, a decaying or broken tooth has the ability to heal itself. Pulp contains cells called odontoblasts, which form new dentin if the diet is good. Here's what Dr. Edward Mellanby had to say about his wife's research on the subject. This is taken from Nutrition and Disease:
Since the days of John Hunter it has been known that when the enamel and dentine are injured by attrition or caries, teeth do not remain passive but respond to the injury by producing a reaction of the odontoblasts in the dental pulp in an area generally corresponding to the damaged tissue and resulting in a laying down of what is known as secondary dentine. In 1922 M. Mellanby proceeded to investigate this phenomenon under varying nutritional conditions and found that she could control the secondary dentine laid down in the teeth of animals as a reaction to attrition both in quality and quantity, independently of the original structure of the tooth. Thus, when a diet of high calcifying qualities, ie., one rich in vitamin D, calcium and phosphorus was given to the dogs during the period of attrition, the new secondary dentine laid down was abundant and well formed whether the original structure of the teeth was good or bad. On the other hand, a diet rich in cereals and poor in vitamin D resulted in the production of secondary dentine either small in amount or poorly calcified, and this happened even if the primary dentine was well formed.Thus, in dogs, the factors that affect tooth healing are the same factors that affect tooth development:
- The mineral content of the diet, particularly calcium and phosphorus
- The fat-soluble vitamin content of the diet, chiefly vitamin D
- The availability of minerals for absorption, determined largely by the diet's phytic acid content (prevents mineral absorption)
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In group 1, oatmeal prevented healing and encouraged new cavities, presumably due to its ability to prevent mineral absorption. In group 2, simply adding vitamin D to the diet caused most cavities to heal and fewer to form. The most striking effect was in group 3, the group eating a grain-free diet plus vitamin D, in which nearly all cavities healed and very few new cavities developed. Grains are the main source of phytic acid in the modern diet, although we can't rule out the possibility that grains were promoting tooth decay through another mechanism as well.Dr. Mellanby was quick to point out that diet 3 contained some carbohydrate (~45% reduction) and was not low in sugar: "Although [diet 3] contained no bread, porridge or other cereals, it included a moderate amount of carbohydrates, for plenty of milk, jam, sugar, potatoes and vegetables were eaten by this group of children." This study was published in the British Medical Journal (1) and the British Dental journal. Here's Dr. Edward Mellanby again:
The hardening of carious areas that takes place in the teeth of children fed on diets of high calcifying value indicates the arrest of the active process and may result in “healing” of the infected area. As might be surmised, this phenomenon is accompanied by a laying down of a thick barrier of well-formed secondary denture... Summing up these results it will be clear that the clinical deductions made on the basis of the animal experiments have been justified, and that it is now known how to diminish the spread of caries and even to stop the active carious process in many affected teeth.Dr. Mellanby first began publishing studies showing the reversal of cavities in humans in 1924. Why has such a major medical finding, published in high-impact peer-reviewed journals, faded into obscurity?
Dr. Weston Price also had success curing tooth decay using a similar diet. He fed underprivileged children one very nutritious meal a day and monitored their dental health. From Nutrition and Physical Degeneration (p. 290):
About four ounces of tomato juice or orange juice and a teaspoonful of a mixture of equal parts of a very high vitamin natural cod liver oil and an especially high vitamin butter was given at the beginning of the meal. They then received a bowl containing approximately a pint of a very rich vegetable and meat stew, made largely from bone marrow and fine cuts of tender meat: the meat was usually broiled separately to retain its juice and then chopped very fine and added to the bone marrow meat soup which always contained finely chopped vegetables and plenty of very yellow carrots; for the next course they had cooked fruit, with very little sweetening, and rolls made from freshly ground whole wheat, which were spread with the high-vitamin butter. The wheat for the rolls was ground fresh every day in a motor driven coffee mill. Each child was also given two glasses of fresh whole milk. The menu was varied from day to day by substituting for the meat stew, fish chowder or organs of animals.Dr. Price provides before and after X-rays showing re-calcification of cavity-ridden teeth on this program. His intervention was not exactly the same as Drs. Mellanby, but it was similar in many ways. Both diets were high in minerals, rich in fat-soluble vitamins (including D), and low in phytic acid.
Price's diet was not grain-free, but used rolls made from freshly ground whole wheat. Freshly ground whole wheat has a high phytase (the enzyme that degrades phytic acid) activity, thus in conjunction with the long yeast rises common in Price's time, it would have broken down nearly all of its own phytic acid. This would have made it a source of minerals rather than a sink for them. He also used high-vitamin pastured butter in conjunction with cod liver oil. We now know that the vitamin K2 in pastured butter is important for bone and tooth development and maintenance. This was something that Dr. Mellanby did not understand at the time, but modern science has corroborated Price's finding that K2 is synergistic with vitamin D in promoting skeletal and dental health.
If I were to design the ultimate dietary program to heal cavities that incorporates the successes of both doctors, it would look something like this:
- Rich in animal foods, particularly full-fat pastured dairy products (if tolerated). Also meat, organs, fish, bone broths and eggs.
- Fermented grains only; no unfermented grains such as oatmeal, breakfast cereal, crackers, etc. No breads except true sourdough (ingredients should not list lactic acid). Or even better, no grains at all.
- Limited nuts; beans in moderation, only if they're soaked overnight or longer in warm water (due to the phytic acid).
- Starchy vegetables such as potatoes and sweet potatoes.
- A limited quantity of fruit (one piece per day or less), but no refined sweets.
- Cooked and raw vegetables.
- Sunlight, high-vitamin cod liver oil or vitamin D3 supplements.
- A generous amount of pastured butter.
- No industrially processed food.
Preventing Tooth Decay
Meet Sir Edward Mellanby, the discoverer of vitamin D. Along with his wife, Dr. May Mellanby, he identified dietary factors that control the formation and repair of teeth and bones. He also identified the cause of rickets (vitamin D deficiency) and the effect of phytic acid on mineral absorption. Truly a great man! This research began in the 1910s and continued through the 1940s.What he discovered about tooth and bone formation is profound, disarmingly simple and largely forgotten. I remember going to the dentist as a child. He told me I had good teeth. I informed him that I tried to eat well and stay away from sweets. He explained to me that I had good teeth because of genetics, not my diet. I was skeptical at the time, but now I realize just how ignorant that man was.
Tooth structure is determined during growth. Well-formed teeth are highly resistant to decay while poorly-formed teeth are cavity-prone. Drs. Mellanby demonstrated this by showing a strong correlation between tooth enamel defects and cavities in British children. The following graph is drawn from several studies he compiled in the book Nutrition and Disease (1934). "Hypoplastic" refers to enamel that's poorly formed on a microscopic level.
The graph is confusing, so don't worry if you're having a hard time interpreting it. If you look at the blue bar representing children with well-formed teeth, you can see that 77% of them have no cavities, and only 7.5% have severe cavities (a "3" on the X axis). Looking at the green bar, only 6% of children with the worst enamel structure are without cavities, while 74% have severe cavities. Enamel structure is VERY strongly related to cavity prevalence.What determines enamel structure during growth? Drs. Mellanby identified three dominant factors:
- The mineral content of the diet
- The fat-soluble vitamin content of the diet, chiefly vitamin D
- The availability of minerals for absorption, determined largely by the diet's phytic acid content
Optimal tooth and bone formation occurs only on a diet that is sufficient in minerals, fat-soluble vitamins, and low in phytic acid. Drs. Mellanby used dogs in their experiments, which it turns out are a good model for tooth formation in humans for a reason I'll explain later. From Nutrition and Disease:
Thus, if growing puppies are given a limited amount of separated [skim] milk together with cereals, lean meat, orange juice, and yeast (i.e., a diet containing sufficient energy value and also sufficient proteins, carbohydrates, vitamins B and C, and salts), defectively formed teeth will result. If some rich source of vitamin D be added, such as cod-liver oil or egg-yolk, the structure of the teeth will be greatly improved, while the addition of oils such as olive... leaves the teeth as badly formed as when the basal diet only is given... If, when the vitamin D intake is deficient, the cereal part of the diet is increased, or if wheat germ [high in phytic acid] replaces white flour, or, again, if oatmeal [high in phytic acid] is substituted for white flour, then the teeth tend to be worse in structure, but if, under these conditions, the calcium intake is increased, then calcification [the deposition of calcium in the teeth] is improved.Other researchers initially disputed the Mellanbys' results because they weren't able to replicate the findings in rats. It turns out, rats produce the phytic acid-degrading enzyme phytase in their small intestine, so they can extract minerals from unfermented grains better than dogs. Humans also produce phytase, but at levels so low they don't significantly degrade phytic acid. The small intestine of rats has about 30 times the phytase activity of the human small intestine, again demonstrating that humans are not well adapted to eating grains. Our ability to extract minerals from seeds is comparable to that of dogs, which shows that the Mellanbys' results are applicable to humans.
Drs. Mellanby found that the same three factors determine bone quality in dogs as well, which I may discuss in another post.
Is there anything someone with fully formed enamel can do to prevent tooth decay? Drs. Mellanby showed (in humans this time) that not only can tooth decay be prevented by a good diet, it can be almost completely reversed even if it's already present. Dr. Weston Price used a similar method to reverse tooth decay as well. I'll discuss that in my next post.
Dietary Fiber and Mineral Availability
Mainstream health authorities are constantly telling us to eat more fiber for health, particularly whole grains, fruit and vegetables. Yet the only clinical trial that has ever isolated the effect of eating a high-fiber diet on overall risk of death, the Diet and Reinfarction Trial, came up with this graph:
Oops! How embarrassing. At two years, the group that doubled its fiber intake had a 27% greater chance of dying and a 23% greater chance of having a heart attack. The extra fiber was coming from whole grains. I should say, out of fairness, that the result wasn't quite statistically significant (p less than 0.05) at two years. But at the very least, this doesn't support the idea that increasing fiber will extend your life. I believe this the only diet trial that has ever looked at fiber and mortality, without also changing other variables at the same time.
Why might fiber be problematic? I read a paper recently that gave a pretty convincing answer to that question: "Dietary Fibre and Mineral Bioavailability", by Dr. Barbara F. Hartland. By definition, fiber is indigestible. We can divide it into two categories: soluble and insoluble. Insoluble fiber is mostly cellulose and it's relatively inert, besides getting fermented a bit by the gut flora. Soluble fiber is anything that can be dissolved in water but not digested by the human digestive tract. It includes a variety of molecules, some of which are quite effective at keeping you from absorbing minerals. Chief among these is phytic acid, with smaller contributions from tannins (polyphenols) and oxalates. The paper makes a strong case that phytic acid is the main reason fiber prevents mineral absorption, rather than the insoluble fiber fraction. This notion was confirmed here.
As a little side note, polyphenols are those wonderful plant antioxidants that are one of the main justifications for the supposed health benefits of vegetables, tea, chocolate, fruits and antioxidant supplements. The problem is, many of them are actually anti-nutrients. They reduce mineral absorption, reduce growth and feed efficiency in a number of species, and the antioxidant effect seen in human plasma after eating them is due largely to our own bodies secreting uric acid into the blood (a defense mechanism?), rather than the polyphenols themselves. The main antioxidants in plasma are uric acid, vitamin C and vitamin E, with almost no direct contribution from polyphenols. I'm open to the idea that some polyphenols could be beneficial if someone can show me convincing data, but in any case they are not the panacea they're made out to be. Thanks to Peter for cluing me in on this.
Whole grains would be a good source of water-soluble vitamins and minerals, if it weren't for their very high phytic acid content. Even though whole grains are full of minerals, replacing refined grains with whole grains in the diet (and especially adding extra bran) actually reduces the overall absorption of a number of minerals (free text, check out table 4). This has been confirmed repeatedly for iron, zinc, calcium, magnesium and phosphorus. That could well account for the increased mortality in the DART trial.
Refining grains gets rid of the vitamins and minerals but at least refined grains don't prevent you from absorbing the minerals in the rest of your food. Here's a comparison of a few of the nutrients in one cup of cooked brown vs. unenriched white rice (218 vs. 242 calories):
Brown rice would be quite nutritious if we could absorb all those minerals. There are a few ways to increase mineral absorption from whole grains. One way is to soak them in slightly acidic, warm water, which allows their own phytase enzyme to break down phytic acid. This doesn't seem to do much for brown rice, which doesn't contain much phytase.
A more effective method is to grind grains and soak them before cooking, which helps the phytase function more effectively, especially in gluten grains and buckwheat. The most effective method by far, and the method of choice among healthy traditional cultures around the world, is to soak, grind and ferment whole grains. This breaks down nearly all the phytic acid, making whole grains a good source of both minerals and vitamins.
The paper "Dietary Fibre and Mineral Bioavailability" listed another method of increasing mineral absorption from whole grains that I wasn't aware of. Certain foods can increase the absorption of minerals from whole grains high in phytic acid. These include: foods rich in vitamin C such as fruit or potatoes; meat including fish; and dairy.
Another point the paper made was that the phytic acid content of vegetarian diets is often very high, potentially leading to mineral deficiencies. The typical modern vegetarian diet containing brown rice and unfermented soy products is very high in phytic acid and thus very low in absorbable minerals. The more your diet depends on plant sources for minerals, the more careful you have to be about how you prepare your food.
Oops! How embarrassing. At two years, the group that doubled its fiber intake had a 27% greater chance of dying and a 23% greater chance of having a heart attack. The extra fiber was coming from whole grains. I should say, out of fairness, that the result wasn't quite statistically significant (p less than 0.05) at two years. But at the very least, this doesn't support the idea that increasing fiber will extend your life. I believe this the only diet trial that has ever looked at fiber and mortality, without also changing other variables at the same time.
Why might fiber be problematic? I read a paper recently that gave a pretty convincing answer to that question: "Dietary Fibre and Mineral Bioavailability", by Dr. Barbara F. Hartland. By definition, fiber is indigestible. We can divide it into two categories: soluble and insoluble. Insoluble fiber is mostly cellulose and it's relatively inert, besides getting fermented a bit by the gut flora. Soluble fiber is anything that can be dissolved in water but not digested by the human digestive tract. It includes a variety of molecules, some of which are quite effective at keeping you from absorbing minerals. Chief among these is phytic acid, with smaller contributions from tannins (polyphenols) and oxalates. The paper makes a strong case that phytic acid is the main reason fiber prevents mineral absorption, rather than the insoluble fiber fraction. This notion was confirmed here.
As a little side note, polyphenols are those wonderful plant antioxidants that are one of the main justifications for the supposed health benefits of vegetables, tea, chocolate, fruits and antioxidant supplements. The problem is, many of them are actually anti-nutrients. They reduce mineral absorption, reduce growth and feed efficiency in a number of species, and the antioxidant effect seen in human plasma after eating them is due largely to our own bodies secreting uric acid into the blood (a defense mechanism?), rather than the polyphenols themselves. The main antioxidants in plasma are uric acid, vitamin C and vitamin E, with almost no direct contribution from polyphenols. I'm open to the idea that some polyphenols could be beneficial if someone can show me convincing data, but in any case they are not the panacea they're made out to be. Thanks to Peter for cluing me in on this.
Whole grains would be a good source of water-soluble vitamins and minerals, if it weren't for their very high phytic acid content. Even though whole grains are full of minerals, replacing refined grains with whole grains in the diet (and especially adding extra bran) actually reduces the overall absorption of a number of minerals (free text, check out table 4). This has been confirmed repeatedly for iron, zinc, calcium, magnesium and phosphorus. That could well account for the increased mortality in the DART trial.
Refining grains gets rid of the vitamins and minerals but at least refined grains don't prevent you from absorbing the minerals in the rest of your food. Here's a comparison of a few of the nutrients in one cup of cooked brown vs. unenriched white rice (218 vs. 242 calories):
Brown rice would be quite nutritious if we could absorb all those minerals. There are a few ways to increase mineral absorption from whole grains. One way is to soak them in slightly acidic, warm water, which allows their own phytase enzyme to break down phytic acid. This doesn't seem to do much for brown rice, which doesn't contain much phytase. A more effective method is to grind grains and soak them before cooking, which helps the phytase function more effectively, especially in gluten grains and buckwheat. The most effective method by far, and the method of choice among healthy traditional cultures around the world, is to soak, grind and ferment whole grains. This breaks down nearly all the phytic acid, making whole grains a good source of both minerals and vitamins.
The paper "Dietary Fibre and Mineral Bioavailability" listed another method of increasing mineral absorption from whole grains that I wasn't aware of. Certain foods can increase the absorption of minerals from whole grains high in phytic acid. These include: foods rich in vitamin C such as fruit or potatoes; meat including fish; and dairy.
Another point the paper made was that the phytic acid content of vegetarian diets is often very high, potentially leading to mineral deficiencies. The typical modern vegetarian diet containing brown rice and unfermented soy products is very high in phytic acid and thus very low in absorbable minerals. The more your diet depends on plant sources for minerals, the more careful you have to be about how you prepare your food.
A few thoughts on Minerals, Milling, Grains and Tubers
One of the things I've been noticing in my readings on grain processing and mineral bioavailability is that it's difficult to make whole grains into a good source of minerals. Whole grains naturally contain more minerals that milled grains where the bran and germ are removed, but most of the minerals are bound up in ways that prevent their absorption.
The phytic acid content of whole grains is the main reason for their low mineral bioavailability. Brown rice, simply cooked, provides very little iron and essentially no zinc due to its high concentration of phytic acid. Milling brown rice, which turns it into white rice, removes most of the minerals but also most of the phytic acid, leaving mineral bioavailability similar to or perhaps even better than brown rice (the ratio of phytic acid to iron and zinc actually decreases after milling rice). If you're going to throw rice into the rice cooker without preparing it first, white rice is probably better than brown overall. Either way, the mineral availability of rice is low. Here's how Dr. Robert Hamer's group put it when they evaluated the mineral content of 56 varieties of Chinese rice:
Potatoes and other tubers contain much less phytic acid than whole grains, which may be one reason why they're a common feature of extremely healthy cultures such as the Kitavans. I went on NutritionData to see if potatoes have a better mineral-to-phytic acid ratio than grains. They do have a better ratio than whole grains, although whole grains contain more total minerals.
Soaking grains reduces their phytic acid content, but the extent depends on the grain. Gluten grain flours digest their own phytic acid very quickly when soaked, due to the presence of the enzyme phytase. Because of this, bread is fairly low in phytic acid, although whole grain yeast breads contain more than sourdough breads. Buckwheat flour also has a high phytase activity. The more intact the grain, the slower it breaks down its own phytic acid upon soaking. Some grains, like rice, don't have much phytase activity so they degrade phytic acid slowly. Other grains, like oats and kasha, are toasted before you buy them, which kills the phytase.
Whole grains generally contain so much phytic acid that modest reductions don't free up much of the mineral content for absorption. Many of the studies I've read, including this one, show that soaking brown rice doesn't really free up its zinc or iron content. But I like brown rice, so I want to find a way to prepare it well. It's actually quite rich in vitamins and minerals if you can absorb them.
One of the things many of these studies overlook is the effect of pH on phytic acid degradation. Grain phytase is maximally active around pH 4.5-5.5. That's slightly acidic. Most of the studies I've read soaked rice in water with a neutral pH, including the one above. Adding a tablespoon of whey, yogurt, vinegar or lemon juice per cup of grains to your soaking medium will lower the pH and increase phytase activity. Temperature is also an important factor, with 50 C (122 F) being the optimum. I like to put my soaking grains and beans on the heating vent in my kitchen.
I don't know exactly how much adding acid and soaking at a warm temperature will increase the mineral availability of brown rice (if at all), because I haven't found it in the literature. The bacteria present if you soak it in whey, unfiltered vinegar or yogurt could potentially aid the digestion of phytic acid. Another strategy is to add the flour of a high-phytase grain like buckwheat to the soaking medium. This works for soaking flours, perhaps it would help with whole grains as well?
So now we come to the next problem. Phytic acid is a medium-sized molecule. If you break it down and it lets go of the minerals it's chelating, the minerals are more likely to diffuse out of the grain into your soaking medium, which you then discard because it also contains the tannins, saponins and other anti-nutrients that you want to get rid of. That seems to be exactly what happens, at least in the case of brown rice.
So what's the best solution for maximal mineral and vitamin content? Do what traditional cultures have been doing for millenia: soak, grind and ferment whole grains. This eliminates nearly all the phytic acid, dramatically increasing mineral bioavailiability. Fermenting batter doesn't lose minerals because there's nowhere for them to go. In the West, we use this process to make bread, which would probably be a good food if it weren't for the gluten. In Africa, they do it to make ogi, injera, and a number of other fermented grain dishes. In India, they grind rice and beans to make idli and dosas. In the Phillipines, they ferment ground rice to make puto. Fermenting ground whole grains is the most reliable way to improve their mineral bioavailability and nutritional value in general.
But isn't having a rice cooker full of steaming brown rice so nice? I'm still working on finding a reliable way to increase its nutritional value.
The phytic acid content of whole grains is the main reason for their low mineral bioavailability. Brown rice, simply cooked, provides very little iron and essentially no zinc due to its high concentration of phytic acid. Milling brown rice, which turns it into white rice, removes most of the minerals but also most of the phytic acid, leaving mineral bioavailability similar to or perhaps even better than brown rice (the ratio of phytic acid to iron and zinc actually decreases after milling rice). If you're going to throw rice into the rice cooker without preparing it first, white rice is probably better than brown overall. Either way, the mineral availability of rice is low. Here's how Dr. Robert Hamer's group put it when they evaluated the mineral content of 56 varieties of Chinese rice:
This study shows that the mineral bio-availability of Chinese rice varieties will be [less than] 4%. Despite the variation in mineral contents, in all cases the [phytic acid] present is expected to render most mineral present unavailable. We conclude that there is scope for optimisation of mineral contents of rice by matching suitable varieties and growing regions, and that rice products require processing that retains minerals but results in thorough dephytinisation.It's important to note that milling removes most of the vitamin content of the brown rice as well, another important factor.
Potatoes and other tubers contain much less phytic acid than whole grains, which may be one reason why they're a common feature of extremely healthy cultures such as the Kitavans. I went on NutritionData to see if potatoes have a better mineral-to-phytic acid ratio than grains. They do have a better ratio than whole grains, although whole grains contain more total minerals.
Soaking grains reduces their phytic acid content, but the extent depends on the grain. Gluten grain flours digest their own phytic acid very quickly when soaked, due to the presence of the enzyme phytase. Because of this, bread is fairly low in phytic acid, although whole grain yeast breads contain more than sourdough breads. Buckwheat flour also has a high phytase activity. The more intact the grain, the slower it breaks down its own phytic acid upon soaking. Some grains, like rice, don't have much phytase activity so they degrade phytic acid slowly. Other grains, like oats and kasha, are toasted before you buy them, which kills the phytase.
Whole grains generally contain so much phytic acid that modest reductions don't free up much of the mineral content for absorption. Many of the studies I've read, including this one, show that soaking brown rice doesn't really free up its zinc or iron content. But I like brown rice, so I want to find a way to prepare it well. It's actually quite rich in vitamins and minerals if you can absorb them.
One of the things many of these studies overlook is the effect of pH on phytic acid degradation. Grain phytase is maximally active around pH 4.5-5.5. That's slightly acidic. Most of the studies I've read soaked rice in water with a neutral pH, including the one above. Adding a tablespoon of whey, yogurt, vinegar or lemon juice per cup of grains to your soaking medium will lower the pH and increase phytase activity. Temperature is also an important factor, with 50 C (122 F) being the optimum. I like to put my soaking grains and beans on the heating vent in my kitchen.
I don't know exactly how much adding acid and soaking at a warm temperature will increase the mineral availability of brown rice (if at all), because I haven't found it in the literature. The bacteria present if you soak it in whey, unfiltered vinegar or yogurt could potentially aid the digestion of phytic acid. Another strategy is to add the flour of a high-phytase grain like buckwheat to the soaking medium. This works for soaking flours, perhaps it would help with whole grains as well?
So now we come to the next problem. Phytic acid is a medium-sized molecule. If you break it down and it lets go of the minerals it's chelating, the minerals are more likely to diffuse out of the grain into your soaking medium, which you then discard because it also contains the tannins, saponins and other anti-nutrients that you want to get rid of. That seems to be exactly what happens, at least in the case of brown rice.
So what's the best solution for maximal mineral and vitamin content? Do what traditional cultures have been doing for millenia: soak, grind and ferment whole grains. This eliminates nearly all the phytic acid, dramatically increasing mineral bioavailiability. Fermenting batter doesn't lose minerals because there's nowhere for them to go. In the West, we use this process to make bread, which would probably be a good food if it weren't for the gluten. In Africa, they do it to make ogi, injera, and a number of other fermented grain dishes. In India, they grind rice and beans to make idli and dosas. In the Phillipines, they ferment ground rice to make puto. Fermenting ground whole grains is the most reliable way to improve their mineral bioavailability and nutritional value in general.
But isn't having a rice cooker full of steaming brown rice so nice? I'm still working on finding a reliable way to increase its nutritional value.
How to Eat Grains
Our story begins in East Africa in 1935, with two Bantu tribes called the Kikuyu and the Wakamba. Their traditional diets were mostly vegetarian and consisted of sweet potatoes, corn, beans, plantains, millet, sorghum, wild mushrooms and small amounts of dairy, small animals and insects. Their food was agricultural, high in carbohydrate and low in fat.
Dr. Weston Price found them in good health, with well-formed faces and dental arches, and a dental cavity rate of roughly 6% of teeth. Although not as robust or as resistant to tooth decay as their more carnivorous neighbors, the "diseases of civilization" such as cardiovascular disease and obesity were nevertheless rare among them. South African Bantu eating a similar diet have a low prevalence of atherosclerosis, and a measurable but low incidence of death from coronary heart disease, even in old age.
How do we reconcile this with the archaeological data showing a general decline in human health upon the adoption of agriculture? Humans did not evolve to tolerate the toxins, anti-nutrients and large amounts of fiber in grains and legumes. Our digestive system is designed to handle a high-quality omnivorous diet. By high-quality, I mean one that has a high ratio of calories to indigestible material (fiber). Our species is very good at skimming off the highest quality food in nearly any ecological niche. Animals that are accustomed to high-fiber diets, such as cows and gorillas, have much larger, more robust and more fermentative digestive systems.
One factor that reconciles the Bantu data with the archaeological data is that much of the Kikuyu and Wakamba diet came from non-grain sources. Sweet potatoes and plantains are similar to the starchy wild plants our ancestors have been eating for nearly two million years, since the invention of fire (the time frame is debated but I think everyone agrees it's been a long time). Root vegetables and starchy fruit have a higher nutrient bioavailibility than grains and legumes due to their lower content of anti-nutrients and fiber.
The second factor that's often overlooked is food preparation techniques. These tribes did not eat their grains and legumes haphazardly! This is a factor that was overlooked by Dr. Price himself, but has been emphasized by Sally Fallon. Healthy grain-based African cultures typically soaked, ground and fermented their grains before cooking, creating a sour porridge that's nutritionally superior to unfermented grains. The bran was removed from corn and millet during processing, if possible. Legumes were always soaked prior to cooking.
These traditional food processing techniques have a very important effect on grains and legumes that brings them closer in line with the "paleolithic" foods our bodies are designed to digest. They reduce or eliminate toxins such as lectins and tannins, greatly reduce anti-nutrients such as phytic acid and protease inhibitors, and improve vitamin content and amino acid profile. Fermentation is particularly effective in this regard. One has to wonder how long it took the first agriculturalists to discover fermentation, and whether poor food preparation techniques or the exclusion of animal foods could account for their poor health.
I recently discovered a paper that illustrates these principles: "Influence of Germination and Fermentation on Bioaccessibility of Zinc and Iron from Food Grains". It's published by Indian researchers who wanted to study the nutritional qualities of traditional fermented foods. One of the foods they studied was idli, a South Indian steamed "muffin" made from rice and beans. Idlis happen to be one of my favorite foods.
The amount of minerals your digestive system can extract from a food depends in part on the food's phytic acid content. Phytic acid is a molecule that traps certain minerals (iron, zinc, magnesium, calcium), preventing their absorption. Raw grains and legumes contain a lot of it, meaning you can only absorb a fraction of the minerals present in them.
In this study, soaking had a modest effect on the phytic acid content of the grains and legumes examined (although it's generally more effective). Fermentation, on the other hand, completely broke down the phytic acid in the idli batter, resulting in 71% more bioavailable zinc and 277% more bioavailable iron. It's safe to assume that fermentation also increased the bioavailability of magnesium, calcium and other phytic acid-bound minerals.
Fermenting the idli batter also completely eliminated its tannin content. Tannins are a class of molecules found in many plants that are toxins and anti-nutrients. They reduce feed efficiency and growth rate in a variety of species.
Lectins are another toxin that's frequently mentioned in the paleolithic diet community. They are blamed for everything from digestive problems to autoimmune disease, probably with good reason. One of the things people like to overlook in this community is that traditional processing techniques such as soaking, sprouting, fermentation and cooking, greatly reduce or eliminate lectins from grains and legumes. One notable exception is gluten, which survives all but the longest fermentation and is not broken down by cooking.
Soaking, sprouting, fermenting, grinding and cooking are the techniques by which traditional cultures have been making the most of grain and legume-based diets for thousands of years. We ignore these time-honored traditions at our own peril.
Dr. Weston Price found them in good health, with well-formed faces and dental arches, and a dental cavity rate of roughly 6% of teeth. Although not as robust or as resistant to tooth decay as their more carnivorous neighbors, the "diseases of civilization" such as cardiovascular disease and obesity were nevertheless rare among them. South African Bantu eating a similar diet have a low prevalence of atherosclerosis, and a measurable but low incidence of death from coronary heart disease, even in old age.
How do we reconcile this with the archaeological data showing a general decline in human health upon the adoption of agriculture? Humans did not evolve to tolerate the toxins, anti-nutrients and large amounts of fiber in grains and legumes. Our digestive system is designed to handle a high-quality omnivorous diet. By high-quality, I mean one that has a high ratio of calories to indigestible material (fiber). Our species is very good at skimming off the highest quality food in nearly any ecological niche. Animals that are accustomed to high-fiber diets, such as cows and gorillas, have much larger, more robust and more fermentative digestive systems.
One factor that reconciles the Bantu data with the archaeological data is that much of the Kikuyu and Wakamba diet came from non-grain sources. Sweet potatoes and plantains are similar to the starchy wild plants our ancestors have been eating for nearly two million years, since the invention of fire (the time frame is debated but I think everyone agrees it's been a long time). Root vegetables and starchy fruit have a higher nutrient bioavailibility than grains and legumes due to their lower content of anti-nutrients and fiber.
The second factor that's often overlooked is food preparation techniques. These tribes did not eat their grains and legumes haphazardly! This is a factor that was overlooked by Dr. Price himself, but has been emphasized by Sally Fallon. Healthy grain-based African cultures typically soaked, ground and fermented their grains before cooking, creating a sour porridge that's nutritionally superior to unfermented grains. The bran was removed from corn and millet during processing, if possible. Legumes were always soaked prior to cooking.
These traditional food processing techniques have a very important effect on grains and legumes that brings them closer in line with the "paleolithic" foods our bodies are designed to digest. They reduce or eliminate toxins such as lectins and tannins, greatly reduce anti-nutrients such as phytic acid and protease inhibitors, and improve vitamin content and amino acid profile. Fermentation is particularly effective in this regard. One has to wonder how long it took the first agriculturalists to discover fermentation, and whether poor food preparation techniques or the exclusion of animal foods could account for their poor health.
I recently discovered a paper that illustrates these principles: "Influence of Germination and Fermentation on Bioaccessibility of Zinc and Iron from Food Grains". It's published by Indian researchers who wanted to study the nutritional qualities of traditional fermented foods. One of the foods they studied was idli, a South Indian steamed "muffin" made from rice and beans. Idlis happen to be one of my favorite foods.
The amount of minerals your digestive system can extract from a food depends in part on the food's phytic acid content. Phytic acid is a molecule that traps certain minerals (iron, zinc, magnesium, calcium), preventing their absorption. Raw grains and legumes contain a lot of it, meaning you can only absorb a fraction of the minerals present in them.
In this study, soaking had a modest effect on the phytic acid content of the grains and legumes examined (although it's generally more effective). Fermentation, on the other hand, completely broke down the phytic acid in the idli batter, resulting in 71% more bioavailable zinc and 277% more bioavailable iron. It's safe to assume that fermentation also increased the bioavailability of magnesium, calcium and other phytic acid-bound minerals.
Fermenting the idli batter also completely eliminated its tannin content. Tannins are a class of molecules found in many plants that are toxins and anti-nutrients. They reduce feed efficiency and growth rate in a variety of species.
Lectins are another toxin that's frequently mentioned in the paleolithic diet community. They are blamed for everything from digestive problems to autoimmune disease, probably with good reason. One of the things people like to overlook in this community is that traditional processing techniques such as soaking, sprouting, fermentation and cooking, greatly reduce or eliminate lectins from grains and legumes. One notable exception is gluten, which survives all but the longest fermentation and is not broken down by cooking.
Soaking, sprouting, fermenting, grinding and cooking are the techniques by which traditional cultures have been making the most of grain and legume-based diets for thousands of years. We ignore these time-honored traditions at our own peril.