Magnesium and Insulin Sensitivity

From a paper based on US NHANES nutrition and health survey data (1):

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:

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:

1. 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.
   
2. 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.
   
3. Repeat the cycle. The process will gradually improve until 96% or more of the phytic acid is degraded at 24 hours.
   

This process probably depends on two factors: fermentation acidifies the soaking medium, which activates the phytase (phytic acid-degrading enzyme) already present in the rice; and it also cultivates microorganisms that produce their own phytase. I would guess the latter factor is the more important one, because brown rice doesn't contain much phytase.

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 made of 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:

1. The mineral content of the diet, particularly calcium and phosphorus
   
2. The fat-soluble vitamin content of the diet, chiefly vitamin D
   
3. The availability of minerals for absorption, determined largely by the diet's phytic acid content (prevents mineral absorption)
   

What about humans? Drs. Mellanby set out to see if they could use their dietary principles to cure tooth decay that was already established. They divided 62 children with cavities into three different diet groups for 6 months. Group 1 ate their normal diet plus oatmeal (rich in phytic acid). Group 2 ate their normal diet plus vitamin D. Group 3 ate a grain-free diet and took vitamin D.

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 was not low in carbohydrate or even 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 (1932, 1: 507) 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 such as meat, organs, fish, bone broths, full-fat pastured dairy (if tolerated) and eggs.
  
• Fermented grains only; no unfermented grains such as oatmeal, breakfast cereal, crackers, etc. No breads except sourdough because they typically aren't made from fresh flour.
• No 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.
  
• Moderate quantities of fruit, but no refined sweets.
  
• Moderate quantities of well-cooked vegetables.
  
• Sunlight, high-vitamin cod liver oil or vitamin D3 supplements.
  
• Generous amounts of pastured butter.
• No industrially processed food.
  

This diet would maximize mineral absorption while providing abundant fat-soluble vitamins. It probably isn't necessary to follow it strictly. For example, if you eat more mineral-rich foods such as dairy and bone broths, you can probably get away with more phytic acid. Or you might be able to heal cavities eating like this for only one or two meals a day, as Dr. Price demonstrated.

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:

1. The mineral content of the diet
2. The fat-soluble vitamin content of the diet, chiefly vitamin D
   
3. The availability of minerals for absorption, determined largely by the diet's phytic acid content
   

Teeth and bones are a mineralized protein scaffold. Vitamin D influences the quality of the protein scaffold that's laid down. For the scaffold to mineralize, the diet has to contain enough minerals, primarily calcium and phosphorus. Vitamin D allows the digestive system to absorb the minerals, but it can only absorb them if they aren't bound by phytic acid. Phytic acid is an anti-nutrient found primarily in unfermented seeds such as grains. So the process depends on getting minerals (sufficient minerals in the diet and low phytic acid) and putting them in the right place (fat-soluble vitamins).

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.

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:

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 very low in phytic acid. 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.