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Q: Should I Eat Soy? Part 9
A: Another of the claims made by Enig and Fallon is that soy foods, because they contain phytic acid, block the absorption of minerals like calcium, magnesium, copper, iron and zinc in the intestinal tract. They claim that vegetarians who consume tofu risk severe mineral deficiencies, and that zinc deficiency causes a “spacey feeling that some vegetarians may mistake for the high of spiritual enlightenment”.
It is true that soy is high in phytates, as are beans, grains, nuts and seeds. Yet Enig and Fallon do not suggest cutting out those foods for this reason. Although phytates can block the absorption of minerals, this is only a problem if a person consumes enormous amounts of foods containing them. This would mean, for example, a diet consisting of all soy or wheat bran. There is no evidence that a serving or two per day of soy has this effect. And, when soy foods are fermented, such as in tempeh or miso, phytate levels are reduced to about a third of their initial levels.
There is, by the way, no evidence that vegetarians experience mineral deficiencies. In fact, the National Cattleman’s Beef Association has even stated publicly “Well planned vegetarian diets can meet dietary recommendations for essential nutrients.”
Fallon and Enig provide no supporting documentation for their claim about vegetarians and mineral deficiencies, or for their claim about zinc deficiencies making people “spacey”.
Following are observations of mineral level for people following a vegetarian diet:
- Zinc – the levels of zinc in hair, saliva and blood of vegetarians are usually in normal range. Studies of pregnant women, for whom zinc deficiency is particularly harmful, show no differences in zinc levels between vegetarian and non-vegetarian women.
- Iron – vegetarian diets are high in Vitamin C, which enhances iron absorption. And, there is no evidence of iron deficiencies among vegetarians.
- Copper – vegetarian diets tend to be higher in copper
- Magnesium – vegetarian diets are generally so much higher in this mineral, that this more than compensates for any block due to phytate consumption. In fact, vegetarians consistently show higher levels of this mineral than their meat-eating counterparts.
- Calcium – hundreds of studies show that vegetarians have healthier bones, better calcium balance and less osteoporosis than meat eaters.
On the other hand, studies show that meat and dairy eaters often have significant mineral deficiencies, particularly calcium:
- In January 2001, the American Journal of Nutrition published a study that concluded that there was a direct link between animal protein consumption and bone loss. In this study, funded by the National Institutes of Health, more than 1000 women ages 65 to 80, were grouped into three categories – high ratio of animal protein to vegetable protein, a middle range and a low range. The women in the high range category had three times the rate of bone loss as the women in the low group, and four times the number of fractures after adjustments for estrogen supplementation, smoking and every other variable.
Fallon and Enig claim that we have such high rates of osteoporosis because Americans have substituted soybean oil for butter and do not take in enough Vitamin D to facilitate calcium absorption. But they ignore the fact that exposure to sunlight is the principal source of Vitamin D in humans. According to a report in 1999 in The American Journal of Nutrition, blood levels of Vitamin D-deficient people do not begin to rise until 4000IU per day are consumed. In order to rely on butter for elevations in blood levels of Vitamin D, 4 pounds per day would have to be consumed! Studies consistently show that people who do not have skin exposure to sunlight as a source of Vitamin D cannot get enough from the diet – it must come from supplementation.