Travel down the health food aisle of your nearest major grocery store, and you're likely to see tofu, soy milk, soy cheese, and soy burgers. Soy, derived from the bean native to East Asia, is also present in many snack bars and other processed foods.
But is soy really a health food? Many experts would answer with an emphatic No.
Dr. Joseph Mercola of mercola.com says, "I regularly see women who have had thyroid problems as a result of consuming soy products regularly... Unfermented soy has many negative digestive inhibitors and potent hormones that typically will not push your body in a direction of health.
"Further, soy formula is one of the absolute worst foods you can give to your child, as it will expose them to very high levels of hormones that can have negative influences on them as they grow older."
What's the Problem with Soy?
Like any food, the soy bean contains many different chemicals, and some of these chemicals can negatively affect your health.
A 1997 study in the medical journal Lancet confirmed that soy contains glycosides of genistein and daidzein - plant-based chemicals that mimic estrogen. (These chemicals are also known as isoflavones or phytoestrogens.) Phytoestrogens can be especially harmful to developing children and may produce adverse hormonal effects.
"Plants such as soy are making oral contraceptives to defend themselves," explains Claude Hughes, Ph.D., a neuroendocrinologist at Cedars-Sinai Medical Center. "They evolved compounds that mimic natural estrogen. These phytoestrogens can interfere with the mammalian hormones involved in reproduction and growth - [an evolutionary] a strategy to reduce the number and size of predators."
"A soy-fed baby receives the equivalent of five birth control pills' worth of estrogen every day," says Dr. Mercola. High soy consumption has been linked to slow physical maturation among boys, early puberty among girls, and infertility.
Other research suggests that high levels of manganese in soy-based baby formulas can lead to brain damage and altered behaviors. Soy formulas also have a much higher concentration of aluminum than milk-based formulas. Some scientific reports from as far back as the 70s and 80s suggest that a soy-based diet can impair the immune systems of infants.
Soy contains strong enzyme inhibitors that can interfere with digestion and lead to gastric distress, amino acid deficiencies, enlargement of the pancreas, and possibly even cancer. These inhibitor chemicals are partially deactivated by normal cooking, but they're not totally deactivated, and they can still have a negative impact on health.
Soy also contains goitrogens, which depress thyroid function, as well as high levels of phytic acid, which can block the uptake of essential minerals in the intestinal tract.
In 2000, the FDA approved a "health claim" and allowed manufacturers of certain soy foods to claim that soy may reduce the risk of heart disease. Two senior U.S. government scientists, Doctors Daniel Doerge and Daniel Sheehan, disagreed with the FDA decision and wrote a letter of protest in which they stated:
- Isoflavones in soy have effects similar to estrogen.
- Chemicals in soy may increase the risk of estrogen-dependent breast cancer.
- Soy may lead to health problems in animals, including altered sexual development and thyroid disorders.
- "There is abundant evidence that some of the isoflavones found in soy demonstrate toxicity in estrogen-sensitive tissues and in the thyroid."
- "During pregnancy in humans, isoflavones per se could be a risk factor for abnormal brain and reproductive tract development."
Moreover, in today's world, most soy is genetically modified and contaminated by pesticides.
Soy Consumption in Asia
While many Americans may associate soy consumption with Asia, good health, and longevity, according to Dr. Mercola, "The Chinese did not eat unfermented soybeans as they did other legumes such as lentils because the soybean contains large quantities of natural toxins or 'anti-nutrients.'"
Soy was traditionally grown as a nitrogen fixer for crop rotation in China. It was not widely served as a food until the discovery of fermentation techniques, which produced tempeh, natto, miso, and soy sauce.
A 1998 survey in Japan showed that the Japanese really don't eat that much soy. A Japanese man typically eats about 8 grams of soy a day, according to Soy Online Service. One chunk of tofu and a two glasses of soy milk contain 220 grams of soy! Also consider that the Japanese traditionally eat tofu as part of a mineral-rich fish broth. Vegetarians who consume tofu as a substitute for meat may be at-risk for mineral deficiencies.
Editor's Note: My step-mother is actually from Japan, and she laughed at me the first time that she saw me put soy sauce on my rice; that is not a custom in Japan.
The Healthy Forms of Soy
"Please recognize that fermented soy products are typically not associated with many of these problems and actually are reasonable to include in your diet. These products include miso, natto and tempeh," advises Dr. Mercola.
As opposed to cooking, the long process of fermentation deactivates many of the natural toxins found in soy. Fermented soy products like soy sauce, tempeh, miso, and natto are safe to eat. (But keep an eye on the sodium content in your soy sauce!) In fact, natto, made from fermented soy beans, contains the enzyme nattokinase, which is a powerful weapon against blood clots. Natto offers other health benefits, too, but many Westerners are put off by its pungent odor, strong flavor, and sticky consistency.
Soy & Food Allergies
Soy is one of the "Big Eight" food allergens that also include peanuts, tree nuts, milk, fish, shellfish, eggs, and wheat. Soy can be difficult to avoid because it's such a common ingredient in processed foods. If you have a soy allergy, consider investing in
Soy Allergy Restaurant Cards; they just might save your life.
Soy allergy is most common among infants, and many infants outgrow the allergy by the age of two. Ironically, many infants drink soy formula because of a milk allergy; however, Dr. Mercola claims that "soy formula is one of the absolute worst foods you can give to your child."
The Royal College of Australian Physicians also warn parents that soy formula may not be the answer to milk allergies: "Soy protein can cause intolerance reactions with gastrointestinal symptoms as well as acute anaphylaxis, and up to 40% of infants intolerant of cow's milk also develop soy protein intolerance."
Soy may also play a role in the extreme increase in peanut allergies over the past decade. Robyn O'Brien of allergykids.com explains, "What we're finding is that there's a dramatic correlation between the introduction of genetically engineered soy, which was introduced in 1996, and within that first year, there was a 50% increase seen in soy allergies. And within the first five years of the introduction of genetically engineered soy, there was a doubling of peanut allergy.
"Studies are showing now that there are allergens in this genetically engineered soy, and they are 41% similar to peanut allergen. Consider how prevalent soy is and how it's used in processed foods; it's pervasive. And so, to have suddenly introduced an allergen like that into the food supply in the last 10 years, and then to also see this correlation in the number of children with food allergies, I think it's something that merits additional studies."
Take Responsibility for Your Own Health
This article merely skims the tip of the iceberg when it comes to scientific research on soy. If you have a child on an soy-based formula, if you have a soy allergy, or if you eat a diet high in soy products (particularly if you're a vegetarian), please do more research on your own.
Originally published in the
January 2008 issue of
Allergy Consumer Report.
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