By now we have all been sufficiently confused about the merits and dangers of soy.
Ancient writings from China suggest that the soybean was traditionally considered unfit for human consumption. The reason may be that the soybean is uniquely endowed with certain toxic anti-nutrients that are now being linked to breast cancer, thyroid disease, menstrual and fertility issues as well as severe allergies, compromised immunity and brain damage(1).
On the other side of the aisle there is compelling research that soy can offer formidable defense against cardiovascular disease, numerous forms of cancer, osteoporosis, and menopausal symptoms (2).
Join me as I delve into this very heated debate in search of some answers. I’ve done my best to include as much research from both sides as possible, before presenting my own professional view.
What is an anti-nutrient?
Many plants are protected by toxic anti-nutrients to ward off insects and animals that might otherwise eat them. Beans in particular are famous for these anti-nutrients which, as many of us may know from experience, can make them a challenge to digest.
Unlike most beans, the anti-nutrients in soy don’t wash or cook off and according to the research by soy opponents, they present significant health risks.
Anti-nutrients come in a variety of forms. Below I’ve listed the main components of soy that, according to many experts, are a definite cause for concern.
Breaking it down: Soy’s troubling compounds—and the soy supporters’ rebuttal
- The first troubling group of anti-nutrients is called the phytates. Phytates bind to minerals like zinc, calcium, magnesium, iron and copper, and may strip them from the body, resulting in mineral deficiencies. Along with enzyme inhibitors, phytates may block the absorption of nutrients from soy, so that any possible benefit is effectively negated (4). That said, soy protein has been used successfully in treating mild and moderate protein-energy malnutrition in some of the world’s sickest children, indicating that the nutrients in soy can be extremely available and nutritious (5).
- Goitrogens are substances that inhibit thyroid function. When the thyroid is compromised, it may enlarge in an attempt to absorb necessary missing nutrients, resulting in a mass called a goiter. Soy inhibits the thyroid’s uptake of iodine, thus driving up the thyroid stimulating hormone (TSH) in an attempt to boost thyroid function. In 1991, Japanese researchers reported that consumption of as little as 30 grams or 2 tablespoons of soybeans per day for only one month resulted in a significant increase in thyroid stimulating hormone(6)—a sign of impaired thyroid function. Soy supporters argue that in individuals with an otherwise healthy thyroid, no significant changes have been recorded (9).
- Genestein and Diadzen, the isoflavone molecules in soy, inhibit an enzyme involved in thyroid hormone synthesis and may suppress thyroid function as well (7). These isoflavones have also been reported to disturb liver function, reproductive hormones, and fertility (8). Experts that recommend soy acknowledge this, but argue that in otherwise healthy individuals, studies show that soy products have no negative effects on thyroid function (9).
- In vitro studies suggest that isoflavones inhibit synthesis of estradiol and other steroid hormones (10). In 1992, the Swiss health service estimated that 100 grams of soy protein, which equals about 4 protein shakes, provided the estrogenic equivalent of a birth control pill (11). Soy supporters say that genistein is actually estrogenic in a positive way. According to this theory, it interacts directly with the notorious HER2 cancer-causing gene, inhibiting its activation by cellular machinery and preventing cancer promotion (12).
Today, soy manufacturers are acutely aware of the anti-nutrient issue and claim they are removed during processing (3). The only risk, according to them, is when one eats raw soy beans, which they say to avoid.
Fermentation: The ancient solution
In China, the discovery that soy could be cultured or fermented brought with it a shift in soy’s reputation. While unfermented soy was still avoided as a food, the fermentation process appeared to free soy from the toxic anti-nutrients and, moreover, actually released some amazing health benefits. During the Ming Dynasty, the fermented soy food natto actually found its way into Chinese Medicine’s Materia Medica, as a nutritional remedy for many health conditions.
Today, many experts believe that fermentation is the only way to neutralize the dangerous anti-nutrients in soy.
Perhaps soy may be best classified as a medicine (in its fermented state) rather than a food.
The Ayurvedic Perspective
According to Ayurveda, soy is a very hard protein to digest and was not a traditional part of the Ayurvedic diet. In fact, some Ayurvedic doctors are strongly against soy and do not consider it a digestible food. Perhaps the knowledge of its anti-nutrient content spurned caution in India as well.
Energetically, it was considered heavy and dulling for the mind. It was generally believed that soy acts more like a nut than a bean and is therefore pacifying for vata. Still, because of its difficulty to digest and somewhat rajasic, or stimulating, nature, soy was rarely used medicinally.
Interestingly, fermented foods are also not favored in Ayurveda, and fermented soy products were never a part of the Ayurvedic diet. According to Ayurveda, fermented foods may aggravate vata and are considered tamasic, or dulling for the mind. As a result, fermented foods were not used in Ayurveda and the medicinal nature of fermented soy foods such as natto was unknown.
In summary, soy is generally avoided in Ayurveda, while some Ayurvedic experts allow it in moderation. Soy should not be your main source of protein.
Soy in the West
In the west, soy products have become an industry. From soy milk to soy pills and soybean oil in just about every processed food, Americans are getting way too much soy. Even the promoters of soy encourage moderation and advise that soy not be the major source of protein in one’s diet.
It can also be very difficult to get non-genetically-modified—or non-GMO—soy in the west, which may in itself be enough of a reason to avoid it.
Natto – Ancient Chinese Medicine, Applied
As I’ve mentioned, traditionally fermented soy foods like miso, traditionally brewed soy sauce, tempeh and natto are proven safe on both sides of the aisle and have documented beneficial health properties. Natto, in particular, has been documented and safely used for cardiovascular and circulatory support in the west for the past 20 years.
Natto is extremely high in vitamin K2, which is rich in fibrinolytic enzymes called NattoKinase.
A fibrinolytic enzyme is an enzyme which protects the body from clot formation. Blood clots, or thrombi, can block blood flow in the arteries of the heart and brain and cause angina, heart attack or stroke. Protective fibrinolytic enzymes are produced by the body but, as we age, production of these enzymes declines.
It has been determined that nattokinase actually has four times greater the fibrinolytic activity than plasmin, the body’s own endogenous fibrinolytic enzyme (13)*.
Conclusion: Well, is soy friend, or foe?
Now that we’ve taken a look at the research from both sides of the isle, glanced at soy’s history, and taken into consideration the perspectives of two ancient systems of medicine, what’s the verdict? Here’s my take on it:
- Soy should not be your main source of protein. Avoid soy pills. Avoid or reduce soy milk, soy cheese and other processed soy foods.
- A note on tofu: in Japan, tofu is significantly more cultured with a much stronger taste than it is here in the states. American tofu should be eaten in moderation.
- Enjoy traditionally fermented soy products such as miso, tempeh, natto, and traditionally brewed soy sauce. Still, make sure even these products are organic and non-GMO. Very important!
- Consider including natto either as a food in your diet, or the enzyme nattokinase as a supplement, to maintain the optimal health of your arteries and protect them from atherosclerosis and blood clots.*
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3. Palacios MF, Easter RA, Soltwedel KT, et al. Effect of soybean variety and processing on growth performance of young chicks and pigs. J Anim Sci. 2004 Apr;82(4):1108-14.
4**. Fallon S, Enig M. Soy Alert – Tragedy and Hype. Nexus Magazine. 2000 Apr-May;7(3).
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6. Y Ishizuki, et al, The effects on the thyroid gland of soybeans administered experimentally in healthy subjects, Nippon Naibunpi Gakkai Zasshi 1991 767: 622-629
7. (Divi RL, Doerge DR. Inhibition of thyroid peroxidase by dietary flavonoids. Chem Res Toxicol. 1996 Jan-Feb;9(1):16-23.
8**. K D R Setchell , et al, Dietary estrogens – a probable cause of infertility and liver disease in captive cheetahs, Gastroenterology 93: 225-233 (1987); A S Leopold, Phytoestrogens: Adverse effects on reproduction in California Quail, Science 1976 191: 98-100; Drane HM et al, Oestrogenic activity of soya-bean products, Food Cosmetics and Technology 1980 18: 425-427; S Kimura, et al. Development of malignant goiter by defatted soybean with iodine-free diet in rats, 1976, Gann 67: 763-765; C Pelissero, et al, Estrogenic effect of dietary soy bean meal on vitellogenesis in cultured Siberian Sturgeon Acipenser baeri, Gen Comp End 83: 447-457; Braden et al, The oestrogenic activity and metabolism of certain isoflavones in sheep, Australian Journal of Agricultural Research 1967 18:335-348.
9. Doerge DR, Sheehan DM. Goitrogenic and estrogenic activity of soy isoflavones. Environ Health Perspect. 2002 Jun;110 Suppl 3:349-53.
10**. W M Keung, Dietary estrogenic isoflavones are potent inhibitors of B-hydroxysteroid dehydrogenase of P testosteronii, Biochemical and Biophysical Research Committee 1995 215:1137-1144; S I Makela, et al, Estrogen specific 12 B-hydroxysteroid oxidoreductase type 1 (E.C. 126.96.36.199) as a possible target for the action of phytoestrogens, PSEBM, 1995 208:51-59.
11**. Bulletin de L’Office Federal de la Sante Publique, No 28, July 20, 1992.
12. Sakla MS, Shenouda NS, Ansell PJ, Macdonald RS, Lubahn DB. Genistein affects HER2 protein concentration, activation, and promoter regulation in BT-474 human breast cancer cells. Endocrine. 2007 Aug;32(1):69-78
13. Suzuki Y, Kondo K, Ichise H, Tsukamoto Y, Urano T, Umemura K. Dietary supplementation with fermented soybeans suppresses intimal thickening. Nutrition. 2003 Mar; 19 (3): 261-4
**Tragedy and Hype: The Third International Soy Symposium – Part II. Sally Fallon and Mary G. Enig, PhD
Life Extension Magazine July 2010. Is Soy Safe?. Oscar Rodriguez