Studies on soy consumption are often conflicting and confusing. According to new research presented at an American Association of Cancer Research meeting in Philadelphia, the more isoflavone-containing soy products a young woman eats, the lower her odds for developing invasive breast cancers. Yet an increase in soy consumption has been linked to thyroid disease and vitamin malabsorption. There is no doubt soy consumption in North America is on the rise. Soy is marketed as a health food but is becoming a common addition to our processed foods and beverages. We outline below some of the reasons to exercise caution with soy and the importance of consuming only organic, non-gmo, fermented forms such as miso, tempeh and natto.
Why has soy become so prevalent in North American foods? Because it is cheap. Case in point: two recent class action lawsuits against prisons in Florida and Illinois were initiated by inmates who were fed a diet of 70% soy products and subsequently experienced an onslaught of health problems including heart palpitations, constipation alternating with serious diarrhea, hypothyroidism, thyroid disease, and chronic infections. Gretl Plessinger, a spokeswoman for the Department of Corrections explains “if soy products were eliminated, we conservatively estimate the cost to taxpayers would double for inmate food.” More of a concern is the rising use of processed GMO soy in school cafeterias and hidden in processed foods as an inexpensive filler.
Soy is typically thought as a health food or healthy ingredient in our foods. The Asian diet is often an underlying reference of the benefits of soy because the incidence of breast cancer and osteoporosis is lower in Asia. However the North American use of soy has expanded into many unfermented and highly processed forms such as soy milk, soy chips, soy protein isolates, soy flour, soy cheese, soy burgers, and soy ice cream which are often accompanied by other harmful ingredients such as sugar and preservatives. More importantly, unfermented processed soy contains harmful “anti-nutrients” such as phytates, enzyme inhibitors and goitrogens.
If not removed through a process such as fermentation, these “anti-nutrients” can cause malnutrition and endocrine disruption. Phytate, or phytic acid, binds to zinc, copper, iron, magnesium and calcium in the digestive tract and can prevent absorption of these nutrients. The goitrogens in soy are harmful because they block thyroid hormone production, which lowers the heart rate and inhibits oxygen from entering cells. Phytates can accentuate this effect by blocking the minerals needed for thyroid hormone production. Even whole food forms of unfermented soy (such as edamame) have high levels of phytates.
The Japanese fermented soy bean food known as “natto” is a great source of vitamin K2 which aids calcium absorption and helps keep calcium out of the arteries. Natto has a sticky texture and a strong flavor. We recently tried adding it to miso soup and it blended in wonderfully. But since natto is fermented using friendly bacteria, it is most beneficial if eaten uncooked.