Is Soy Safe? The Risks and Benefits of Soy

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 prevalence of soy in our foods, in ingredients such as soy flour and soybean oil, present the challenge of identifying and reducing our soy intake. The soy isoflavone “genistein”, (which can be particularly problematic in high doses), is contained in North American commercial soybean products in amounts as high as 60 mg per serving. This compares to traditional Asian diets of fermented miso and tempeh that contain around 5 mg of genistein a day. Unfermented soy can also inhibit glucose from getting into cells and inhibit the activity of enzymes known as tyrosine kinases which are involved in the transfer of energy between molecules. It is in this way that soy can interfere with cancer cell division, which is a plus for cancer patients, but not necessarily for the general healthy population.
We should aim to mirror the traditional Asian diet when it comes to soy consumption. For the reasons outlined above, processed and unfermented soy products such as soy milk, tofu, and even edamame should be avoided. Only fermented soy should be consumed in order to obtain the health benefits and to avoid the energy-reducing effects of soy in normal healthy cells.  Fermented soy foods such as miso, natto, and tempeh are the most beneficial and least harmful forms.




Miso is a fermented soy bean paste that has a salty and buttery flavor and probiotic qualities. Miso is most commonly found in miso soup. Miso paste is a great addition other soups and salad dressings, marinades, and sauces.



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.




Tempeh can be consumed cooked or uncooked, marinated, and/or added to salads, stir fries, soups, or stews. It is an excellent meat alternative because of it’s thick texture and nutritional content. Tempeh’s fermentation process and the retention of the whole soy bean give it a higher protein, fiber, and vitamin content compared to tofu.


Sources:; OrlandoSentinel;

Written and posted by Jessica Cerka in New York

Image Credits: Asakusa Diary; FotoosVanRobin from Netherlands;;
Disclaimer: The information in this article and on this website is not intended to diagnose, treat, cure or prevent any disease. None of the products mentioned in this article or on this website are intended to diagnose, treat, cure or prevent any disease. The information in this article is not intended to provide personal medical advice, which should be obtained from a medical professional. This information is made available with the understanding that the author and publisher are not providing medical, psychological, or nutritional counseling services on this site. The information on this Web site does not cover all possible uses, actions, precautions, side effects, and interactions. Liability for individual actions, opinions, or omissions based upon the contents of this site is expressly disclaimed. This information has not been evaluated or approved by the U.S. FDA.

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