Soy food and Thyroid Dysfunction

by Pankaj Kotak, M.Sc., N.D.

Hypothyroidism is the most common form of thyroid dysfunction. It is most frequently found in women and the elderly. Epidemiological studies of various sections of population indicate that soy foods cause thyroid dysfunction, especially hypothyroidism in which the thyroid gland becomes underactive leading to decreased production of T3 & T4 hormones and an elevated level of TSH.

Goitrogens are substances that interfere with the iodine uptake resulting in the suppression of thyroid function. Soybeans are rich sources of soy isoflavones which are a class of chemicals called phytoestrogens. Scientific studies have found that soy isoflavones are goitrogenic in nature. Researchers have identified two goitrogenic soy isoflavones, genistein and daidzein that suppress the function of thyroid.

Children who consume soybeans as part of infant formula (baby food) are at a higher risk as they grow up. An epidemiologic study of teenage children diagnosed with autoimmune thyroid diseases such as Hashimoto's thyroiditis or Graves' disease found that those consuming soy formula as infants had twice the prevalence of this autoimmune disease. People who develop goiter due to feeding of soy formula during their infancy can reverse it by changing to cow milk or iodine-supplemented diets.

Women need to be very careful about including soy in their diet because they are 5 to 8 times more likely than men to suffer from thyroid dysfunction. Women are especially at high risk during pregnancy and postmenopausal years. One of the most popular myths about soybean is that it is a complete protein. Like all legumes, soybeans are deficient in sulfur-containing amino acids methionine and cystine. In heavily processed foods such as soy milk and protein powders, the processing denatures fragile amino acid lysine, making the end product even more deficient in amino acids.

A major problem with soybeans is that the majority of them are genetically modified (GM) seeds. As of 2008, almost 95% soybeans available in the US are GM foods. Scientific studies have found GM foods to be dangerous to health.

Hypothyroidism can be reversed by the following:

  • Including coconut oil in the diet. Alternatively, it can be used to massage the body.
  • Avoid goitrogenic foods such as turnips, cabbage, mustard, cassava root, pine nuts, millet & peanuts
  • Avoid sugar, processed foods & trans fats from partially hydrogenated oils
  • Use relaxation techniques such as meditation to relieve stress
  • Get some sunlight, preferably during the early morning or late afternoon
  • Do daily exercise. Aerobic exercise is especially helpful.


  1. Doerge DR., et al. Goitrogenic and Estrogenic Activity of Soy Isoflavones. Environmental Health Perspectives. June 2002;110 Suppl 3:349-53.
  2. Divi RL., et al. Anti-thyroid isoflavones from soybean: isolation, characterization, and mechanisms of action. Biochemical Pharmacology. 1997 Nov 15;54(10):1087-96.
  3. Fort P., et al. Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children. Journal of the American College of Nutrition. 1990 Apr;9(2):164-7.
  4. Hydovitz JD. Occurrence of goiter in an infant on a soy diet. NEJM. 1960;262:351-353.

Warning: The reader of this article should exercise all precautionary measures while following instructions on the home remedies from this article. Avoid using any of these products if you are allergic to it. The responsibility lies with the reader and not with the site or the writer.
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