Soy products reportedly exacerbate symptoms of hypothyroidism. Lethargy, weight gain, cold sensitivity and depression are difficult enough to cope with -- and you don't need to do anything to make your condition worse. However, medical experts indicate that you don't need to shelve soy foods entirely. Studies do not show a link between consuming soy products and thyroid function.
Hypothyroidism
Hypothyroidism is a medical condition that occurs when your thyroid produces insufficient amounts of the hormones thyroxine, or T-4, and triiodothyronine, or T-3. These hormones are essential for regulating your body temperature and helping your body use fats and carbohydrates. Hashimoto's thyroiditis, an autoimmune disorder, is the most common form of hypothyroidism, according to MayoClinic.com, although an underactive thyroid can also be the result of treatment of hyperthyroidism, radiation treatments, surgical removal of the thyroid and the use of certain medications. Some people believe that soy products make existing hypothyroid disease worse -- they may even believe that eating soy foods triggers hypothyroidism.
Theory
The reason soy products have a bad reputation with some people is the isoflavones that soy contains. These same isoflavones are believed to relieve symptoms of menopause, such as hot flashes, although studies conducted on soy show mixed results when used for this purpose. Dr. Celeste Robb-Nicholson, editor-in-chief for "Harvard Women's Health Watch," states that studies conducted in animals dating to the late 1950s reveal that genistein and daidzein, the primary isoflavones in soy, inhibit an enzyme the thyroid needs to produce thyroid hormone. However, this effect is ultimately negated by dietary iodine.
Review
Researchers at Loma Linda University in California published an article in the medical journal "Thyroid" in March 2006 that reviewed various studies conducted on the effect of soy on thyroid function. The concern researchers addressed was how soy affected absorption of synthetic thyroid medications. They noted that 13 of 14 clinical trials showed that soy had little or no effect on thyroid function and went on to state that adults with hypothyroidism do not need to avoid soy foods, as long as their intake of iodine is adequate.
Conclusion
Robb-Nicholson and Mayo Clinic endocrinologist Todd B. Nippoldt concur with these findings. Nippoldt indicates that if you have hypothyroidism, it's best to take thyroid hormone replacement medication on an empty stomach and wait four hours before you consume soy. He goes on to state that there is no "hypothyroidism diet" proven to positively affect thyroid function. As long as you make sure you get enough iodine, you shouldn't need to eschew tofu, soy milk and soy burgers. The recommended dietary allowance of iodine for adults is 150 mcg. Saltwater fish, mollusks and crustaceans are sources of iodine, as is iodized table salt.
References
- MayoClinic.com: Hypothyroidism (Causes); June 2010
- Harvard Healthbeat: Do Soy Products Cause Hypothyroidism?; Celeste Robb-Nicholson, M.D.
- "Thyroid"; Effects of Soy Protein and Soybean Isoflavones; M. Messina, G. Redmond; March 2006
- MayoClinic.com: Soy: Does It Worsen Hypothyroidism?; Todd B. Nippoldt, M.D.; December 2010
- MayoClinic.com; Hypothyroidism Diet: Can Certain Foods Increase Thyroid Function?; Todd B. Nippoldt, M.D.; November 2010
- Medline Plus Medical Encyclopedia: Soy; May 2009
Member Comments