Soy Safety & Side Effects

Safety

According to Web Md, "Taking dietary supplements with soy extracts is POSSIBLY SAFE when used short-term (up to 6 months). Long-term use of high doses of soy dietary supplements is POSSIBLY UNSAFE." 

According to the National Center for Complementary and Integrative Health states, "Long-term use of soy isoflavone supplements might increase the risks of endometrial hyperplasia (a thickening of the lining of the uterus that may lead to cancer). Soy foods do not appear to increase the risk of endometrial hyperplasia. It is uncertain whether soy isoflavone supplements are safe for women" (Soy, 2016).

I found a study that "investigated the relationship between soy isoflavone [found in foods] intake and the risk of nulliparity (condition of a woman not bearing offspring) and null gravidity (a woman who has not been pregnant).  It was a cross-sectional study (a type of study that analyzes data collected from a population at a specific point in time) of 11,688 North American Adventist (a branch of Protestantism) women aged 30–50 years old regarding childbearing. 54 percent of the women were vegetarians and had a healthy lifestyle with a low prevalence of smoking and alcohol use. Between isoflavone intake and the likelihood of ever having become a mother, women who had high (≥40 mg/day) isoflavone intakes (12% of this group of women), the adjusted lifetime probability of giving birth to a live child was reduced by approximately 3%. In comparison to women with low (<10 mg/day) intake. A 13%  risk was found between the isoflavone intake and the risk of null gravidity of women who have never been pregnant with (≥40 mg/day) isoflavone intake. These relationships were found mainly in women who reported problems becoming pregnant" (Jacobsen et al, 2014). 

Side Effects

Web Md says, "Soy can cause some mild side effects such as constipation, bloating, and nausea. It can also cause allergic reactions involving rash and itching in some people. There is concern that taking high doses might cause abnormal tissue growth in the uterus."

According to Live Strong, "Researchers at the Weston A. Price Foundation say soy isoflavones have a direct correlation with increased thyroid disease. Soy isoflavones can cause goiter and hypothyroidism by interfering with thyroid hormone synthesis. Thyroid dysfunction typically can be avoided as long as sufficient levels of iodine are added to the product, which is a protocol followed by most commercial producers of soy products. Even with sufficient levels of iodine, however, high doses of soy supplements can lead to thyroid cancer as well. Products made with soy isoflavones can cause migraine headaches in some people, the Mayo Clinic says. People with allergic reactions can have low-grade headaches as a result of increased heart rate or heart palpitations. Doctors at Penn State University say too little research is available on the ultimate consequences of taking high levels of soy isoflavone supplements. Although soy isoflavones that occur naturally in soybeans, tofu and tempeh generally are considered safe for healthy adults, supplements can pose additional unknown dangers. Soy powders and pills often contain levels of isoflavones that do not fall within safe parameters. To prevent thyroid or cancer-causing side effects, consumers should limit soy consumption to 100 milligrams or less per day" (Ray, 2013).

A study in The Journal of Clinical Endocrinology and Metabolism reported "that researchers fed some subjects 16 mg of Soy Isoflavones, the amount found in a typical vegetarian diet. Others 2 mg of Soy Isoflavones found in most omnivore's diets. The subjects fed 16 mg were 3x more likely to cause patients to convert subclinical hypothyroidism to overt clinical hypothyroidism. The study is here" (Gilkerson, 2016).

Bibliography

Gilkerson, Trisha. "5 Foods That Can Wreck Your Thyroid." Whole New Mom. Mediavine Publisher Network, 05 Aug. 2016. Web. 29 Dec. 2016. <http://wholenewmom.com/health-concerns/5-foods-avoid-hypothyroidism-thyroid-disease-thyroid-diet/>.

Jacobsen, Bjarne, Karen Jaceldo-Siegel, Synnøve Fønnebø Knutsen, Jing Fan, Keiji Oda, and Gary E. Fraser. "Soy Isoflavone Intake and the Likelihood of Ever Becoming a Mother: The Adventist Health Study-2." International Journal of Women's Health (2014): 377. World Cat. Web. 29 Dec. 2016.

Ray, Linda. "Soy Isoflavones Side Effects." LIVESTRONG.COM. Leaf Group, 24 Oct. 2013. Web. 28 Dec. 2016. <http://www.livestrong.com/article/111587-soy-isoflavones-side-effects/>.

"Soy." National Institutes of Health. U.S. Department of Health and Human Services, 01 Dec. 2016. Web. 29 Dec. 2016. <https://nccih.nih.gov/health/soy/ataglance.htm>.

http://www.webmd.com/vitamins-supplements/ingredientmono-975-SOY.aspx?activeIngredientId=975&activeIngredientName=SOY

Last Edited: December 29, 2016