As it turns out, the risks of soy to hormone health are significant. It is not the middle aged health panacea for women that is is promoted to be! If your doctor is harping on the benefits of soy to alleviate your discomfort, find a new doctor!
Studies show that even small amounts of unfermented soy has the potential to disrupt female hormonal balance. This amount is only 45 mg isoflavones – a bit more than a single cup of soymilk!
“Women taking soy isoflavone tablets to alleviate hot flashes and prevent bone loss at the time of menopause might want to reconsider,” says Silvina Levis, M.D., the director of the osteoporosis center at the University of Miami’s Miller School of Medicine.
A recent study published in the August 2011 issue of the Archives of Internal Medicine examined 248 menopausal women over a 2 year period to see if 200 mg of isoflavones per day were a help in alleviating the symptoms of menopause including bone loss.
200 mg per day is equivalent to twice the highest intake through food sources in typical Asian diets.
At the end of the 2 year period, women taking a placebo versus women taking the isoflavone supplement showed no differences in bone loss or menopausal symptoms such as hot flashes and night sweats.
In fact, nearly half (48%) of the women taking isoflavones experienced hot flashes compared with just 31% of women who took the placebo!
Stay. Far. Away.
Studies Showing That Soy Messes Up Your Hormones
Soy Wake Up Call #1
A 1991 study found that eating only 2 TBL/day of roasted and pickled soybeans for 3 months to healthy adults who were receiving adequate iodine in their diet caused thyroid suppression with symptoms of malaise, constipation, sleepiness, and goiters (Nippon Naibunpi Gakkai Zasshi 1991, 767: 622-629)!
Still think munching on edamame is a healthy habit?
Soy Wake Up Call #2
Six premenopausal women with normal menstrual cycles were given 45 mg of soy isoflavones per day. This is equivalent to only 1-2 cups of soy milk or 1/2 cup of soy flour! After only one month, all of the women experienced delayed menstruation with the effects similar to tamoxifen, the anti-estrogen drug given to women with breast cancer (American Journal of Clinical Nutrition 1994 Sep;60(3):333-340).
Soy Wake Up Call #3
Dietary estrogens in the form of soy foods were found to have the potential to disrupt the endocrine system with the effects in women similar to taking the breast cancer drug tamoxifen (Proceedings of the Society for Experimental Biology and Medicine 1995 Jan;208(1):51-9).
Soy Wake Up Call #4
Estrogens consumed in the diet even at low concentrations were found to stimulate breast cells. The effect is much like the pesticide DDT which increases enzymatic activity leading to breast cancer. (Environmental Health Perspectives 1997 Apr;105 (Suppl 3):633-636).
Soy Wake Up Call #5
The soy isoflavones genistein and daidzein appear to stimulate existing breast cancer growth indicating risk in consuming soy products if a woman has breast cancer. (Annals of Pharmacotherapy 2001 Sep;35(9):118-21).
Soy Wake Up Call #6
Direct evidence that soy isoflavones genistein and daidzein suppress the pituitary-thyroid axis in middle-aged rats fed 10 mg soy isoflavones per kilo after only 3 weeks as compared with rats eating regular rat chow. (Experimental Biology and Medicine 2010 May;235(5):590-8).
Soy Bottom Line
In conclusion, soy messes with your thyroid and disrupts the delicate balance of breast tissue and it doesn’t take very much soy at all to start the snowball down the hill to hormone imbalance with only a cup or so of unsweetened soy milk per day representing a significant risk.
Think you don’t eat much soy?
Next time you go shopping, just for grins check the label on everything you buy.
Soy is in EVERYTHING!
The scary truth is that if you eat processed foods (even organic), you are eating plenty of soy. Worse, you are probably consuming far more than you know even if you don’t drink soya milk or eat soy protein bars.
If you are still unconvinced and need more information, check out this article on the over 170 studies on the adverse effects of soy isoflavones from 1950-2010.
Sarah, The Healthy Home Economist
Sarah Pope has been a Health and Nutrition Educator since 2002. Her work is dedicated to helping families effectively incorporate the principles of ancestral diets within the modern household. She is a sought after lecturer around the world for conferences, summits, and podcasts.
Her work has been covered by major media including USA Today, ABC, NBC, and many others.