Soy Isoflavones Supplement Review

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Soy Isoflavones
  Evaluated for:
Effectiveness Rating Effectiveness Rating
Menopausal hot flashes
+1 (Slight Evidence)


  • Soy isoflavones are probably the active ingredient in soy that behave like mild estrogens. These soy isoflavones are most likely the biologic cause for the reduction in the number and intensity of hot flashes in study participants who took 160 mg of soy isoflavones (as soy protein). These women reported that they felt better physically, psychologically and sexually.
  • Soy is inexpensive, nutritious and a good source of protein.
  • Soy may lower cholesterol and blood pressure.
  • A study of Japanese women taking large doses of soy isoflavones for long periods showed no increase in occurrence or severity of breast cancer.


  • It is hard to draw any conclusions about soy isoflavones as a class because each study used different amounts and types of soy isoflavones, making it impossible to compare the studies. The ideal composition and amount of soy isoflavones is therefore unknown.
  • Because of its possible mild estrogen-like effect, a theoretical concern exists about soy intake in women who have a personal or strong family history of breast cancer. A study of this effect would be long, difficult and expensive to create, and is therefore not likely any time soon.

In general, women with a personal history of breast cancer should consult their physician before adding soy products. People with an allergy to soy should not take it. It is important to work with your health care provider to understand the potential risks and benefits.

DOSAGE:There is not enough conclusive evidence for us to make a specific dosage recommendation. In one trial we evaluated, women gained some relief from 160 mg per day. This seems like a good dose to try first.

CONCLUSION:We conclude that soy isoflavones appear promising for easing menopausal hot flashes, but there is not enough evidence for us to support its use. While some people may find them to be helpful, the dosing is unclear. We recommend you consult your physician if you have a history of breast cancer. If you do elect to try it, remember to include it in your list of medications when you visit your doctor and other health care providers.

“Soy Isoflavones.” LLC, 2013. 12 July 2011.
“Soy.” Natural Standard –The Authority on Integrative Medicine. Natural Standard, 2013.
“Soy.” Natural Medicines Comprehensive Database. Therapeutic Research Faculty, 2013. 8 November 2013.

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