Soy Isoflavones

What is Soy Isoflavones

Soy isoflavones are phenolic phytoestrogens extracted from the soybean, Glycine max, a member of the legume family.

The soy isoflavones are present in the plant as glycosides; once ingested, they yield the active isoflavonoids daidzein, genistein, and glycetin. Foods such as tofu, tempeh, miso, textured vegetable protein, soy milk and soy cheese are rich in soy isoflavones; soy sauce is not a significant source.

Genistein and daidzein are also found in lesser amounts in natural foods such as chickpeas, lentils, and beans, as well as herbs (see Red clover monograph). Epidemiologically, high consumption of soy is associated with low rates of cardiovascular disease, hormone-dependent cancers, and menopausal symptoms.

 In October 1999, the FDA authorized health claims for reduced risk of heart disease on foods containing at least 6.25 g/serving of soy protein, if the food also meets low fat, low saturated fat, and low cholesterol requirements. Whole soy-foods (e.g., tofu), may also qualify if they contain no added fat (i.e., other than soybean-derived fat).

Soy isoflavone supplements are claimed to reduce hot flashes during menopause, maintain bone density, maintain prostate health, and to promote cardiovascular health. However, these health claims need to be sufficiently evaluated scientifically.

Brand Name


Indications & Dosage

  • hot flashes
  • hypercholesterolemia
  • menopause
  • nutritional supplementation
  • osteoporosis prophylaxis

Side Effects

  1. anaphylactoid reactions
  2. constipation
  3. diarrhea
  4. dyspepsia
  5. dyspnea
  6. flatulence
  7. goiter
  8. headache
  9. hypothyroidism
  10. insomnia
  11. migraine
  12. nausea
  13. pruritus
  14. rash
  15. urticaria
  16. vomiting

Monitoring Parameters

  • laboratory monitoring not necessary


  • asthma
  • atopy
  • breast cancer
  • breast-feeding
  • children
  • dialysis
  • hepatic disease
  • infants
  • infertility
  • peanut hypersensitivity
  • pregnancy
  • prostate cancer
  • prostatic hypertrophy
  • renal failure
  • renal impairment
  • soya lecithin hypersensitivity
  • thyroid disease


There are no drug interactions associated with Soy Isoflavones products.


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