Setchell KD, 2005

Soy Isoflavones and Their Estrogenic Effects

Among the various constituents of soy, isoflavones are the primary phytoestrogens that can influence hormonal activity in humans. One of their key biological effects is their ability to inhibit aromatase enzymes.

How Isoflavones Affect Estrogen Levels:

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• Aromatase is an enzyme responsible for converting androgens (e.g., testosterone) into estrogens (e.g., estradiol).

• By inhibiting aromatase, soy isoflavones can lead to increased estradiol production, thereby amplifying estrogenic activity in the body.

• This effect can contribute to hormone-related changes, particularly in individuals who are sensitive to estrogen levels, such as postmenopausal women, men, and individuals at risk for hormone-dependent cancers.

Implications of Increased Estrogenic Activity:

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• Potential Benefits: May help with menopausal symptoms, bone health, and cardiovascular protection.

• Potential Risks: May influence conditions like breast cancer, prostate health, and reproductive function, particularly with long-term high intake.

This highlights why soy isoflavone consumption needs to be monitored, especially in populations sensitive to hormonal fluctuations.

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Citation : Setchell KD, Clerici C, Lephart ED, Cole SJ, Heenan C, Castel-lani D, et al. S-equol, a potent ligand for estrogen receptor beta, is the exclusive enantiomeric form of the soy isofavone metaboliteproduced by human intestinal bacterial fora. Am J Clin Nutr.2005;81(5):1072–9.