Urinary estrogen metabolites during a randomized soy trial.

Area of Science:

• Endocrinology
• Nutritional Science
• Oncology

Background:

• Soy consumption is hypothesized to reduce breast cancer risk.
• This protective effect may be mediated by changes in estrogen metabolism.
• Equol producer status might influence the benefits of soy isoflavones.

Purpose of the Study:

• To investigate the impact of soy foods on the ratio of 2-hydroxy (OH) to 16α-OH estrogens (E(1)) in premenopausal women.
• To determine if equol producer status modifies the effect of soy on estrogen metabolism.

Main Methods:

• A randomized, crossover study involving 82 premenopausal women.
• Participants consumed high-soy (2 servings/day) and low-soy (<3 servings/week) diets for 6 months each.
• Urinary estrogen metabolites and isoflavonoids were measured using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.

Main Results:

• A high-soy diet led to a statistically significant increase in the 2:16α-OH E(1) ratio (P = 0.05).
• This increase was associated with a nonsignificant decrease in 16α-OH E(1).
• Beneficial changes in the ratio were observed in both equol producers and nonproducers.

Conclusions:

• Soy foods appear to beneficially influence estrogen metabolism in premenopausal women.
• This effect on the 2:16α-OH E(1) ratio is independent of equol producer status.
• Findings support a role for soy in potentially mitigating breast cancer risk through estrogen modulation.