Abstract
Background: Flavonoids potentially exert anti-cancer effects, as suggested by their chemical structures and supported by animal studies. In observational studies, however, the association between flavonoids and breast cancer, and potential underlying mechanisms, remain unclear. Objective: To examine the relationship between flavonoid intake and sex hormone levels using timed blood samples in follicular and luteal phases in the Nurses’ Health Study II among premenopausal women. Methods: Plasma concentrations of estrogens, androgens, progesterone, dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), prolactin, and sex hormone-binding globulin (SHBG) were measured in samples collected between 1996 and 1999. Average flavonoid were calculated from semiquantitative food frequency questionnaires collected in 1995 and 1999. We used generalized linear models to calculate geometric mean hormone concentrations across categories of the intake of flavonoids and the subclasses. Results: Total flavonoid intake generally was not associated with the hormones of interest. The only significant association was with DHEAS (p-trend = 0.02), which was 11.1% (95% confidence interval (CI): −18.6%, −3.0%) lower comparing the highest vs. lowest quartile of flavonoid intake. In subclass analyses, the highest (vs. lowest) quartile of flavan-3-ol intake was associated with significantly lower DHEAS concentrations (−11.3% with 95% CI: −18.3%, −3.7%, p-trend = 0.01), and anthocyanin intake was associated with a significant inverse trend for DHEA (−18.0% with 95% CI: −27.9%, −6.7%, p-trend = 0.003). Conclusion: Flavonoid intake in this population had limited impact on most plasma sex hormones in premenopausal women. Anthocyanins and flavan-3-ols were associated with lower levels of DHEA and DHEAS.
Highlights
Flavonoids, a diverse group of polyphenols, consist of more than 5000 different compounds produced in plants [1,2]
The only significant trends were that women with higher flavonoid intakes, especially that of flavan-3-ol and anthocyanins, had lower plasma DHEA and DHEA sulfate (DHEAS) concentrations; this has been associated with decreased risk of premenopausal breast cancer in the same cohort [33], as well as in a large pooled analysis [6]
Flavonoids in general have been considered as phytochemicals with the potential for antioxidant and anti-inflammatory activity [34,35], the antioxidant capacity is limited after extensive metabolism that is sufficient to reduce plasma indices of oxidant status in vivo
Summary
Flavonoids, a diverse group of polyphenols, consist of more than 5000 different compounds produced in plants [1,2]. They have been considered one of the active components in fruits and vegetables that have antioxidant, anti-inflammatory, and anti-proliferative properties [3]. Flavonoids potentially exert anti-cancer effects, as suggested by their chemical structures and supported by animal studies. The association between flavonoids and breast cancer, and potential underlying mechanisms, remain unclear. Objective: To examine the relationship between flavonoid intake and sex hormone levels using timed blood samples in follicular and luteal phases in the Nurses’ Health Study II among premenopausal women. Results: Total flavonoid intake generally was not associated with the hormones of interest
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