Objective: Although reduction of vasomotor symptoms (VMS; hot flashes and night sweats) has been reported in postmenopausal women who used isoflavones, a clear dose response has not been shown, has largely not been reported for perimenopausal women, and has largely only been reported for reducing prevalent VMS, not preventing newly developing VMS. We analyzed longitudinal data from the Study of Women’s Health Across the Nation for the relation of dietary phytoestrogen and fiber intake to incident VMS in this multiracial/ethnic cohort.
Methods: The Study of Women’s Health Across the Nation included 3,302 premenopausal and early perimenopausal women, 1,651 of whom reported no VMS at baseline and were followed with annual visits for 10 years. Dietary intakes of isoflavones, coumestrol, lignans, and fiber were assessed by a food frequency questionnaire at baseline and in annual visits 5 and 9 and interpolated for intervening years. The number of days experiencing VMS in the past 2 weeks was self-reported annually. Using multinomial logistic regression with generalized estimating equations, we modeled incident VMS in relation to isoflavones, lignans, fiber, coumestrol, or total phytoestrogen intake and covariates.
Results: No consistent monotonic relations were observed between any dietary phytoestrogen or fiber and incident VMS, although adjusted odds ratios for some individual quartiles were statistically significant.
Conclusions: For certainty of any effect of dietary phytoestrogens or fiber on the prevention of incident VMS, a randomized, placebo-controlled, double-masked trial with sufficient numbers of women in different racial/ethnic, menopausal status, and metabolic groups over years of follow-up is required, but our results suggest that a clinically significant or large effect is improbable.
From the 1University of California Davis School of Medicine, Davis, CA; 2University of Massachusetts Medical School, Worcester, MA; and 3University of California Los Angeles David Geffen School of Medicine, Los Angeles, CA.
Received June 7, 2012; revised and accepted August 2, 2012.
Funding/support: The Study of Women’s Health Across the Nation received grant support from the NIH, Department of Health and Human Services, through the National Institute on Aging, National Institute of Nursing Research, and NIH Office of Research on Women’s Health (grants NR004061, AG012505, AG012535, AG012531, AG012539, AG012546, AG012553, AG012554, and AG012495). The Study of Women’s Health Across the Nation Phytoestrogen Ancillary Study was supported by grant AG030448.
Financial disclosure/conflicts of interest: None reported.
The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute on Aging, National Institute of Nursing Research, Office of Research on Women’s Health, or National Institutes of Health (NIH).
Address correspondence to: Ellen B. Gold, PhD, Department of Public Health Sciences, University of California Davis, Med Sci 1C, One Shields Avenue, Davis, CA 95616. E-mail: firstname.lastname@example.org