Women who eat a lot of soy-based foods or fiber don’t seem to have fewer menopause symptoms, according to a new study.
The findings add to other studies that have found no benefits from eating extra amounts of soy, a food abundant in dietary estrogen.
“It might be a dead end,” said William Wong, a professor at Baylor College of Medicine who has studied the effects of soy protein on menopause symptoms.
Plant-based estrogens, also called phytoestrogens, are found in foods such as seeds, nuts and soybeans. Their chemical structure is similar to human estrogens.
Hormone replacement therapy, based on estrogen among other hormones, is effective in reducing hot flashes and other menopause symptoms, but carries some risks of heart disease and cancer, a large federally funded study released a decade ago found.
Researchers have been testing whether plant estrogens can offer benefits, perhaps without the risks.
“Many women can’t or don’t want to take hormones,” making dietary estrogen an appealing alternative, said Ellen Gold, the lead author of the study and a professor at the University of California Davis School of Medicine.
But studies on plant estrogens have been mixed.
A review of 17 studies on soy supplements has found that the pills can reduce the frequency and severity of hot flashes, while some individual trials on soy protein pills have found no benefits (see Reuters Health reports of April 27, 2012 reut.rs/K95gLr and August 8, 2011 reut.rs/prmTwt).
To see if women who choose to eat more phytoestrogens have an easier time through menopause, Gold and her colleagues tracked 1,651 women for 10 years.
At the beginning of the study, none of the women had gone through menopause.
Each year the researchers followed up with them to gather any reports of hot flashes or night sweats, and every few years the women filled out a food survey.
By the end of the study, Gold’s team could find no consistent pattern between the amount of phytoestrogens eaten and how often or how severely women experienced hot flashes and night sweats.
The same was true for how much fiber the women ate.
In some cases, the researchers did see a relationship between one type of dietary estrogen and menopause symptoms, but it didn’t always carry through when they examined women of different ethnicities or looked at different points in time.
Those apparent results, they write in the journal Menopause, may have been due to chance.
Gold said it’s possible that for some subsets of women, plant estrogens might have a benefit, but they weren’t able to tease that out in this study.
“I think the more promising avenue for us in the future is to see if there are some women who might benefit,” she told Reuters Health.
Wong, who was not part of the study, is less optimistic because of the negative results seen in long term studies of women taking soy protein supplements.
“After looking at our own clinical trial data and others, we don’t see it,” he told Reuters Health. “I think we should move on.”
SOURCE: Menopause, October 29, 2012.
Phytoestrogen and fiber intakes in relation to incident vasomotor symptoms: results from the Study of Women’s Health Across the Nation
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.
Gold, Ellen B. PhD; Leung, Katherine MPH; Crawford, Sybil L. PhD; Huang, Mei-Hua DrPH; Waetjen, L. Elaine MD; Greendale, Gail A. MD