Women who eat a lot of soy-based foods or fibre don't seem to have fewer menopause symptoms, according to a U.S. study - the latest research to find no benefits from eating extra amounts of soy, a food abundant in dietary estro-gen.
Hormone replacement therapy, based on estrogen and other hormones, is effective in reducing hot flashes and other menopause symptoms, but carries some risks of heart disease and cancer.
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, but some individual trials on soy protein pills have found no benefits.
"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 but was not part of the study.
To see if women who choose to eat more phytoe-strogens 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, whose findings appeared in the journal Menopause, 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 phytoestro-gens eaten and how often or how severely women experienced hot flashes and night sweats.
The same was true for how much fibre 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. But those apparent results may simply have been due to chance, they wrote.
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.
Wong 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."