Menopausal women should eat soy twice a day to ease hot flashes, according to scientists.
Researchers from the University of Delaware conducted the most comprehensive study to date on the effects of soy on menopause and found that daily servings reduced the frequency and severity of hot flashes by up to 26 percent.
They reached the conclusion after reviewing 19 previous studies that examined more than 1,200 women.
Soy was first put forward as a natural treatment for menopause by Japanese researchers who noticed that women in the country, where soy consumption is high, experienced fewer hot flashes than Western women.
Previous research into the subject proved inconclusive, but the Delaware scientists claimed that discrepancies in the findings were down to small sample sizes and inconsistent methodology.
"When you combine them all, we've found the overall effect is still positive," according to Professor Melissa Melby, a medical anthropology professor and co-author of the study.
Ingesting at least 54 milligrams of soy isoflavones -- chemicals in the legume that exert a mild estrogen-like effect -- daily for six weeks to a year reduces menopause hot flash frequency by 20.6 percent and severity by 26 percent, compared to a placebo, the researchers said.
They also found that isoflavone supplements with at least 19 milligrams of genistein -- one of the two main types of isoflavones -- were more than twice as effective.
Melby added, "Eating soy foods, or using supplements derived from whole soybeans, may work better for women."
The findings were published in Menopause: The Journal of the North American Menopause Association.