FRIDAY, Aug. 31 (HealthDay News) -- Flaxseed may be one way to reduce the bothersome hot flashes of menopause, Mayo Clinic researchers report.

A small pilot study found that postmenopausal women not on estrogen who used dietary flaxseed daily reported a 50 percent reduction in hot flashes over the course of six weeks.

"Flaxseed worked very well," said Dr. Sandhya Pruthi, director of the Mayo Breast Clinic at the Mayo Clinic in Rochester, Minn. "The women who used it said it really helped them."

But another expert, Dr. Wulf H. Utian, executive director of the North American Menopause Society, cautioned that the study was too preliminary to prove that flaxseed is effective.

While hormone replacement therapy, particularly estrogen, is effective against hot flashes, its long-term use has fallen out of favor since the large study known as the Women's Health Initiative found an increased risk of heart disease, breast cancer and other problems with long-term HRT use. So, Pruthi and her team were looking at options for women who suffered from hot flashes but didn't want to take estrogen.

They enrolled 29 postmenopausal women, median age 55, in the study. To join, the women had to have at least 14 hot flashes a week for at least one month.

"Flaxseed has some natural phytoestrogens," Pruthi said, explaining how it, like the hormone estrogen, could possibly have an effect on hot flashes.

Over the course of the study, the women sprinkled 40 grams of crushed flaxseed daily into yogurt or cereal or mixed it with orange juice or water.

In the end, 21 women completed the study; others had dropped out because of side effects. Of those who finished, the researchers said, the frequency of hot flashes declined 50 percent, and the hot flash score -- a combined measure of a flash's severity and frequency -- was found to have decreased about 57 percent.

"By the second or third week, most women noticed improvement," Pruthi said, adding that she is now planning a larger study to compare flaxseed to a placebo.

Until those results are in, Utian is not convinced the flaxseed is a proven treatment for hot flashes.

"This reduction [in the pilot study] could fall into the placebo effect," he said.

The study was also relatively brief, he added. And many women experiencing menopause suffer many more hot flashes than 14 a week. (Fifteen of the Mayo study women reported 10 or more a week, but 13 reported 2 to 9 a week.)

Utian added, however, that he was not aware of any harm in eating flaxseed.

And Pruthi said that because the fiber content gave some women in the study abdominal discomfort, those that find it hard on the stomach should consider starting at a lower dose and working up.

Her research was just published in the summer 2007 issue of the Journal of the Society for Integrative Oncology.

More information

To learn more about hot flashes, visit Breast cancer.org.