NEW YORK (Reuters Health) - Women with hot flashes related to menopause are unlikely to find relief with the herbal supplement black cohosh -- alone or in combination with other herbal therapies -- according to a report released this week.

"We were disappointed by the findings," said Dr. Katherine M. Newton in a news release, "because many women want an alternative to hormone therapy and many have assumed that black cohosh is a safe, effective choice."

Newton, the principal investigator of the study which appears in the Annals of Internal Medicine this week, and colleagues from the Group Health Cooperative in Seattle studied 351 menopausal women, between the ages of 45 and 55, experiencing at least two hot flashes or night sweats each day.

The women were randomly assigned to one of five treatment groups: 160 milligrams of black cohosh daily; a multi-botanical supplement containing 200 milligrams black cohosh and 9 other herbal ingredients including alfalfa, pomegranate and Siberian ginseng; a multi-botanical supplement plus increased soy consumption; hormone therapy (estrogen with or without progestin); or inactive 'placebo' capsules.

After 3, 6, and 12 months, black cohosh was no better than placebo in reducing the frequency or severity of hot flashes or night sweats, the team found. The same was true for the other herbal products.

As expected, women who were given hormone therapy had significantly fewer hot flashes and night sweats than women given placebo. However, "While hormone therapy is still the most effective treatment for hot flashes, recent studies have shown that it poses serious risks," Newton noted, such as the risk of heart disease, stroke, and some types of cancer.

The "good news" from this study, according to Dr. Carol M. Mangione of the University of California, Los Angeles, is that women in the placebo group experienced about a 30 percent reduction in the severity and frequency of hot flashes and night sweats during the year-long study.

This should help reassure women that with time these bothersome symptoms will ease up on their own, Mangione writes in a commentary accompanying the study. Mangione also notes that it's too soon to throw in the towel on the potential benefits of soy on the symptoms of menopause. Because most women in the soy group did not increase their soy intake to the target level, "this trial probably was not an adequate test of dietary soy" for treatment of menopausal symptoms, she writes.

It is "easy and probably safe" for women experiencing hot flashes and night sweats to increase their intake of soy and see whether it helps, Mangione adds.