While an array of alternative therapies promise to ease menopausal symptoms, none has strong enough evidence to back it up, according to a research review published Monday.

Individual studies have suggested that some of these therapies - particularly soy supplements and the herb black cohosh - are effective for symptoms like hot flashes and night sweats. But the overall evidence has been mixed, researchers say in the new report, with some studies being too flawed to produce reliable results.

For now, women should take a “buyer beware” attitude toward over-the-counter fixes, said lead study author Dr. Anne Nedrow of the Oregon Health and Science University in Portland.

“If women want to try an alternative therapy, like black cohosh, it’s probably safe to,” she told Reuters Health. But they should also know, Nedrow said, that such therapies have not been proven to work, and that the claims on product labels and ads are not necessarily true.

She and her colleagues report their findings in the Archives of Internal Medicine.

Hormone replacement therapy, or HRT, is known to alleviate menopausal symptoms. But ever since a large U.S. trial in 2002 showed that HRT raises the risks of heart attack, stroke and breast cancer, many women have turned to alternative therapies - ranging from soy extracts to herbs to acupuncture.

Some of these treatments, however, have been little researched, or when they have, the studies have been small, short-term or otherwise poorly designed.

For their study, Nedrow and her colleagues reviewed the results of controlled clinical trials where an alternative therapy was pitted against a placebo or a comparison therapy. Such trials are considered the gold standard for showing whether a treatment has true effects.

They identified 48 studies that had been published in English-language medical journals. Fifteen were fair- or good-quality studies of phytoestrogens, plant substances that have weak estrogen-like activity. Soy extracts and red clover supplements are among the most studied sources of phytoestrogens.

But of the 15 trials Nedrow’s team examined, only four showed phytoestrogens to be effective for menopausal symptoms.

Similarly, trials of other supplements, such as vitamin E, the herb kava and the hormone DHEA, often yielded mixed results or were poor quality, according to the researchers.

Of four trials that examined black cohosh, the largest one found that the herb eased hot flashes, mood swings and problems with sleep and sexual function. The other three, however, found no such benefits.

Non-supplement remedies - like exercise, relaxation, acupuncture and magnet therapy - showed no clear benefits for menopausal symptoms, the review found.

Nedrow said that a common denominator in many studies was the large “placebo effect,” which means that many women who unknowingly had an inactive treatment nonetheless reported improvements in their symptoms.

This has been seen in many studies of menopausal symptoms, Nedrow pointed out. In one study of estrogen replacement, she noted, half of the women given a placebo said their hot flashes improved.

If some women find relief owing to a placebo effect, Nedrow said, that’s not necessarily a bad thing - as long as they’re taking something that’s safe.

A concern with long-term use of soy supplements, she noted, is endometrial hyperplasia, an abnormal thickening of the lining of the uterus. And research has shown black cohosh can be toxic to the liver.

Women who do opt to take an alternative menopausal remedy should be sure to let their doctors know, Nedrow advised. Otherwise, she noted, any adverse effects might go unrecognized.

SOURCE: Archives of Internal Medicine, July 24, 2006.