According to Barbour Warren, co-author of the fact sheet and BCERF research associate, women - especially those with a high risk of breast cancer - should have reservations about taking these herbal supplements because a lack of regulatory oversight means the marketplace is a "mess".
He drew on statistics which show that 23 percent of middle-aged American women use herbal medicines for a variety of purposes, such as for premenstrual or menopausal symptoms, to aid in breast feeding or to decrease breast cancer risk.
Despite conceding that they might prove to have beneficial effects and possibly even be used in conventional medicine in the future, Warren said that clinical trials carried out to date have not been well designed.
Not everyone in the herbal industry and scientific community agrees.
Responding to the presentation of a Mayo Clinic study in May that concluded that black cohosh is ineffective for alleviating menopause symptoms, Mark Blumenthal, founder and executive director of ABC, said:
"Most of the clinical trials published to date on black cohosh have demonstrated positive results in helping to treat various symptoms of menopause. The evidence supporting the benefits and relative safety of this traditional herb is becoming increasingly clear."
At least 14 clinical trials on black cohosh preparations support their safety and efficacy in treating menopause-related symptoms, including hot flashes, perspiration and mood swings, according to Gail Mahady, assistant professor of Pharmacy Practice at the University of Illinois at Chicago, who has reviewed most of the research on black cohosh for a monograph for the World Health Organization.
But of breast cancer, Warren said: "There is no direct evidence that any herbal medicines can increase or decrease breast cancer risk." Some can have estrogen-like effects, which he said raises concern over their long-term use.
In the past, researchers thought that phytoestrogens could block the effect of estrogen in the body and reduce breast cancer risk, but Warren said that current thinking on the subject is veering the other way, as women on high soy phytoestrogen diets have been shown to experience greater cell multiplication in the breast, which may be a preliminary step in cancer formation, encouraging latent cancer cells to grow too.
The herbals market has not emerged unscathed from conflicting reports over the safety and efficacy of hormone replacement therapy and natural alternatives to menopause management. In February Australia's Novogen attributed a two percent fall in US sales of its red clover-based supplements in the first six months of 2004 to consumer confusion.
Warren also said: "There is no focused safety testing of herbal medicines or even reporting of adverse effects, so when people do have adverse effects there's no mechanism to pool that data."
The American Herbal Products Association is an advocate of serious adverse effects reporting for herbals. But in the past it has asked the FDA to take into account relevant information on the traditional use of herbs when substantiating claims for products that contain them.
Black cohosh has been used for many years by Native Americans to ease the symptoms of painful menstruation, child birth and menopause symptoms. It is approved for these uses in German.
Red clover also has a long history in folk medicine, where it is also used as a diuretic and cough expectorant.
In April two National Institutes of Health agencies announced that they are funding five university-based dietary supplement research centers over the next five years with the aim of furthering our knowledge of their mechanisms and phytochemical constituents.
One of the five beneficiaries is the University of Illinois, which will continue its clinical trial at its Botanical Dietary Supplements for Women's Health program to determine if black cohosh and red clover provide relief of menopausal symptoms, and conduct basic and clinical research into the standardization, metabolism and toxicity of botanicals and support research training in pharmacognosy.