March 26, 2002 -- Alternative remedies are more popular than ever, and women are now seeking "natural" solutions for the unpleasant symptoms of menopause. But natural doesn't always mean safe. In fact, researchers have found that certain herbs may increase a woman's risk of breast cancer.

"Our studies show that dong quai and ginseng stimulate the growth of [breast cancer] cells," write Paula Amato, MD, from the department of obstetrics and gynecology at Houston's Baylor College of Medicine, and colleagues. Their findings appear in the most recent issue of Menopause.

The team tested four herbs commonly used to fight hot flashes and other menopausal symptoms: dong quai, ginseng, black cohosh, and licorice root. They looked at what effect each of the herbs had on samples of human breast cancer cells and whether they had any estrogen-like properties either in a test tube or in live mice.

None of the herbs exhibited estrogen-like effects, but the dong quai and the ginseng both "significantly induced growth" of the cancer cells, the researchers write.

Besides the fact that the effectiveness of these herbs has not been scientifically proven, there's also the potential for dangerous herb-drug interactions, the researchers write. There have already been reports of uterine bleeding problems from the combined effects of dong quai and blood thinner medications.

Right now, without FDA regulation, there is little if any guarantee of what these preparations contain -- there's no standardization for formulas, dosage, or labeling accuracy.

"Despite their widespread use, little is known about the safety and efficacy of these herbs. Double-blind, randomized, placebo-controlled trials assessing the safety and efficacy of these treatments are needed. Use of these herbs in humans warrants caution pending further study," they write.