Natural routes

Americans bought more than $18 billion of dietary supplements last year, with women doing most of the purchasing. Many herbal products are marketed primarily to women for health concerns such as menstrual and menopausal symptoms, conception, osteoporosis and breast cancer.

Many herbal supplements recommended for women’s health -- soy and flax, for example -- come from plants with chemicals that mimic the female hormone estrogen. Others, such as black cohosh and chaste berry, are thought to act on other hormones in women’s bodies. The herbs below are among those for which there is a significant body of clinical research. But a note of caution: Although these products have been the subject of more research than some other supplements, the debate about their effectiveness continues.

Elena Conis

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Flaxseed

Linum usitatissimum

Flaxseed oil is an excellent source of alpha-linolenic acid, an omega-3 essential fatty acid important for cell membrane structure. Flaxseed oil is used for cardiovascular health, menopause and constipation. It is also taken to relieve inflammation associated with lupus, fibrocystic breasts and arthritis. Because many studies have shown that diets rich in alpha-linolenic acid (such as the Mediterranean diet) reduce the risk of heart attacks, high blood pressure and high cholesterol, supplements containing the acid often are recommended to women nearing menopause. Pregnant women, breast cancer patients and people taking blood-thinning drugs or undergoing surgery should avoid flax supplements.

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Chaste berry

Vitex

Chaste berry, also known as Vitex, is most often used to treat PMS and some menopausal symptoms -- and there’s good evidence that the supplement is useful for these purposes. There’s less evidence to support taking it, as some herbalists suggest, for such conditions as menstrual irregularity, amenorrhea, endometriosis and infertility. Some manufacturers recommend taking the product in the morning, but there is no evidence supporting such a recommendation. Side effects may include headache, upset stomach, hair loss, rash and nausea. Women who are pregnant, on hormone therapy or have uterine or breast cancer should avoid the berries and supplements containing them. Despite the name, there’s no evidence that the berries decrease libido (or keep you chaste).

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Soy

Glycine max

Many studies have linked soy-rich diets with good heart health, but the effects of soy supplements are less clear. Most provide high concentrations of isoflavones -- plant chemicals that behave similarly to human estrogen. Soy products and isoflavone supplements are promoted for, among other things, controlling menopausal symptoms and preventing cancer, osteoporosis and heart disease. Soy protein powders may not contain the same concentration of isoflavones as capsules, so check labels. Soy foods are safe, but the safety of concentrated isoflavones has not been well studied. Women with breast cancer should avoid soy supplements.

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Evening primrose

Oenothera biennis

The reputed therapeutic value of the native North American evening primrose is derived from the oil in its tiny seeds. Native Americans and early settlers used it to treat wounds and skin conditions such as acne and eczema. Today, primrose oil is marketed to treat breast pain, PMS and menopausal symptoms. Evening primrose oil contains vitamin E and gamma-linolenic acid (GLA), an omega-6 fatty acid that’s abundant in most diets. Studies of primrose oil have produced conflicting and inconclusive evidence. Though generally considered safe, evening primrose oil may increase the likelihood of pregnancy complications and the risk of seizures in people prone to them.

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Black cohosh

Cimicifuga racemosa

Centuries ago, Native Americans began using the black cohosh plant for menopause, menstrual cramps and insomnia. These days, black cohosh is most often used to alleviate symptoms of menopause, and some side effects -- such as hot flashes -- of breast cancer treatment. Among herbs recommended for menopause, black cohosh is known for its reputed effectiveness -- and adverse effects, including nausea, stomach pain, diarrhea, weight gain, headache and dizziness. Black cohosh can also increase the risk of miscarriage in pregnant women and interfere with oral contraceptives.