Exercise may help older women maintain their bone density, but adding the supplement black cohosh to the routine does not bring any extra benefits, a new study suggests.

Researchers found that among 128 postmenopausal women they studied for one year, those who were randomly assigned to regularly exercise generally maintained their bone density. In contrast, women who were assigned to a “wellness” group that got only light, infrequent exercise showed a decline in their bone density, on average.

But while exercise appeared to help women hang on to their bone mass, the herb black cohosh showed no added effects. Among exercisers, those who were randomly assigned to take the supplement each day showed no bone-density advantage after one year.

Black cohosh extracts are marketed as a “natural” form of hormone replacement therapy and most commonly used to treat hot flashes and other symptoms of menopause. Some lab research, but not all, suggests the herb may have estrogen-like activity in the body.

The new study appears to be the first to look at the effects of black cohosh on bone density, according to lead researcher Michael Bebenek of the University of Erlangen, in Germany.

While in theory, a substance with estrogen-like effects could protect women’s bone density, the benefits of black cohosh for bone health is “still doubtful,” Bebenek told Reuters Health in an email.

He and his colleagues report the findings in the medical journal Menopause.

For their study, the researchers recruited 128 women who had gone through menopause within the past one to three years.

They randomly assigned 86 women to an exercise program that interspersed six weeks of higher-intensity activities designed to protect bone mass - like high-impact aerobics and strength training - with 10 weeks of more-moderate exercise designed to improve heart health. The latter included activities like brisk walking and step aerobics.

Half of the exercisers also took a 40-milligram black cohosh supplement each day.

The remaining 42 women were assigned to a “wellness” group that performed low-intensity activities, like light walking, stretching and balancing exercises, for one hour a week.

After one year, women in both exercise groups showed no significant change in bone density at the spine, while those in the wellness group showed a 2 percent decline, on average. Exercisers had a slight increase in bone mass at the hip - about 0.5 percent - versus an average dip of 0.6 percent in the wellness group; that difference was not, however, significant in statistical terms.

The researchers found no significant bone-mass differences between exercisers on black cohosh and those who did not take the supplement.

Bebenek’s team also looked for any changes in the study participants’ Framingham risk scores - an estimate of a person’s odds of suffering a heart attack or dying from heart disease in the next 10 years. The score is based on age, smoking history, blood pressure and cholesterol levels and whether a person has diabetes.

Overall, the researchers found no clear effects of exercise or exercise-plus-black-cohosh on the women’s risk scores.

At the end of the study, women in the exercise-only group were estimated to have a 6 percent chance of suffering a heart attack or dying from heart disease in the next 10 years; that risk was 7 percent and 7.8 percent in the black cohosh and wellness groups, respectively. However, the differences in the groups’ score changes over time were not significant in statistical terms.

The bottom line, according to the researchers, is that the study “again clearly demonstrated” the positive effects of exercise on postmenopausal women’s bones. Whether black cohosh has any bone-health benefits, however, remains in question.

SOURCE: Menopause, online March 9, 2010.