Narrator: This is Science Today. A plant-based estrogen has been found to prevent osteoporosis at lower doses than the more commonly prescribed animal-based estrogens. Harry Genant, director of the Osteoporosis Research Group at the University of California, San Francisco says plant-based estrogens also produced fewer side effects.

Genant: So this was a fairly exciting development because it presents the opportunity for women to utilize this form of estrogen at a low dose with very few side effects and in particular without troublesome vaginal bleeding or other side effects such as breast tenderness, headaches, nausea.

Narrator: The majority of these women stop estrogen therapy because of unpleasant reactions.

Genant: So if one were able to prescribe a form of estrogen in which the side effects were really minimal, yet the positive effects on the skeleton as well as on the cardiovascular system, then one could anticipate a wider utilization of estrogen and far superior compliance.

Narrator: For Science Today, I'm Larissa Branin.