WASHINGTON — Long-term multivitamin use has no impact on the risk of common cancers, cardiovascular diseases or overall mortality in postmenopausal women, according to a study led by researchers at the Fred Hutchinson Cancer Research Center and published in the current issue of Archives of Internal Medicine.

The study examined the effects of multivitamins on nearly 162,000 women enrolled in the Women’s Health Initiative, and the women were followed for about eight years. Forty-two per cent of participants reported using multivitamins on a regular basis, and the study found no significant differences in the risk of cancer, heart diseases or death between multivitamin users and non-users.

"The Women’s Health Initiative is one of the largest studies ever done on diet and health," said Marian L. Neuhouser, lead author of the study. "Thus, because we have such a large and diverse sample size, including women from 40 sites across the nation, our results can be generalized to a healthy population."

About half of Americans use dietary supplements, collectively spending more than $20 billion a year on such products. Researchers said scientific data supporting health benefits of supplements is lacking.

"The motivations for supplement use vary, but common reasons include the belief that these preparations will prevent chronic diseases such as cancer and cardiovascular disease," the authors of the study said. "These views are often fueled by product health claims, consumer testimonials and an industry that is largely unregulated owing to the 1994 Dietary Supplement and Health Education Act."