May 18 (HealthDay News) -- Multivitamins may help women live longer by preventing parts of their DNA from shortening, a new study has found.

Telomeres, or the end portion of chromosomes, protect chromosomes from damage. Because telomeres shorten slightly when cells divide, researchers speculated that preventing this shortening could protect new cells and thus reduce the effects of aging.

"This study provides the first epidemiological evidence that multivitamin use is associated with longer leukocyte telomeres among women," said lead researcher Dr. Honglei Chen, head of the Aging & Neuroepidemiology Group at the U.S. National Institute of Environmental Health Sciences. "It is not yet clear if this association is causal."

The report appears in the June issue of the American Journal of Clinical Nutrition.

For the study, Chen's team analyzed data on 586 women participating in the Sisters Study, which included women who had breast cancer and their cancer-free siblings. As part of that study, the women were asked about their use of vitamin supplements over a 12-year span. The researchers also took blood samples and tested DNA.

"We found that multivitamin use was associated with longer leukocyte telomeres," Chen said. "Compared with nonusers, daily multivitamin users had, on average, 5.1 percent longer leukocyte telomeres."

This corresponds to about 9.8 years less age-related telomere shortening, the researchers noted.

Vitamins C and E from diet also were associated with longer telomeres, Chen said.

But, whether the vitamins preserved telomere length or actually lengthened life is not clear, Chen said.

"We could not exclude the possibility that the association could be explained by a healthy lifestyle," he said. "Although shorter telomere length has been linked to higher mortality and higher risk of chronic diseases, it is premature to conclude that multivitamin use is associated with slower aging process."

The study was funded by the U.S. National Institutes of Health.

Dr. David Katz, director of the Prevention Research Center at Yale University School of Medicine, thinks there are mixed messages about the value of taking vitamins, and until there is some definitive science on the issue, taking them is a personal decision.

"Most recent studies of vitamin supplements have yielded discouraging results," Katz said. "This study clearly goes the other way, suggesting that a multivitamin may help protect our chromosomes, and thus ourselves, from aging."

There are important limitations to the study, Katz noted. For one, vitamin use was observed, not assigned. "Perhaps healthier people less prone to the effects of aging were also the ones more likely to take vitamins," he added.

In addition, the health effects of slightly longer telomeres are not well-established, Katz said. "In looking at the details of the study, it becomes clear that telomere length did not go up consistently with vitamin exposure; the most frequent use of multivitamins was not associated with the longest telomeres."

SOURCES: Honglei Chen, M.D., Ph.D., head, Aging & Neuroepidemiology Group, U.S. National Institute of Environmental Health Sciences, Research Triangle Park, N.C.; David Katz, M.D., director, Prevention Research Center at Yale University School of Medicine, New Haven, Conn.; June 2009, American Journal of Clinical Nutrition