A diet rich in vegetables, fruit, nuts, legumes, unrefined grains, fish and olive oil may guard against aging at the cellular level. (Marvin Joseph/The Washington Post)

Women who eat a Mediterranean-style diet may live longer than those who don’t, according to a new study that looked at one marker of aging.

Women in the study who ate more Mediterranean foods — such as vegetables, fruit, nuts, legumes, unrefined grains, fish and olive oil — and drank moderate amounts of wine with their meals had longer telomeres in their blood cells. Telomeres are sequences of DNA that form protective caps at the ends of chromosomes.

Telomeres get shorter every time a cell divides, so their length is thought to be a measure of a cell’s aging. Stress and inflammation may also shorten people’s telomeres, the researchers said in the study, published last week in the journal BMJ.

The Mediterranean diet is rich in antioxidants and anti-inflammatory compounds, and it may buffer that shortening, said the study’s senior author, Immaculata De Vivo, an associate professor at Brigham and Women’s Hospital and Harvard Medical School. [Extending Life: 7 Ways to Live Past 100]

“To our knowledge, this is the largest population-based study specifically addressing the association between Mediterranean diet adherence and telomere length in healthy, middle-aged women,” De Vivo said in a statement. “Our results further support the benefits of adherence to this diet to promote health and longevity.”

The study included nearly 4,700 women who were participating in the Nurses’ Health Study, a long-term study following the health of more than 120,000 nurses working in the United States. The researchers measured the length of telomeres in blood cells from samples the nurses gave in 1989 and 1990. The researchers also scored the women’s diets on a scale from zero to 9, with a higher number indicating greater adherence to the Mediterranean diet.

They found that women with higher scores tended to have longer telomeres than women with lower scores.

“Our findings showed that healthy eating, overall, was associated with longer telomeres,” said study co-author Marta Crous-Bou, a postdoctoral fellow in the Brigham and Women’s Channing Division of Network Medicine. “However, the strongest association was observed among women who adhered to the Mediterranean diet.”

For every point higher that a woman’s diet scored, her telomere length corresponded with about 1.5 years less of aging, the researchers found. For example, two women with a three-point difference in their diet scores would show, on average, a 4.5-year difference in aging in their telomeres. This is comparable to the difference between smokers and nonsmokers (4.6 years), active and less-active women (4.4 years) and women with high phobic-anxiety scores and low phobic-anxiety scores (6 years), the researchers said.

No one food in the diet stood out as lengthening telomeres. Future research may determine more specifically which aspects of the diet are associated with increased telomere length, De Vivo said.

She and her colleagues cautioned that the study has several limitations. The researchers measured the women’s telomere length at only one point in time and did not look at whether changes in diet may influence telomere length as time goes on. Moreover, many of the women in the study are of European ancestry, and telomere dynamics may be different in people of other ethnicities.

Still, the study shows that the Mediterranean diet, “the cornerstone of dietary advice in cardiovascular disease prevention,” is linked with slower aging, said Peter Nilsson, a professor at Skane University Hospital in Sweden, who was not involved in the research. His comments appear in an opinion piece published along with the study in the journal.

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