A new study, published in the British Medical Journal, monitored the health of 4,676 middle-aged nurses over more than a decade, analysing the impact of the diet on a component of DNA called telomeres.
Researchers in the US found that those who adhered to the diet, which is based on oily fish, poultry, fresh fruit and vegetables, showed fewer signs of ageing in their cells.
Telomeres are stretches of DNA which protect genetic codes, and have been compared to the plastic tips of shoelaces as they keep chromosones from scrambling. They often shorten as a person grows older.
The Harvard-based researchers concluded there was a link between the Mediterranean diet and longer telomeres, which they suggest can be affected by a person's lifestyle.
The report said: "In summary, greater adherence to the Mediterranean diet was significantly associated with longer leukocyte telomere length, a marker of biological ageing.
"The results further support the benefits of adherence to the Mediterranean diet for promoting health and longevity."
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Dr Mike Knapton, associate medical director at the British Heart Foundation, said the results added weight to the view that the diet could help prevent age-related illnesses such as cardiovascular disease.
He said: "Longer telomeres may partially explain the link between diet and risk of cardiovascular disease.
"These results reinforce our advice that eating a balanced and healthy diet can reduce your risk of developing heart disease."