By: Dr. Geoffrey Modest
An analysis of the Nurses’ Health Study found that those who ate more of a Mediterranean diet had longer telomeres, supporting the health and longevity results from this diet found in other trials (see BMJ 2014;349:g6674). Telomeres undergo attrition with somatic cell division, affecting their ability to prevent loss of genomic DNA at the ends of linear chromosomes, with shorter telomere length considered a biomarker of aging. This attrition is increased with oxidative stress and inflammation, so that age-related attrition rates varies considerably from individual to individual. 
The interest in this study is that the Mediterranean diet (one rich in vegetables, fruits, nuts, legumes, and unrefined grains; lots of olive oil but low intake of saturated lipids; lots of fish with less meat; and of course moderate intake of alcohol, esp wine at meals) is particularly antioxidant and anti-inflammatory.
In brief:
–Nurses’ Health Study is prospective cohort study of 121,700 female registered nurses aged 30-55yo, completing biennial questionnaires, including up to 130 food items, beginning in 1976. 32,825 provided blood samples. A Mediterranean diet score was assessed based on the self-assessed dietary questionnaire over time.
–In this nested case-controlled study, 4676 women were selected as healthy controls (free of major diseases). mean age was 59.
Results:
–They found the expected inverse relationship between age and telomere length (p <0.001). smokers also had shorter telomeres (p=0.02)
–There was a statistically significant relationship between Mediterranean diet score and telomere length, controlling for BMI, pack years of smoking, physical activity, total caloric intake, postmenopausal hormone therapy, age at menopause, history of hypertension, socioeconomic status.
–The difference in those with high adherence to a Mediterranean diet translated to an average 4.5 years of aging, similar to the difference between smokers and non-smokers (4.6 years) and highly active vs less active women (4.4 years).
So, this result confirms other studies that the Mediterranean diet is a healthy one: in observational and some interventional studies this diet seems to reduce mortality, chronic diseases (especially cardiovascular), and increases the likelihood of healthy aging. In addition, it confirms other studies finding that the rate of attrition of telomeres is modifiable. This study, however, is observational and does not have the rigor of a randomized intervention study. also, they only controlled for certain variables, not including assessments of life stressors (socioeconomic status being a not-so-great surrogate for this), which have been shown to be associated with accelerated telomere shortening. In addition there was only one measurement of telomere length — the results would have been more impressive if they assessed changes in individual’s telomere length over time and assessed the association with their diet, controlling for the other variables. But, overall, this study is concordant with many others showing the importance of the Mediterranean diet.