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Reported STROBE guidelines have been the basis for reporting our results. The mean age of the participants was 59 (SD 6. Additional adjustment for postmenopausal hormone therapy, age at menopause, history of hypertension, socioeconomic status, and case-control study set (batch), did not change the estimates (data not shown).

Additional adjustment for body mass index, pack years of smoking, physical activity, and total caloric intake did not alter the estimates. Multivariable adjusted least square means of leukocyte telomere length z scores (and their corresponding confidence intervals) by diet score quarters. Notably, whereas higher Alternate Mediterranean Diet score was significantly associated with longer leukocyte telomere length, none of the individual components showed an association with leukocyte telomere length, emphasizing the importance of examining the relation between dietary patterns, in addition to separate dietary factors, and health.

This suggests that the association may be a consequence of the global effect of the overall Mediterranean diet. The difference in telomere length for each one point change in the Alternate Mediterranean Diet score corresponded on average to 1. A three point change in the Alternate Mediterranean Diet score would correspond to on average 4. Our results are consistent with previously published literature on the benefits of a healthy lifestyle, particularly diet, and telomere length.

To date, only one study has assessed the association between telomere length, telomerase activity, and different adherence to a Mediterranean diet. The authors may be capturing survivor bias rather than an association between telomere length and adherence to a Mediterranean diet.

Only two studies have examined the relation between a healthy lifestyle pattern and leukocyte telomere length. Studies on the association between specific dietary factors and telomere length have yielded inconsistent results. No significant associations were observed for intakes of vitamin D or fruits and vegetables. The authors report that one of the advantages of using a Mediterranean diet score rather than focusing on the food components is the generation of fairly consistent results with respect to health benefits, whereas studies focusing on the components or food groups are often contradictory.

As summarized by Trichopoulou et al,56 chance, non-differential misclassification, and residual confounding may have more important consequences when individual food items are evaluated rather than a multi-component, unidimensional score. The benefits on health and aging from a greater adherence to the Mediterranean diet have been largely described. Adherence to the Mediterranean diet has been linked to lower all cause mortality, reduced incidence of major cardiovascular diseases and other chronic diseases, and greater health and wellbeing in people surviving to older ages.

The lack of an association with individual components is not surprising. Studies have proposed a possible synergy among the nutrient rich foods included in the Mediterranean diet that fosters favorable changes in intermediate pathways of cardiometabolic risk, such as insulin sensitivity and resistance to oxidation and inflammation,5 63 supporting the role of the Mediterranean diet as a whole.

The strengths of our study include the large and well characterized study population, detailed assessment of dietary habits as well as other sociodemographic and lifestyle characteristics, and validated food frequency questionnaires and dietary scores.

However, potential limitations should be considered. The cross sectional design precludes us from establishing a temporal association between dietary habits and telomere length. Although all analyses were adjusted for multiple covariates, unmeasured or residual confounding could still be present.

Validation of self reported variables potentially associated with telomere length, such as self reported diabetes, hypertension, and obesity, has been done previously. In summary, greater adherence to the Mediterranean diet was significantly associated with longer leukocyte telomere length, a marker of biological aging. Our results further support the health benefits of adherence to the Mediterranean diet. Finally, we acknowledge Patrice Soule and Esther Orr for their laboratory assistance, and Meir J Stampfer, Walter Willet, and JoAnn Manson for their insightful comments on the manuscript.

MC-B analyzed the data and wrote the first draft of the manuscript. MC-B and IDV contributed to all aspects of the study design, data collection, data analysis and interpretation, and the writing of the article.