Mediterranean dietary pattern and cancer incidence: results from the NIH-AARP diet and health study

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Background: There is growing evidence that the Mediterranean diet has a beneficial role in health and longevity. However, little is known about the possible influence of the Mediterranean dietary pattern on cancer risk.

Objective: We investigated the relation between adherence to a Mediterranean dietary pattern and multiple cancer incidence in a US population.

Methods: A cohort of 492,308 U.S. men and women, 50-71 years old in 1995, and free of cancer was followed for 5 years. Diet was assessed at baseline through a validated food frequency questionnaire. Adherence to the Mediterranean diet was assessed by a 9-point Mediterranean diet score (with higher scores indicating greater adherence). We used the median values specific to each sex as cut off points. Cox proportional hazards regression models were used to estimate multivariate relative risks (MVRR) with adjustment for age, sex, race, total energy, body mass index, smoking, education and marital status. Analyses were conducted in the entire cohort and stratified by sex.

Results: During five years of follow-up, 31,844 cancers were documented - 21,891 in men and 9,953 in women. Adherence to the Mediterranean dietary pattern was associated with a reduction in all cancer incidence in both men and women. The multivariate relative risks (MVRR), with increasing levels of adherence were 1.0, 0.98 (95% confidence interval (CI), 0.95-1.0), and 0.94 (95% CI, 0.91-0.97). The association between the Mediterranean dietary pattern and cancer incidence was stronger for smoking related cancers (head & neck, esophagus, pancreas, bladder & lung cancer) than for other cancers (the MVRR for the former comparing the top (6-9 points) versus the bottom levels (0-3 points) of adherence was 0.84 (95% CI, 0.79-0.90). The risk reduction was more apparent for cancers of the oral cavity and pharynx (MVRR, 0.71 (95%CI, 0.56-0.91) and lung (MVRR, 0.79, 95%CI, 0.72-0.86). Statistically significant decreased risks were also seen for cancers of the digestive tract combined (MVRR, 0.89; 95%CI, 0.82-0.96). When comparing the top versus the bottom level of adherence there was no overall association for male related (prostate and other male genital) or female related (breast, endometrial, ovarian and other female genital) cancers (the MVRRs were 0.98, (95%CI, 0.93-1.03) and 1.02 (95% CI, 0.94-1.10), respectively). Sensitivity analyses examining interactive effects between the Mediterranean dietary pattern and lifestyle factors including smoking are underway.

Conclusions: Adherence to a Mediterranean dietary pattern may play an important role in preventing cancer at several sites, especially head and neck, digestive tract, and lung.