A prospective study of Mediterranean diet and risk of prostate cancer

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Introduction: We prospectively investigated the association between a Mediterranean-type diet pattern and risk of prostate cancer (PCa) in the Health Professionals Follow-up Study.
 Methods: We used a slightly modified version of the 10-point Mediterranean diet scale as constructed by A. Trichopoulou and colleagues, with a higher score indicating closer adherence to this diet pattern. Our scale assigns participants 1 point for being above the median in intake of vegetables, legumes, fruits and nuts, cereals, fish and the ratio of polyunsaturated to saturated lipids; 1 point for being below the median in dairy intake and meat intake; and 1 point for alcohol intake between 10 and 50 grams per day. Between 1986 and 2004, 4075 incident PCa cases were confirmed. We used multivariable Cox proportional hazard models adjusted for known PCa risk factors. We calculated hazard ratios (HRs) for total, advanced, and fatal PCa, which are clinically relevant categories when evaluating PCa risk.
 Results: Men who scored highest on the Mediterranean diet scale were less likely to be current smokers, had higher alcohol consumption and higher vigorous physical activity, and were more likely to use multivitamins than men with the lowest scores. Of the 47,721 men in this analysis, 29.7% had a diet score of 6 or higher. Mediterranean diet was not associated with total PCa (HR [95% CI] for a score of ≥6 vs ≤3: 1.04 [0.96, 1.13], advanced PCa (1.00 [0.82, 1.21]), or fatal PCa (0.95 [0.74, 1.22]). An inverse association for advanced and fatal disease was observed in men of Southern European (SoEur) ancestry who closely adhered to a Mediterranean-type dietary pattern. SoEur men having a diet score of ≥6 had a 31% decrease in risk of advanced PCa (HR=0.69 [0.47, 1.00]) and a 19% decrease in risk of fatal PCa (HR=0.81 [0.52, 1.27]) compared to non-SoEur men with a diet score ≤3, additionally adjusting for tomato sauce intake. Tomato sauce intake, which was weakly correlated with Mediterranean diet score in both non-SoEur (ρ=0.09) and SoEur men (ρ=0.11), was independently inversely associated with total, advanced, and fatal prostate cancer, and these reductions in risk were stronger in SoEur men (p_interaction=0.07 for total, 0.24 for advanced, and 0.07 for fatal PCa). SoEur men with a diet score ≥6 and high tomato sauce intake had a 74% reduced risk of advanced PCa (HR=0.26 [0.08, 0.83]) and a 68% reduced risk of fatal PCa (0.32 [0.08, 1.32]), compared to non-SoEur men with a diet score ≤3 and low tomato sauce intake.
 Conclusion: A Mediterranean-type dietary pattern was associated with a reduction in PCa risk only in SoEur men, with further reductions in risk if coupled with high tomato sauce intake. Mediterranean diet may capture some other protective factor or SoEur ancestry may capture long-term adherence to this dietary pattern, as well as long-term tomato sauce intake, which may lower PCa risk.