Association of Plant-Based Diet Index with Prostate Cancer Risk.

BACKGROUND Plant-based diets are associated with multiple health benefits and a favorable environmental impact. For prostate cancer, previous studies suggest a beneficial role of specific plant-based foods (e.g., tomatoes) and a potentially harmful role of specific animal-based foods (e.g., meat, dairy). However, less is known about plant-based dietary patterns. OBJECTIVE To examine the relationship between Plant-based Diet Indices and prostate cancer risk, including clinically relevant disease. DESIGN This was a prospective cohort study including 47,239 men in the Health Professionals Follow-up Study (1986-2014). Overall and healthful Plant-based Diet Indices were calculated from food frequency questionnaires. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) to examine the risk of incident prostate cancer (total and by clinical category), among men ages < 65 and ≥ 65. RESULTS 6,655 men were diagnosed with prostate cancer over follow-up, including 515 with advanced stage at diagnosis, 956 with lethal disease (metastasis or death) and 806 prostate cancer deaths. Greater overall plant-based consumption was associated with a significantly lower risk of fatal prostate cancer (HR 0.81, 95% CI 0.64,1.01; p-trend = 0.04). In men age < 65, higher Plant-based Diet Index was associated with a lower risk of advanced, lethal and fatal prostate cancer. Moreover, greater consumption of a healthful plant-based diet was associated with lower risks of total (HR 0.84; 95% CI 0.73,0.98; P-trend = 0.046) and lethal prostate cancer (HR 0.56; 95% CI 0.34,0.94; P-trend = 0.03) at age < 65. There were no associations between overall or healthful Plant-based Diet Indices with prostate cancer among men ≥ 65 years. Less than 1% of participants followed a strict vegetarian or vegan diet. CONCLUSIONS AND RELEVANCE This prospective study provides supportive evidence that greater consumption of healthful plant-based foods is associated with a lower risk of aggressive forms of prostate cancer, with stronger benefit among men age < 65.