Purpose: Studies have controversially suggested that prostate cancer, the most common cancer among Western men, is less common among those with a high intake of tomato products and lycopene. We examine multivariable associations between the intake of tomatoes and lycopene, and risk of prostate cancer.
Methods: In a prospective study of 27,934 Adventist men without prevalent cancer, Cox proportional hazard regression analyses were used to address the objectives. Dietary measurement error was partially corrected with regression calibration.
Results: 1226 incident cases of prostate cancer, 355 of them aggressive, were identified during 7.9 years of follow-up. Consumption of canned and cooked tomatoes more than four times a week was associated with a HR = 0.72 (95% CI 0.55, 0.94, P = 0.02) comparing to risk in those never consuming this food. Treating this as a continuous variable, adjusting for confounders, produces a similar result, HR = 0.86 (95% CI 0.75, 0.99), comparing 64 g/day with zero intakes (questionnaire data). Regression calibration, although less precise, suggests a yet stronger and statistically significant inverse relationship, comparing a 24-h dietary recall intake of 71 g/day canned and cooked tomato product, with zero intake. Uncalibrated multivariable-adjusted competing risk analyses do not find differences in tomato associations between aggressive and non-aggressive prostate cancers although power for aggressive cancers is limited.
Conclusion: Consumption of canned and cooked tomatoes may reduce the risk of prostate cancer. These products contain more available lycopene. However, an observational study cannot exclude confounding by some unidentified, prostate cancer preventive factor. Clinical Trial Registry: ClinicalTrials.gov Identifier: NCT03615599.
Keywords: Cohort study; Lycopene; Prostate cancer; Seventh-day adventists; Tomatoes.