Consumption of canned and cooked tomatoes may be associated with a decreased risk of prostate cancer (PCa), according to investigators.

A prospective study of 27,934 Adventist men free of cancer at enrollment found that consumption of canned and cooked tomatoes 5 to 6 times a week was significantly associated with a 28% decreased risk of PCa compared with never consuming this food after adjusting for multiple potential confounders, Gary E. Fraser, MBChB, PhD, of Loma Linda University in Loma Linda, California, and colleagues reported in Cancers Causes & Control. The study found no significant association between PCa and consumption of raw tomatoes, tomato soup, tomato sauce, and tomato-based vegetable juice.

“If our findings are explained by the lycopene contents of the tomato products, it is noted that lycopene is absorbed to a different degree by consumption of different tomato-based products,” the investigators wrote. “Bioavailability is better if the tomatoes have been heated, as this facilitates the separation of the lycopene from the carrier proteins.”

Dr Fraser’s team studied men enrolled in the Adventist Health Study-2. At baseline, study participants filled out self-administered food frequency questionnaires in which they reported their average frequency of intake of various foods and beverages and serving sizes during the past year. During a mean follow-up of 7.9 years, the investigators identified 1226 new PCa cases, 355 of them aggressive.


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In a discussion of study strengths, the investigators noted that their data are based on extensive information on dietary habits, “which makes it possible to estimate the intake of lycopene and we have, at least to some extent, been able to correct for the considerable misclassification that complicates most studies in nutritional epidemiology.” With regard to limitations, the authors acknowledged that they collected data on dietary habits only at baseline.

Some previous studies have found associations between high intake of lycopene, a carotenoid with antioxidant properties, and a reduced risk of PCa. For example, among 47,365 men in the Health Professionals Follow-Up Study, the highest vs lowest quintile of lycopene intake was significantly associated with a 16% reduced risk of PCa, according to findings published in 2002 in the Journal of the National Cancer Institute. Compared with consumption of less than 1 serving of tomato sauce per month, consumption of 2 or more servings per week was significantly associated with a 28%, 35%, and 36% reduced risk of organ-confined, advanced, and metastatic PCa, respectively.

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A systematic review and meta-analysis of 24 published studies found that the highest category of tomato intake, compared with the lowest category, was significantly associated with a 16% reduced risk of PCa, according to findings published in Scientific Reports in 2016.

References

Fraser GE, Jacobsen BK, Knutsen SF, et al. Tomato consumptions and intake of lycopene as predictors of the incidence of prostate cancer: the Adventist Health Study-2 [published online February 25, 2020]. Cancer Causes Control.  doi: 10.1007/s10552-020-01279-z

Giovannucci E, Rimm EB, Liu Y, et al. A prospective study of tomato products, lycopene, and prostate cancer risk. J Natl Cancer Inst. 2002;94:391-398. doi: 10.1093/inci/94.5.391 

Xu X, Li J, Wang X, et al. Tomato consumption and prostate cancer risk: a systematic review and meta-analysis. Sci Rep. 2016;6:37091.  doi: 10.1038/srep37091