Do lycopene and tomatoes protect against prostate cancer?
The association between tomatoes, lycopene, and lower prostate cancer risk is plausible, but not yet proven firmly enough to justify specific supplement recommendations. Tomatoes as part of a varied diet is a sensible choice; taking lycopene in isolation has no proven added value at this time.
Tomatoes and lycopene are associated with a lower risk of prostate cancer in several meta-analyses, but the relationship is not straightforward. A meta-analysis of 26 studies involving more than 17,500 cases and over 563,000 participants showed a trend, but the primary result was just short of statistical significance. The effect only became significant after sensitivity analyses. The dose-response relationship appears to be linear between 9 and 21 mg of lycopene per day.
Higher blood levels of lycopene are significantly associated with a lower risk. However, that association levels off above a certain concentration in the blood, meaning more is not necessarily better. Longer follow-up periods and correction for age and body weight strengthened the protective association in the analyses.
Not all meta-analyses are positive. A meta-analysis of 17 prospective studies found only modest reductions in risk that were not statistically significant, for lycopene intake, serum lycopene, and tomato products alike. Another meta-analysis of 24 studies found an overall weak protective effect, but that effect disappeared when cohort studies were examined separately. There was also considerable variation between studies and indications of publication bias. Protective effects appeared only in Asian and Oceanian populations, not in others.
Animal research is more consistently positive: tomatoes and lycopene inhibit prostate tumor growth in multiple animal models. Notably, whole tomato food works better than pure lycopene, suggesting that other compounds in tomatoes also play a role. A small intervention study in humans showed that eating tomato sauce daily for three weeks before prostate surgery led to less oxidative damage to the DNA of tumor tissue and lower PSA levels in the blood. These are mechanistic signals, but the study was too small to draw firm conclusions.
For lycopene supplements, there is insufficient evidence to make a recommendation. The foundation is stronger for a dietary pattern rich in vegetables and fruit, including tomatoes and tomato products, although large randomized trials are lacking. An umbrella review of meta-analyses confirms the association with lower prostate cancer rates, but rates the quality of evidence for most outcomes as low or very low.
Based on multiple meta-analyses and an umbrella review. The meta-analyses vary in design and outcome; publication bias has been demonstrated in at least one analysis. No large randomized trials are available. All associations are observational; causality has not been established.
Does green tea protect against cancer?
Drinking green tea is not a proven protection against cancer: cell and animal research is promising, but studies in humans contradict each other too often to draw a firm conclusion. A few cups a day is probably harmless; concentrated supplements are less certainly so.
Does aspirin or ibuprofen protect against colorectal cancer?
Both aspirin and ibuprofen are associated with a lower risk of colorectal cancer, but the side effects are serious enough that you should not start using them preventively without first consulting your doctor.
Does using the contraceptive pill increase my risk of cancer?
The pill demonstrably lowers the risk of ovarian and uterine cancer, but slightly raises the risk of breast cancer with long-term use or use before a first pregnancy. Discuss your personal situation with your GP or gynaecologist if you have any doubts.
Is it true that circumcision protects against penile cancer and HPV?
Circumcision early in life is associated with a clearly lower risk of invasive penile cancer and a reduced likelihood of carrying HPV, but part of that protection operates through the prevention of phimosis. HPV vaccination is a better-supported prevention step for most people.
Does drinking coffee protect against liver cancer?
Drinking coffee is consistently associated with a lower risk of liver cancer, and that association is better supported than for most other cancer types. Three or more cups per day appears to offer the most protection, but if you are pregnant, keep your intake low.
Should I, as a man, get tested for prostate cancer with the PSA test?
Whether the PSA test is worthwhile depends on your personal risk. Men aged 55 to 69 with an elevated risk, such as a family history or Black ethnicity, have the greatest reason to discuss this with their GP.