Men who want to reduce their risk of developing prostate cancer by altering their diet should eat tomatoes or tomato products rather than rely on lycopene supplements, suggest researchers from Ohio State University, Columbus. 502-65-8

Consumption of lycopene, an antioxidant that gives tomatoes their red colour, has been associated with reduced risk of prostate cancer in epidemiological studies. However, the new study, conducted in rats, indicates that other components found in tomatoes may also be associated.

The researchers assigned 194 male rats with prostate cancer to diets containing whole tomato powder or pure lycopene, or to a control diet. After four weeks, the rats were further divided into two groups, one with unlimited access and one with restricted access to food.

The researchers found that rats fed a diet that included whole tomato products survived longer than rats in the other groups (their risk of prostate cancer death was 26 per cent lower). Animals in the tomato-fed, energy-restricted group fared even better, showing a 32 per cent drop in risk. No benefit from lycopene alone was seen in either the energy-restricted or unrestricted groups.

“Our observations support the concept that tomato products contain components in addition to lycopene that may inhibit prostate carcinogenesis,” the researchers say. They add that many men are consuming lycopene-containing supplements in the hope that they may prevent prostate cancer or enhance the treatment of their prostate cancer. “We suggest that a focus on interventions with whole tomato products and energy balance should be a priority while clinical studies simultaneously investigate the risks and benefits of lycopene supplementation.”

The study, which lasted 14 months, is published in the Journal of the National Cancer Institute (2003;95:1578).

The authors of an accompanying editorial (ibid, p1563), Dr Peter Gann, Northwestern University, Chicago, and Dr Frederick Khachik, University of Maryland, point out that plant compounds evolved as sets of interacting compounds. This complexity limits the usefulness of seeking to identify single protective compounds.