Eating tomatoes or tomato products on a regular basis can help combat the risk of prostate cancer, according to new research released this week. But the researchers stressed that more studies were necessary to see whether lycopene supplements could be as effective as the lycopene in the tomatoes.
Writing in the 6 March issue of the Journal of the National Cancer Institute, Dr Edward Giovannucci and colleagues from Harvard School of Public Health and Harvard Medical School in Boston, said that previous studies had produced conflicting results regarding an association between the consumption of tomato products and prostate cancer risk.
Dr Giovannucci's team looked at data from 47,365 men who participated in the Health Professionals Follow-up Study. The subjects completed dietary questionnaires in 1986, 1990, and 1994. Between 1986 and 1998, 2481 men were diagnosed with prostate cancer.
Based on the questionnaire results, the authors were able to calculate the amount of lycopene consumed daily from all food sources. Men with a median lycopene intake of 18,780 µg/day had a risk of 0.84 for developing prostate cancer relative to men with an intake of 3415 µgs/day.
A natural antioxidant related to vitamin A, lycopene produces the red colour in tomatoes. Like all antioxidants, the plant chemical attacks the oxygen-free radicals that can damage DNA, leading to cancer.
Tomato sauce seemed to have a particularly beneficial effect, according to the study's authors. The relative risk was 0.77 among men who consumed two or more servings of tomato sauce per week compared with men who consumed less than one serving per month. Dr Giovannucci said that cooking raw tomatoes, as is done to make tomato sauce, may break down cell walls of the fruit and allow the body to absorb more of the lycopene.
The link between lycopene and tomatoes was reinforced when the team controlled for fruit and vegetable intake as well as olive oil use. The associations were observed separately in men of Southern European descent or other Caucasian ancestry.
The team also investigated the effects of tomato juice, pizza, watermelon and pink grapefruit, along with salsa, ketchup and other tomato-based condiments.
"From the available data, we suggest that increased consumption of tomato and tomato-based products may be prudent," the researchers said. "Efficacy and safety of pills containing only lycopene, however, would need to be specifically evaluated."