A recent study suggests whole tomatoes offer better protection from prostate cancer than lycopene supplements alone. The research, published in the Journal of the National Cancer Institute (Vol. 95, No. 21: 1578-1586), found that rats fed tomato powder (including seeds and skins) had less risk of dying from prostate cancer than rats fed a diet containing only lycopene.

Lycopene is a nutrient that gives tomatoes their red color. Several studies have suggested that lycopene-rich foods might reduce the risk of prostate cancer, and many men take lycopene supplements in hopes of preventing the disease. But this new study suggests they may be better off eating tomatoes instead.

"Our findings strongly suggest that risks of poor dietary habits cannot be reversed simply by taking a pill," said study co-author Steven Clinton, MD, PhD, associate professor of hematology and oncology, and human nutrition at Ohio State University. "We must focus more on choosing a variety of healthy foods, exercising, and watching our weight."

Clinton and colleagues from the University of Illinois, Urbana-Champaign, divided 194 male rats into three diet groups. One group received a control diet, a second received the control diet plus lycopene, and the third group received the control diet plus whole tomato powder. Within each diet group, the rats were again divided into two groups: one with unlimited access to food, and one that was fed 80% of the average daily intake of rats in the free-feeding group. All the rats were treated with a compound that made them develop prostate cancer.

Rats fed whole tomato powder did better than rats in the other two dietary groups. Rats on the free-feeding tomato powder diet had a 26% lower risk of dying from prostate cancer compared to animals on the control diet. Rats on the calorie-restricted tomato powder diet had a 32% lower risk compared to those on the control diet. There was little survival difference between rats fed lycopene alone and those on the control diet.

While the findings don't rule out lycopene as an important compound in prostate cancer prevention, they do suggest it works best in the presence of other nutrients found in tomatoes and other foods.

In an accompanying editorial, Peter Gann and Frederick Khachik point out that this study "weighs heavily in the debate about whether cancer prevention is best achieved via whole foods versus via single compounds." Another example they cite is that of beta carotene. It was thought that this compound, found in many vegetables, was responsible for their cancer-protective effect. Yet, when it was given to smokers as a single compound during clinical trials, not only was it not protective, it appeared to increase their chance of developing cancer.

The latest findings provide another opportunity to emphasize the importance of a diet rich in fruits and vegetables, said Carmen Rodriguez, an epidemiologist with the American Cancer Society. ACS and other groups recommend that people eat at least five servings of fruit and vegetables every day.

"I try to tell my patients it's reasonable to consider including tomato products within that recommendation," said Clinton. Men would do well to eat five to seven servings of tomato products each week, he added.

What kind of tomato product is best has not been firmly established, Clinton noted.

"Whole tomatoes and processed – juice, soup, sauce – all can be considered healthy ways to get tomato products," he said. "Right now I'd use the word 'variety.' "