Men who eat at least 10 servings a week of tomato-based foods are up to 45 percent less likely to develop prostate cancer, Harvard University researchers report.
A six-year study of the dietary habits of 47,000 men found that pizza, spaghetti sauce and other foods rich in tomato substantially lowered the risk of prostate cancer. A report on the study will be published Wednesday in the Journal of the National Cancer Institute.
Dr. Edward Giovannucci, a researcher at the Harvard School of Public Health, said that tomato-based products and strawberries were the only foods of 46 fruits and vegetables checked that seemed to have a protective effect against prostate cancer. And the benefits of tomatoes came from several forms of the food: sauce, juice, raw and even when cooked into pizza.
“We found that more was better,” said Giovannucci. He said men who had 10 or more servings a week had a 45 percent reduction in the rate of prostate cancer, while those who ate only four to seven servings of the tomato-based food had a 20 percent reduction in the cancer.
Spaghetti sauce was the most common tomato-based food eaten by the men in the study group.
Giovannucci cautioned that the findings should not be interpreted to mean that men should load up on tomato products. “These findings support the idea that people should eat a variety of fruits and vegetables,” he said. Nutrients in other foods may be protective against other types of cancers, said Giovannucci.
The researcher said that tomatoes are rich in an anti-oxidant called lycopene. In fact, tomatoes and tomato products accounted for almost 90 percent of the lycopene in the diet of the men studied.
Giovannucci said the study found that other nutrients, such as beta carotene and vitamin A, had no effect on the rate of prostate cancer. However, he said, these nutrients may be protective against other types of cancers as some research has suggested.
The protective effects of tomatoes had been suggested in some earlier studies of prostate cancer rates. Giovannucci said that the research had found that prostate cancer was less common in southern Mediterranean countries, such as Italy and Greece, where tomato-based foods are a major part of the diet.
In the new study, Giovannucci said that cooked tomato products seemed to be more protective than either juice or raw tomatoes. It could be, he said, that when tomatoes are heated during cooking, the cells burst and release more lycopene.
The study is based on dietary survey taken of 47,000 males in the health professions between the ages of 40 and 75. The first survey was taken in 1986 and the men were followed and periodically re-examined. At the end of the study, in 1992, there were 812 cases of prostate cancer among those in the study group. The researchers then compared the dietary history of those who developed prostate cancer with those who did not.