Why would eating tomatoes and tomato sauce help prevent prostate cancer? Tomatoes contain the antioxidant lycopene, and antioxidants are believed to neutralize free radicals—chemical compounds in the body that have been implicated in a number of diseases, including cancer. The theory that foods containing lycopene may reduce the risk of prostate cancer has been heavily researched. Unfortunately, some 16 studies on the subject have yielded conflicting results.

A large study published in the recent issue of the Journal of the National Cancer Institute provides strong evidence that eating tomatoes and tomato products may reduce a man's risk of developing prostate cancer. In fact, this study is an extension of a previous study that suggested tomato products might reduce the risk of prostate cancer.

About the study

Researchers at Harvard University's Medical School and School of Public Health studied 47,365 men in the Health Professionals Follow-up Study (HPFS)—a large study of 51,529 male health professionals who were between 40 and 75 when the study began in 1986. At the start of the study and every two years thereafter, HPFS participants completed a mailed questionnaire about age, marital status, height, weight, ancestry, medications, smoking history, disease history, and physical activity. In 1986, 1990, and 1994, they also answered a dietary questionnaire that assessed how frequently they ate various foods and the portion sizes.

For this recent study of lycopene, tomato products and prostate cancer risk, the researchers analyzed data from the HPFS study from 1992 through 1998. Their original study covered only 1986 to 1992, so this study provided six more years of follow-up data on the same men. This study did not include men who already had cancer (other than melanoma) in 1986, and those who either did not complete at least 70 items on the dietary questionnaire or ate more than 4200 calories or less than 800 calories per day.

The researchers compared the tomato/lycopene consumption of men who developed prostate cancer with the tomato/lycopene consumption of those who did not. In addition to overall tomato/lycopene intake, they also measured the men's consumption of tomato sauce, which contains lycopene in a form that is most easily used in the body.

The findings

As in the first HPFS study from 1986 to 1992, the results of this study (1992-1998) confirmed that frequent tomato or lycopene intake is associated with lower risk of prostate cancer.

Specifically, men with the highest tomato/lycopene intake were 16% less likely to develop prostate cancer than men with the lowest intake. Additionally, men who ate 2 or more servings of tomato sauce per week were 23% less likely to develop prostate cancer than men who ate less than 1 serving per month. And the men who ate 2 or more servings of tomato sauce per week were 35% less likely to develop prostate cancer that had spread beyond the prostate. Finally, the risk reduction associated with eating tomato sauce was much stronger among men older than 65 than among men younger than 65.

In calculating these statistics, the researchers controlled for other factors that may affect the risk of prostate cancer, such as age and overall fruit and vegetable consumption. In fact, they found that total fruit and vegetable consumption did not affect the risk of prostate cancer.

There are limitations to this study, however. As in all studies of dietary habits, researchers must rely on the participants to recall their eating patterns accurately. In addition, it's possible that some other factor not accounted for in this study significantly affected the risk of prostate cancer.

How does this affect you?

Should men start eating more tomato products? Absolutely, and so should women. The findings of this study serve to remind us all to include tomatoes and tomato sauce among the fruits and vegetables we eat each day. This study also adds to mounting evidence that lycopene-rich foods, especially tomato sauce, may reduce a man's risk of developing prostate cancer.

Other foods containing lycopene include:

  • Tomatoes, tomato juice, and tomato paste
  • Ketchup
  • Pizza and lasagna (due to the tomato sauce)
  • Watermelon
  • Pink grapefruit
  • Tomato-based soups and stews