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DIET AND PROSTATE CANCER: THIS TIME ITS VEGETABLES

(December 2001)

A recent issue of the Journal of the National Cancer Institute contains a provocative study on diet and prostate cancer from a very good group in Seattle, Washington. Most prostate cancer occurs after age 65, but they decided to study the role of diet in men under 65 with a confirmed diagnosis of prostate cancer.

They analyzed the diet by a self-administered questionnaire during the three- to five-year period before diagnosis in 628 men with prostate cancer and 602 controls. There was no relation to fruit intake, but those who consumed 28 or more vegetable servings a week had a 35 percent reduced risk of prostate cancer compared to men who consumed 14 or less servings a week.

Men eating three or more servings per week of one type of vegetables, the crucifers (broccoli, cole slaw or cabbage, brussel sprouts, cauliflower) had a 41 percent reduction in risk compared to those eating less than one serving a week.

No protection was found for tomatoes, pizza, or spaghetti sauce. These are sources of the lycopenes and other compounds that others have claimed are protective.

Eating carrots at least three times a week reduced risk by 34 percent.

The authors concluded these results suggest that "high consumption of vegetables, particularly cruciferous vegetables, is associated with a reduced risk of prostate cancer".

Commentary: There are some inconsistencies in the data about the effects of total vegetable intake in that, as the number of servings of vegetables per week increases, there is not the smooth curve of increasing protection that one would expect.

As the authors point out, of eight previous studies, only one other supports their findings. They, in turn, do not support the current prostate cancer prevention diet fad of increased lycopenes (in tomatoes, tomato sauce, tomato paste). That diet is also based on contradictory studies.

If vegetables are so helpful, what about Seventh Day Adventists and Mormons? They eat lots of vegetables and have lower rates for many cancers, but no significant reduction in prostate cancer occurrence or deaths.

The findings here can only be applied to those under 65 years of age. Many studies of diet and prostate cancer indicate that what applies to younger men may not be found in older men - and vice versa.

So what should people believe? Is there a way of reducing the risk of prostate cancer through the diet?

The answer is maybe, but, at present, we do not have enough consistent evidence to recommend for or against any diet or dietary prescription.

Cohen, J., Kristal, A., and Stanford, J. Fruit and vegetable intake and prostate cancer risk. Journal of the National Cancer Institute. Vol 92. (January 5) Pgs 61-69. 2000.

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