Drinking Less, Not Eating More Veggies, Will Cut Cancer Risk

Have we got our priorities wrong?  Based on published research, I’ve been plugging the health value of moderate alcohol and plenty of veggies, for years.  But it seems    this may be the wrong focus, according to a review published in the British Journal of Cancer. The author is Professor Key of the Cancer Epidemiology Unit, Oxford University, UK.

The surprising conclusion reached by Professor Key is that little hard evidence has accrued during the last 30 years that consumption of fruit and vegetables protects against cancer.  He has analyzed the available data with respect to several specific cancers, together with the role of obesity and alcohol consumption.

Cancers of the oral cavity and pharynx are caused mostly by tobacco and alcohol.  In case-control studies, there’s a 50% reduction in such cancer in people taking high amounts of fruit and vegetables.  However, the use of tobacco and alcohol are usually associated with low intakes of fruit and vegetables, which weakens the findings considerably.

Other cancers evaluated – stomach, colorectal, lung, breast, and prostate – were less ‘positive’ with regard to a protective effect of vegetables.  For stomach, breast, and prostate cancer, associations between diet and risk were very small or non-existent.  With colorectal and lung cancer there were weak associations suggesting a beneficial interaction, but they could easily be caused by effects of dietary fiber or less smoking, respectively.

The main importance of this review, however, lies in the realization that people who have a high intake of fruit and vegetables are much less likely to smoke or to have a moderately high alcohol intake than people with low consumption of fruit and vegetables.  Thus the risk of heavy smoking to cause lung cancer is 500 times greater than the protective effect of high fruit intake.  A similar ‘trade-off’ can occur with alcohol intake, which is a prime cause of obesity, and thus increases the risk of several types of cancer – colon, pancreas, esophagus, and kidney.

In summary, it seems clear that the widespread belief that an increase in fruit and vegetable consumption would produce important reductions in cancer rates was too optimistic.  The best current advice on diet and cancer should include recommendation to continue adequate amounts of fruit and vegetables, but far more emphasis should be placed on the effects of obesity and high alcohol intake on cancer risk.