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PHILADELPHIA, PENNSYLVANIA. Several previous studies have linked dairy foods with risk of prostate
cancer. The cause of the link was initially attributed to the fat content of these foods, but it may be that their
calcium content suppresses the body’s production of vitamin D, a potential protective factor against prostate
cancer. As dairy products are widely promoted and have certain health benefits, researchers from the Fox
Chase Cancer Center investigated the link to prostate cancer using a group of men from the first National
Health and Nutrition Examination Epidemiologic Follow-up Study.
They followed 3,612 men from across the US for about eight years, during which time 131 were diagnosed with prostate cancer. Food questionnaires were given at the start of the study, when the participants were, on average, 58 years of age. The men consumed an average of 13 portions per week of dairy products, varying from three to 23 portions. Calcium intake was 730 mg on average and vitamin D intake was 172 IU on average (well below the recommended daily intake of 400 IU). Analysis showed that men in the highest third for dairy intake were 2.2 times more likely to develop prostate cancer than those in the lowest third. When each food was studied separately, risk was increased with low-fat milk but not whole milk or any other dairy food. Calcium intake also increased risk by the same amount, but in further analyses only calcium from milk was significant. Calcium supplements did not increase risk.
The authors suggest that their findings support the vitamin D suppression hypothesis. They explain that the
suppressive effects of the calcium from whole milk may be countered by fortification with vitamin D, but low-
fat milk has a lower vitamin D content, as it is a fat-soluble vitamin. On the other hand, prostate cancer may
simply be diagnosed more in the higher social groups which tend to drink low-fat milk and are more likely to
attend screening. In conclusion, the authors state that the increased risk from dairy may occur through a
calcium-related pathway. They add that the link must be clarified, as both calcium and low-fat milk may be
important in avoiding osteoporosis and colon cancer.
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