High calcium intake may increase risk of prostate cancer
PSA Rising, September 22, 2001. More evidence from a large, long term study of men's diet and health has found that calcium intake from dairy products may increase the risk of prostate cancer.
Published in the American Journal of Clinical Nutrition, the new study is part of the ongoing Physicians' Health Study at Harvard. A team led by June Chan tracked connections between dairy product and calcium consumption and prostate cancer in a large group of male U.S. physicians.
Compared with the men who consumed less than half a serving of dairy products daily, men who took more than two and a half servings had a 34% higher risk of developing prostate cancer.
The study group of 20,885 male physicians filled in questionnaires about their own diet and lifestyle between 1982 and 1995. During 11 years of follow-up, 1012 of the men reported that they had developed prostate cancer. The investigators created a dairy score for each participant by summing up the daily calcium contributions from each of 5 common dairy foods.
Men in the highest of five levels of dairy product consumption had a significant 34% greater risk of prostate cancer when compared to those who consumed the lowest levels. When calcium intake was examined apart from dairy product consumption, the risk ratio was 30% higher for advanced prostate cancer and 47% higher for nonadvanced cases.
Of the dairy products consumed by the participants, only skim milk was individually positively associated with prostate cancer risk, perhaps because it accounted for 48% of total consumption of dairy foods.
This suggests that it is not fat in dairy foods but calcium that caused the increased risk for prostate cancer
Dietary calcium, the researchers believe, increases prostate cancer risk by suppressing the body's production of a form of vitamin D. Vitamin D is thought to protect against prostate cancer. The most active form of it, 1,25-dihydroxyvitamin D3, is blocked by calcium.
By looking at vitamin D metabolites in a some of the men in the doctors' study, the Harvard researchers found that those with the highest calcium consumption (more than 600 mg/day) had in their blood 17% lower concentrations of 1,25-dihydroxyvitamin D3 than those in the lowest calcium consumption (less than or equal to 50 mg/day).
This study did not look at calcium intake int he form of over the counter pills, but previous studies limited to supplements found similar risk ratios.
"These findings may serve to interject a note of caution into the current enthusiastic promotion of a higher intake of calcium in the United States,"
Chan says.
Chan, June M, et al. Dairy products, calcium and prostate cancer risk in the Physicians' Health Study. Am J Clin Nutr 2001;74:549-54.
FULL TEXT ARTICLE:
http://faseb.org./ajcn/October/12192-Chan2.pdf
American Journal of Clinical Nutrition
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