Calcium & Prostate Cancer

Do high calcium intakes increase the risk of prostate cancer?

Recent epidemiologic studies have raised concern that high calcium intakes are associated with increased risk of prostate cancer. A large prospective cohort study in the U.S. followed more than 50,000 male health professionals for 8 years and found that men whose calcium intake was 2,000 mg/day or more had a risk of developing advanced prostate cancer that was 3 times higher than men whose calcium intake was less than 500 mg/day and a risk of developing metastasized prostate cancer that was more than 4 times greater. The results of a case-control study in Sweden that compared the calcium consumption of 526 men diagnosed with prostate cancer to that of 536 controls were similar. Neither study found calcium intake to be associated with an increased risk of total prostate cancer or non-advanced prostate cancer. More recently, another prospective study of U.S. physicians found that increased intake of calcium from dairy foods was associated with an increased risk of prostate cancer. Although this study did not examine supplement use, each 500 mg/day increase in calcium from dairy foods was associated with a 16% increase in the risk of prostate cancer (advanced and non-advanced). The physiologic mechanisms underlying the relationship between calcium intake and prostate cancer are not yet clear. High levels of dietary calcium may lead to decreased circulating levels of calcitriol, the active form of vitamin D. In experimental studies conducted in prostate cancer cell lines and animal models, calcitriol has been found to have protective effects. However, the findings of studies conducted in humans on serum calcitriol levels and prostate cancer risk have been much less consistent.

Not all epidemiologic studies have demonstrated an association between calcium intake and prostate cancer. In total, 7 out of 14 case-control studies and 5 out of 9 prospective cohort studies have reported statistically significant positive associations between prostate cancer and some measure of dairy product consumption. Of those studies that have examined calcium intake, 3 out of 6 case-control studies and 2 out of 4 cohort studies reported statistically significant associations between prostate cancer and calcium intake. One Serbian case-control study found increased calcium intake to be associated with a decreased risk of prostate cancer. The lack of agreement among these studies suggests complex interactions among risk factors for prostate cancer. Until the relationship between calcium and prostate cancer is clarified, it is reasonable for men to consume a total of 1,000 to 1,200 mg/day of calcium (diet and supplements combined), which is the adequate intake level recommended by the Food and Nutrition Board of the Institute of Medicine.

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