tate cancer risk for calcium intakes of 2,000 mg/day and higher compared with intakes less than 700 mg/day. High calcium intake (≥ 2,000 mg/day), however, was significantly associated with risk for advanced prostate cancer. When calcium supplements (≥ 500 mg/day) were analyzed, controlled for total calcium intake, a weak association was found for prostate cancer risk. Dairy product intake was not associated with risk for prostate cancer. The report from the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR, 2007) concluded that the relationship between prostate cancer and milk and dairy product intake is inconsistent from both cohort and case–control studies, and there is limited evidence suggesting that milk and dairy products are a cause of prostate cancer. A food-use questionnaire administered at baseline to participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study explored associations between intake of certain foods and nutrients and risk for incident prostate cancer in a large cohort of male smokers ages 50 to 69 years. This study analyzed intake of calcium and dairy foods and found no associations with development of prostate cancer (Chan et al., 2000). In a longitudinal follow-up of this cohort, Mitrou et al. (2007) found a graded positive association between increasing total calcium intake and total prostate cancer risk. A prospective study of male participants ages 40 to 75 years from the Health Professionals Follow-Up Study (HPFS) examined whether calcium and fructose intake were risk factors for prostate cancer (Giovannucci et al., 1998). Calcium intake exceeding 2,000 mg/day was found to be associated with higher risk for total, advanced, and metastatic prostate cancer. Further, supplemental calcium intake above 900 mg/day was associated with metastatic prostate cancer risk at all levels of total calcium intake. In a follow-up analysis of this cohort, Giovannucci et al. (2006a) found a significantly increased risk for advanced prostate cancer associated with increasing total calcium intake and for fatal prostate cancer associated with supplemental calcium intakes of 401 mg/day and above. The WCRF/AICR (2007) concluded that there is a probable association between diets high in calcium and prostate cancer.
In the case of intervention studies, one randomized controlled multicenter clinical trial based on 672 men (mean age 61.8 years) living in the United States examined risk for prostate cancer from supplemental calcium intake. Participants received either 3 g of calcium carbonate or placebo daily for 4 years and were followed for up to 12 years for prostate cancer diagnosis (Baron et al., 2005). Over the entire study period, risk for prostate cancer was lower in the calcium-supplemented group than in controls (relative risk [RR] = 0.83; 95% CI: 0.52–1.32) but was not statistically significant. For specific years in the study, increase in prostate cancer risk was statistically significant between baseline and year 6 (RR = 0.52; 95% CI: 0.28–0.98) and between years 2 and 6 (RR = 0.44; 95% CI: 0.21–0.94).