• Maria V Grau, John A Baron, Robert S Sandler, Robert W Haile, Michael L Beach, Timothy R Church, and David Heber.
• Department of Community and Family Medicine, Dartmouth Medical School, Lebanon, NH, USA. maria.grau.sepulveda@dartmouth.edu
• J. Natl. Cancer Inst. 2003 Dec 3; 95 (23): 1765-71.

BackgroundCalcium and vitamin D both appear to have antineoplastic effects in the large bowel. Although these nutrients are inter-related metabolically in bone and in the normal intestine, their potential interactions in large-bowel carcinogenesis are not well understood.MethodsWe assessed independent and joint effects of calcium supplementation and vitamin D status on adenoma recurrence in 803 subjects in a multi-center, placebo-controlled randomized clinical trial of calcium supplementation for the prevention of colorectal adenoma recurrence. Serum levels of 25-hydroxy [25-(OH)] vitamin D and 1,25-dihydroxy [1,25-(OH)2] vitamin D levels were determined, and the Taq I and Fok I polymorphisms in the vitamin D receptor (VDR) gene were analyzed by polymerase chain reaction. Risk ratios (RRs) for any adenoma recurrence were computed for calcium supplementation within groups defined by serum vitamin D levels and for serum vitamin D levels within treatment groups. Associations of VDR polymorphisms with recurrence risk were also evaluated. All statistical tests were two-sided.ResultsAmong subjects with baseline 25-(OH) vitamin D levels at or below the median (29.1 ng/mL), calcium supplementation was not associated with adenoma recurrence, whereas among those with levels above the median, calcium supplementation was associated with a reduced risk (RR = 0.71, 95 % confidence interval [CI] = 0.57 to 0.89, P for interaction =.012). Conversely, serum 25-(OH) vitamin D levels were associated with a reduced risk only among subjects receiving calcium supplements (RR per 12 ng/mL increase of vitamin D = 0.88, 95% CI = 0.77 to 0.99, P for interaction =.006). VDR polymorphisms were not related to adenoma recurrence and did not modify the associations with vitamin D or calcium.ConclusionsCalcium supplementation and vitamin D status appear to act largely together, not separately, to reduce the risk of colorectal adenoma recurrence. VDR genotype does not appear to be associated with risk.

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