Calcium supplements for the prevention of colorectal adenomas

Background and Methods Laboratory, clinical, and epidemiologic evidence sug gests that calcium may help prevent colorectal adenomas. We conducted a ran domized, double-blind trial of the effect of supplementation with calcium c arbonate on the recurrence of colorectal adenomas. We randomly assigned 930 subjects (mean age, 61 years; 72 percent men) with a recent history of col orectal adenomas to receive either calcium carbonate (3 g [1200 mg of eleme ntal calcium] dairy) or placebo, with follow-up colonoscopies one and four years after the qualifying examination. The primary end point was the propo rtion of subjects in whom at least one adenoma was detected after the first follow-up endoscopy but up to (and including) the second follow-up examina tion. Risk ratios for the recurrence of adenomas were adjusted for age, sex , lifetime number of adenomas before the study, clinical center, and length of the surveillance period. Results The subjects in the calcium group had a lower risk of recurrent ade nomas. Among the 913 subjects who underwent at least one study colonoscopy, the adjusted risk ratio for any recurrence of adenoma with calcium as comp ared with placebo was 0.85 (95 percent confidence interval, 0.74 to 0.98; P =0.03). The main analysis was based on the 832 subjects (409 in the calcium group and 423 in the placebo group) who completed both follow-up examinati ons. At least one adenoma was diagnosed between the first and second follow -up endoscopies in 127 subjects in the calcium group (31 percent) and 159 s ubjects in the placebo group (38 percent); the adjusted risk ratio was 0.81 (95 percent confidence interval, 0.67 to 0.99; P=0.04). The adjusted ratio of the average number of adenomas in the calcium group to that in the plac ebo group was 0.76 (95 percent confidence interval, 0.60 to 0.96; P=0.02). The effect of calcium was independent of initial dietary fat and calcium in take. Conclusions Calcium supplementation is associated with a significant - thou gh moderate - reduction in the risk of recurrent colorectal adenomas. (N En gl J Med 1999;340:101-7) (C) 1999, Massachusetts Medical Society.