Calcium

In a randomised double-blind study involving 913 patients, Baron et al. [30] observed that calcium supplementation (1200 mg of elemental calcium daily) moderately reduced the risk of recurrence of adenomatous polyps of the large bowel. The adjusted risk ratio for any recurrence of adenoma with calcium compared with placebo was 0.85 (95% CI 0.74–0.98, P = 0.03). The adjusted ratio of the average number of adenomas in the calcium group to that in the placebo group was 0.75 (95% CI 0.60–0.96, P = 0.02). The effect of calcium was independent of initial dietary fat and calcium intake [30].

The randomised double-blind 3-year intervention study by Hofstadt et al. [31] showed that a mixture of calcium and antioxidants had a beneficial effect on adenoma recurrence, though not on adenoma growth; the effects of calcium could be disentangled from those of antioxidants. In the study of Bonithon-Kopp et al. [29], which tested the efficacy of fibre and calcium supplements in prevention of colorectal neoplastic polyp recurrence, the rate of recurrence was statistically non-significantly decreased in the calcium (2 g daily) treatment group. The adjusted OR for recurrence was 0.66 (95% CI 0.38–1.17; P = 0.16)

The evidence suggesting that calcium supplementation decreases risk of colorectal adenomas is not yet sufficient to recommend its use to the general population as a strategy to prevent colorectal cancer.