Study Confirms: Calcium and Vitamin D Cannot Prevent Colon Cancer

Vitamin D has been in the news a lot lately, being dubbed a magic bullet to control anything from COPD to Alzheimer’s disease. However, a new study published in the New England Journal of Medicine has thwarted belief in one such preventive role of both vitamin D and calcium. The study attempted to confirm epidemiologic and preclinical data that hinted at a protective effect rendered by vitamin D and calcium against colorectal neoplasia.

The randomized, double-blind, placebo-controlled trial recruited 2259 participants to receive either a daily dose of vitamin D₃, calcium carbonate, both, or neither. The entire population recruited for the trial had recently been diagnosed with adenomas, with no known colorectal polyps remaining following a complete colonoscopy. With a follow-up colonoscopy anticipated at 3 or 5 years after the baseline evaluations, the primary endpoint of the trial was adenomas diagnosed during the period between the randomization and the anticipated surveillance colonoscopy.

The trial found that a significant proportion of participants adhered to the study procedures: only 3% did not have a colonoscopic examination a year after randomization and nearly 5% either dropped out, were lost to follow-up, or died. So the final analysis included 2088 participants—92.4% of the original number. The follow-up evaluations identified 3131 potentially neoplastic lesions in 1301 participants; pathologic evaluations were only available for 3012 of those lesions in 1280 participants. So overall, of the 2059 participants who could be examines, adenomas were diagnosed in 880 (43%) participants.

Analysis of these data did not find any effect of any of the interventions on an individual’ risk of developing adenomas. The adjusted risk ratio (RR) for any adenoma among patients taking vitamin D compared with patients not taking it was 0.99 (95% confidence interval [CI], 0.89 to 1.09); the adjusted RR among patients taking calcium as compared with those who did not was 0.95 (95% CI, 0.85 to 1.06); and among patients taking vitamin D plus calcium versus those taking calcium alone, the adjusted RR was 1.01 (95% CI, 0.88 to 1.15).

The results of this study proved the null hypothesis, contradicting popular belief. Although the authors did serendipitously discover a slightly lower risk of adenomas in those with a lower body mass index who were supplemented with calcium, they attribute the finding to chance. “Our findings with regard to vitamin D are not inconsistent with a modest chemopreventive potential, but they do not support the more marked chemopreventive effect that has sometimes been posited,” the authors concluded.