Vitamin D and Calcium Fail to Reduce Colon Tumor Risk

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Observational studies have suggested that higher intake of vitamin D or calcium may reduce the risk of colorectal tumors, but a randomized trial has found that neither nutrient is effective.

Researchers recruited 2,259 patients who had had adenomas — benign tumors of the colon or rectum — removed during a colonoscopy. They had no remaining polyps after their procedures. The scientists randomly assigned them to receive a daily dose of either 1,000 units of vitamin D, 1,200 milligrams of calcium, both or neither. Three to five years later, the patients had repeat colonoscopies to see the rate at which each group developed new polyps.

Over all, 43 percent of the patients developed one or more adenomas. But taking vitamin D, calcium, both or neither resulted in no significant difference in the number of adenomas found.

Even those subjects whose vitamin D levels were initially low received no benefit from the supplements.

The study, in The New England Journal of Medicine, was large enough to detect even modest effects, and adherence to treatment was high. The researchers acknowledge that a longer follow-up or a larger vitamin D dose might have produced different results.

“There’s a strong lobby for supplements in general, and vitamin D is getting a lot of attention these days,” said the lead author, Dr. John A. Baron, a research professor at the University of North Carolina Gillings School of Global Public Health. “But it doesn’t have the benefits we thought it had.”