The nutrients calcium and vitamin D work in tandem, not separately, to reduce the risk of colorectal cancer, according to a new reported in the Journal of the National Cancer Institute. The research builds on an earlier finding that people who take calcium supplements have a lower risk of adenoma polyps – benign tumours that are precursors to cancer of the colon or rectum. More than 800 people participated in the Calcium Polyp Prevention Study, a four-year randomized trial that documented the benefits of calcium supplementation for preventing the growth of the benign tumours.

The recent analysis found that calcium supplements prevented adenomas only among individuals with baseline vitamin D levels that were higher than average. Similarly, serum vitamin D levels were associated with reduced adenoma recurrence only among individuals taking calcium supplements.

These findings “provide a strong indication that vitamin D and calcium have a joint antineoplastic effect in the large bowel,” the authors write, but are essentially ineffective without the other. They add that “further investigation is needed to understand the mechanistic basis of the vitamin D/calcium interaction and to clarify the amount of intake of each nutrient required for optimum protective effect.”

Dartmouth Medical School, Dec 2, 2003