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Calcium and vitamin D prevent colon cancer

LEBANON, NEW HAMPSHIRE. There is some evidence that both calcium and vitamin D help prevent colon cancer; however, it is not clear whether they act independently or together in doing so. A group of researchers from 6 major American research centers now report that a combination of a high calcium intake and a high blood level of vitamin D are required in order to achieve meaningful protection.

Their study involved 803 patients who had had at least one colon adenoma (benign tumour) removed during the 3 months preceding the start of the study. The participants were randomized to receive either a placebo or 3 grams/day of calcium carbonate providing 1200 mg/day of elemental calcium for a 4-year period. Colonoscopy was performed 1 and 4 years after study entry to check for the recurrence of adenomas. The researchers measured the blood serum level of 25-hydroxy [25-(OH)] vitamin D and 1,25-dihydroxy vitamin D. The median 25-(OH) vitamin D level was 29.1 ng/mL and the median 1,25-dihydroxy vitamin D level was 41.8 pg/mL at the start of the study period.

The researchers found no association between calcium supplementation and adenoma recurrence nor between 25-(OH) vitamin D level and adenoma recurrence. However, they did find a highly significant benefit of a combination of high vitamin D levels and calcium supplementation. Participants who supplemented with calcium and also had serum levels of 25-(OH) vitamin D above 29.1 ng/mL were found to have an average 29% lower risk of adenoma recurrence. The researchers conclude that calcium and vitamin D act together to prevent adenoma recurrence.
Grau, MV, et al. Vitamin D, calcium supplementation, and colorectal adenoma: results of a randomized trial. Journal of the National Cancer Institute, Vol. 95, December 3, 2003, pp. 1765-71
Jacobs, ET, et al. Research and public health implications of the intricate relationship between calcium and vitamin D in the prevention of colorectal neoplasia. Journal of the National Cancer Institute, Vol. 95, December 3, 2003, pp. 1765- 71

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