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.