A study published in the December 2003 Journal of the National Cancer Institute detailed the findings of the Dartmouth Medical School in Lebanon, New Hampshire that calcium and vitamin D work together to reduce colorectal cancer risk.In past studies, vitamin D and calcium separately protected against the development of abnormal growths in the large intestine. These findings suggest that these two nutrients work synergistically in protecting the colon just as they do in protecting the bones.
The study analyzed data provided by 803 participants in the Calcium Polyp Prevention Study, which found that supplementation with 1200 milligrams calcium a day was associated with a lower risk of recurrence of colorectal adenomas, or polyps, which can be a precursor of colorectal cancer.
Researchers, led by Maria V Grau, MD, found that calcium supplements reduced the risk of polyp recurrence only among individuals whose vitamin D levels were higher than the median at the study's onset. Conversely, serum vitamin D levels were associated with a lower risk of polyps reoccurring only among participants who were taking calcium supplements.
In an accompanying editorial in the Journal of the National Cancer Institute, Dr. Elizabeth T Jacobs and colleagues speculate that the presence of adequate calcium might allow for the diversion of 1,25-hydroxyvitamin D3 to antitumor activities. 1,25-hydroxyvitamin D3 is produced from 25-hydroxyvitamin D, and is the form of vitamin D found to have antiproliferative effects in colon cancer.
The researchers concluded that the findings "provide a strong indication that vitamin D and calcium have a joint antineoplastic effect in the large bowel."
J Natl Cancer Inst. 2003;95:1736-1737,1765-1771.