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Vitamin D, calcium do not reduce risk for colorectal adenomas
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Daily supplementation with vitamin D, calcium or both did not significantly decrease risk for recurrent colorectal adenomas, according to the results of a randomized, double blind, placebo-controlled trial.
“Epidemiological and animal data have suggested that vitamin D and/or calcium supplementation might interfere with the development of cancer in the large bowel,” John A. Baron, MD, from the University of North Carolina and Chapel Hill, told Healio Gastroenterology. “Our research group conducted a clinical trial to see if these supplements would prevent the occurrence of colorectal adenomas.”
John A. Baron
From July 2004 to July 2008, Baron and colleagues enrolled 2,259 patients aged 45 to 75 years who had one or more colorectal adenoma removed in the prior 4 months, had no known polyps remaining after colonoscopy, and were expected to undergo a follow-up colonoscopy in 3 to 5 years.
In a partial factorial design, they randomly assigned patients to 1,000 IU vitamin D3 daily, 1,200 mg per day calcium as carbonate daily, both or neither (women could elect to be assigned to calcium or calcium plus vitamin D). The treatment period lasted until follow-up colonoscopy.
The mean net increase in serum 25-hydroxyvitamin D levels among patients who received vitamin D was 7.83 ± 13.4 ng/mL toward the end of the treatment period. At least one adenoma was diagnosed during follow-up in 43% of patients.
The adjusted RRS for recurrent adenomas were as follows for each intervention:
- vitamin D vs. no vitamin D (0.99; 95% CI, 0.89-1.09);
- calcium vs. no calcium (0.95; 95% CI, 0.85-1.06);
- vitamin D plus calcium vs. calcium alone (1.01; 95% CI, 0.88-1.15); and
- vitamin D plus calcium vs. neither (0.93; 95% CI, 0.8-1.08).
Similar results were observed for advanced adenomas, and for proximal vs. distal adenomas. Few adverse events occurred.
“We were surprised to find that neither vitamin D at 1,000 IU per day nor calcium at 1,200 mg per day affected the risk of these polyps over 3 to 5 years of use,” Baron said. “Of course, if we used higher doses or a longer treatment period we might have seen different results. Because of the extensive background of research for calcium, we still think it may provide a benefit, at least in some people. More research is needed to understand what vitamin D can do.” – by Adam Leitenberger
Disclosures: Baron reports grant support from the NIH and nonfinancial support from Lederle/Pfizer during the conduct of the study. In addition, Baron reports a patent related to the chemopreventive use of calcium (U.S. patent #6251439). Please see the full study for a list of all other researchers’ relevant financial disclosures.
Perspective
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Michael J. Hall, MD, MS
In Western populations, colorectal adenomas are commonplace among adults and are a known precursor to colorectal cancer, which will be diagnosed close to 150,000 Americans in 2015. In addition to population-based access to colonoscopy screening at age 50, additional efforts to lower risk of colorectal cancer in adults have focused on chemoprevention. At least one large randomized trial in the past has shown that calcium supplementation can modestly reduce the risk of recurrent adenomas in patients who have previously had an adenoma. Retrospective and observational data have also associated lower serum levels of vitamin D with myriad poorer health outcomes including colorectal cancer outcomes.
In this study, patients with a previous diagnosis of colorectal adenoma were randomized to receive vitamin D supplementation, calcium supplementation, neither, or both in a 2 x 2 factorial design. While 43% of patients developed at least one new adenoma in the observation period, neither calcium supplementation, vitamin D supplementation, nor their combination significantly affected the risk of recurrent adenoma.
It should be noted that it remains feasible that longer term reductions in adenoma number (or size, or dysplastic features) and colorectal cancers may in the future be seen despite a lack of short term impact on the primary outcome reported here. However, with this negative result, calcium and vitamin D supplementation currently join an unfortunate list of chemopreventive agents that have failed at short-term colonoscopy follow-up to have a measurable impact on colorectal cancer precursor lesions, the most notable of which includes dietary fiber supplementation.
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