A team of scientists from the University of North Carolina in Chapel Hill found that calcium and vitamin D show little efficacy in colon cancer prevention. The team reported that patients who took one of the two supplements or both still developed precancerous lesions or polyps after their first colonoscopy.
The recent findings are at odds with at least three studies suggesting that calcium and vitamin D may shield patients from precancerous growths’ recurrence. Past studies suggested that the protective role continued long after patients ceased to take the supplements.
The findings challenged a series of small clinical trials including te latest research’s lead author’s work on the virtues of calcium supplementation in colon cancer prevention. Dr John Baron, lead author of the UNC study, found in 1999 that calcium pills cut risk of colorectal polyps by a significant amount.
But the recent data was a surprise. Dr. Baron explained that the UNC study is the first to assess vitamin D’s protective role in colon cancer and the largest to assess how effective calcium is.
“We were especially surprised by the calcium data,”
He also added that he and his team plan to see what changed between the current trial and the 1999 one and explain differences.
Researchers monitored 2.259 people diagnosed with colorectal polyps, non-cancerous growths that can lead to colon cancer. Patients underwent colonoscopy and had their polyps removed. The UNC team monitored them for five years.
Half of volunteers were asked to take either 1,000 IU of vitamin D3 or 1,200 mg of calcium per day. The rest of the participants were given both supplements or a placebo. After three to five years, participants underwent another colonoscopy to see whether their polyps grew back.
About 43 percent of those who took vitamin D supplements and/or calcium saw their polyps recur. Researchers suggested that 1,000 UI for vitamin D was not enough to grant it a protective role. The team couldn’t tell whether larger doses of vitamin D may prevent colon cancer and cut polyp risk. Nevertheless, higher doses may be toxic, Baron argued.
Last year, a review of several randomized studies on the effects of vitamin D in cardiovascular disease, hip fracture, and cancer prevention showed no statistically significant results.
UNC researchers declined to comment on calcium supplementation’s role in preventing colon cancer. They needed to study the issue further.
The recent study was published this week in the New England Journal of Medicine and was funded by the National Cancer Institute. Pfizer Consumer Healthcare offered the study agents.
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