“What makes this study significant is that clinicians are routinely screening for vitamin D in routine health checks, and often recommending that patients take supplements”, said Elizabeth L. Barry, PhD, a researcher at Dartmouth-Hitchcock’s Norris Cotton Cancer Center and at the Geisel School of Medicine at Dartmouth. A few women who went for the calcium were given supplements of vitamin D while others were placebo. The research challenges past studies that had found dietary supplements may help prevent precancerous growths’ recurrence.
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“That was a big surprise”. According to John Baron, study’s lead author and professor of medicine at the University of North Carolina at Chapel Hill, many people have given vitamin D appreciation because it is considered to prevent many health problems. Pfizer Consumer Healthcare offered the study agents.
Half of volunteers were asked to take either 1,000 IU of vitamin D3 or 1,200 mg of calcium per day. Women were eligible to elect to receive calcium in addition to random assignment to vitamin D or placebo. The team adjusted results for age, sex, income, substance abuse and other risks and the results were the same: may not cut colon cancer risk. The team couldn’t tell whether larger doses of vitamin D may prevent colon cancer and cut polyp risk. Anyone considering long-term use is advised to talk with a doctor about the risks and benefits. They found that vitamin D and calcium supplements did not work in removing polyps, pre-cancerous colorectal adenomas. “We plan to look at this trial and our previous trial to see if we can explain the difference in findings”.
The study results, published today in the New England Journal of Medicine, did not support earlier observational studies suggesting a link between lower colorectal cancer risk with higher vitamin D blood levels or greater calcium intake. The participants had precancerous adenomas removed, with none remaining after a colonoscopy, and were further divided into four groups. The polyps were removed through a surgical procedure called colonoscopy.
Daily supplementation with vitamin D3, calcium did not significantly reduce the risk of recurrent adenomas. Participants taking calcium doses did not fare better, with 45.3% developing polyps as opposed to the 47.5% who were not given the supplement.
“This shows that what works in a dish and even what works in animal models doesn’t always work in humans”, Ahnen says. Past studies suggested that the protective role continued long after patients ceased to take the supplements.
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The researchers also said they would rule out the possibility of vitamin D preventing advanced stages of colon cancer. They needed to study the issue further. “But at least in this setting, at this dose, with this population and measuring these outcomes, vitamin D and calcium supplementation did not appear useful”.
