Vitamin D, calcium offered little protection against adenomas in large study

Last Updated: 2015-10-14

By Gene Emery

NEW YORK (Reuters Health) - Calcium and vitamin D supplements did not reduce the long-term risk of adenomas in people who have previously had at least one pre-cancerous growth removed from the colon, according a study that followed 2,259 volunteers for three to five years.

Recommending the two supplements "has been a trend," chief author Dr. John Baron of the University of North Carolina at Chapel Hill told Reuters Health by phone. The new findings "should put a dent into it."

The study, released online October 14 by the New England Journal of Medicine, comes as nearly 50,000 people die from colorectal cancer in the U.S. each year.

Previous research, including tests on animals, had suggested that both vitamin D and calcium can lower the risk of colorectal cancer, but small studies designed to see if they can actually cut the odds have been conclusive.

But Dr Wafik El-Deiry of the Fox Chase Cancer Center in Philadelphia, who was not connected with the research, said he's not sure the study will change practice because "most of the use of vitamin D and the data that's been out there would really support its use in patients who have already had colorectal cancer," not people with polyps.

"To my knowledge, most people out there who have had a polyp would not have been advised to take vitamin D, or calcium for that matter," he told Reuters Health in a telephone interview.

In the new test, the volunteers all had adenomatous polyps removed within the previous 120 days.

One quarter - 420 - were assigned to take 1000 IU of vitamin D-3 daily, 419 were asked to take 1,200 mg of calcium as carbonate, 421 were supposed to take both, and 415 were assigned to placebo. All tablets were packaged identically.

Woman could choose to be in the calcium group or in the calcium plus vitamin D group, but everyone else was randomized. Volunteers who wanted to take a multivitamin were given one without calcium or vitamin D.

The supplements increased vitamin D and calcium levels, but had no effect on the likelihood of recurrent adenomas.

The rates of one or more adenomas were 42.8% with vitamin D and 42.7% without, 45.3% with calcium and 47.6% without, and 45.7% with both calcium and vitamin D and 48.2% with neither.

"The findings for advanced adenomas also did not suggest meaningful effects," the researchers said. Advanced growths showed up in roughly 10% of all groups.

"The people who advocate for vitamin D were recommending as much as 2000 units a day or more," said Dr. Baron. "Whether our study would take the wind out of those sails, I don't know."

The researchers did find, however, that the lower a person's body-mass index, the greater the likelihood that calcium supplementation would significantly lower the adenoma risk (P=0.02). A similar trend was not seen with vitamin D.

In addition, calcium recipients had fewer myocardial infarctions than those not receiving calcium. The rates were 1.1% with calcium and 0.2% without (P=0.03).

However, "we had so few (cardiac) events, it smells like a chance finding," said Dr. Baron. "It wasn't on our radar as an official end point."

"More and more studies are suggesting that high-doses of supplements, at a minimum, are not helpful and, in a few instances, can be harmful for an American-type population," Dr. Baron said. "One message might be that spending money and energy taking supplements might not be so beneficial."

"In a lot of people's minds, if you can prevent polyps, you can prevent cancer," said Dr. El-Deiry of Fox Chase. "These results are certainly interesting, but vitamin D is likely to be more important at the cancer stage than the polyp stage."

SOURCE: http://bit.ly/1jjfih6

N Engl J Med 2015.