According to a recent study, calcium and vitamin D have been proven ineffective in preventing the recurrence of precancerous polyps which can lead to colon cancer.
The results, published in the New England Journal of Medicine on October 15, fly in the face of prior research from the last 15 to 20 years, which had suggested that dietary supplements diminish the risk of developing malignant growths in the colon.
Dr. John Baron, professor of medicine at the University of North Carolina School of Medicine, had actually conducted one of those early reports around 20 years ago, and now wanted to test if the findings would hold true.
The former study was replicated in its entirety, by including the same type of patients, as well as identical agents and settings.
2,259 subjects, aged 45 to 75, were included in the new trial, and all of them had recently had surgeries for removing adenomas (precancerous colon polyps). Before starting the experiment, the participants underwent colonoscopies, in order to ensure that they were indeed polyp-free.
On a daily basis, for around 3 to 5 years, some of them took a placebo, others took 1,200 milligrams of calcium carbonate, another group took 1,000 IU of vitamin D, while a fourth category took both supplements.
Following this trial period, they had colonoscopies again, to determine to what extent they had been guarded against adenoma recurrence.
It was established that 43% of the subjects had precancerous polyps again, and there was no significant difference between those who had been given a placebo and those who took supplements.
Therefore, it appears that taking calcium or vitamin D is to no avail when it comes to lowering colorectal cancer risk, explains study co-author Elizabeth Barry, assistant professor of epidemiology and community and family medicine at Dartmouth’s Geisel School of Medicine in New Hampshire.
According to Dr. Baron, the findings were extremely surprising, given that calcium’s cancer-fighting properties have been well-documented. As a result, this recent research has been declared an “important negative study” by Dr. Arun Swaminath, director of the inflammatory bowel disease program at Lenox Hill Hospital in New York City.
The trial does have certain limitations, such as the fact that relatively low doses of vitamin D and calcium were administered to high-risk patients, over a limited period. Also, it may be that the participants’ medical profile is different now, as obesity rates have soared.
Follow-up research is currently under way in order to establish if beneficial effects appear for higher doses or extended lengths of time, or if the supplements work best for people who haven’t had adenomas yet.
Meanwhile, experts advise people to take other preventive measures against colorectal cancer, such as having “surveillance colonoscopies”, keeping physically fit, consuming fruit and vegetables and avoiding red and processed meat.
Image Source: Flickr