Washington D.C,: A recent study has negated the supposed colon cancer-preventing benefits of calcium and vitamin D supplements.
The results of a 2,259-person study conducted at 11 academic medical centers showed that dietary supplementation with vitamin D and/or calcium after removal of pre-cancerous colorectal adenomas (aka polyps) does not reduce risk of developing future adenomas.
Despite promising findings in models of the disease and in previous, smaller trials, the study offers strong evidence against the usefulness of these supplements in the prevention of future polyps.
Co-author Dennis J. Ahnen from the University of Colorado Cancer Center said that after a patient has colonic polyps removed it would be great to be able to offer a way for that patient to reduce his or her risk of developing future polyps or colorectal cancer. Unfortunately, this trial shows that taking vitamin D or calcium is probably not very useful in this setting.
“In addition to knowing what works, it’s important to discover what doesn’t work,” Ahnen says. “This way we can both move on to researching additional, promising strategies and also avoid prescribing treatments that have no effect.”
Ahnen points out that this study specifically examined the possible effects of these supplements against the formation of new precancerous polyps and that it could be that vitamin D and/or calcium work later in the process of carcinogenesis to prevent dangerous cancers, but not their precancerous predecessors.
Overall, though, the authors write that they have “no ready explanation” for these negative findings that seem to controvert the promise of many previously published studies.
The study is published in New England Journal of Medicine.