While some studies have predicted recently that calcium and Vitamin D supplements would help prevent colon cancer, researchers from the University fo Colorado Cancer center have proved it wrong in their new study.
Based on the results of their study conducted on 2,259 persons at 11 academic medical centers they said 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.
Dennis J. Ahnen from the University of Colorado Cancer Centre said once a patient has colonic polyps removed it failed to reduce his or her risk of developing future polyps or colorectal cancer.
"In addition to knowing what works, it’s important to discover what doesn’t work," Ahnen says.
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, said Ahnen.
In lab studies, vitamin D has been shown to slow the growth of cancer cells through inhibiting the growth of new blood vessels required to feed a cancer’s growth, and also by directly causing the death of cancer cells. In addition, vitamin D supplementation in mouse models of cancer lower the risk of developing the disease.
“This shows that what works in a dish and even what works in animal models doesn’t always work in humans,” Ahnen says.
Similar is true of calcium supplementation: In population studies, people with higher calcium intake have lower incidence of colorectal cancer, and previous, smaller human trials have shown promise for calcium in the prevention of colorectal cancer.
“This was particularly surprising,” Ahnen says, “since one of our own previous trials showed that calcium supplementation could modestly reduce the risk of new polyp formation.”
The study has been published in New England Journal of Medicine.
Dennis Ahnen, MD, investigator at CU Cancer Center, and colleagues, show no reduced risk of colonic polyps with vitamin D and/or calcium supplements.