If it seems that we are constantly being bombarded with confusing and conflicting information about Vitamin D, it's because we are.
Past data have suggested it helps prevent cancer and osteoporosis, falls in the elderly, heart attacks, Alzheimer's and other chronic diseases. Additionally, there has been, a steady pool of experimental, epidemiological and clinical trial data suggesting that increased serum levels of Vitamin D or increased Vitamin D intake and increased calcium intake confer some degree of protection against recurrence of colon polyps. Not surprisingly, a new study published in NEJM shows that this is another red herring.
Colorectal cancer is the the third most common cancer in males and females in the U.S. and the third most common cause of cancer death and it is preventable! The lifetime chance of developing colon cancer is about 5%.
Early detection via screening colonoscopies and removal of polyps (precancerous lesions found in the bowel, also known as adenomas) has been part and parcel in the steady decline in the number of deaths attributable to colon cancer, in addition to diagnosing cancer at an earlier stage and better treatments.
Previous studies had shown that Vitamin D and calcium supplementation, when taken together, had some antineoplastic effects in the large bowel. The prospect of decreasing the risk of polyp formation, hence colon cancer, is quite exciting, given how many people die from it each year.
In a randomized, double-blind placebo controlled trial, investigators supplemented vitamin D, calcium or both to see whether or not indeed it was successful at preventing recurring colorectal adenomas in patients who had recently undergone polypectomies.
The study included 2,259 participants, who were assigned to receive Vitamin D, calcium, both or neither. After 3 or 5 years at follow-up 43% of participants had one or more adenomas, meaning by the time the participants had their second screening additional polyps were found. No significant difference was observed between the treatment groups or the control group.
These results seemed to surprise the investigators, particularly with regard to calcium which had shown promise in their own past research. One of the co-authors of the paper, Dr. Dennis J. Ahnen, of the the University of Colorado Cancer Center and professor of Gastroenterology at the Denver VA Medical Center, states "Unfortunately, this trial shows that taking Vitamin D or [c]alcium is probably not very useful...This shows that what works in a dish and even what works in animal models doesn't always work in humans."
Dr. Ahnen hypothesized that perhaps "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...More work is required..."
For the general population, it would behoove us to maintain adequate levels of Vitamin D and calcium and include a diet rich in fiber. I have a distinct feeling that it will not be so easy to D/C (discontinue) the discussion regarding Vitamin D and Calcium just yet.