Epidemiological studies have shown that calcium and vitamin D supplementation lower the risk for developing colorectal cancer and colon polyps, which are a pre-cancerous growth. The strong evidence of these studies that focus on past history is not supported by clinical trials that focus their data on evidence gathered in the future.
The New England Journal of Medicine published the results of a study conducted in February 2006 that examined the effects of a seven year supplementation with calcium and Vitamin D on colorectal cancer incidence in postmenopausal women.
The study enrolled over 18,000 participants from the Women's Health Initiative. They were randomized to receive either 1000mg of calcium and 400 IU of Vitamin D daily or placebo. At completion of the study colorectal cancer and polyp incidence were documented as well as routine testing and abdominal symptoms.
The researchers found no statistically significant difference between the treatment and placebo groups (168 verses 154 cases) when it came to incidence of colorectal cancer or polyps. Women in each group also reported similar routine testing and abdominal symptoms.
Though the results were not as most had hoped, and did not support the previous findings from epidemiological studies, the authors do not negate the protective effect that supplementation may bring. Colorectal cancer can grow quite slowly, as well as the fact that habits and lifestyle choices made throughout ones whole life may affect the incidence of cancer or polyps. They suggest that longer term studies are needed to determine if the protective effect exists.
Posted by Kristopher Foster on May 2, 2006 10:17 AM
