Researchers in Europe have once again found that people with higher levels of Vitamin D have a much lower risk of colon cancer. The findings add to a growing body of evidence that suggests Vitamin D may prevent colon cancer and possibly even improve survival in those who have the disease.
For the current study, researchers examined the link between blood levels of Vitamin D as well as dietary Vitamin D and calcium, and reviewed who was at risk for colorectal cancer.
Rearchers based their findings on information from the European Prospective Investigation into Cancer Study (EPIC), a study of more than 520,000 people from 10 Western European countries. The study participants gave blood samples and completed detailed diet and lifestyle questionnaires between 1992 and 1998.
During the follow-up period, 1,248 patients were diagnosed with colorectal cancer. Researchers compared their lifestyle and diet to the same number of healthy patients. Participants with Vitamin D levels below 10ng/ml formed the lowest group, and those with levels above 40ng/ml formed the highest group. The researchers discovered that those with the highest blood levels of Vitamin D had a nearly 40% decrease in colorectal cancer risk than those with the lowest levels. However, Vitamin D experts recommend that optimal levels should be even higher than 40ng/ml, which raises the question whether higher levels would have shown even greater protection.
However, researchers went on to say it's unclear if supplements are better at increasing blood levels of Vitamin D than a balanced diet and moderate exposure to outdoor sunlight. This is a surprising position to take when it is known that dietary intake can only provide a small fraction of what is needed and that the vast majority of North Americans and Europeans have Vitamin D levels well below what is considered optimal.
Researchers went on to caution that the long-term effects of taking large doses of Vitamin D supplements have not been well studied.
"Our findings suggest that the potential cancer risk benefits of higher Vitamin D levels should be balanced with caution for the toxic potential. Before any public health recommendations can be made for Vitamin D supplementation, new randomized trials are needed to test the hypothesis that increases in blood levels of vitamin D are effective in reducing colorectal cancer risk without inducing serious adverse events." This conservative statement produced a rapid response from Dr. William Grant of SUNARC, one of the original researchers who identified Vitamin D deficiency as a cause of cancer. In correspondence to the BMJ Dr Grant pointed out that Vitamin D intake of more than 10,000IU/day has no adverse effects. He went on to explain that his and others research have shown that optimal levels can be best obtained with doses between 1800 and 4000IU/day.
Colorectal cancer is the third most common cancer in men and women in the U.S., according to the American Cancer Society.
The original article in the BMJ can be viewed here
Dr. Williams Grants extensive response can be viewed here