The risk of colon cancer can be reduced by 50 percent by taking a daily supplement of vitamin D-3, according to researchers at Moores Cancer Center of the University of California at San Diego (UCSD). Researchers reported that their studies showed that taking 1000 IU, or 25 mcg, of vitamin D daily would sharply reduce the chance of a person getting colon cancer. Colon cancer is diagnosed in about 145,000 Americans each year and claims about 56,000 U.S. lives each year.
"Studies over the last 25 years have shown that vitamin D is associated with preventing colon cancer, but we haven't known how much is needed to produce a benefit," said Edward D. Gorham, assistant adjunct professor of Family and Preventive Medicine at UCSD School of Medicine and a cancer epidemiologist affiliated with the Moores UCSD Cancer Center.
"This paper establishes the target level of vitamin D that could reduce the incidence of colorectal cancer by half," Gorham said. Intake of 1,000 IU/day of vitamin D, half the safe upper intake established by the National Academy of Sciences, was associated with 50 percent lower risk (of colorectal cancer).
Individuals with vitamin D blood levels of 33 nanograms per milliliter, generated through modest sunlight exposure, also had a 50 percent lower incidence of colorectal cancer.
"Interventional studies, or clinical trials, are needed to further define the relationship between vitamin D and colon cancer," Dr Gorham said, "but such studies could take more than 20 years to complete. Since the safety of daily intake of vitamin D3 in the recommended range has been thoroughly assessed and confirmed by the National Academy of Sciences, and the benefits found so far in observational studies are considerable, expanded use of vitamin D as a public health measure should not be delayed."
The findings are based upon an extensive systematic review of scientific papers on the relationship of blood serum levels or oral intake of vitamin D with risk of colorectal cancer published worldwide between 1966 and 2004. Forty four articles were identified; 18 articles met the study's criteria for inclusion. A majority (10) of the studies found that inadequate vitamin D status was significantly associated with higher risk of colorectal cancer. The other eight studies ranged from a borderline association to no association.
The researchers ran a cost/benefit analysis and concluded "preventing approximately half of colorectal cancer incidence by a program that would ensure vitamin D adequacy could save an estimated $20 billion per year." It could also prevent about 28,000 deaths per year, he said.
"BACKGROUND: Inadequate photosynthesis or oral intake of Vitamin D are associated with high incidence rates of colorectal cancer, but the dose-response relationship has not been adequately studied.
METHODS: Dose-response gradients from observational studies of Vitamin D intake and serum 25-hydroxyvitamin D were plotted as trend lines. The point on each linear trend line corresponding to an odds ratio of 0.50 provided the prediagnostic Vitamin D intake or 25-hydroxyvitamin D concentration associated with 50% lower risk compared to <100IU/day Vitamin D or <13ng/ml serum 25-hydroxyvitamin D. Medians of these values were determined.
RESULTS: Overall, individuals with >or=1000IU/day oral Vitamin D (p<0.0001) or >or=33ng/ml (82nmol/l) serum 25-hydroxyvitamin D (p<0.01) had 50% lower incidence of colorectal cancer compared to reference values.
CONCLUSIONS: Intake of 1000 IU/day of Vitamin D, half the safe upper intake established by the National Academy of Sciences, was associated with 50% lower risk. Serum 25-hydroxyvitamin D of 33ng/ml, which is known to be safe, also was associated with 50% lower risk. Prompt public health action is needed to increase intake of Vitamin D(3) to 1000IU/day, and to raise 25-hydroxyvitamin D by encouraging a modest duration of sunlight exposure. "
Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Harold L, Newmarke, Giovannucci E, Wei M, Holick MF. Vitamin D and the prevention of colorectal cancer. The Journal of Steroid Biochemistry and Molecular Biology, Volume 97, Issues 1-2, October 2005, Pages 179-194.
Press Release October 2005, University of California, San Diego