Vitamin D and prevention of colorectal cancer

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 33 ng/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 D3 to 1000 IU/day, and to raise 25-hydroxyvitamin D by encouraging a modest duration of sunlight exposure.