Does vitamin D lower cancer risk?

　　There is a growing body of evidence from studies that observie large groups of people (not yet tested in clinical trials) that vitamin D may have helpful effects on some types of cancer, including cancers of the colon, prostate, and breast. Vitamin D is obtained through skin exposure to ultraviolet (UV) radiation and through diet, particularly products fortified with vitamin D such as milk and cereals, and supplements. But many Americans do not get enough vitamin D.

　　The current national recommended levels of intake of vitamin D (200 to 600 IU per day) may not be enough to meet needs, especially among those with little sun exposure, the elderly, people with dark skin, and breastfed babies who only take in breast milk. More research is needed to define the best levels of intake and blood levels of vitamin D for cancer risk reduction, but recommended intake is likely to fall between 200 and 2,000 IU, depending on age and other factors. To reduce the health risks linked with UV radiation exposure while getting the most potential benefit from vitamin D, a balanced diet, supplementation, and limiting sun exposure to small amounts are the preferred methods of obtaining vitamin D.