Narrator:        This is Science Today. A study looking into the relationship between vitamin D levels in the blood and the risk of breast and colon cancer across the globe has estimated that 600,000 cases of these cancers could be prevented each year by adequate intake of vitamin D. Cedric Garland, a cancer prevention specialist at the Moores Cancer Center at the University of California, San Diego, recommends levels that correspond to 2000 International Units per day. And you won't get this level of vitamin D just drinking milk ...

Garland:         You'd need to drink twenty glasses of milk to prevent half of colorectal cancer and fifty glasses of milk a day to prevent half the incidence of breast cancer.

Narrator:        Garland says the wisest choice is to get some vitamin D through dietary sources, such as milk, but also take supplements. And for those not at risk for skin cancer, to get a few minutes of sun per day with at least 40 percent of the skin exposed because the UV rays from the sun trigger vitamin D synthesis in the skin. For Science Today, I'm Larissa Branin.