Study: Add Vitamin D To Lower The Risk Of Cancer

Study after study has suggested that vitamin D can lower cancer risk, complemented by lab experiments showing that the “sunshine vitamin” can help prevent cancer cells from growing and spreading. Now, in a report published in Nutrition Reviews, researchers estimate that thousands of incidences of breast and colon cancers might be averted if people in colder climates raised their vitamin D levels.

Much of the previous research regarding the effect of vitamin D on cancer risk evaluates the rate of cancer diagnosis at different latitudes of the globe—for example, the rates of breast, colon and ovarian cancer are lower in sunnier regions of the world than in Northern climates where cold winters limit sun exposure.

For the Nutrition Reviews report, published in the August issue, researchers at the University of California delved more deeply into the comparison of cancer rates between climates. Using data on average wintertime blood levels of vitamin D and rates of breast and colon cancers in 15 countries, the researchers found that rates of the diseases tended to fall as average vitamin D levels climbed.

The protective effect against colon cancer seemed to begin when blood levels of vitamin D reached 22 nanograms per milliliter (ng/mL); for breast cancer, that number was 32 ng/mL.

Currently, the average late-winter vitamin D level among Americans is 15-18 ng/mL; based on their data, the researchers predict that 60,000 cases of colon cancer and 85,000 cases of breast cancer could be prevented every year if Americans were able to maintain a vitamin D level of at least 55ng/mL. Worldwide, those figures could be 250,000 and 350,000, respectively.

"This could be best achieved with a combination of diet, supplements and short intervals—10 or 15 minutes a day—in the sun," says lead study author Cedric F. Garland, M.D., a cancer prevention specialist at the University of California San Diego.

He adds that spending a matter of minutes in the midday sun, with 40 percent of the skin exposed, should be enough; for fair-skinned people, just three minutes in the sun can be adequate, while darker-skinned people may need about 15 minutes.

Garland and his colleagues also recommend that, in addition to modest sun exposure, adults get 2,000 IU of vitamin D per day—which is the current upper intake level set by U.S. health officials.

Vitamin D is produced naturally by the body following exposure to sunlight and also can be ingested through fortified products like milk, soy milk and cereal grains or found in wild salmon, Atlantic mackerel, sardines and shrimp.