MONDAY, Feb. 12, 2007 (HealthDay News) -- Certain amounts of vitamin D may be able to prevent up to half of breast cancer cases and two-thirds of colorectal cancer cases in the United States, according to two studies by researchers at the Moores Cancer Center at the University of California, San Diego, and colleagues at other centers.
In one study, the researchers reviewed two previous studies of 1,760 women and found that those with the highest blood levels of 25-hydroxyvitamin D, or 25(OH)D, had the lowest risk of breast cancer.
"The data were very clear, showing that individuals in the group with the lowest blood levels (less than 13 nanograms of 25(OH)D per milliliter) had the highest rates of breast cancer, and the breast cancer rates dropped as the blood levels of 25-hydroxyvitamin D increased," study co-author Cedric Garland said in a prepared statement.
"The serum level associated with a 50 percent reduction in risk could be maintained by taking 2,000 international units of vitamin D3 daily, plus, when the weather permits, spending 10 to 15 minutes a day in the sun," Garland said.
The study appears online in the current issue of the Journal of Steroid Biochemistry and Molecular Biology.
In the second study, researchers reviewed data from 1,448 people who took part in five previous colorectal cancer studies.
"Through this meta-analysis, we found that raising the serum level of 25-hydroxyvitamin D to 34 ng/ml would reduce the incidence rates of colorectal cancer by half," study co-author Edward G. Gorham said in a prepared statement.
"We project a two-thirds reduction in incidence with serum levels of 46ng/ml, which corresponds to a daily intake of 2,000 IU of vitamin D3. This would be best achieved with a combination of diet, supplements and 10 to 15 minutes per day in the sun," Gorham said.
The study was published online Feb. 6 in the American Journal of Preventive Medicine.
The U.S. National Cancer Institute has more about cancer prevention.