Vitamin D cuts cancer risk in study of U.S. women

By Will DunhamFri Jun 8, 2:16 PM ET
Large doses of vitamin D may reduce the risk of cancer, according to a four-year U.S. study published on Friday involving nearly 1,200 women over the age of 55 in rural Nebraska.
Women who took calcium and a dose of vitamin D almost three times the U.S. government's recommended daily intake for middle-aged adults saw a 60 percent lower incidence of all cancers than women not taking the vitamin, the study found.
The study, conducted by researchers at the Creighton University School of Medicine in Omaha, Nebraska, was published in the American Journal of Clinical Nutrition.
Joan Lappe, a Creighton professor of medicine who led the study, said vitamin D may be an effective way to guard against cancer but many people worldwide do not get enough of it.
"I'm really very excited because I think the vitamin D deficiency issue is a major health concern that we need to address, and perhaps this will bring it to the forefront," Lappe said in a telephone interview.
Lappe said additional research is needed to figure out whether the protective effect seen in the older white women also applied to men, younger women and other ethnic groups.
The American Cancer Society reacted cautiously, calling it a small study. Only 50 of the 1,179 women developed cancer, making broad conclusions difficult, said Dr. Michael Thun, who heads epidemiological research for the society.
Thun said another weakness was that the researchers initially did not set out to examine the effect of vitamin D on cancer, but on bone health in post-menopausal women.
"The results are provocative" but not sufficient for the society to recommend people take vitamin D supplements to ward off cancer, Thun said in a telephone interview.
A number of studies have found protective properties from higher intake of vitamin D for cancers and other ailments. For example, other researchers in December found people with higher levels of vitamin D had a lower risk of multiple sclerosis.
SUNLIGHT EXPOSURE
The body makes the vitamin after being exposed to sunlight. Not many foods are naturally rich in it. It is found in fatty fish such as salmon and milk commonly is fortified with it.
Vitamin D promotes absorption of calcium necessary for healthy teeth and bones. It is also important to nerve cells, including the brain, and seems to act as a regulator of the immune system.
The women in the study were from a nine-county area of rural eastern Nebraska and had no known cancers for at least a decade before it began in 2000.
They were broken into three groups, either getting 1,400 to 1,500 mg of a calcium supplement daily, getting that calcium plus 1,100 IU (international units) of vitamin D3, or getting placebos.
After four years, 20 women in the placebo group got cancer, 17 in the calcium-only group got cancer and 13 in the vitamin D3 and calcium group got cancer.
Figuring some women may have entered the study with undiagnosed cancer, the researchers excluded the results in the first year and assessed only the final three. The findings became even more powerful, with the women getting calcium and vitamin D3 experiencing a 77 percent lower cancer risk.
The researchers found no statistically significant difference in cancer risk for the groups getting calcium alone or placebos.
(Additional reporting by Natasha Elkington)