Vitamin D may reduce colorectal, breast cancer risks

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vitamin DRaising vitamin D levels by taking supplements and absorbing a little bit of sunshine each day may help prevent colorectal and breast cancers, said two studies.

A high blood level of vitamin D could help reduce the risk of breast cancer by half and of colorectal cancer by two-thirds, the studies found.

Vitamin D is a fat soluble vitamin that is found in food and is made in the body because sunlight's UV rays trigger vitamin D synthesis in the skin. US health authorities have not established a recommended daily allowance for the vitamin due to insufficient scientific evidence.

For the breast cancer study, published online in the Journal of Steroid Biochemistry and Molecular Biology, researchers analyzed data from two earlier studies on the response to vitamin D doses among 1,760 people.

"The data were very clear, showing that individuals in the group with the lowest blood levels had the highest rates of breast cancer, and the breast cancer rates dropped as the blood levels of 25-hydroxyvitamin D increased," said study co-author Cedric Garland.

"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," he said.

The colorectal cancer research, published online in the American Journal of Preventive Medicine, analyzed five studies on 1,448 individuals that explored the association of blood levels of vitamin D with colon cancer risk.

The incidence rate of colorectal cancer could be reduced by half with a serum level 34 nanograms per milliliter (ng/ml), the study found.

"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," said study co-author Edward Gorham.

The researchers highlighted the importance of limiting sun exposure to avoid skin cancer risks.

They said a fair-skinned white person could get an adequate dose of vitamin D by spending 10 to 15 minutes in the noontime sun on a clear day with 50 percent of skin area exposed to the sun, while darker skinned people may need to stay as long as 25 minutes under the sun to achieve a similar benefit.

The two studies were conducted by a core team of cancer prevention specialists at the Moores Cancer Center at University of California, San Diego (UCSD), and other colleagues.

Copyright © 2007 Agence France Presse

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