SAN DIEGO -- A study by University of California, San Diego scientists shows that an adequate amount of vitamin D could prevent as many as 600,000 annual cases of breast and colorectal cancer worldwide.

In the study made public Wednesday, Dr. Cedric F. Garland, a cancer prevention specialist at UCSD's Moores Cancer Center, estimated that 250,000 cases of colorectal and 350,000 cases of breast cancer could be prevented globally by increasing intake of vitamin D, particularly in countries north of the equator.

Vitamin D is available through diet, supplements and skin exposure to sunlight.

"The message is, depending on where you live, you may need to consider taking in considerably higher levels of vitamin D than those currently recommended," Garland said.

Researchers recommended the intake of 2,000 international units per day of vitamin D for a reduction in colorectal cancer, and the same amount to help prevent breast cancer, plus moderate sun exposure.

"This could be best achieved with a combination of diet, supplements and short intervals -- 10 to 15 minutes a day -- in the sun," Garland said.

The study's authors encouraged people to speak with their doctors to get an appropriate dosage recommendation.

The study, which will be published in this month's edition of the journal Nutrition Reviews, combined data from surveys of vitamin D levels during the winter from 15 countries.

It was authored by Garland, Dr. Sharif B. Mohr, Dr. Edward D. Gorham and Frank C. Garland of UCSD's Moores Cancer Center and William B. Grant of the Sunlight, Nutrition and Health Research Center in San Francisco.