(RxWiki News) Adults need around 4,000 to 8,000 IU daily of vitamin D to maintain levels of healthful vitamin D metabolites in the range needed to reduce the risk of several diseases by about half.
Vitamin D helps combat breast cancer, colon cancer, multiple sclerosis and type 1 diabetes, according to co-author Dr. Cedric Garland, a professor of family and preventive medicine at the University of California at San Diego.
Only 400 IUs of vitamin D were required to vanish rickets in the 20th century, Garland said. Current guidelines call for 600 IUs per day. A National Academy of Sciences Institute of Medicine (IOM) committee announced that 4,000 IU a day of vitamin D appears safe for adults and children 9 and older. Garland called this amount "comfortably under" the 10,000 IU/day the IOM Committee Report considers as the lower limit of risk.
For the study, several thousand people who were asked to take vitamin D supplements ranging from 1,000 to 10,000 IU per day underwent blood tests to determine the levels of vitamin D metabolites circulating in their blood.
Only about 10 percent of the U.S. population has appropriate levels of vitamin D, which is produced in the skin from direct sunlight exposure, according to some studies. The vitamin is also found in fortified foods and milk, and in supplemental form.