En español | A report from the Institute of Medicine setting new guidelines for vitamin D and calcium increases the recommended level of D but actually maintains the same or decreases the recommended levels for calcium.
Most Americans and Canadians, the report states, are getting enough vitamin D and calcium, although older men and women may fall short.
The long-awaited 2010 recommendations update those set in 1997. (See box at right.)
The report also notes that taking more than 4,000 IU of vitamin D daily (up from 2,000 IU) or 2,000 mg of calcium daily (down from 2,500 mg) increases the risk for harm.
In the years since the first report was published, studies have linked these two nutrients, both individually and combined, to a surprisingly wide range of health benefits, including lower blood pressure, reduced risk of bone fracture and decreased risk of breast cancer, as well as protection against heart disease, Parkinson's disease and type 2 diabetes.
As a result, scientists have called for high levels of vitamin D from supplements, anywhere from 1,000 to 2,000 IU a day, in addition to sun exposure, fortified foods and mutivitamins.
Although the report confirms the role of calcium and vitamin D for bone health, it points out that studies of vitamin D for other health problems have yielded conflicting and mixed results.
Very high levels of vitamin D (above 10,000 IU a day) may cause kidney and tissue damage. Evidence of possible risks at lower levels is limited, but some studies offer tentative signals about adverse health effects. The report also notes that standards for vitamin D blood test results have not been based on rigorous studies and could lead to doctors diagnosing vitamin D deficiency when people have enough.