In the news: Report sets new dietary intake levels for vitamin D and calcium

In recent years, many studies have suggested that we take much more vitamin D than we do now — especially those of us living in northern climes who may get too little sunlight to produce adequate amounts in the skin. Many scientists have advocated vitamin D doses of 1,000 to 2,000 international units (IU) a day — much higher than the present recommended dose — to prevent a host of chronic conditions. But the report of an expert panel convened by the Institute of Medicine (IOM) concluded in November 2010 that high doses of vitamin D aren't necessary and might even be harmful. Many people — including many clinicians and researchers — were taken by surprise.

To reach its decision, the panel evaluated data correlating bone disease with blood levels of 25-hydroxyvitamin D (25OHD), which is made from food and supplements and, in the skin, in response to sunlight. They determined that a blood level of 20 nanograms per milliliter (ng/ml) was adequate to prevent bone disease in at least 97.5% of the population. Citing a lack of standardized lab methods and reporting, the panel also cast doubt on the widespread practice of vitamin D testing. Many labs currently specify 30 to 70 ng/ml as the normal range; that would make most of the North American population vitamin D deficient.