Americans at risk of vitamin D deficiency

An increasing number of Americans have insufficient levels of vitamin D, a new report has concluded.

Scientists from the University of Colorado compared levels of vitamin D in data collected for the Third National Health and Nutrition Examination Survey between 1988 and 1994 to those collected during a 2001-2004 survey and found the average blood levels of the vitamin appear to have decreased during that time.

The decline was particularly striking among African-Americans, only 3 percent of whom were found to have the recommended levels in 2004.

In addition to poor diet, the researchers believe, a decline in outdoor physical activity and improved campaigns to reduce sun exposure may have contributed to this phenomenon.

They also believe the recommended doses – 200 international units per day from birth to age 50, 400 IUD from age 51 to 70 and 600 IUD for adults age 71 and older – may be insufficient to address the deficit.

"Increased intake of vitamin D (1,000 IUD or more), particularly during the winter months and at higher latitudes, would improve vitamin D status and likely improve the overall health of the U.S. population," they wrote in the March 23 issue of Archives of Internal Medicine .

Clinicians believe that insufficient levels of vitamin D are not only associated with rickets and other bone problems in children, but have also been linked to disorders such as heart disease and cancer in adults.