Why Vitamin D is Important for Health

The body needs vitamin D to help it absorb calcium, which is a requisite for healthy bones. Muscles and nerves need vitamin D to function properly, and it helps the immune system fight off disease. Too little can lead to thin, brittle bones; extremely high levels can be toxic.

Vitamin D can be absorbed naturally from sunlight or obtained through foods or dietary supplements.

The National Institute of Medicine defines sufficient vitamin D by the amount registered in the blood: as a serum 25-hydroxyvitamin D value of 50-125 nmol/L. A value of 30-49 nmol/L is defined as inadequacy and less than 30 nmol/L is considered a deficiency.

Vitamin D Deficiency Study

For their report, the researchers analyzed data from 2001 to 2006 from the National Health and Nutrition Examination Survey. It included people aged 1 and older.

The analysis showed that though vitamin D deficiency became more common in the United States between 1988-1994 and 2001-2002, the study found, risk for the deficiency did not change between 2001-02 and 2005-06.

About 4% of males 12 years and older had vitamin D levels that put them at risk for deficiency in 1988-1994, and 17% were at risk for inadequacy. Those numbers had risen to 7% and 22%, respectively, by 2001-2002, according to the study.

Among females 12 and older, vitamin D deficiency rose from 7% in 1988-1994 to 11% in 2001-2002. However, the proportion of females with inadequate levels of vitamin D dropped from 30% to 25% in that time.

The analysis showed that the risk for vitamin D deficiency differed by age, sex and race or ethnicity.

By age, the risk for vitamin D deficiency ranged from 1% to 8% among males and from 1% to 12% among females. For both sexes, the risk for vitamin D deficiency was lowest among children aged 1 to 8 and increased significantly until age 30 in men and age 18 in women. After that, the risk for vitamin D deficiency changed little as people aged, the study found.

Whites were less likely to be at risk for vitamin D deficiency than blacks or Mexican-Americans.

Among women of childbearing age, those who were pregnant or lactating were less likely to be at risk for vitamin D deficiency than those who weren't pregnant or lactating.

SOURCE: U.S. National Center for Health Statistics, news release, March 30, 2011