Most Americans Deficient in Vitamin D

Doctors advise U.S. Institutes of Medicine to raise vitamin D requirements

Critically ill patients, premenopausal women and most Americans are deficient in or need more vitamin D, and doctors want the U.S. to raise its recommendation, in four new studies.

A small study of critically ill patients led doctors to ask if low vitamin D levels cause, contribute to, or are an effect of major illness. Researchers found that nearly half of 42 people hospitalized in intensive care (ICU) were deficient in vitamin D, and the sicker they were, the lower their vitamin D levels. Three who died had the lowest vitamin D levels.

Study author, Dr. Paul Lee, believes body tissues demand more vitamin D during illness. “Vitamin D appears to have roles in controlling sugar, calcium, heart function, gut integrity, immunity, and defense against infection. (Because) patients in ICU suffer from different degrees of inflammation, infection, heart dysfunction, diarrhea and metabolic dysregulation, vitamin D deficiency may play a role in each of these common ICU conditions.”

In a vitamin D study, about 90 premenopausal women living in Maine, average age 22, took a placebo in the spring and summer, then half the group continued on placebo while the other half took 800 IU of vitamin D per day during fall and winter. Vitamin D in the placebo group remained low, but 80 percent of women in the vitamin D group had adequate vitamin D levels.

A study of more than 32,000 U.S. adults found that those with adequate levels of vitamin D fell by nearly half, to 23 percent from 45 percent, over the 16-year period from 1988 to 2004. During this time, researchers say people started spending less time outdoors and eating less healthy foods.

In a related U.S. study, scientists estimate that of the 83 million of those under age 21, 7.6 million are deficient in vitamin D (9 percent) and 51 million have low levels (61 percent). Doctors advising the U.S. Institutes of Medicine say that low vitamin D increases chances for heart disease and diabetes and want the agency to raise vitamin D requirements.

Reference: New England Journal of Medicine; April 30, 2009, Vol. 360, No. 18, 1912-4.