Study Shows 24% of People in U.S. Are at Risk for Inadequate Blood Levels of Vitamin D
By Denise Mann
WebMD Health News
Reviewed by Laura J. Martin, MD
March 30, 2011-- Two-thirds of Americans are getting enough vitamin D, according to a new analysis by researchers from the National Center for Health Statistics.
Vitamin D is often called the "sunshine vitamin" because our bodies make it when exposed to sunlight. It is found in some fatty fish such as salmon and tuna, and in cheese and eggs. It is often added to milk.
In recent years, vitamin D deficiency has been linked to a host of diseases and conditions, including brittle bones, heart disease, diabetes, certain cancers, and autoimmune diseases.
The analysis shows that from 2001 to 2006, 67% of Americans age 1 or older had blood levels of vitamin D that fell between 50 to 125 nanomoles per liter, which is considered adequate. Another 24% were at risk for inadequate levels of vitamin D, with blood levels of 30 to 49 nmol/L; 8% were at risk of deficiency, which is defined as less than 30 nmol/L. Just 1% of the population has blood levels that were too high.
In November 2010, an Institute of Medicine (IOM) panel called for a modest increase in vitamin D, raising the recommended daily intake to 600 international units (IU) for everyone aged 1-70 and to 800 IU for adults older than 70 to improve bone health
In the study, those who were at the lowest risk for vitamin D deficiency or inadequacy were children, males, non-Hispanic whites, and women who were pregnant or breastfeeding. The risk of deficiency was lowest in children ages 1 to 8 and increased with age until about age 30, the study showed.
The analysis was based on data from the National Health and Nutrition Examination Surveys that includes about 5,000 Americans each year.
Assessing Risk of Low Vitamin D
"Risk of inadequacy doesn't mean everyone in this range is inadequate; just that the probability starts to rise," says Catharine Ross, PhD, professor and Dorothy Foehr Huck Chair of the department of nutritional sciences at Pennsylvania State University, in an email. Ross was the chair of the IOM panel that issued the recent recommendations.
"All in all, the [new analysis] is expected and consistent with the IOM report," she says. "The report showed that many people maintain excellent health in this range."
But "there are still segments of the population that are at higher risk of vitamin D deficiency," says Michal L. Melamed, MD, an assistant professor of medicine and epidemiology and population health at Albert Einstein College of Medicine.
"For these individuals, taking a supplement or spending a little bit of time in the sun probably is not harmful unless they have a family or personal history of melanoma," she says. "There are a number of health benefits to adequate vitamin D, most notably on bones. But other studies suggest it can reduce risk for cancer, cardiovascular disease, and high blood pressure."
The new data showed that the prevalence of those at risk for vitamin D deficiency or inadequacy did not change between 2001 and 2006. "It is reassuring that there wasn't an increase in recent years," Melamed says. "The problem is not getting worse, but there is definitely a difference compared with 20 years ago."
Catharine Ross, PhD, professor, Dorothy Foehr Huck Chair, department of nutritional sciences, Pennsylvania State University.
Michal L. Melamed, MD, assistant professor, medicine and epidemiology and population health, Albert Einstein College of Medicine.
Loker, A.C. NCHS Data Brief, March 2011.
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