Americans Low on Vitamin D

Study Shows Rise in Number of Americans With Low Vitamin D Levels

From the WebMD Archives

March 25, 2009 -- Low vitamin D levels among adults are fast becoming a growing epidemic and could spell trouble for the future health of the nation, according to a new study.

Researchers found that not only has the number of Americans with low vitamin D levels increased, but average vitamin D levels among adults have also decreased from 1994 to 2004.

Vitamin D is produced by the skin in response to sunlight and is also found in vitamin D fortified foods, such as milk.

Low vitamin D levels are already known to cause rickets in children and weaken bones in adults. Recent studies also have linked low vitamin D levels with cancer, heart disease, infection, and other health problems.

Researchers say the results suggest that current recommendations for vitamin D supplementation may not be high enough to address the increasing health problem of low vitamin D levels.

The Institute of Medicine currently recommends vitamin D supplementation at the following levels:

• 200 international units (IU) per day from birth to 50 years of age

• 400 IU per day for adults aged 51 to 70

• 600 IU per day for adults 71 and older.

Too Little Vitamin D

In the study, researchers compared vitamin D levels in blood samples from participants of the 1988-1994 and 2001-2004 National Health and Nutrition Examination Survey.

They found the average vitamin D level dropped from 30 nanograms per milliliter to 24 nanograms per milliliter from 1994 to 2004. In addition, the percentage of people with vitamin D deficiency (below 10 nanograms per milliliter) increased from 2% to 6%; fewer people had healthy vitamin D levels of 30 nanograms per milliliter or higher (45% vs. 23%) during the study period. The increase in prevalence of vitamin D deficiency was especially striking in non-Hispanic black Americans, rising from 9% to 29% in the same 10-year period.

Researchers say vitamin D levels may have dropped as a result of people spending less time outside and avoiding the sun.

"Current recommendations for dosage of vitamin D supplements are inadequate to address this growing epidemic of vitamin D insufficiency," write researcher Adit A. Ginde, MD, MPH, of the University of Colorado Denver School of Medicine and colleagues in the Archives of Internal Medicine. "Increased intake of vitamin D (greater than or equal to 1,000 IU/d) -- particularly during the winter months and at higher latitudes -- and judicious sun exposure would improve vitamin D status and likely improve the overall health of the U.S. population."

WebMD Health News Reviewed by Elizabeth Klodas, MD, FACC on March 25, 2009



Ginde, A. Archives of Internal Medicine, March 23, 2009; vol 169: 626-632.

News release, American Medical Association.


© 2009 WebMD, LLC. All rights reserved.

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