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Got (Enough) Vitamin D?

Posted by Justice Wright, USDA Research, Education, and Economics mission area in Research and Science
Apr 18, 2012

This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from USDA’s rich science and research portfolio.

April, the springboard to warm, sunny weather, is National Minority Health Month—a good time to focus on the sun, vitamin D insufficiency for African-Americans, and the ways that monitoring its intake have improved.

Vitamin D is primarily produced by exposure to the sun’s ultraviolet rays. However, African-Americans have more melanin in their skin, resulting in the reduction of the body’s ability to make the vitamin from sun exposure.

Researchers at the Agricultural Research Service (ARS) Western Human Nutrition Center at the University of California-Davis have a preliminary model that predicts an individual requirement of vitamin D based on diet, sun exposure and skin tone. Research physiologist Charles B. Stephensen and his colleagues studied the levels of sun exposure from volunteers of African-American or European ancestry.  The data suggests that those with low levels of sun exposure needed additional vitamin D to reach a target blood level of 50 nanomoles of vitamin D per liter of plasma.

Vitamin D is primarily produced by exposure to the sun’s ultraviolet rays
Vitamin D is primarily produced by exposure to the sun’s ultraviolet rays

The current recommended daily allowance of vitamin D for U.S. children and adults (1 – 70 yr of age) is 600 international units.

In order to consume more of the vitamin, known to reduce the risk of cancer, heart disease, diabetes, and other health conditions to which African-Americans already have a higher predisposition, diets must be rich in foods containing vitamin D. It’s important to read the nutritional labels on sources of vitamin D such as milk and fruit juices to determine the amount supplied. Now, USDA researchers at the Beltsville Human Nutrition Research Center (BHNRC) in Beltsville, Md., have developed better ways to analyze this critical nutrient in food and supplements. The Beltsville center is part of the ARS, USDA’S principal intramural scientific research agency.

Recently featured in the March 2012 issue of Agricultural Research, BHNRC chemist Craig Byrdwell has pioneered new, highly precise techniques in using multiple instruments that measure molecules in parallel. This method provides much more information about food samples than single instruments used alone. There are very few foods in nature that contain vitamin D, but this new science-based vitamin D analysis from ARS will advance the analytical values of foods and supplements that were previously unavailable.

Read more about the ARS national program for human nutrition monitoring in Agricultural Research magazine's March 2012 issue.

Category/Topic: Research and Science