Vitamin D important for bone health but other benefits unproven

Vitamin D’s role in maintaining good health has been a frequent topic of discussion lately. Is it really the super supplement it’s often made out to be?

“Some health advisors and commercial product promoters are making claims and statements that may be hard for vitamin D to live up to,” says Susan Nitzke, a nutrition specialist with the University of Wisconsin-Extension.

Some recent studies show that vitamin D may have benefits far beyond its well-known role of working with calcium and other nutrients to strengthen bones and teeth. “The media has been quick to report the studies that show marvelous benefits for vitamin D,” says Nitzke. “But studies that fail to show such benefits tend to go unnoticed.”

The Institute of Medicine, a group that sets national nutrient standards, has reviewed vitamin D research and revised its official Recommended Dietary Allowances (RDAs) for vitamin D. The new RDAs are somewhat higher than the previous values for some age groups, but not as high as many experts had predicted. The new RDAs state that North Americans should aim for an intake of 600 International Units (IUs) of vitamin D per day. People age 71 and older may need more–as much as 800 IUs per day.

The Institute of Medicine’s new RDA report also states that many people are over-supplementing with vitamin D. “If you routinely use supplements with more than 4,000 IUs per day, there are potential risks,” says Nitzke, who agrees with the Institute of Medicine’s recommendation that most people can meet their needs for vitamin D by eating foods with vitamin D. Examples are fortified milk and milk products, fortified cereals, salmon and other fatty fish.

Limited amounts of vitamin D can be produced within the body. In Wisconsin, and other states where exposure to sunlight is limited in winter months, the production of vitamin D within the body is reduced. Vitamin D’s formation in response to sun exposure is also reduced among older adults and African Americans and others with darkly pigmented skin.

“The best way to know if you are getting enough vitamin D is to ask your doctor for a blood test,” says Nitzke. “But unfortunately there is disagreement about what those blood levels should be.” The Institute of Medicine says 20 nanograms per milliliter of blood is enough to promote good bone health for practically all individuals.

A podcast featuring Susan Nitzke answering questions on the latest findings related to vitamin D is available at http://fyi.uwex.edu/news/2010/12/21/new-daily-vitamin-d-recommendations/

More information on health and nutrition is available from the 2010 Dietary Guidelines for Americans (http://www.health.gov/dietaryguidelines) or your county Extension office. Contact information is available at http://yourcountyextensionoffice.org

The Institute of Medicine’s report on Vitamin D is available online: http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D.aspx

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