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Are You Getting Enough Vitamin D?

Most people know that being exposed to the sun's rays can be harmful (it can increase the risk of skin cancer), but they may not know there's a risk of too little sun.

Sun exposure is actually beneficial when obtained in small doses-such as 15 minutes or less several times a week. The sun's ultraviolet rays actually trigger vitamin D synthesis in the skin. Vitamin D is important because it helps us absorb calcium from the digestive system for our bones.

The days are getting shorter as winter approaches, and people are less exposed to the sun. Even if they are getting sun exposure, the winter sun is too weak to be beneficial.

A vitamin D deficiency prevents new bone tissue from hardening, a condition known as rickets in children and osteomalacia in adults. It can also result in bone loss and causes muscle weakness, which creates an increased tendency to fall.

Research studies have also found that insufficient levels of vitamin D may also contribute to developing different types of cancer such as breast, colon and prostate cancer, as well as heart disease and diabetes.

Here's what you need to know about vitamin D:

Older adults-The skin of adults aged 50 and older does not synthesize vitamin D efficiently and the kidney is less able to convert vitamin D to its active hormone form.

People with darker skin color-The melanin content is higher in people with darker skin, which reduces the skin's ability to produce vitamin D from sunlight.

People with fat malabsorption-Because vitamin D is a fat-soluble vitamin, people with a reduced ability to absorb dietary fat, such as those with Crohn's disease, cystic fibrosis, celiac disease or liver disease, or those who have had part or all of their stomach or intestines removed (as a result of gastric bypass surgery, for example), may not adequately absorb vitamin D.

People with limited sun exposure-Homebound individuals, people living in northern latitudes like New England and Alaska, and those who wear more protective clothing are at risk for vitamin D deficiency.

This article originally appeared in UC Health Line (12/06/05), a service of the NetWellness.org Academic Health Center Public Relations Communications Department and was adapted for use on NetWellness with permission, 2006.

For more information:

Go to the Osteoporosis health topic, where you can:

Last Reviewed: Dec 29, 2008

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Professor of Medicine
Director, Bone Health and Osteoporosis Center
College of Medicine
University of Cincinnati