Vitamin D aids in the absorption of calcium and helps build and grow strong bones. According to a study cited by "Scientific American," more than 75 percent of Americans are deficient in the sunshine vitamin and are at risk of a variety of different health conditions, from heart disease to diabetes and certain cancers. There are three ways to get vitamin D, direct sunlight on the skin, diet and supplements. Certain factors can prevent proper absorption.
Sunscreen
The best way to get vitamin D, according to Michael Holick, M.D., from Boston University Medical School's vitamin D skin and bone research laboratory is by exposing your skin to direct sunlight 15 minutes a day, three days a week. It's important to forgo sun block during this time. A sunscreen with SPF 15 can block the absorption of vitamin D by 99 percent, says Holick.
Medication Interaction
Certain medications interfere with the absorption of vitamin D. Taking corticosteroids can prevent the body from metabolizing vitamin D. Corticosteroid are used for the treatment of inflammation. Weight loss and cholesterol reducing drugs can also interfere with absorption of the vitamin.
Dietary Fat Malabsorption
As a fat-soluble vitamin, individuals need dietary fat in the stomach for absorption. Syndromes responsible for nutrient malabsorption include cystic fibrosis and Crohn's disease, which interferes with vitamin D absorption. MayoClinic.com explains that people with irritable bowel syndromes are at risk for vitamin D deficiency due to the inability to metabolize fat correctly.
Obesity
People who are obese may have trouble absorbing vitamin D from the sun. A body mass index of 30 or more, considered obese and morbidly obese, may qualify a person for needing more than the supplemental vitamin D to prevent deficiency. People who are obese do not have trouble synthesizing the vitamin through direct sunlight on the skin, but rather, the subcutaneous fat under the surface of the skin alters how the vitamin is released into circulating blood. Gastric bypass patients are also at risk for vitamin D deficiency because of changes in vitamin D absorption, according to research in the February 2008 "Obesity Surgery."
References
- "The New England Journal of Medicine"; Vitamin D Deficiency; Michael Holick, M.D.; July 2007
- Scientific American; Vitamin D Deficiency Soars in the U.S., Study Says; March 2009
- Office of Dietary Supplements: Vitamin D
- MayoClinic.com: Vitamin D
- "Obesity Surgery"; Vitamin D and the Bariatric Surgical Patient; C.W. Compher, et al.; February 2008
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