Vitamin D, one of the 13 essential vitamins, facilitates the absorption of calcium making it vital to the growth and development of strong bones. Vitamin D also plays a vital role in immune function and reducing inflammation and may be useful in preventing certain cancers, high blood pressure and autoimmune diseases. Although most people produce adequate levels of vitamin D through exposure to the ultraviolet rays from the sun, some groups of adults may suffer from vitamin D deficiency and require supplements for treatment.
Types
Vitamin D supplements may contain either vitamin D2 or vitamin D3. Plants naturally produce vitamin D2. Synthetic vitamin D2, also known as ergocalciferol, is produced by the ultraviolet irradiation of yeast. The human body produces vitamin D3 when stimulated by the ultraviolet rays of the sun. The D3, known as cholecalciferol, found in dietary supplements comes from the irradiation of the substance 7-dehydrocholesterol in lanolin -- a substance secreted by the glands in sheep.
Adequate Intake
The National Institute of Medicine Food and Nutrition board provides recommendations for the adequate intake of vitamin D. The adequate intake describes the amount of the vitamin needed to meet the needs of the majority of healthy people. The adequate intake, or AI, for adults ages 19 to 50 is 5 mcg. Those ages 51 to 70 require 10 mcg of vitamin D per day while those over 71 need 15 mcg per day.
Deficiency Syndrome
Adults may develop a vitamin D deficiency due to the failure to intake enough vitamin D, a lack of sun exposure or a malabsorption syndrome that interferes with the absorption and use of vitamin D. A vitamin D deficiency causes a medical condition known as osteomalacia. Characterized by weak, soft bones, osteomalacia causes pain, bone fractures and muscle weakness. The treatment for osteomalacia includes taking vitamin D supplements along with calcium and phosphates to strengthen the bones.
At Risk Groups
Certain groups of adults are at higher risk for developing a vitamin D deficiency. Older adults often suffer from a deficiency because their skin cannot produce as much vitamin D even with adequate sun exposure. Adults with dark skin produce more melanin, which inhibits the production of vitamin D. Vitamin D is a fat-soluble vitamin, which means the body absorbs it along with dietary fat. Digestive conditions such as Crohn's disease or cystic fibrosis inhibit the absorption of fats and therefore the absorption of vitamin D. Obese adults require more vitamin D because the fat layers under the skin inhibit the production of vitamin D triggered by the sun. All of these high risk groups benefit from taking vitamin D supplements to avoid a deficiency before it starts.
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