Vitamin D is a fat-soluble vitamin your body stores for use as needed. Exposure to sunlight triggers vitamin D production in your body; however, this vitamin is also available from stand-alone supplements, multivitamin supplements and food sources. Inadequate reserves of this vitamin may contribute to health problems.
Vitamin D levels of 20 to 50 nanograms per milliliter of blood are typically considered normal, according to the University of Washington. Levels between 8 and 20 ng/mL are considered insufficient, and levels below 8 ng/mL are considered deficient.
Recommended Daily Intake
The recommended daily intake of vitamin D for adults and children over 1 year of age, including breastfeeding and pregnant women, is 15 mcg, according to the Linus Pauling Institute at Oregon State University. Adults over the age of 70 should consume 20 mcg of vitamin D, and infants should consume 10 mcg of this vitamin daily.
Food Sources
Several foods common in the United States can help you meet your intake requirements of vitamin D. These include eggs, salmon, herring, mackerel, sardines and tuna. Cereals and dairy products such as milk, cheese and yogurt are sometimes fortified with vitamin D. Check product labels carefully -- not all dairy products and cereals contain this vitamin. Cod liver oil is also an abundant source of vitamin D; however, it is also high in vitamin A, which can be toxic to your body, according to the University of Maryland Medical Center.
Benefits and Functions
Vitamin D aids in the absorption of calcium through intestinal walls and the reabsorption of calcium that your kidneys filter from your bloodstream. Improving the absorption and retention of calcium in your body may aid in the maintenance of strong bones and teeth. Vitamin D may also improve immune system function, helping your body ward off bacterial, viral and fungal infections. It may also help regulate blood pressure and decrease your risk of hypertension.
Considerations
A deficiency of vitamin D may cause your body to draw calcium from your bones to maintain normal calcium levels, which can increase your risk of osteoporosis. Severe deficiency in children and adolescents may contribute to rickets, a condition characterized by bone deformities. Vitamin D deficiency may also decrease insulin production and glucose tolerance in diabetics, which may increase hyperglycemic symptoms and complications such as fainting, fatigue, coma and death.
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