You need vitamin D for strong bones and teeth, but too much vitamin D from large doses of dietary supplements can build up and become toxic. Your body stores excess vitamin D in your fat cells. Speak with your doctor before taking large amounts of vitamin D supplements.
Vitamin D Functions
Vitamin D acts as hormone that stimulates your small intestine to absorb calcium from the foods you eat. Calcium is needed for the structural components of bones and teeth. Vitamin D also stimulates absorption of phosphate and magnesium, which are also involved in bone metabolism. It also regulates cell growth and is needed for nerve, muscle and immune system function. Vitamin D also has anti-inflammatory properties.
Dietary Reference Intakes
The Institutes of Medicine set the dietary reference intakes based on age. Males and females both need 600 international units of vitamin D every day until the age of 70, when the recommendation goes up to 800 IU per day. A vitamin D deficiency may lead to osteopenia in adults or rickets in children. Both diseases result in weakened bones, which can cause deformities in children and bone pain and muscle weakness in adults.
Sources of Vitamin D
Your body makes vitamin D when your skin is exposed to ultraviolet light. The time of year, time of day, use of sun screen, cloud cover and smog can affect the amount of exposure you receive from the sun. Only small amounts of vitamin D come from foods such as oily fish, beef liver, cheese and egg yolks. Vitamin D is also available as a dietary supplement and is often combined with calcium.
Precautions
Vitamin D can become toxic if you take large doses of dietary supplements for long periods of time. Symptoms include loss of appetite, weight loss and irregular heartbeat. Too much vitamin D can also increase the levels of calcium in your blood, which can eventually lead to heart, blood vessel and kidney damage. Excess sun exposure will not cause vitamin D toxicity, but you should avoid excess sun exposure because it may increase your risk for skin cancer.
References
- Office of Dietary Supplements; Dietary Supplement Fact Sheet: Vitamin D; June 2011
- Colorado State University; Vitamin D; R. Bowen; April 2010
- New York State Department of Health; Vitamin D and Healthy Bones; February 2004
- Institute of Medicine; DRIs for Calcium and Vitamin D; November 2010
- Centers for Disease Control and Prevention; Fat-Soluble Vitamins & Micronutrients: Vitamin D; July 2008
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