Vitamin D

Definition: Vitamin D is a fat-soluble vitamin. It's not found in many foods unless they have been fortified. Normally, your body makes vitamin D when your skin is exposed to sunlight.

Vitamin D is required by your body to absorb and utilize calcium, which keeps your bones and teeth strong. A deficiency of vitamin D leads to weakened bones and rickets in children and osteomalacia in adults.

Although sunlight exposure is the main source of vitamin D, the Institute of Medicine has set a daily requirement for dietary vitamin D.

Daily Requirements

• Up to age 70: 600 International Units (IUs) per day
• Ages 71 and older: 800 IUs per day

Research studies indicate that having insufficient levels of vitamin D may be correlated with an increased risk of cancer, multiple sclerosis, diabetes and high blood pressure.

Vitamin D is found naturally in just a few foods such as oily fish, however milk and breakfast cereals are usually fortified with vitamin D. Vitamin D supplementation may be beneficial for many people, especially during the winter or if you avoid sun exposure. Vitamin D supplementation is often recommended for people who take calcium supplements to prevent osteoporosis.

There are two types of vitamin D supplements, either D₂, which is also called ergocalciferol or D₃, cholecalciferol. Both forms will raise your body's stores of vitamin D, however, cholecalciferol is becoming the preferred form for vitamin D supplements.

Taking vitamin D supplements in large doses for extended periods of time may result in vitamin D toxicity, so the Institute of Medicine determined tolerable upper levels to be:

• Ages 1-3: 2500 IUs per day
• Ages 4-8: 3000 IUs per day
• Ages 9 and above: 4,000 IUs per day

Vitamin D toxicity does not occur from the vitamin D that your body makes when your skin is exposed to the sun.

Also Known As: Cholecalciferol, ergocalciferol

_Sources:

_{"Dietary Supplement Fact Sheet: Vitamin D." NIH. Updated 08/2007.}

_{Otten JJ, Hellwig JP, Meyers LD. "Dietary Reference Intakes: The Essential Guide to Nutrient Requirements." IOM, 2006.}