Vitamin D is found in cells throughout the body and is vital for many other health functions, as well. It participates in the nerve and muscle function, as well as in the function of the immune system and in the reduction of inflammation.
How can I get vitamin D?
The body makes vitamin D when skin is directly exposed to the sun outdoors. During the warmest months, for example, 5 to 30 minutes of exposure between 10 AM and 3 PM several times a week to the face, arms, legs, or back without sunscreen may be enough to produce sufficient vitamin D. However, excessive exposure to the sun increases the risk of skin cancer. When out in the sun, wear protective clothing and apply sunscreen with a sun protection factor of 8 or more. Cloudy days, shade, and having dark-colored skin cut down on the amount of vitamin D the skin makes. People who avoid the sun, who cover their bodies with sunscreen or clothing, or who live in the northern half of the United States during the winter months should include good sources of vitamin D in their diets or take a supplement. Vitamin D is found in supplements in two different forms: D2 (ergocalciferol) and D3 (cholecalciferol). Both increase vitamin D in the blood, but the D3 form may do it better and keep levels raised for a longer time.
Vitamin D in American diets is found mostly in fortified foods:
• Fatty fish such as salmon and tuna, as well as fish liver oils, are among the best sources.
• Beef liver, cheese, egg yolks and some mushrooms provide small amounts.
• Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart. But foods made from milk, like cheese and ice cream, are usually not fortified.
• Vitamin D is added to many breakfast cereals and to some brands of orange juice, yogurt, margarine, and soy beverages. Check the labels for more information.
Am I getting enough vitamin D?
The amount of vitamin D required depends on your age. Average daily recommended amounts for different ages are listed below in International Units (IU):
Children and most adults 200 IU
Adults 51–70 years 400 IU
Adults 71 years and older 600 IU
Pregnant and lactating women 200 IU
Measuring blood levels of 25-hydroxyvitamin D is the best test to check the levels of vitamin D in the body. In general, levels below 15 nanograms per milliliter (ng/mL) are inadequate, and levels above 200 ng/mL are too high. Some nutrition experts think a blood level of at least 30 ng/mL is best for overall good health. By these measures, some Americans are vitamin D deficient and almost no one has levels that are too high.
What precautions do I need to take with vitamin D?
When amounts of vitamin D in the blood become too high, it can lead to toxicity--
nausea, vomiting, poor appetite, constipation, weakness and weight loss. In addition, by raising blood levels of calcium, too much vitamin D can cause confusion, disorientation and problems with heart rhythm. Excess vitamin D can also damage the kidneys. The safe upper limit for vitamin D is 1,000 IU/day for infants and 2,000 IU for children and adults. Vitamin D toxicity almost always occurs from overuse of supplements. Excessive sun exposure doesn't cause vitamin D poisoning because the body limits the amount of this vitamin it produces. Like most dietary supplements, vitamin D may interact or interfere with other medicines or supplements. Tell your health care providers about any dietary supplements and medicines you take.
Source: Copied from JACA Healthy Living Fact Sheet May/June 2010