What is vitamin D?
Vitamin D is a fat-soluble vitamin that's formed when skin is exposed to the sun's ultraviolet rays. Vitamin D is also found in food and dietary supplements.

There are two major types of vitamin D:
• Vitamin D3 (cholecalciferol) is made naturally by the body when its exposed sun; it’s also found in certain foods.
• Vitamin D2 (ergocalciferol) is the most common form found in supplements; it's also used to fortify certain foods, such as milk.

Both types of vitamin D must be converted in the liver and kidneys to its active form to be useful to the body.

What does vitamin D do?
The main function of vitamin D is to maintain normal levels of calcium and phosphorus in the blood, which helps support bone mineralization (hardening of bones), assists with cell function and proper nerve and muscle function. Vitamin D is needed for normal growth.
Vitamin D deficiency may result in: muscle and bone pain, diabetes, fibromyalgia, psoriasis gum disease, mood disorders, depression, improper immune function, osteoporosis, cancer, and autoimmune disease.

What are good sources of vitamin D?
Sun: the main source of vitamin D comes from exposure to the sun's UVB rays.
Food:
    • Fish: vitamin D naturally in certain types of fish, such as herring, mackerel, salmon, and sardines.
    • Fortified Foods:  milk, some juice products, breakfast cereals, and other foods fortified with vitamin D
Supplements:
Multivitamins and calcium supplements provide vitamin D, but the amount varies widely so it's important to read labels. Vitamin D3 (cholecalciferol) is the preferred form. Vitamin D2 (ergocalciferol) is 25 percent less potent. You can find Vitamin D3 in pill form, as well as in drops.  

What is the recommended vitamin D intake?

In the United States, the Institute of Medicine's recommendations for vitamin D intake are as follows:
    • Birth to 50: 200 IU (5 mcg)
    • 51-70: 400 IU (10 mcg)
    • Over 71: 600 IU (15 mcg)
    • Pregnant and nursing women: 200 IU (5 mcg)

These recommendations were set in 1997. There is growing consensus that vitamin D reference intakes need to be reassessed, based on increasing evidence that vitamin D insufficiency is widespread in the general population and that vitamin D plays a key role in bone health and the prevention of chronic health conditions.

FOOD	Vitamin D IU
Catfish 3 oz	570
Salmon, canned  1/4 cup	480
Salmon, wild  3 ½ oz	500
Salmon, farmed  3 ½ oz	75-200
Mackerel, 3 ½ oz	345
Shrimp  3 oz	290
Tuna, 3 oz	200
Soymilk, Silk 1 c	120
Milk	100
Dannon Lite and Fit Yogurt  6 oz	80
Fortified Breakfast Cereal	40
Egg 1	20
Cod Liver Oil, 1 T	1200
Sensible sun exposure (6-20 minutes, between 10 a.m. -3 p.m., May-Sept.	10,000 – 20,000

Who may require extra vitamin D?
    • People with limited sun exposure: The amount of vitamin D formed from exposure to the sun is affected by season and latitude. In general, we don’t get enough UVB rays to form vitamin D during the fall and winter months in our area.
    • People who are homebound, women who wear robes and head coverings for religious reasons, and people whose jobs or work hours limit their exposure to sunlight are likely not obtaining significant amounts of vitamin D from sunlight.
    • People who use sunscreen: The use of sunscreen prevents the formation of vitamin D, too. Even sunscreen with an SPF of 8, an amount found in many daily moisturizers, can greatly reduce vitamin D production.
    • People with greater skin pigment: People with darker skin have more melanin, the pigment that gives skin its color. Melanin absorbs UV rays, which reduces the skin's ability to produce vitamin D. The more pigment in a person's skin, the more important it is that he or she consume enough vitamin D.
    • Older people: Older people are at greater risk of vitamin D deficiency, as the ability to produce vitamin D dwindles with age. In fact, vitamin D levels in elderly subjects have been found to be approximately 30 percent of the levels found in young adults.
    • People who can't properly absorb fat (fat malabsorption): Vitamin D requires some dietary fat in order to be absorbed in the small intestine. People with conditions that cause fat malabsorption, such as cystic fibrosis, celiac disease, Crohn's disease, and chronic liver disease, are more prone to vitamin D deficiency.
    • People with kidney disease may not be able to convert vitamin D to its active form.

Side effects and safety:
Vitamin D is a fat-soluble vitamin. This means that, if consumed in excess, it can build up in the body and cause toxic symptoms, unlike vitamin C and other water-soluble vitamins. Because the buildup is slow, it can take months or years before toxic levels are reached. The safe upper limit of vitamin D is 2,000 IU (50 mcg) for men and women. For infants (up to 12 months), the safe upper limit is 1,000 IU (25 mcg).  There is growing evidence suggesting that these upper limits may be too low. Until a new limit is set, however, it's recommended that you not exceed the upper limit unless under physician supervision. People with hyperparathyroidism or sarcoidosis should not consume vitamin D, unless they have consulted their physician.

Possible drug interactions:
The combination of vitamin D and calcium should not be taken with thiazide diuretics, because it could lead to excess calcium levels in the body. Consult your physician before taking either. People taking calcium-channel blockers should not take vitamin D and calcium, unless under a doctor's supervision, because it may interfere with the effect of the medication. Certain medications, such as phenytoin (Dilantin), primidone (Mysoline), phenobarbital, valproic acid (Depakene), corticosteroids, cimitidine (Tagamet), heparin, isoniazid (INH) and rifampin may interfere with the absorption or activity of vitamin D.