Vitamin D

"Faith and prayer are the vitamins of the soul; man cannot live in health without them." - Mahalia Jackson

Technically not a "vitamin," vitamin D is in a class by itself. Its metabolic product, calcitriol, is actually a hormone that targets over 2000 genes in the human body. Current research has implicated vitamin D deficiency as a major factor in the pathology of at least 17 varieties of cancer as well as heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, periodontal disease, and more.

Vitamin D's main function is to increase the flow of calcium into the bloodstream, by promoting absorption of calcium and phosphorus from food in the intestines, and reabsorption of calcium in the kidneys; enabling normal mineralization of bone. In children, vitamin D deficiency causes rickets, which results in skeletal deformities. In adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones. Populations who may be at a high risk for vitamin D deficiencies include the elderly, obese individuals, exclusively breastfed infants, and those who have limited sun exposure.

Vitamin D3 is made in the skin in response to UVB ultraviolet light when the UV index is greater than 3. This occurs daily in the tropics, midday during last spring, summer, and early fall in temperate regions, and almost never within the arctic circles. It is nearly impossible to overdose on D through exposure to sunlight. In 10-30 minutes an equilibrium is reached and D breaks down in the skin just as fast as it's being created.

On the other hand it is possible to overdose on D via supplements. A sustained intake of 1250 micrograms/day (50,000 IU) can produce overt toxicity within months. The National Institute of Health has set a safe upper limit at 2000 IU/day.

In many countries, foods such as milk, yogurt, margarine, oil spreads, breakfast cereal, pastries, and bread are fortified with D vitamins. Fortified milk typically provides 100 IU per cup, or a quarter of the daily recommended intake for adults over age 50.

Natural sources of vitamin D include:

Fatty fish species like Herring, Catfish, Salmon, Mackerel, Sardines, Tuna, and Eel.
Fish liver oils, such as the famous cod liver oil. 1 Tablespoon (15 ml) provides 1,360 IU.
A whole egg, provides 20 IU
Beef liver, 3.5 oz cooked, provides 15 IU

Bottom Line

"Good studies have suggested that there is little to be gained by ingesting extra beta-carotene, vitamin C, vitamin E, folic acid, etc., but I think the data on vitamin D will hold up and we should all continue to follow the new information with great interest. I have seen many patients with chronic fatigue syndrome and fibromyalgia improve dramatically as they have begun taking 4,000 units of vitamin D3." - Bryan Arling, M.D. in USNews health column

[Note: do not exceed levels of 2000 IU per day without consulting a doctor first.]

http://www.mayoclinic.com/health/vitamin-d/NS_patient-vitamind
http://www.vitamindcouncil.org/