Vitamin D helps the formation of bone and the absorption of calcium and phosphorus from the intestine. Known as the sunshine vitamin because it is produced when the skin is exposed to ultraviolet light, Vitamin D was once thought to be useful only in the prevention of rickets in children and severe bone loss in adults. The discovery of how to isolate this nutrient that helps the body absorb calcium led to a Nobel Prize in chemistry in 1928.
Recent studies on Vitamin D, specifically Vitamin D3 cholecalciferol, however, have paid a lot of attention not just to what Vitamin D does to the human body, but also to the harm that its deficiency can cause. A growing number of scientists today believe that vitamin D deficiency can be devastating to our overall health.
 Daily Dose of Vitamin D
Vitamin D is naturally found in few foods other than oily fish. Most of what we get is synthesized in the skin as it absorbs the sun's ultraviolet light. Just 15 short minutes in the summer sun produces a blast of 10,000 international units. Ancient humans spent all their time outdoors and got such doses. By contrast, the US government recommends a mere 200 to 600 IU a day, depending on age--what you get in two to six cups of fortified milk.
Ultraviolet B light contained in sunshine converts Vitamin D precursors in the skin to vitamin D. To become active, the body then converts Vitamin D to 1,25-dihydroxyvitamin D, the only form that the body can use. This activation occurs via a two-step process: the first in the liver and the second in the kidneys.
The truth on how much sun exposure is required is that we do not know exactly and there is significant variation among individuals. The recommendation is to get 15 minutes of sun at the peak of the day -- 11 a.m. to 3 p.m. -- to the face, neck and arms, three times a week. However, this amount of sun has not been proven to be enough. Also, more sun is needed to make vitamin D with increasing age and increasing amounts of skin pigment.
This is why many researchers feel that more and more people who are leading indoor lives may be at risk of developing Vitamin D deficiency. In fact, many vitamin D researchers take supplements with 2,000 IU a day or more.
 Current Research on Vitamin D Deficiency
Vitamin D is a steroid hormone precursor that has recently been found to play a role in a wide variety of diseases. Current research indicates Vitamin D deficiency plays a role in causing seventeen varieties of cancer-- (colon, esophageal, gallbladder, gastric, pancreatic, rectal, small intestinal, bladder, kidney, prostate, breast, endometrial, ovarian, Hodgkin's lymphoma, and non-Hodgkin's lymphoma)-- as well as heart disease, stroke, hypertension, autoimmune diseases, diabetes, depression, chronic pain, osteoarthritis, osteoporosis, muscle weakness, muscle wasting, birth defects, and periodontal disease.
- The National Cancer Institute in the US gathered scientists to review the nutrient's ability to reduce cancer risk, particularly of the breast, colon, prostate and lung in March 2008.
- This suggests that in the future, Vitamin D could also play a role in cancer treatment. One recent study found that lung cancer patients who either got a lot of sun or had a high intake of Vitamin D had three times the survival rate of their counterparts with lower Vitamin D levels.
- In 2007, the federal Agency for Healthcare Research and Quality issued an evidence-based review of Vitamin D that found it to be key for bone health at all ages, including in the prevention of falls in the elderly.
- One analysis looked at the effects of Vitamin D supplements on mortality in 18 randomized trials of 57,311 people (originally performed to assess vitamin D's bone effects). It found that the supplements reduced the overall death rate by a statistically significant 7%, according to results published in the September 10, 2007 Archives of Internal Medicine.
 How Does Vitamin D Work?
Scientists are not sure exactly how Vitamin D works to ward off cancer. One theory is that the wonder vitamin is known to stimulate white blood cells to produce a powerful natural antibiotic called cathelicidin. In the Mar. 24, 2006 issue of Science, scientists found that when white blood cells were mixed with blood serum samples from African-Americans (who are prone to low vitamin D levels), they produced 63% less of this antibiotic than if the cells were mixed with blood samples from Caucasians. It could well be that Vitamin D is able to somehow turn on powerful antimicrobial genes.
Vitamin D research, thus, could show new directions to the treatment of cancer and infections in the future.
 The Bottomline
All the research on Vitamin D is in nascent stages at the moment. Its effects on bone health are proven, but all these other research findings are still speculative. There are no sureties that if scientists gave Vitamin D supplements to a completely healthy person, s/he would be healthier ten years later.
However, anyone who has been outdoors will agree that getting out in the open uplifts one's mood and lightens the heart. While the jury is out on Vitamin D supplements, there certainly can not be any harm in trying to be outdoors (and get Vitamin D naturally in the bargain) at least for one hour a day. Just don't forget that sunscreen!
 Vitamin D and good health
Medical studies around the world have proven the benefits of Vitamin D in association with:
- Cellular Health: including breast, colon and prostate cancers
- Bone Health: including osteoporosis, hip fractures, osteomalacia and hip fractures
- Organ Health: including high blood pressure, hypertension and heart disease
- Mental Health: including SAD, PMS, depression and general mood
- Auto-immune Diseases: including multiple sclerosis, Type 1 diabetes and rheumatoid arthritis
- Skin Disorders: including psoriasis
- Obesity and exercise programmes
 Did You Know?
- Regular and moderate amounts of unprotected UV exposure are absolutely necessary for good health.
- Since most multivitamins only contain 400 IU of Vitamin D, a person needs to take two and a half a day to get the recommended daily dose of 1000 IU, thereby exposing the body to an overload of Vitamin A, which in excessive amounts has been associated with birth defects and osteoporosis.
- Vitamin D supplements provide the same benefits as sunshine but if taken in too large a dose, can cause Vitamin D toxicity, whereas sun exposure does not.
- The human body cannot make Vitamin D in the UK or any location above 40 degrees north in the winter months.
- Tanned skin protects you against sunburn, thought to be the main cause of melanoma. If you avoid getting sunburned, the benefits of moderate sun exposure will far outweigh the possible dangers.
- The human body's ability to manufacture Vitamin D diminishes fourfold from age twenty to age seventy.
- Vegan Society
- Vitamin D Council
- Vitamin D- Did You Know...?