Description: Vitamin D deficiency is known to cause several bone diseases (shown below) and is becoming of more importance globally as its role in our health is better understood.


- Rickets, a childhood disease characterized by impeded growth, and deformity, of the long bones.
-Osteomalacia, a bone-thinning disorder that occurs exclusively in adults and is characterised by proximal muscle weakness and bone fragility.
-Osteoporosis, a condition characterized by reduced bone mineral density and increased bone fragility.

Vitamin D malnutrition may also be linked to an increased susceptibility to several chronic diseases such as high blood pressure, tuberculosis, cancer, periodontal disease, multiple sclerosis, chronic pain, depression, schizophrenia, seasonal affective disorder and several autoimmune diseases.

Vitamin D requirements increase with age, while the ability of skin to convert decreases. In addition the ability of the kidneys to convert calcidiol to its active form also decreases with age, prompting the need for increased vitamin D supplementation in elderly individuals.
The American Pediatric Associations advises vitamin D supplementation of 200 IU/day (5µg/d) from birth onwards. Health Canada recommends 400IU/day (10µg/d). While infant formula is generally fortified with vitamin D, breast milk does not contain significant levels of vitamin D, and parents are usually advised to avoid exposing babies to prolonged sunlight. Therefore, infants who are exclusively breastfed are likely to require vitamin D supplementation beyond early infancy, especially at northern latitudes.

Obese individuals may have lower levels of the circulating form of vitamin D, probably because of reduced bioavailability, and are at higher risk of deficiency. Patients with chronic liver disease or intestinal malabsorption disorders may also require larger doses of vitamin D.

The use of sunscreen with a sun protection factor (SPF) of 8 inhibits more than 95% of vitamin D production in the skin. Recent studies showed that, following the successful "Slip-Slop-Slap" health campaign encouraging Australians to cover up when exposed to sunlight to prevent skin cancer, an increased number of Australians and New Zealanders became vitamin D deficient. Ironically, there are indications that vitamin D deficiency may lead to skin cancer. To avoid vitamin D deficiency some dermatologists recommend supplementation along with sunscreen use.

The reduced pigmentation of light-skinned individuals tends to allow more sunlight to be absorbed even at higher latitudes, thereby reducing the risk of vitamin D deficiency. However, at higher latitudes (above 30°) during the winter months, the decreased angle of the sun's rays, reduced daylight hours, protective clothing during cold weather, and fewer hours of outside activity, diminish absorption of sunlight and the production of vitamin D. Because melanin acts like a sun-block, prolonging the time required to generate vitamin D, dark-skinned individuals, in particular, may require extra vitamin D to avoid deficiency at higher latitudes. At latitudes below 30° where sunlight and day-length are more consistent, vitamin D supplementation may not be required. Individuals clad in full body coverings during all their outdoor activity, most notably women wearing burquas in daylight, are at risk of vitamin D deficiency. This poses a lifestyle-related health risk mostly for female residents of conservative Muslim nations in the Middle East, but also for strict adherents in other parts of the world.

The exact long-term safe dose of vitamin D is not entirely known, but dosages up to 60 micrograms (2,400 IU) /day in healthy adults are believed to be safe. The U.S. Dietary Reference Intake Tolerable Upper Intake Level (UL) of vitamin D for children and adults is 50 micrograms/day (2,000 IU/day).

A 2006 study published in the Journal of the American Medical Association, reported evidence of a link between Vitamin D deficiency and the onset of Multiple Sclerosis; the authors posit that this is due to the immune-response suppression properties of Vitamin D.

In 2005, scientists released a metastudy which demonstrated a beneficial correlation between vitamin D intake and prevention of cancer. Drawing from a meta-analysis of 63 published reports, the authors showed that intake of an additional 1,000 international units (IU) (or 25 micrograms) of vitamin D daily reduced an individual's colon cancer risk by 50%, and breast and ovarian cancer risks by 30%. Research has also shown a beneficial effect of high levels of calcitriol on patients with advanced prostate cancer. A randomised intervention study involving 1,200 women, published in June 2007, reports that vitamin D supplementation (1,100 international units (IU) / day) resulted in a 60% reduction in cancer incidence, during a four-year clinical trial, rising to a 77% reduction if cancers diagnosed in the first year (and therefore more likely to have originated prior to the intervention) were excluded. A recent study using data on over 4 million cancer patients from 13 different countries showed a marked difference in cancer risk between countries classified as sunny and countries classified as less–sunny for a number of different cancers.

In June 2007, The Canadian Cancer Society began recommending that all adult Canadians consider taking 1000 IU of vitamin D during the fall and winter months (when typically the country's northern latitude prevents sufficient sun-stimulated production of vitamin D). This kind of recommendation is a first for cancer agencies.

Research has also suggested that cancer patients who have surgery or treatment in the summer — and therefore make more endogenous vitamin D — have a better chance of surviving their cancer than those who undergo treatment in the winter when they are exposed to less sunlight.

Role in coronary disease prevention
Research indicates that vitamin D plays a role in preventing or reversing coronary disease. As with cancer incidence, the same qualitative inverse correlations exist between coronary disease incidence and serum vitamin D levels, seasonal solar exposure,in temperate latitudes but not tropical latitudes.