Vitamin D

Vitamin D is different from other essential vitamins because our own bodies can manufacture it with sunlight exposure. The main function of vitamin D is to regulate the absorption of calcium and phosphorus in our bones and aid in cell to cell communication throughout the body. Frequent exposure of the skin to sunlight promotes sufficient vitamin D synthesis without the need for supplements, however, adults who have darker skin pigmentation or frequently wear sun protection during outdoor activities are often vitamin D deficient.

Five forms of vitamin D have been discovered, vitamin D1, D2, D3, D4, D5. The two forms that seem to matter to humans the most are vitamin D2 (ergocalciferol) and vitamine D3 (cholecalciferol).

Which vitamin D is more important for humans, vitamin D2 or D3?

Both vitamins D2 and D3 are used in human nutritional supplements. Pharmaceutical forms include calcitriol (1alpha, 25-dihydroxycholecalciferol), doxercalciferol and calcipotriene. The majority of scientists state that D2 and D3 are equally effective in our bloodstream. However, new research is beginning to suggest that D3 is more effective.

What do we need vitamin D for?

Vitamin D is essential for the "formation, growth, and repair of bones and for normal calcium absorption and immune function" and there are studies to suggest that "higher levels of vitamin D in the blood are associated with reduced risks of colorectal cancer; however, the research results overall have been inconsistent."

• It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially the maintenance of healthy bones.
• It is an immune system regulator.
• Aids the immune system - vitamin D may be an important way to arm the immune system against disorders like the common cold.
• MS risk - it may reduce the risk of developing multiple sclerosis. Multiple sclerosis is much less common the nearer you get to the tropics, where there is much more sunlight.
• Maintaining cognitive functions - vitamin D may play a key role in helping the brain keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.
• Healthy body weight - vitamin D probably plays an important role in maintaining a healthy body weight.
• Asthma symptoms and frequency - it can reduce the severity and frequency of asthma symptoms, and also the likelihood of hospitalizations due to asthma.
• Rheumatoid arthritis - it has been shown to reduce the risk of developing rheumatoid arthritis in women.
• Protects from radiation damage - a form of vitamin D could be one of our body's main protections against damage from low levels of radiation.
• Vitamin D and cancer risk - various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to those whose levels are low. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status in a study carried out by the Cancer Treatment Centers of America.
• T.B. recovery - high vitamin D doses can help people recover from tuberculosis more rapidly, researchers reported in September 2012 in the Proceeding of the National Academy of Sciences (PNAS).
• Heart attack risk - an study published in September 2012 suggested that low levels of vitamin D may increase the risk of heart attack and early death.

Sunlight and vitamin D requirements

Direct sunlight is a great source of vitamin D. However, be careful you do not overdo it. If you live in the tropics and can expose your unprotected skin to two sessions of 15 minutes of sunlight each week your body will naturally produce adequate amounts of vitamin D. The following factors may reduce your body's vitamin D synthesis:

• If you live far from the equator, your sunlight exposure will be less during many months of the year.
• Cloud cover
• Smog
• Sunscreens

Vitamin D Supplementation

If your body cannot produce enough vitamin D because of insufficient sunlight exposure you will need to obtain it from supplements and dietary sources. In the absence of sun exposure 1000 IU of cholecalciferol is required daily for both children and adults. People with dark skin pigmentation and the elderly are more likely to have vitamin D deficiencies.