Posted by : Varun Doshi
On : 03 June 2014
Comments : 4
Views : 3222
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 vitamins D2 (ergocalciferol) and D3 (cholecalciferol).
The information below will tell you how to obtain vitamin D, the different forms of vitamin D, the reasons why we need it, how sunlight plays an important role in its absorption, how much of it we need, and how low absorption can lead to vitamin D deficiency.
How to obtain vitamin D?
Vitamin D for humans is obtained from sun exposure, food and supplements. It is biologically inert and has to undergo two hydroxylation reactions to become active in the body. The active form of vitamin D in the body is called Calcitriol (1,25-Dihydroxycholecalciferol).
Calcitriol promotes the absorption of calcium and phosphorus from food in the gut and reabsorption of calcium in the kidneys - this increases the flow of calcium in the bloodstream. This is essential for the normal mineralization of bone and preventing hypocalcemic tetany.
Hypocalcemic tetany is a low calcium condition in which the patient has overactive neurological reflexes, spasms of the hands and feet, cramps and spasms of the voice box (larynx). Calcitriol also plays a key role in the maintenance of many organ systems.
Various forms of vitamin D
Vitamin D1, molecular compound of ergocalciferol with lumisterol.
Vitamin D2, ergocalciferol (made from ergosterol).
It is produced by invertebrates (animals without a spine, vertebral column), fungus and plants in response to sunlight (UV irradiation). Humans and other vertebrates do not produce vitamin D2. We don't know much about what vitamin D2 does in invertebrates. We know that ergosterol is a good absorber of ultraviolet radiation which can damage DNA, RNA and protein; consequently many scientists believe it may serve as a sunscreen that protects organisms from sunlight damage.
Vitamin D3, cholecalciferol (made from 7-dehydrocholesterol).
Vitamin D3 is made in the skin when 7-dehydrocholesterol reacts with ultraviolet light at 270-300 nm wavelengths - peak vitamin D3 production occurs between 295-297 nm. It is only when the UV index is greater than 3 that these UVB wavelengths are present.
A UV index of more than 3 occurs every day in the tropics, every day during some of spring, all of summer, and parts of autumn in temperate areas, and hardly ever at all in the arctic circles. Temperate regions are all regions outside the tropics and arctic circles. The number of days of the year when the UV index is greater than 3 becomes fewer the further you move away from the tropics.
Vitamin D deficiency is extremely common in northern latitudes and is considered an epidemic in the United States, according to a study published in the American Journal of Clinical Nutrition.1
Vitamin D4, 22-dihydroergocalciferol.
Vitamin D5, sitocalciferol (made from 7-dehydrositosterol).
Which is more important for humans, vitamins 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, say scientists from the University of Colorado Denver School of Medicine, Massachusetts General Hospital and Children's Hospital Boston.
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, according to Dennis Bourdette, chairman of the Department of Neurology and director of the Multiple Sclerosis and Neuroimmunology Center at Oregon Health and Science University, USA.
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, according to research carried out at the Medical College of Georgia, USA.
Asthma symptoms and frequency - it can reduce the severity and frequency of asthma symptoms, and also the likelihood of hospitalizations due to asthma, researchers from Harvard Medical School found after monitoring 616 children in Costa Rica.
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, say radiological experts from the New York City Department of Health and Mental Hygiene.
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.
So do not forget to get your daily dose of sunshine.