What is Vitamin D?
Vitamin D is a steroid vitamin, a group of fat-soluble prohormones, which encourages the absorption and metabolism of calcium and phosphorous. People who are exposed to normal quantities of sunlight do not need vitamin D supplements because sunlight promotes sufficient vitamin D synthesis in the skin.
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).
Researchers at the University of Minnesota found that Vitamin D levels in the body at the start of a low-calorie diet predict weight loss success, suggesting a possible role for vitamin D in weight loss.
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.
What do we need vitamin D for?
1.It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially the maintenance of healthy bones.
2. It is immune system regulator.
3.It 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.
4.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.
5.Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.
6.Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.
7.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.
8.It has been shown to reduce the risk of developing rheumatoid arthritis in women.
9.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.
How much vitamin D do I need?
The information below relates to people who do not have exposure to sunlight.
According to the Food Nutrition Board at the Institute of Medicine of The National Academies, which created the Dietary Reference Intakes (DRIs), people should be intaking the following amounts of vitamin D if nothing is being synthesized (no sunlight exposure):
Children up to 13 years - 5 mcg (200 IU)
14-18 years - 5 mcg (200 IU)
19-50 years - 5mcg (200 IU)
51-70 years - 10 mcg (400 IU)
71+ years - 15 mcg (600 IU)
New Research- Vit D -Too Much Can Be As Unhealthy As Too Little
Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America.
Scientists know that Vitamin D deficiency is not healthy. However, new research from the University of Copenhagen now indicates that too high a level of the essential vitamin is not good either. The study is based on blood samples from 247,574 Copenhageners. The results have just been published in the reputed scientific Journal of Clinical Endocrinology and Metabolism. Vitamin D is instrumental in helping calcium reach our bones, thus lessening the risk from falls and the risk of broken hips. Research suggests that vitamin D is also beneficial in combating cardiac disease, depression and certain types of cancers. The results from a study conducted by the Faculty of Health and Medical Sciences now support the benefits of vitamin D in terms of mortality risk. However, the research results also show higher mortality in people with too high levels of vitamin D in their bloodstream:
We have had access to blood tests from a quarter of a million Copenhageners. We found higher mortality in people with a low level of vitamin D in their blood, but to our surprise, we also found it in people with a high level of vitamin D. We can draw a graph showing that perhaps it is harmful with too little and too much vitamin D, explains Darshana Durup, PhD student. If the blood contains less than 10 nanomol (nmol) of vitamin per liter of serum, mortality is 2.31 times higher. However, if the blood contains more than 140 nmol of vitamin per liter of serum, mortality is higher by a factor of 1.42. Both values are compared to 50 nmol of vitamin per liter of serum, where the scientists see the lowest mortality rate.
More studies are needed
Darshana Durup emphasises that while scientists do not know the cause of the higher mortality, she believes that the new results can be used to question the wisdom of those people who claim that you can never get too much vitamin D, It is important to conduct further studies in order to understand the relationship. A lot of research has been conducted on the risk of vitamin D deficiency. However, there is no scientific evidence for a 'more is better' argument for vitamin D, and our study does not support the argument either. We hope that our study will inspire others to study the cause of higher mortality with a high level of vitamin D," says Darshana Durup. She adds, We have moved into a controversial area that stirs up strong feelings just like debates on global warming and research on nutrition. But our results are based on a quarter of a million blood tests and provide an interesting starting point for further research.
The largest study of its kind
The study is the largest of its kind - and it was only possible to conduct it because of Denmark's civil registration system, which is unique in the Nordic countries. The 247,574 blood samples come from the Copenhagen General Practitioners Laboratory: "Our data material covers a wide age range. The people who participated had approached their own general practitioners for a variety of reasons and had had the vitamin D level in their bloodstream measured in that context. This means that while the study can show a possible association between mortality and a high level of vitamin D, we cannot as yet explain the higher risk, explains Darshana Durup. Therefore in future research project scientists would like to compare the results with information from disease registers such as the cancer register. Financial support is currently being sought for such projects.
(Source-Journal of Clinical Endocrinology and Metabolism)
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