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).
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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.
A study published in the The Journal of Clinical Endocrinology & Metabolism, concluded that Vitamin D2 is much less effective than Vitamin D3 in Humans.2What do we need vitamin D for?
According to the U.S. Department of Health and Human Services3, 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.
Vitamin D In High Doses Accelerates Tuberculosis Recovery
- High doses of the "sunshine" vitamin D can help people with tuberculosis recover more quickly, researchers at Queen Mary, University of London, reported in the Proceedings of the National Academy of Sciences (PNAS). For several decades, heliotherapy - encouraging (tuberculosis) patients to soak up the sun's rays - has been used in Swiss clinics successfully. The authors say they have now shown why this type of therapy is beneficial.
Vitamin D3 is synthesized by the skin when it is exposed to sunlight, specifically ultraviolet light of UVB type at wavelengths between 270 and 300 nm.
In this study, Dr Adrian Martineau and team gave tuberculosis patients high vitamin D doses alongside their normal antibiotic treatment. They found that the patients recovered much more quickly. This is the first study to focus on the effects vitamin D might have on the immune responses of patients receiving therapy for an infectious disease. Low Levels of Vitamin D Linked To Heart Disease
- Low levels of Vitamin D may increase the risk of heart attack and early death, according to a study from the University of Copenhagen and Copenhagen University Hospital.
Although vitamin D is most commonly associated with healthy bones, various population studies have demonstrated that low levels of this vitamin may increase the risk of developing ischemic heart disease, angina, coronary arteriosclerosis, and heart attack.
Other research has suggested that low levels of this vitamin may cause high blood pressure, which increases the risk of heart attack. One particular study in 2009 indicated that vitamin D deficiency in young women may increase the chance of developing systolic hypertension.
In the current study, the largest one yet, the experts gathered and analyzed data of over 10,000 Danes in order to identify the link between low vitamin D levels and ischemic heart disease and death.
Results showed, Dr. Peter Brøndum-Jacobsen, Clinical Biochemical Department, Copenhagen University Hospital, explained, that low Vitamin D levels compared to optimal levels are linked to: - 64% higher risk of heart attack
- 57% higher risk of early death
- 40% higher risk of ischemic heart disease
- at least 81% higher risk of death from heart disease
After controlling for certain variables that could impact the results, the higher risks were still evident. The findings were published in Arteriosclerosis, Thrombosis and Vascular Biology.
This examination was formed from the population study, The Copenhagen City Heart Study, which measured vitamin D levels in blood samples from 1981 to 1983. Scientists used the nationwide Danish registries to follow subjects up to the present.
Børge Nordestgaard, clinical professor at the Faculty of Health and Medical Sciences, University of Copenhagen and senior physician at Copenhagen University Hospital, said:"With this type of population study, we are unable to say anything definitive about a possible causal relationship. But we can ascertain that there is a strong statistical correlation between a low level of vitamin D and high risk of heart disease and early death. The explanation may be that a low level of vitamin D directly leads to heart disease and death. However, it is also possible that vitamin deficiency is a marker for poor health generally."
In order to identify whether low levels of vitamin D have a genuine causal relationship with the risk of heart disease, the team is furthering their investigations.
If their future research supports these findings, it will potentially have an enormous impact on the health of the world population, considering that heart disease is the most common cause of adult death, according to the World Health Organization (WHO). Every year, approximately 17 million die from heart disease.
Børge Nordestgaard concluded:
"The cheapest and easiest way to get enough vitamin D is to let the sun shine on your skin at regular intervals. There is plenty of evidence that sunshine is good, but it is also important to avoid getting sunburned, which increases the risk of skin cancer. Diet with a good supply of vitamin D is also good, but it has not been proven that vitamin D as a dietary supplement prevents heart disease and death."
Recent developments on why we need vitamin D from MNT news- Despite past reports that Vitamin D, the sunshine vitamin, helps with
upper respiratory tract infections (colds), researchers are now saying
it does not help reduce how often or how severely we get colds,
according to a new study in JAMA.
Background information in the study said that the link between insufficient levels of vitamin D and how likely a person is to catch a cold had previously not been scientifically proven.
Many studies that have been carried out on vitamin D and its benefits for respiratory health have produced conflicting results. Scientists at the University Hospital Leuven, Belgium carried out a study expecting to confirm the full benefits of high vitamin D levels on COPD (chronic obstructive pulmonary disease) symptoms and outcomes. Unfortunately, they found that vitamin D supplements make no difference to COPD symptoms or the risk of developing the disease.
However, some randomized, controlled trials have demonstrated the importance of vitamin D in protecting the airways. Researchers from Massachusetts General Hospital reported in August 2012 that respiratory infection risk in winter is lower among Mongolian children who take a daily vitamin D supplement, compared to their counterparts who do not. - The new trial, led by David R. Murdoch, M.D., from the University of
Otago, Christchurch, New Zealand and his team, took place between
February 2010 and November 2011. It involved 322 healthy adult
participants who were given a first dose of 200,000 IU vitamin D3
normally, followed by 200,000 IU a month later, then 100,000 monthly (n
= 161), or a placebo which was given in the same doses (n=161), for 18
months total.
At the start of the investigation, the mean 25-hydroxyvitamin D (25-OHD) level was 29 ng/mL. When the participants were taking vitamin D supplements, their serum 25-OHD levels were increased to over 48 ng/mL, and remained at this level. In the vitamin D group, 593 people experienced URTI episodes, while the placebo group had 611.
According to the experts, they did not detect any important differences in how many URTIs each patient experienced - the vitamin D group individuals had an average of 3.7, while the placebo group had 3.8. Both groups had an average of 12 days of symptoms per episode. The researchers found no difference in the intensity of episodes, or number of work days missed, due to symptoms.
The authors wrote:
"The main finding from this study is that a monthly dose of 100,000 IU of vitamin D3 in healthy adults did not significantly reduce the incidence or severity of URTIs. This result remained unchanged when the analysis included winter season or baseline 25-OHD levels. Further research is required to clarify whether there is benefit from supplementation in other populations and with other dosing regim
Health care professionals, nutritionists, dietitians and alternative therapists have tended to presume that vitamin D protects people from colds and reduces symptom severity among those who become ill.
As mentioned earlier, scores of studies on respiratory infections and conditions have clearly demonstrated the benefits. Scientists from Queen Mary, University of London, reported in September 2012 that vitamin D can help patients with tuberculosis recover more quickly. High Vitamin D Helps Healthy People Stay That Way
- Healthy people with higher vitamin D levels in their blood may enjoy several benefits, apart from improved bone health, researchers from Boston University School of Medicine reported in PLOS ONE.
The authors explained that their study found that higher vitamin D levels in healthy people have a considerable impact on the genes that are involved in several biologic pathways linked to infectious diseases, autoimmune diseases, cardiovascular disease and cancer.
Previous studies have demonstrated that excessively low vitamin D levels are associated with a higher risk of developing the diseases mentioned above. The researchers emphasized that their findings provide further evidence that healthy people who improve their vitamin D status have significantly better immunity and a reduced risk of several diseases. Vitamin D is unique
There are two ways we can obtain vitamin D:- It can be ingested - eaten or drunk
- It can be synthesized by the body when our skin is exposed to the sun
A person's vitamin D level (vitamin D status) is gauged by measuring the blood level of 25-hydroxyvitamin D. When levels go below 20 nanograms per milliliter (ng/mL) the person has vitamin D deficiency. Vitamin D deficiency can cause rickets, other musculoskeletal diseases, and further problems.
Recent studies have linked vitamin D insufficiency (between 21-29 ng/mL) and vitamin D deficiency (<20 ng/mL) to a higher risk of developing:- Cancer
- Autoimmune diseases
- Infectious diseases
- Type 2 diabetes
- Cardiovascular diseases
- Three participants were given 400 International Units (IUs) of vitamin D per day
- Five participants were given 2,000 IUs per day This continued for two months. The researchers collected samples of white blood cells - immune cells - at the beginning and the end of the two-month period. Over 22,500 genes were investigated from the samples to determine whether their activity had increased or decreased after the vitamin D intake.
- Those in the 2000 IUs group achieved a vitamin D status of 34 ng/mL (considered sufficient)
- In the 400 IUs group their vitamin D status was 25 ng/mL (insufficient)
At the end of the trial:291 genes were significantly altered
The gene expression analysis showed "statistically significant alterations in the activity of 291 genes".
When the genes were analyzed further, the scientists found that their biologic functions were related to 160 biologic pathways associated with cardiovascular disease, infectious diseases, autoimmune diseases and cancer.
After examining elements of gene response, or sequences of DNA bases that interact with vitamin D receptors to control gene expression, the researchers also found new genes related to vitamin D status.
To make sure that their findings were accurate, they looked at 12 genes which are known not to have alterations in their level of expression - they remained stable throughout the two months.- Michael F. Holick, PhD, MD, professor of medicine, physiology and biophysics at BUSM, said:
"This study reveals the molecular fingerprints that help explain the non-skeletal health benefits of vitamin D. While a larger study is necessary to confirm our observations, the data demonstrates that improving vitamin D status can have a dramatic effect on gene expression in our immune cells and may help explain the role of vitamin D in reducing the risk for CVD, cancer and other diseases."
This research was supported by a pilot grant from the National Institutes of Health's Clinical Translational Science Institute under grant award # UL-1-RR-25711.Vitamin D - A popular subject to study
Over the last twenty years, there have been hundreds of studies on vitamin D which have been published in peer-reviewed academic journals. Below are examples of some studies:
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