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 D 1 , D 2 , D 3 , D 4 , D 5 . The two forms that seem to matter to humans the most are vitamins D 2 (ergocalciferol) and D 3 (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.
Data collected from the National Health and Nutrition Examination Survey (NHANES), USA found that 9% (7.6 million) of children across the USA, was vitamin D deficient (defined as less than 15 ng/mL of blood), while another 61 percent, or 50.8 million, was vitamin D insufficient (15 to 29 ng/mL) (reference"We expected the prevalence of vitamin D deficiency would be high, but the magnitude of the problem nationwide was shocking," says lead author Juhi Kumar, M.D., M.P.H., a fellow in pediatrics at Children's Hospital at Montefiore Medical Center, The University Hospital and Academic Medical Center for Albert Einstein College of Medicine.
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 We know about 5 forms of vitamin D, of which vitamins D 2 and D 3 are the major forms as far as humans are concerned. They are known collectively as calciferol . Vitamin D 1 , molecular compound of ergocalciferol with lumisterol.
Vitamin D 2 , 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 D 2 . We don't know much about what vitamin D 2 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 D 3 , cholecalciferol (made from 7-dehydrocholesterol).
Vitamin D 3 is made in the skin when 7-dehydrocholesterol reacts with ultraviolet light at 270-300 nm wavelengths - peak vitamin D 3 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 become fewer the further you move away from the tropics.
A human requires ten to fifteen minutes of sun exposure at least twice a week on the face, arms, hands, or back without sunscreen with a greater than 3 UV index for adequate amounts of vitamin D 3 . Longer exposure results in the extra vitamin supply being degraded as fast as it is generated.
Vitamin D 4 , 22-dihydroergocalciferol.
Vitamin D 5 , sitocalciferol (made from 7-dehydrositosterol). Which is more important for humans, vitamins D 2 or D 3 ? Both vitamins D 2 and D 3 are used in human nutritional supplements. Pharmaceutical forms include calcitriol (1alpha, 25-dihydroxycholecalciferol), doxercalciferol and calcipotriene. The majority of scientists state that D 2 and D 3 are equally effective in our bloodstream. However, some say that D 3 is more effective. Animal experiments, specifically on rats, indicate that D 2 is more effective than D 3 . What do we need vitamin D for? 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.
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.
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.
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.
Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.
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.
It has been shown to reduce the risk of developing rheumatoid arthritis in women.
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.
Various studies have shown thatpeople 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 incancerpatients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America. Sunlight and vitamin D requirements 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 If your body cannot produce enough vitamin D because of insufficient sunlight exposure you will need to obtain it from foods and perhaps supplements. Experts say that people with a high risk of vitamin D deficiency should consume 25 ?g (1000 IU) of vitamin D each day so that there is a good level of 25-hydroxyvitamin D in the bloodstream. Elderly people, as well as people with dark skin should consume extra vitamin D for good health.
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 (Четыресто IU) 71+ years - 15 mcg (600 IU) The American Academy of Pediatrics recommends that exclusively or partially breastfed babies should receive supplements of Четыресто UI per day shortly after birth, and when they are weaned they should consume a minimum of 1,000 mL/day of vitamin D fortified formula or whole milk. Non-breastfed infants consuming less than 1,000 mL/day of vitamin D-fortified formula or milk should receive a vitamin D supplement of Четыресто IU per day. It also recommends that older children and adolescents who do not get Четыресто IU per day through vitamin D fortified milk and foods should take a Четыресто IU vitamin supplement each day. Vitamin D and nutrition
Over the last few hundred years human lifestyles have changed. The industrial revolution resulted in more indoor work and less exposure to sunlight. Many societies around the world wore more clothing over the centuries, further reducing skin exposure to sunlight. These changes have brought with them a significant reduction in the natural production of vitamin D and subsequent diseases.
Countries responded to these changes by fortifying some foods with vitamins D 2 and D 3 , examples include breakfast cereals, bread, pastries, oil spreads, margarine, milk and other dairy products. Initially, some scientists complained that nutritional fortification and recommended supplementation doses were not making up for the shortfall. These people were ignored, and sometimes ridiculed - however, over the last few years studies indicate that they may have been right after all.
Not that many foods contain vitamin D. Some fish, such прогнозировании mackerel, as well as fish liver oils are considered to be the best sources. Some vitamin D is also present in beef liver, cheese and egg yolks. Most of these are Vitamin D 3 . Some mushrooms provide variable amounts of vitamin D 2 .
Most of the food sourced vitamin D in the western diet comes from fortified foods - where vitamin D is artificially added. Most US milk is fortified with Сто IU/cup of vitamin D. In the 1930s milk was fortified in many countries to combatrickets, which was a major health problem then.
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After prostate cancer at age 43, I took 2,000IU per day of D3 for 2.5 years, and my blood test was just 15; a low-normal is 25.
Vitamin D Malabsorption posted by R. Ma on 26 Aug 2009 at 10:31 am
I agree. High vitamin D supplementation does not necessarily result in an adequate level in the blood. Perhaps a combination of sun exposure and oral supplementation may be necessary in cases of malabsorption.
How much is too much vitamin D? posted by Minnie George on 26 Jul 2010 at 12:27 pm
My mother is 85 years of age and was told by her physician to take 5000iu of vitamin D per day for 3 months. Is that too much or okay?
'How much is too much Vitamin D?' posted by Toni Beaudin on 7 Aug 2010 at 8:48 am
I'm no expert, but I have been listening to Purity Products opinions. They say that you need 5000 IUs of Vitamin D daily to be taken WITH Mega 3 Fish Oils (to aid in the absorption). It takes about a month before you actually feel the benefits, they say. However, I have just begun taking 5000 IUs of Vitamin D daily, myself, and already seem to 'feel' better. I can't explain it, but I do. So far, I can't seem to find a place that tells me 'how much is too much' either.
I agree. My understanding is that we all need 5000 IUs of Vitamin D DAILY.
'Vitamin D Malabsorbtion' posted by Toni Beaudin on 7 Aug 2010 at 11:00 am
It is my understanding that Vitamin D has to be taken in conjunction with Mega 3 Fish Oils in order for it to be absorbed properly.
Vitamin D Supplementation posted by Shirley Riesz on 13 Aug 2010 at 7:36 pm
Chapter 12 of Cerebrum: Emerging Ideas in Brain Science (2010) published by the Dana Foundation on page
150 it states: "Several randomized, prospective, controlled trials among frail, elderly people strongly suggest that these participants benefit from daily oral supplements of 800 IU or more of vitamin D, which
enhances muscle strength and decreases risks of bone fractures. The current recommended daily allowance for elderly people, 600 IU, is not enough, the research suggests; increasing the dosage in these individuals, particularly those who are inactive (homebound or institutionalized), may prevent or ease some symptoms of frailty. Also, it appears that there is a wide safety margin in dosage -- recent research has detected signs of vitamin D toxicity only after daily doses exceeded 50,000 IU for several days or weeks. [Cannell and Hollis,"Use of Vitamin D in Clincal Practice," Alternative Medicine Review 13, No. 1 (2008): 6-20.] Thus, doubling or even tripling the standard vitamin D supplement doses or fortifying more foods with vitamin D would be very safe."
How much is enough posted by modicia martin on 14 Aug 2010 at 2:17 pm
I live in a tropical island that is Trinidad we have a lot of sun at times so I walk in the sun most of the time, plus I eat food that contains vitamin d do I still have to take the supplement? sometimes I take calcium with vitamin d I am 59 years of age and I want to know if I am doing the right things.
This is my experience... posted by Teresa Monceaux on 24 Aug 2010 at 10:21 pm
I was hurt and sought help from an orthopedist who discovered my Vit D level was 7. I have worked 12 hour night-shifts for 23 years, and rarely see the sun. My MD started me on 10,000 iu Vit D and Triple Strength Omega-3. I was instructed to find the combined EPA and DHA, add those together and take 4000-5000 mg per day. I feel much better and have decreased my inflammatory process in my lab work. I am currently 42 and had thought I was going into early menopause.
Before I started the Vit. D, my cycles had been getting erratic and maybe 4-5 per year over the previous 3 years. All that is improving and getting back to a patterned, normal type cycle. In my youth, they were heavy and painful. That is no longer the case. However, if I stop taking the Vit. D, I spot. Forgive me if this is TMI, but I am convinced a compromised Vit D was throwing me into early menopaus...
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