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Is Vitamin D Really A Vitamin? Technically, no. Vitamins are micronutrients that the body uses in various processes. Vitamin D is a prohormone, a substance that the body converts into a hormone. But that’s a technicality. The thing you need to remember about vitamin D is that your body can make it from sunlight. Making Vitamin DWhat happens is that sunlight (specifically UV-B radiation) hits your skin it reacts with some chemicals (7-dehydrocholesterol) to start making vitamin D. The process is complex and not very interesting. What you need to remember is that around 15 minutes of exposure to sunlight on your hands and face every day is plenty for your body to make enough vitamin D under normal circumstances. If you live up north (or way down south), the atmosphere filters out a lot of the UV-B during winter and you may need more exposure. What Good Is Vitamin D? Lots of good, we just don’t really know exactly how it works. Vitamin D seems to keep your blood pressure low, reduce inflammation and give the immune system a boost -- all beneficial for keeping your heart health and (maybe) even fighting off cancer. We do know that vitamin D is essential for good bone health -– it helps your bones absorb calcium (and calcium is what bones are made of). Kids without exposure to vitamin D can develop rickets (a disease where their legs become extremely bow-legged) and older adults with vitamin D deficiencies may develop bone diseases. Research on vitamin D deficiency and depression, vitamin D deficiency and back pain and vitamin D deficiency and heart attacks all show that vitamin D has a larger role to play than just bone health. Vitamin D has been implicated in auto-immune disease too. Diseases like multiple sclerosis may be caused by vitamin D deficiency (according to some theories -– read more on Multiple Sclerosis and Vitamin D). Types of Vitamin DTwo major forms of vitamin D are vitamin D2 and vitamin D3. Vitamin D2 is also called ergocalciferol and vitamin D3’s other name is cholecalciferol. When you look at supplements, most seem to focus on vitamin D3 (cholecalciferol) and you’ll see that listed as the ingredient. Read below for more on vitamin D supplementation. Who is Vitamin D Deficient? Vitamin D deficiency seems to be common in the U.S. Maybe we are all just spending too much time inside. It is estimated the 25% of U.S. adults have less than 18 nanograms per milliliter of vitamin D (severe vitamin D deficiency). Overall, 40% of men and 50% of women are thought to be lower than the healthy level of vitamin D (28 nanograms per milliliter). The people most at risk are anyone who spends a lot of time indoors (the elderly and the homebound, for example) and people with dark skin (dark skin absorbs less sunlight). Vitamin D Deficiency – What Happens in Your BodyWhen vitamin D levels are low, your body just doesn’t seem to work as well. Vitamin D deficiency has been linked to high blood pressure, insulin problems, diabetes risk, obesity and more. Receptors for vitamin D have been found on pancreatic cells that make insulin (leading to a theoretical connection between vitamin D and diabetes). We know that more heart attacks happen in the winter (when people go outside less and therefore have lower vitamin D levels) and that people survive cancer better in the summer (when their vitamin D levels are higher). But we don’t fully understand why these things are happening or what exactly vitamin D is doing in the body. Vitamin D Deficiency and Risk of DeathIn a study, records from 13,331 adults from a national survey database compiled by the U.S. government were examined to determine a link between death and vitamin D deficiency (defined as lower than 25-hydroxyvitamin D (25(OH)D). Vitamin D levels were tested from 1988 to 1994 and the people were followed until 2000 for information about cause of death. On average, people in the study were followed for 8.7 years. Researchers found that vitamin D deficiency was linked to all-cause mortality. People in with the lowest levels (bottom 25%) of vitamin D had a 26% increase in risk of death during the study period compared to people with the highest levels of vitamin D. This accounted for 3.1% of the mortality risk of the total population. Because the sample was representative of the total U.S. population, we can generalize from this study to say that 3.1% of deaths in the U.S. are linked to vitamin D deficiency. Researchers believe that vitamin D deficiency is an independent risk factor for heart disease and should be consider with other risk factors like family history, high blood pressure or being overweight. Vitamin D deficiency may also be a factor in cancer deaths as well.
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Vitamin D, uz A, E i K, spada u vitamine topive u mastima. Ovaj vitamin prirodno je prisutan u vrlo malo namirnica, međutim, uključuje više biološki aktivnih tvari poznatih pod nazivom kalciferoli. Najpoznatiji egzogeni oblici vitamina D su ergokalciferol (vitamin D2) porijeklom iz biljnih namirnica i kolekalciferol, poznatiji kao vitamin D3, koji se uglavnom nalazi u namirnicama životinjskog porijekla. Endogeni vitamin D podrazumijeva kolekalciferol koji naš organizam može proizvesti sam, i to iz kolesterola pod djelovanjem sunčeve svjetlosti, odnosno UVB zračenja. Bez obzira o kojem obliku vitamina D govorili, svi trebaju proći aktivaciju kroz dva stupnja hidroksilacije koji se događaju u jetri i bubrezima, gdje konačno nastaje aktivni oblik – 1,25 dihidroksi kolekalciferol. Vitamin D ima nekoliko uloga u našem organizmu, od kojih valja naglasiti: - održavanje odgovarajuće razine kalcija i fosfata u serumu i time omogućavanje normalne mineralizacije kostiju te rast i razvoj koštanog tkiva - modulacija rasta stanica, neuromišićnih i imunoloških funkcija - smanjenje upalnih procesa Manjak vitamina D najčešći kod male djece U novorođenčadi status vitamina D uvelike je predodređen vitaminskim statusom majke, o kojem ovisi i količina vitamina D u njezinom mlijeku. Glavni razlozi manjka vitamina D u dojenčadi su: - prehrana zasnovana na majčinom mlijeku ili, ako to nije moguće, dojenačkom mliječnom pripravku - dohrana namirnicama relativno siromašnima vitaminom D - zbog opasnosti od opeklina, mala izloženost suncu Manjak vitamina D može izazvati ozbiljne posljedice na zdravlje djeteta, od kojih je najpoznatiji rahitis. Tu bolest karakterizira demineralizacija koštanog tkiva, što uzrokuje omekšavanje i deformaciju kostiju, odgođen razvoj zubne cakline i dentina, hipokalcemiju, bol u kostima, mišićnu slabost te slabije napredovanje i niski rast. Sva dojenčad i djeca imaju povećan rizik od manjka vitamina D, a u posebno rizične skupine spadaju: - tamnoputa djeca - malo vremena i rijetko izložena suncu (koja većinu vremena provode u zatvorenom prostoru te im je tijelo velikim dijelom pokriveno odjećom) - djeca dojena do kasne dojenačke dobi bez dodavanja vitamina D - djeca koja boluju od kroničnih bolesti Europsko društvo za dječju gastroenterologiju, hepatologiju i prehranu preporučuje suplementaciju vitamina D u dojenčadi od navršenog 1. mjeseca života bez obzira na majčin vitaminski status. S druge strane, poznato je i da vitamin D u velikim dozama može biti toksičan, no predoziranje nije moguće uravnoteženom, pa čak ni njegovim izvorima bogatom, prehranom. Velike doze vitamina D mogu uzrokovati: - hiperkalcemiju, koja se zatim povezuje s pojavom velike žeđi - zaostajanje u rastu - smanjenje apetita - anoreksiju - povraćanje - smanjeni kvocijent inteligencije - kalcifikaciju mekog tkiva i stvaranje bubrežnih kamenaca Najčešći uzrok predoziranja vitaminom D je nekontrolirana suplementacija. Namirnice koje ne smijete izbjegavati Prirodni izvori vitamina D3: - masna riba (sleđ, skuša,tuna, sardine, losos) - ulje jetre bakalara - goveđa jetra i žumanjak Prirodni izvori vitamina D2: - gljive i kvasci Zbog oskudnih prirodnih izvora vitamina D njime se danas obogaćuju mlijeko i mliječni proizvodi te druge namirnice koje su njime prirodno siromašne.