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Updated March 26, 2015. Written or reviewed by a board-certified physician. See About.com's Medical Review Board. Vitamin D deficiency can result in weak, brittle bones. Children who don't get enough may have rickets, and adults with vitamin D deficiency are at a greater risk for osteoporosis. The adequate daily intake for vitamin D is from 200 to 600 International Units (IU); however, some experts believe those numbers should be increased. Three ounces of salmon contains about 800 IU, a cup of milk has just over 100 IU, and one serving of fortified breakfast cereal usually has about 40 IU vitamin D. Symptoms of Deficiency People with vitamin D deficiency may experience bone pain and muscle weakness although the symptoms may be very mild at first. Children who have rickets suffer from soft bones and skeletal deformities. Deficiency in adults will cause osteomalacia, or weakened bones. Your health care provider can order tests that measure the levels of 25-hydroxy vitamin D. Insufficient levels of vitamin D in the blood have been associated with a variety of other health conditions such as diabetes, hypertension, multiple sclerosis and some forms of cancer. However, more research is needed to determine if vitamin D can prevent or treat any of these disorders. Causes of Deficiency Not eating foods that contain vitamin D and not getting enough sun exposure may lead to vitamin D deficiency. Breastfed infants, older adults, housebound individuals and people with dark skin are at higher risk of vitamin D deficiency. People who have fat absorption problems due to conditions such as Crohn's disease, cystic fibrosis, gastric bypass surgery or have liver or kidney conditions may not get enough vitamin D from their diets. You need sun exposure to make vitamin D, but it only takes 5 to 30 minutes of sun exposure on your face, arms, legs or back twice each week without sunscreen to stimulate sufficient vitamin D production. Excessive sun exposure increases your risk of skin cancer, so it's important to use sunscreen and limit your use of tanning beds. Vitamin D is not naturally present in many foods; however, oily fish and especially cod liver oil are rich in vitamin D. Beef liver, eggs and cheese also contain small amounts. Vitamin D is added to some foods like milk and fortified breakfast cereals. Can You Get Too Much? Your body stores fat-soluble vitamins such as vitamin D, but excessive sun exposure will not cause vitamin D toxicity. It would be extremely difficult to get too much vitamin D from foods -- even fortified foods -- unless you consume large amounts of cod liver oil. You can take vitamin D supplements - usually as vitamin D2 or vitamin D3. Taking large doses of these supplements can lead to vitamin D toxicity that causes nausea, vomiting, loss of appetite, constipation, weakness and weight loss. High levels of vitamin D in your body can also raise your blood levels of calcium, which can result in mental confusion and abnormal heart rhythm. If you want to take vitamin D supplements, follow the label directions unless your health care provider tells you differently. Source: Office of Dietary Supplements National Institutes of Health. "Dietary Supplement Fact Sheet: Vitamin D." Accessed September 17, 2010. http://ods.od.nih.gov/factsheets/vitamind/. Disclaimer: The information contained on this site is intended for educational purposes only and is not a substitute for advice, diagnosis or treatment by a licensed physician. You should seek prompt medical care for any health issues and consult your doctor before taking dietary supplements or making any major dietary changes.
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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.