http___medicinabih.info_2009_02_04_vitamin-c__1.xml
1.1 2.1 2.2 2.3 3.1 3.2 3.3 3.4 3.5 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 4.13 4.14 5.1 5.2 5.3 5.4 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 7.1 7.2 7.3 7.4 8.1 9.1
Ascorbic Acid (Sodium Ascorbate, Vitamin C) Vitamin C is the L-enantiomer of ascorbic acid. Commercial vitamin C is often a mix of ascorbic acid, sodium ascorbate and/or other ascorbates. Ascorbic acid is an organic acid and antioxidant also known as vitamin C. Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions (among others) and as a preservative. The L enantiomer of ascorbic acid is also known as vitamin C (the name "ascorbic" comes from its property of preventing and curing scurvy). Primates (including humans) and a few other species, such as the guinea pig, cannot synthesise vitamin C from glucose. Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. These compounds are water soluble and thus cannot protect fats from oxidation: for this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as food antioxidants. Vitamin C is one of the most ubiquitous vitamins ever discovered. Besides playing a paramount role as an anti-oxidant and free radical scavenger, it has been suggested to be an effective antiviral agent by some very respected scientists. Although the antiviral properties of vitamin C remain the subject of great debate in some circles, this water-soluble vitamin remains one of the most popular and important vitamins. Vitamin C is commonly found naturally in peppers, citrus fruits, tomatoes, melons, broccoli, and green leafy vegetables such as spinach, turnip, and mustard greens. The primary function of vitamin C is to assist in the production of collagen, although it is rapidly becoming identified as a key player in detoxifying the body from foreign substances. Although there is somewhat limited documentation, other reported uses of vitamin C are healing wounds and burns, accelerate healing after surgery, decreasing blood cholesterol, reduce blood clotting, offer protection against cancer agents, and extend life. As a participant in hydroxylation, vitamin C is needed for the production of collagen in the connective tissue. These fibres are ubiquitous throughout the body; providing firm but flexible structure. Some tissues have a greater percentage of collagen, especially: skin , mucous membranes , teeth and bones. Vitamin C is required for synthesis of dopamine, noradrenaline and adrenaline in the nervous system or in the adrenal glands. Vitamin C is also needed to synthesise carnitine, important in the tranfer of energy to the cell mitochondria. It is a strong antioxidant. The tissues with greatest percentage of vitamin C — over 100 times the level in blood plasma — are the adrenal glands, pituitary , thymus , corpus luteum, and retina. The brain, spleen, lung, testicle, lymph nodes, liver, thyroid, small intestinal mucosa, leukocytes, pancreas, kidney and salivary glands usually have 10 to 50 times the concentration present in plasma. Sodium ascorbate is ascorbic acid that has been buffered (neutralized) with sodium until the taste is very bland. Sodium ascorbate generally provides 131 mg of sodium per 1,000 mg of ascorbic acid (1,000 mg of sodium ascorbate contains 889 mg of ascorbic acid and 111 mg of sodium). Individuals following low-sodium diets(e.g. for high blood pressure) are generally advised to keep their total dietary sodium intake to less than 2,500 mg/day. Megadoses of sodium ascorbate could significantly increase sodium intake. The most plentiful tissue in the body is collagen, which is a connective tissue. The primary role of Vitamin C is to help this connective tissue. Because collagen is the defense mechanism against disease and infection, and because Vitamin C helps build collagen, it makes sense that it is also a remedy for scurvy by contributes to hemoglobin production. It promotes the production of red-blood-cell in bone marrow. Ascorbic Acid also supports healthy capillaries, gums, teeth, and even helps heal wounds, burns, and broken tissues. It contributes to hemoglobin and red-blood-cell production in bone marrow while even preventing blood clots. The list goes on. It helps heal urinary-tract infections, and helps treat anemia. Another large benefit of this vitamin is the fact that it plays a large role in the production of antibodies. When the immune system is being overworked, for example when a cold strikes or when your body is wounded, Vitamin C comes in to play by beefing up the white blood cell count and function. It also functions as a promoter of interferon, a compound that fights cancer. An example of this would be blocking production of nitrosamines which are thought to be carcinogenic Synonyms: Vitamin C, numerous trade names, l-ascorbic acid, l-(+)-ascorbic acid, l,3-ketothreohexuronic acid Molecular formula: C6H8O6
1.1 2.1 2.2 3.1 4.1 4.2 4.3 5.1 5.2 6.1 7.1 7.2 7.3 7.4 7.5 8.1 9.1 9.2 9.3 10.1 10.2 11.1 11.2 12.1 13.1 13.2 14.1 14.2 15.1 16.1 17.1 18.1 18.2 19.1 19.2 19.3 20.1 21.1 22.1 22.2 22.3 23.1 23.2 24.1 24.2 25.1 26.1 27.1
Šta je vitamin C Vitamin C (askorbinska kiselina) je vrlo važan esencijalni nutrijent, što znači da ga moramo unositi prehranom. Nalazi se gotovo isključivo u svježem voću i povrću. Vitamin C je izrazito nestabilan vitamin, tako da ga kuhanje ili dugotrajno izlaganje zraku u velikoj mjeri uništava. Vitamin C je nužan svim živim bićima, pa tako i čovjeku, zbog njegove uloge u proizvodnji kolagena. Važan je i zbog zaštite vitamina A i E, ali i masnih kiselina od oksidacije. Dovoljne količine vitamina C sprječavaju i liječe bolest skorbut, a pomažu i kod liječenja anemije. Kolagen je vezivno tkivo koje se može opisati kao “međustanično ljepilo”, i kao takvo je prisutno u cijelom tijelu. Vezivno tkivo daje našem tijelu oblik i “drži” organe. Da bi lakše procijenili važnost kolagena, evo 5 tipova kolagena i gdje se koriste: Vidljivo je da je kolagen prisutan u svim dijelovima tijela, a vitamin C igra važnu ulogu u stvaranju kolagena. Naime, prilikom sinteze kolagena, u tijelu se odvijaju mnoge reakcije – unutar i izvanstanične. Vitamin C je aktivan unutar stanice gdje pospješuje hidroksilaciju (dodavanje vodika i kisika) dvjema aminokiselinama: prolinu i lizinu. U kasnijoj fazi reakcije, te dvije kiseline stvaraju kolagen. Bez vitamina C, proces stvaranja kolagena je onemogućen što može prouzročiti brojne probleme u cijelom tijelu. Osim u stvaranju kolagena, ovaj u vodi topiv vitamin ima brojne biološke funkcije. Vitamin C kao jak antioksidant štiti LDL kolesterol od oksidiranja. Istraživanja pokazuju da upravo takav, oksidiranjem “oštećen” LDL dovodi do bolesti srca i krvnih žila. Vitamin C također štiti od srčanih bolesti tako što smanjuje krutost arterija. Antioksidativna svojstva vitamina C djelomično štite pušače, kao i ljude koji su izloženi pasivnom pušenju, od štetnih utjecaja slobodnih radikala. Kontrolirano kliničko ispitivanje je pokazalo da veće količine vitamina C mogu smanjiti štetu uzrokovanu slobodnim radikalima, kao i oksidaciju LDL-a kao posljedicu izloženosti dimu cigarete. Vitamin C igra vrlo bitnu ulogu u procesu zacjeljivanja rana, a ponaša se i kao antihistaminik. Potreban je i kod proizvodnje jetrene žuči, kao i kod detoksikacije alkohola iz tijela. Dnevne potrebe Iako skorbut više gotovo ne postoji u zapadnim zemljama, velik dio medicinske struke smatra da većina ljudi uzima nedovoljne količine vitamina C u svojoj prehrani. Iako je svega 10 mg vitamina C dnevno dovoljno da bi se spriječila pojava skorbuta, unos manje od 50 mg vitamina C dnevno može znatno uvećati rizik od bolesti srca i katarakte. Malaksalost, krvarenje iz desni i dugotrajne modrice rani su znaci nedostatka vitamina C, koji se srećom pojavljuju znatno prije samog skorbuta. Ipak, mnogi stručnjaci skorbut i njegove simptome ne smatraju znakovima nedostatka vitamina C, već zadnjim upozorenjima prije ozbiljnih posljedica. Posebno su ugroženi pušači koji imaju nisku količinu vitamina C i potreban im je unos dodatnih količina vitamina C kako bi održavali potrebnu koncentraciju. Primjećeno je i da žene sa niskom količinom vitamina C u krvi imaju povećan rizik od žučnih kamenaca. Preporučena količina vitamina C RDA predstavlja prosječnu količinu potrebnu da bi se zadovoljile potrebe organizma za vitaminima ili mineralima kod zdravih pojedinaca. RDA mogu varirati ovisno o spolu, dobi ili posebnim stanjima – primjerice u trudnoći. RDA (eng. “Recommended Dietary Allowance” – preporučena dnevna doza) vitamina C za odrasle nepušače je 60 mg dnevno. Kako pušači imaju smanjenu količinu vitamina C, potreban im je unos dodatnih količina vitamina C – do 100 mg dnevno. tablica potreba za vitaminom C: Odnedavno, stručnjaci sugeriraju povećavanje RDA na 100 – 200 mg vitamina C dnevno za odrasle. Potrebe za vitaminom C se povećavaju sa stresom, bilo psihološkim ili fiziološkim. Pušenje smanjuje apsorpciju vitamina C, povećavajući potrebu za njegovim unosom. Kontracepcijska terapija, upotreba kortizona ili estrogenska terapija u menopauzi, također povećavaju potrebu za dodatnim unosom. Kako bakar inaktivira vitamin C, potrebno ga je nadomjestiti dodatnim vitaminom C. Nikotin i estrogen povećavaju količinu bakra u organizmu. Vitamin C djeluje brzo, tako da tijelo “upotrijebi” potrebnu količinu vitamina C, a ostatak u kratkom roku izbaci. Stoga ukupan unos vitamina C treba rasporediti u nekoliko (4-6) doza tijekom cijelog dana. tablica potreba za vitaminom C prema indikacijama legenda REFERENCE: