La Vitamin C, also called ascorbic acid o ascorbate, is a nutrient essential belonging to the group of vitamins water-soluble - as well as all those of group B.
Many animals, including amphibians, reptiles, some birds and mammals, can synthesize vitamin C from glucose. On the other hand, among the Mammals, only man, other primates and the guinea pig DON'T they have this ability due to the deficiency of the enzyme L-gulono-g-lactone oxidase. In this case it must therefore be assumed with the diet.
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Already in the sixteenth century it was known that scurvy could be prevented or cured by administering extracts of pine needles, vegetables or lemon, but only in 1912 Funk hypothesized the presence in green plants of a water-soluble substance with antiscorbutic action, in 1921 this substance was isolated and named vitamin C.
Vitamin C is situated mainly in the food of origin vegetable and only marginally in the liver (offal) and in milk. Instead, stand out for the intake of ascorbic acid: citrus fruits, Other sour fruits (come in kiwi and mele), i pepperoni, parsley, i cabbage, strawberries etc.
Sensitive to oxygen, heat and light, vitamin C is a very delicate nutrient that wastes with storage and various manipulations. Given his thermolability, after cooking, much lower quantities remain, already affected by cutting and therefore by exposure to oxygen (worsened by storage).
Le functions main components of vitamin C gravitate around the riparazione of body tissues, to the production of some neurotransmitters, to the functioning of numerous enzymes, to function immune and that antioxidant. It is used as additive food, for supplements and cosmetics. This is the vitamin most interested from the food supplement industry - especially for its immune and antioxidant role.
Vitamin C - especially in association with NSAIDs such as acetyl salicylic acid - is included in the list of essential medicines of the "World Health Organization" (WHO), among the safest and most effective necessary for the health system. It is available both as a generic drug and as an over-the-counter product.
L'absorption of vitamin C is efficient and occurs in theintestine tenuous. If taken in excessive quantities, the effectiveness of this process decreases. When absent or almost absent in the diet (avitaminosis or hypovitaminosis), it determines the onset of scurvy, which however appears after weeks or months - depending on the fullness of the stocks in liver and in adrenal.In summary: Vitamin C in Brief
Basics of chemistry
Vitamin C is the term used to indicate the redox system ascorbic acid deiroascobic acid, a reversible redox system with a strong antioxidant action. Ascorbic acid is the enol form of 3-keto-L-gulofuranolactone.
For further information: Natural or Synthetic Vitamin C?
Biological role of vitamin C in animals
As anticipated, vitamin C is an essential nutrient for some animals, including humans.
The term generic of vitamin C includes several vitameri which have the same biological activity. THE salts of ascorbate such as'sodium ascorbate el 'calcium ascorbate, mainly used in food supplements, release ascorbate (active ingredient) following digestion.
L'acid ascorbic el 'ascorbate they are both naturally present in the body, as the two forms alternate in base al pH. Oxidized forms of the molecule, such asdehydroascorbic acid, are converted back into ascorbic acid by reducing agents.
In animals, vitamin C acts as cofactor in many enzymatic reactions which mediate a wide variety of essential biological functions, including the healing of the wounds and the synthesis of collagen. In humans, the shortage of vitamin C leads to a altered synthesis of collagen, contributing to symptoms more gravi the scurvy.
Another biochemical role of vitamin C is of antioxidant (a reducing agent) donating electrons to various enzymatic reactions e non-enzymatic. This way yes convert vitamin C in his state oxidized, both like semidehydroascorbic acid That like dehydroascorbic acid. These compounds can be reset one been reduced from glutathione and by the enzymatic mechanisms dependent on the NADPH.For further information: Synthesis of Vitamin C
Biological role of vitamin C in plants
In plants, vitamin C is a substrate forascorbate peroxidase. This enzyme uses ascorbate to neutralize il peroxide of hydrogen excess (H2O2) converting it into water (H2O) and oxygen.
Functions of vitamin C in the body
Vitamin C is needed for numerous processes di hydroxylation catalyzed by some oxygenase (enzymes). It performs important functions such as:
- Biosynthesis of collagen: where it intervenes in the conversion area of proline in hydroxyproline and Lysine in hydroxylisine by the proline hydroxylase and lysine hydroxylase requiring Fe ++ (vitamin C keeps iron in a reduced form);
- Synthesis area of norepinephrine (neurotransmitter) starting from dopamine and, in all likelihood, of the tryptophan in Serotonin;
- Synthesis area of carnitine, essential for the transfer of acyls (fatty acids) in the mitochondria;
- Catabolism area of tyrosine ad fumaric acids e acetacetic through the formation of homogentisinic acid;
- Amidazione of the carboxyterminal end of peptides hormonal which the vasopressin, L 'oxytocin cholecystochinin, L 'adrenocorticotropic hormone (ACTH) and the releasing hormone tireotropin;
- Biosynthesis of bile acids, in fact in guinea pigs subjected to a vitamin deficient diet the synthesis is reduced;
- Stimulation area of reductasi of cytochrome P450, responsible forhydroxylation in position 7-a del cholesterol, necessary for the synthesis ofacid colic;
- Activation dell 'folic acid in tetrahydrofolic acid (FH4), biologically active form;
- Regulation of endogenous levels of histamine, inhibiting its release and promoting its degradation (vitamin C is used for therapeutic purposes to prevent anaphylactic shock, pre-eclampsia and prematurity in complications of pregnancy);
- Biosynthesis of steroid hormones of the adrenal cortex (by hydroxylation); in fact, when the hormonal need in the cortex increases, both cholesterol and vitamin C are depleted;
- Absorption intestinal of the iron (reducing ferric Fe to ferrous and favoring the formation of stable chelates capable of maintaining soluble Fe in an alkaline environment), its transfer from plasma transferrin to tissue ferritin and increased intracellular availability favoring the iron-ferritin bond and increasing the stability of the complex itself;
- Reduction of the efficiency ofabsorption intestinal of the copper, since the oxidized form is more absorbed than the reduced one (at high doses of the vitamin);
- Reduce la toxicity di some minerals (Ni, Pb, V, Cd, Se), which in reduced form are more difficultly absorbed or excreted more quickly;
- Favor l'use of selenium at physiological doses, increasing the bioavailability of some of its organic and inorganic forms;
- Action preventive in cancerogenesi by nitrosamines, inhibiting their synthesis, which occurs in the intestine, by reaction of nitrites with amine groups;
- Reduction of superoxide ions, hydroxyl radicals, Dell 'hypochlorous acid and other powerful oxidants, protecting the DNA structure of proteins and membranes from the damage that these oxidants could cause;
- Constitution, together with vitamin E, of a system of protection against oxidative damage caused by free radicals: i PUFA are protected dai tocopherols, which upon irradiation form phenoxy radicals, the tocotrienoxyls, to be then regenerated at the expense of Vitamin C which forms an ascorbyl radical;
- Immune function, in fact it has been experimentally observed that vitamin C is able to:
- stimulate the production of interferon, which protect cells from viral attacks;
- stimulate the proliferation of neutrophils;
- protect proteins frominactivation by free radicals produced during the oxidative processes that occur in neutrophils;
- stimulate the summary of humoral thymic factor and to the antibodies of the IgG and IgM classes.
Vitamin C and health
The latest scientific evidence DON'T support the use of vitamin C for prevention the common cold; there are, however, some indications that "regular use of ascorbic acid may reduce la duration".
It is not clear if theintegration of vitamin C affect on cancer risk, cardiovascular diseases o dementia. Can be hired for orally or for injection.
Adverse reactions of vitamin C administration
Vitamin C is generally well tolerated. High doses can cause discomfort gastrointestinal, mall in forehead, sleep disorders e redness of the skin. Vitamin C is indeed beneficial for the skin. The normal doses are safe during the pregnancy. The "United States Institute of Medicine" recommends DON'T take large doses.For further information: Vitamin C and Tumors
Vitamin C deficiency and scurvy
Lo scurvy is the disease resulting from vitamin C deficiency. Without the latter, the collagen produced by the body is too much unstable to perform its function and many other enzymes in the body cannot function.
Scurvy is characterized by skin spots e bleeding, render "spugnose", growth hair "corkscrew"And poor healing of wounds. The skin lesions I am more plentiful on thighs and legs; also appear: pallor, trough e low level of outdoor general motor. In advanced scurvy they manifest themselves wounds suppuranti, perdita di teeth, anomalies bone and, finally, death. The human body can only store a certain amount of vitamin C and thus, if new supplies are not consumed, the body's stores are depleted.
In the past, numerous studies were conducted on experimentally induced scurvy. Part of these occurred on conscientious objectors during the Second World War in Great Britain, another on prisoners from the state of Iowa (USA), between the late 60s and 80s. The latter developed the first signs of scurvy about four weeks later the beginning of the free diet of vitamin C, whereas in the previous British study they were needed six to eight months, probably thanks to the preload evaluation with 70 mg / the to six weeks before the pro-scorbutic diet was administered. In both studies, blood levels of ascorbic acid were too low to be accurately measured. Both reported that all obvious symptoms can be inverted con l 'integration only 10 mg / the.
Vitamin C toxicity
Too much vitamin C in the diet DON'T is absorbed e excess levels in the blood are quickly excreted in urine, then presents a toxicity acute noticeably low. More di 2-3 g can cause indigestion, in particular if hired a empty stomach.
However, the intake of vitamin C in the form of sodium ascorbate e calcium ascorbate can reduce at the minimum this effect. Other symptoms reported for high doses of vitamin C include: nausea, cramps abdominals e Diarrhea. These effects are attributed to action osmotic of vitamin C not absorbed through the intestine. In theory, a high intake of vitamin C can cause absorption excessive di iron. A summary of reviews related to vitamin C supplementation in healthy subjects DON'T highlighted this problem but DON'T has not even tested this possibility on people with hemochromatosis hereditary.
Il risk that the excess of vitamin C can favor i kidney stones è controversial. Reports on the formation of renal lithiasis associated with excessive ascorbic acid intake are in fact limited only to subjects with pre-existing renal disease. Data from epidemiological studies DON'T support an association between excessive ascorbic acid intake and the formation of kidney stones in apparently healthy individuals, although a large multi-year study reported an increase nearly two times higher than normal.
Vitamin C requirement
Different national agencies have established different recommendations on vitamin C intake for adults:
- 40 mg / die: India National Institute of Nutrition, Hyderabad;
- 45 mg / die o 300 mg / settimana: World Health Organization;
- 80 mg / die: European Commission Council on nutrition labeling;
- 90 mg / day (males) and 75 mg / day (females): Health Canada 2007;
- 90 mg / day (males) and 75 mg / day (females): United States National Academy of Sciences;
- 100 mg / die: Japan National Institute of Health and Nutrition;
- 110 mg / die (maschi) e 95 mg / die (femmine): European Food Safety Authority.
EFSA (European Food Safety Authority) has made higher recommendations for adults and also for children:
- 20 mg / day from 1 to 3 years;
- 30 mg / day for 4 to 6 years;
- 45 mg / day from 7 to 10 years;
- 70 mg / day from 11 to 14 years;
- 100 mg / day for males aged 15-17 years;
- 90 mg / day for females aged 15-17 years;
- for pregnancy 100 mg / day;
- for lactation 155 mg / day.
India, on the other hand, has set much lower recommendations:
- 40 mg / day for 1 year onwards;
- 60 mg / day for pregnancy;
- 80 mg / day for breastfeeding.
Clearly, there is no consensus between countries.
I smoking of cigarettes and people exposed to passive smoking have plasma levels of vitamin C lower than non-smokers. Smoke inhalation is thought to cause oxidative damage, running out of this vitamin.
The US Institute of Medicine has estimated that smokers need 35 mg / day more of vitamin C than non-smokers, but has not formally set a higher RDA for smokers.
A meta-analysis showed one inverse relationship between taking vitamin C and lung cancer, although he concluded that they are necessary further research to confirm this consideration.
In 2000, the Institute of Medicine de US National Academy of Sciences set a Tolerable upper intake level (UL) for adults of 2000 mg / the. This amount was chosen because human studies reported diarrhea and other gastrointestinal disturbances a dosage> 3000 mg / die. This is the lowest observed adverse effect level (LOAEL), which means that other adverse effects were seen at higher doses.
The European Food Safety Authority (EFSA) reviewed the matter in 2006 and concluded that DON'T there is sufficient evidence to establish a UL for vitamin C. The Japan National Institute of Health and Nutrition looked into the same issue in 2010 and drew the same conclusion.For further information: Megadoses of vitamin C
Foods rich in vitamin C
The richest natural sources of vitamin C are fruit e vegetables. This is the most widely used dietary supplement and is available in a variety of forms, including tablets, drink mixes and capsules.
Foods are generally a good source of Vitamin C vegetable origin, but that depends on the variety area of plant, from the conditions of soil, from climate where she grew up, from duration of the collection, from the conditions of storage and by the method of preparazione. Since some plants were analyzed fresh while others were dried (thus, artificially increasing the concentration of individual components such as vitamin C), the data is potentially subject to variation. The quantity is expressed in mg / 100 g of edible portion.
Note: cooking can reduce the vitamin C content of vegetables by about 60%, probably due to greater enzymatic destruction. Longer cooking times can be added to this effect.
Vitamin C is also found in fruit and vegetables in November and December.
|Food||mg / 100 g|
|Prugne Kakadu||1000 5300|
|Malacca o amala||445|
|Red and yellow peppers||128|
|Loganberry (blackberry x red raspberry), red currant, Brussels sprouts||80|
|Passion fruit, Spinach||30|
|Potato, green melon||20|
|Carrot, apple, asparagus||6|
Sources of animal origin
Foods of animal origin DON'T they provide a lot of vitamin C; the little content comes in large part destroyed from heat cooking. For example, raw chicken liver contains 17,9 mg / 100 g but, when fried, the content does decreases at 2,7 mg / 100 g. Chicken eggs DON'T they contain vitamin C, neither raw nor cooked. Vitamin C is present in human breast milk at 5,0 mg / 100 g and 6,1 mg / 100 g in a sample of infant formula; cow's milk contains only 1,0 mg / 100 g.
Absorption and Transport
Absorption of vitamin C
Vitamin C comes absorbed in the proximal part of thebowel outfit for facilitated Na + dependent transport; absorption decreases in old age, in the cases of acloridria and infections intestinal.
Il degree of absorption for dietary doses it is high 70÷90 %, but declines for doses > 1 g; aspirin inhibits its absorption.
Transport of vitamin C
Vitamin C comes transported in plasma dall 'albumin in the form of ascorbic acid, that enters in cells like dehydroascorbic acid - L 'insulin promotes the passage and glucose inhibits it.
Once in, the dehydroascorbic acid comes reduced ad ascorbic acid which is mainly concentrated in cytoplasm where it performs the function of antioxidant.For further information: Vitamin C Antioxidant Additive
Deposit and Disposal
Vitamin C storage
The vitamin C pool in the body human and approx 1,5÷5 g, could be accumulated especially in liver and in adrenal glands, this explains why the symptoms give shortage only appear after 4 months.
Elimination of vitamin C
Il catabolism of dehydroascorbic acid occurs for hydrolysis of the ring with the formation of 2,3-diketo-L-gulonic acid, which can be decarboxylated to CO2 and compounds with 5 carbon atoms (xylose, xylonic acid) or oxidized to oxalic acid and compounds with 4 carbon atoms ( threonic acid).
Ascorbic acid comes eliminated mainly with urine; it is partially reabsorbed in the renal tubules by active Na + dependent transport, which together with intestinal absorption represents a homeostatic regulation mechanism.For further information: Ascorbic acid - Vitamin C: how much and in what form
Vitamin C supplements
Vitamin C supplements help the body to take ascorbic acid, but is this supplement really necessary? As we underline in the article dedicated to ascorbic acid supplements: "if we want to rely on the advice of official medicine, the integration of vitamin C is not necessary, but not dangerous, unless you take real megadoses. Since often the truth lies in the middle, most experts in favor of this practice recommend daily dosages ranging from 180/360 to 500/1000 mg / day. "
So let's see what are the vitamin C supplements that we can find on the market.
Before resorting to the use of natural remedies and supplements to strengthen the immune system, it is always good ask for the prior opinion of your doctor, even more so if you suffer from pathologies, if you are in particular conditions (for example, pregnancy or breastfeeding) and / or if you are following drug therapies. This is because even natural products can interfere with the action of drugs and medicines, can cause unwanted effects and can present contraindications to use.
Furthermore, remember that it is good to buy titrated and standardized products in active ingredients; only in this way, in fact, is it possible to really know which and how many active substances you are taking.GloryFeel® Vitamin C 1000mg High Dose | 200 Tablets | Vegan, Lactose Free, Gluten Free | Strengthening the Immune System by € 17,95 € 19,95 -10% Check offer
Glory Feel is a high-dose vitamin C supplement, designed to promote the proper functioning of our immune system and the production of collagen. A single tablet contains 1000 mg of Vitamin C and a pack contains 200 tablets, a number that should cover the need for 15 months. It is a vegan product that does not contain gluten or lactose. Additionally, Glory Feel was made from ingredients that do not contain GMOs, artificial fertilizers or pesticides.Vitamin C 1000 mg | 180 tablets (Supply For 6 Months) Dietary Supplements Nu U Nutrition yes € 16,97 Check out the offer
Nu U Nutrition is a vitamin C supplement. Each Nu U Nutrition product tablet contains 1000 mg of ascorbic acid; the package contains a quantity of tablets that cover the needs of 6 months. It is a product made in the United Kingdom that does not contain lactose, soy or gluten and which is also suitable for those who follow a vegetarian or vegan diet, as it does not contain ingredients of animal origin. Amazon reviews on this supplement are very positive, many users consider it a great product: easy to swallow, despite the size of the pill, it is also a very affordable product.
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