Vitamin C - Benefits, Deficiency Symptoms And Food Sources
Alternative name :: Ascorbic Acid
Vitamin C, also known as ascorbic acid, is the antiscorbutic factor. It is a water-soluble vitamin, which is essential for the normal functioning of the body. Unlike most mammals, human beings do not have the ability to make their own vitamin C. We must therefore, obtain it from the diet.
Scurvy had been known as a dreaded disease since ancient times. In 1747, Dr. James Lind, a British physician, found that oranges and lemons could cure scurvy. During the same period, Captain Cook was able to reduce the incidence of scurvy on his ongoing voyages by stocking up fresh fruits and vegetables. The antiscorbutic factor was isolated in 1928 by Dr. Szent-Gyorgyi and its chemical structure was elucidated by him and Dr. C G King in 1932.
Of all the water-soluble vitamins, vitamin C is the most unstable and easily destroyed vitamin. It is highly soluble in water and gets easily destroyed by oxygen, alkalis and high temperature. Vitamin C is easily oxidized to dehydroascorbic acid, which is also active. The oxidation is accelerated by heat, light, alkalis, oxidative enzymes and traces of metals such as copper and iron. Oxidation is inhibited to a marked degree in an acid reaction and when the temperature is reduced. Vitamin C is easily destroyed during cooking.
On an average, about 50% of the vitamin C in foods is lost during different cooking procedures, although these could be higher than the quoted figure. On the contrary, fermentation and germination result in significant increase in the vitamin C content of foodstuffs.
Vitamin C is the most widely taken supplement in America . And with good reason. It is responsible for the formation, maintenance, and repair of collagen, the substance that forms the foundation of skin, ligaments, cartilage, vertebral discs, joint linings, capillary walls, and the bones and teeth.
Functions of vitamin C
Vitamin C serves several metabolic functions - as an enzyme cofactor, an antioxidant, a protective agent, and as a reactant with transition metal ions. Each of these functions involves the oxidation/reduction properties of the vitamin. Vitamin C is easily oxidized and this forms the basis of most of its functions in the body.
The first step in the formation of bone is a fibrous network, which consists largely of a protein called collagen. More generally speaking, collagen is found in the 'connective tissue' or the tissue, which holds together different tissues or organs, including the walls of the blood vessels. One of the principal functions of vitamin C is in the formation of collagen. In the synthesis of collagen, vitamin C is essential for the hydroxylation (addition of-OH groups) of amino acids - proline and lysine. The hydroxyamino acids hydroxyproline and hydroxylysine - are essential constituents of collagen. Thus, vitamin C is important in the healing of wounds and fractures, and in maintaining the integrity of blood capillaries.
Vitamin C also plays an important role in other hydroxylation reactions. These involve the conversion of amino acid tryptophan to serotonin, an important neurotransmitter, and the conversion of amino acid tyrosine to norepinephrine. Vitamin C is also required for the breakdown of cholesterol to bile acids.
Vitamin C is required for the conversion of folacin to tetrahydrofolic acid, the active form of the vitamin. Vitamin C also enhances the absorption of iron by reducing the ferric ion to ferrous. It also promotes resistance to infections through the immunologic activity of leukocytes (white blood cells).
Vitamin C is an important antioxidant and thus has a role in the protection of vitamins A and E and polyunsaturated fatty acids from excessive oxidation. By virtue of its antioxidant property, vitamin C can quench potentially toxic reactive species (free radicals) from causing oxidative damage to body tissues.
Benefits of vitamin C
Daily allowances of vitamin C
Typical doses of vitamin C range from 500 milligrams to 2 grams per day. However, many people increase their dosage to 4 to 5 grams a day when coming down with cold to produce an antihistaminic effect. High doses of supplemental vitamin C may help to detoxify some carcinogens in the stomach prior to digestion of the vitamin.
Rich sources of vitamin C
Vitamin C is found in berries, citrus fruits, and green vegetables. Good sources include asparagus, avocados, beet greens, black currants, broccoli, Brussels sprouts, cantaloupe, collards, dandelion greens, dulse, grapefruit, kale, lemons, mangos, mustard greens, onions, oranges, papayas, green peas, sweet peppers, persimmons, pineapple, radishes, rose hips, spinach, strawberries, Swiss chard, tomatoes, turnip greens, and watercress.
Deficiency symptoms of vitamin C
A deficiency of vitamin C impairs collagen formation and retards healing of bone fractures. Two of the most notable signs of vitamin C deficiency reflect its role in maintaining the integrity of blood vessels. The gums bleed easily around the teeth and capillaries under the skin break spontaneously, producing pinpoint haemorrhages.
The first symptoms of scurvy include weakness, fatigue, loss of appetite, depression, and swollen gums, which bleed profusely on touching. Muscles, including the heart muscle, begin to degenerate. The skin becomes rough, brown, scaly and dry. Wounds fail to heal as scar tissue does not form. Bone rebuilding falters; the ends of long bones become softened, malformed, painful and prone to fractures. The joints become swollen and painful. Since vitamin C is involved in iron metabolism, anemia is often associated with scurvy.
Edema (water retention) also happens with a shortage of vitamin C, and weakness, a lack of energy, poor digestion, painful joints and bronchial infection and colds are also indicative of an under-supply.
Vitamin C toxicity
The easy availability of vitamin C supplements and publication of materials claiming that vitamin C is a cure for colds and cancers have led thousands of people to take large doses of vitamin C. The main adverse effects produced due to excessive vitamin C intake include nausea, abdominal cramps, and diarrhea. Another toxic effect could be the formation of oxalate stones in kidney because the breakdown of vitamin C yields oxalates. Vitamin C supplements are toxic for people with iron overload because it promotes iron absorption. An upper intake level of 2g vitamin C per day has been suggested to prevent gastrointestinal disturbances from excessive intakes.
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