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Vitamin C (ascorbic acid) review
Basics: a water-soluble vitamin, essential for the oxidation of phenylalanine and tyrosine, required for collagen synthesis.
Benefits: vitamin C helps build and maintain tissues and strengthening immune system, help decrease total and LDL cholesterol and triglycerides, protects against heart disease.
Dosage: 75 mg per day for nonsmoking women and 90 mg per day for nonsmoking men, 110 mg per day for female smokers and 125 mg per day for male smokers.
Sources: green peppers, citrus fruits and juices, strawberries, tomatoes, broccoli, turnip greens and other leafy greens, sweet and white potatoes.
Deficiency: vitamin C deficiency symptoms include tiredness, muscle weakness, joint and muscle aches, a rash on the legs, and bleeding gums.
Overdose: generally non-toxic, overdoses (more than 2,000 mg daily) may cause diarrhea, gas, or stomach upset.
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Vitamin C (ascorbic acid)

Vitamin C, also known as ascorbic acid is a water-soluble vitamin that is an essential part of life. It has a molecular formula of C6H8O6 and a molecular mass of 176.12. In 1937 the Nobel Prize for chemistry was awarded to Walter Haworth for his work in
determining the structure of ascorbic acid, and the prize for Medicine that year went to Albert Szent-Györgyi for his studies of the biological functions of ascorbic acid. In its natural state, ascorbic acid appears in the form of a white to yellowish crystal or powder. Commercial vitamin C is often a mix of ascorbic acid, sodium ascorbate and/or other ascorbates. Because the vitamin is water-soluble, it must be regularly replenished and is commonly found in fresh fruits, especially in the citrus family that is dominated by oranges, lemons, limes, and tangerines. Vitamin C is also abundant in green leafy vegetables.

An essential nutrient found mainly in fruits and vegetables. The body requires vitamin C to form and maintain bones, blood vessels, and skin. Vitamin C is perhaps the most popular vitamin among the common nutrients and biochemicals. Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. Once ingested, vitamin C is readily absorbed by the intestines and continues its journey through the watery components tissues that make up the human body, helping to build collagen protein while doubling as an antioxidant along the way. Together with flavonoids, polyphenolics and water insoluble compounds such as alpha-tocopherol (vitamin E), l-ascorbic acid contributes to the overall intake of "free radical scavengers" or "anti-oxidative metabolites" in the human diet. Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions (among others) and as a preservative.


Vitamin C (ascorbic acid) functions, uses, and health benefits

Vitamin C has multiple functions as either a coenzyme or cofactor. Vitamin C is responsible for helping to build and maintain our tissues and strengthening our immune system. Vitamin C is essential for the oxidation of phenylalanine and tyrosine, the conversion of folacin to tetrahydrofolic acid. Vitamin C may modulate prostaglandin synthesis to favor the production of
eicosanoids with antithrombotic and vasodilatory activity. 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 transfer of energy to the cell mitochondria. Ascorbic acid is required for collagen synthesis and has a structural role in bone, cartilage and teeth.

The antioxidant properties of vitamin C - Vitamin C is one of many antioxidants. Antioxidants are nutrients that block some of the damage caused by free radicals, which are by-products that result when our bodies transform food into energy. Vitamin C neutralizes potentially harmful reactions in the watery parts of the body, such as the blood and the fluid inside and surrounding cells. Vitamin C may help decrease total and LDL cholesterol and triglycerides, as well as increase HDL levels. Vitamin C's antioxidant activity may be helpful in the prevention of some cancers and cardiovascular disease. The antioxidant properties of vitamin C are thought to protect smokers, as well as people exposed to secondhand smoke, from the harmful effects of free radicals. Vitamin C strengthens the collagen structure of arteries, lowers total cholesterol, and blood pressure, an inhibits platelet aggregation.

Vitamin C and heart disease - Vitamin C may protect against heart disease by reducing the stiffness of arteries and the tendency of platelets to clump together. Long-term administration of vitamin C reverses endothelial vasomotor dysfunction in patients with coronary artery disease. Under most circumstances, dietary vitamin C is adequate for protecting against the development of or consequences from cardiovascular disease. When taken with vitamin E, vitamin C helps protect LDL ("bad") cholesterol from oxidation, thus preventing plaque buildup in coronary arteries. Individuals with high blood levels of vitamin C have significantly reduced risk of stroke. The risk of stroke was inversely related to vitamin C in the bloodstream. Vitamin C improves nitric oxide activity. Nitric oxide is needed for the dilation of blood vessels, potentially important in lowering blood pressure and preventing spasms of arteries in the heart that might otherwise lead to heart attacks. Vitamin C has reversed dysfunction of cells lining blood vessels. The normalization of the functioning of these cells may be linked to prevention of heart disease.

Vitamin C and cancer - Vitamin C may have cancer-preventive activity, at least for certain types of cancer. As a powerful antioxidant, vitamin C may help to fight cancer by protecting healthy cells from free-radical damage and inhibiting the proliferation of cancerous cells. Vitamin C to improve the antineoplastic activity of doxorubicin, cisplatin and paclitaxel. The mechanism of the effect may be pro-oxidant, not antioxidant, activity of the vitamin in potentiating the effects of these chemotherapeutic agents. High concentratins of ascorbic acid in gastric juice may reduce the risk of gastric cancer by inhibiting the formation of carcinogenic N-nitroso compounds. Ascorbic acid is toxic to viruses and bacteria and other such harmful cells. It is also toxic to cancerous cells and a little less toxic to non-cancerous cells and so it is used therapeutically in cancer therapy. Many of the pollutants which now pervade our environment can cause carcinogenic, toxic or mutagenic effects. Vitamin C may be able to combat these harmful effects, in part by stimulating detoxifying enzymes in the liver.

Vitamin C and cllagen, connective tissue - 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. Vitamin C is involved in the hydroxylation of proline to from hydroxyproline in the synthesis of collagen, a protein substance on which the integrity of cellular structure in all fibrous tissues depends. Collagen is the "glue" that strengthens many parts of the body, such as muscles and blood vessels. Collagen is a protein needed to develop and maintain healthy teeth, bones, gums, cartilage, vertebrae discs, joint linings, skin and blood vessels. Vitamin C is essential for the healing of wounds, and for the repair and maintenance of cartilage, bones, and teeth.

Vitamin C and immune system - Vitamin C may be useful as an immune stimulator and modulator in some circumstances. Vitamin C promotes resistance to infection through the immunologic activity of leukocytes, the production of interferon, and the process of inflammatory reaction, or the integrity of the mucous membranes. Vitamin C stimulates the immune system. Through this function, along with its antioxidant function, it may help in the prevention and treatment of infections and other diseases. There is some evidence that vitamin C inhibits the replication of human immunodeficiency virus 1 (HIV-1).

Other functions of vitamin C - Vitamin C has been reported to reduce activity of the enzyme, aldose reductase, in people. Aldose reductase is the enzyme responsible for accumulation of sorbitol in eyes, nerves, and kidneys of people with diabetes. Vitamin C levels in the eye decrease with age and that supplementing with vitamin C prevents this decrease, possibly leading to a lower risk of developing cataracts. Vitamin C may be helpful in protecting against some of the lipid oxidation caused by smoking. Vitamin C may be helpful in chronic diseases characterized by oxidative damage to biological molecules. People with recurrent boils (furunculosis) may have defects in white blood cell function that are correctable with vitamin C supplementation.


Vitamin C (ascorbic acid) dosage, intake, recommended daily allowance (RDA)

The recommended dietary allowance (RDA) for vitamin C in nonsmoking adults is 75 mg per day for women and 90 mg per day for men. For smokers, the RDAs are 110 mg per day for women and 125 mg per day for men. A dose of 200 milligrams daily is almost enough to maximize plasma and lymphocyte levels. Increased intakes of vitamin C are required to maintain normal plasma levels under acute emotional or environmental stress such as trauma, fever, infection, or elevated environmental temperatures. Full blood and tissue saturation is achieved with daily intakes of 200-500mg per day (in 2-3 divided doses).

Sources of vitamin C (ascorbic acid)

The body does not produce vitamin C, so it must be obtained through the diet and/or in the form of supplements. All fruits and vegetables contain some amount of vitamin C. Foods that tend to be the highest sources of vitamin C include green peppers, citrus fruits and juices, strawberries, tomatoes, broccoli, turnip greens and other leafy greens, sweet and white potatoes, and cantaloupe. Vegetables such as broccoli, sweet green and red peppers, potatoes (with skin), tomatoes, and Brussels sprouts are good sources. Cabbage and many dark green leafy vegetables are all good sources of vitamin C. Other excellent sources include papaya, mango, watermelon, brussels sprouts, cauliflower, cabbage, winter squash, red peppers, raspberries, blueberries, cranberries, and pineapples. Raw and cooked leafy greens (turnip greens, spinach), red and green peppers, canned and fresh tomatoes, potatoes, winter squash, raspberries, blueberries, cranberries and pineapple are also rich sources of Vitamin C. Ascorbic acid is a relatively fragile molecule and it may be lost from foods during preparation, cooking, and/or storage. Ascorbic acid is easily destroyed by oxidation, particularly in the presence of heat and alkalinity, and because it is highly soluble in water, it is often discarded in cooking water. Although the vitamin occurs in small amounts in animal tissues, it is usually destroyed either by exposure to air or by processing before it reaches the table.

Vitamin C (ascorbic acid) deficiency

Vitamin C deficiency results in an underhydroxylation of proline and lysine in collagen which results in a lower melting temperature of the resulting collagen fibers which causes a breakdown of the protein collagen needed for connective tissue, bones and dentin, the major portion of teeth. Pregnancy, breastfeeding, gastrointestinal diseases, and hyperthyroidism increase the need for vitamin C. Other vitamin C deficiency symptoms include general weakness, fluid retention, depression and anemia. Vitamin C deficiency can also cause slower wound-healing, increased susceptibility to infections, male infertility and increased genetic damage to sperm cells, which may lead to birth defects. A lack of vitamin C leads eventually to scurvy. Scurvy is a condition caused by a lack of vitamin C (ascorbic acid) in the diet. Signs of scurvy include tiredness, muscle weakness, joint and muscle aches, a rash on the legs, and bleeding gums. In the past, scurvy was common among sailors and other people deprived of fresh fruits and vegetables for long periods of time. The disease was especially prevalent in seamen on long sea voyages during the sixteenth and seventeenth centuries who primarily ate nonperishable foods that lacked this essential vitamin.

Vitamin C (ascorbic acid) overdose, toxicity, side effects

Vitamin C is water soluble and is regularly excreted by the body. While vitamin C is generally non-toxic, however, in high doses (more than 2,000 mg daily) it can cause diarrhea, gas, or stomach upset. At high doses, some people can experience gastrointestinal side effects such as stomach cramps, nausea, and diarrhea and may increase the risk of developing kidney stones. Intake of large amounts of vitamin C can deplete the body of copper, an essential nutrient. Vitamin C increases the absorption of iron and should be avoided by people with iron overload diseases. Those who have kidney problems should check with a healthcare provider before taking vitamin C supplements. Infants born to mothers taking 6,000 mg or more of vitamin C may develop rebound scurvy due to a sudden drop in daily intake. People with hemochromatosis should not take vitamin C supplements because of enhanced accumulation of non-heme iron in the presence of this vitamin.