Vitamin C

Vitamin C, the L-enantiomer of ascorbic acid, is a water-soluble vitamin used by the body for several purposes.

Sources

Citrus fruits (lime, lemon, orange, grapefruit) and tomatoes are very high in vitamin C. Other foods that are good sources of vitamin C include papaya, broccoli, brussels sprouts, blackberries, strawberries, cauliflower, spinach, cantaloupe, and blueberries. Any excess of vitamin C is generally excreted in the urine. Most animals can synthesize their own vitamin C, but some animals, including primates, guinea pigs, and humans, cannot. Vitamin C was first isolated in 1928, and in 1932 it was found to cure scurvy.

Functions of Vitamin C in the Body

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, including:

• skin
• mucous membranes
• teeth
• bones

Vitamin C is also required for synthesis of dopamine, noradrenaline and adrenaline in the nervous system or in the adrenal glands. It is a strong antioxidant.

Lack of ascorbic acid in the daily diet leads to a disease called scurvy, a form of avitaminosis that is characterized by:

• loose teeth
• superficial bleeding
• fragility of blood vessels
• poor healing
• compromised immunity
• mild anaemia

Daily Requirement

The dietary amounts recommended by various authorities are 50-150 mg of ascorbic acid per day. High doses (thousands of mg) are used but may result in diarrhea.

In April 1998 Nature reported alleged carcinogenic and teratogenic effects of excessive doses of vitamin C. This was given a great deal of prominence in the world's media. The effects were noted in test tube experiments, and on only two of the 20 markers of free radical damage to DNA. They have not been supported by further evidence from living organisms. Almost all mammals manufacture their own Vitamin C in amounts equivalent to human doses of thousands of mg per day. The vitamin is used widely in orthomolecular medicine and no harmful effects have been reported even in doses of 10,000 mg per day or more.

Vitamin C is needed in the diet to prevent scurvy. It also has a reputation for being useful in the treatment of colds and flu. The evidence to support this idea, however, is ambiguous.

Theraputic Uses

Nobel Prize winning chemist Linus Pauling began actively promoting vitamin C in the 1960s as a means to greatly improve human health and resistance to disease.

A minority of medical and scientific opinion continues to see vitamin C as being a low cost and safe way to treat infectious disease and to deal with a wide range of poisons.