Vitamin C may be shown on labels as L-ascorbic acid. It is water-soluble, and not stored by the body, so you need to eat or drink some every day, preferably two or three times a day. Although the RDA for both adults and children is very low, many people have been taking up to 3g (3,000mg) a day since the 70s, with no ill effect.

Vitamin C is one of the four main antioxidant nutrients. Its known effects include:

promotion of iron absorption
providing resistance to infection
maintaining healthy collagen
activating folic acid
production of anti-stress hormones
production of substances used in the brain and nervous system
maintaining healthy bones, teeth, blood and sex organs
with beta-carotene, lowers risks of cancer.
See Note for smokers
anti-histamine

A deficiency of this important vitamin causes weakness, general tiredness, muscle and joint pains, irritability, bleeding gums and loose teeth. The deficiency disease is scurvy, which has been virtually eliminated in the West.

This vitamin has been the subject of numerous studies over the years since its discovery. Some of the most interesting include:

In June 1999, the Linus Pauling Institute, Oregon State University showed that Vitamin C in the body does not interact with metals to become a pre-oxidant, as had been previously thought. On the contrary, Vitamin C acts as an antioxidant, with beneficial effects on health.
A study of 85,000 nurses who took a daily supplement of at least 360mg of Vitamin C for 16 years found a 30% reduction in their risk of heart disease (Cardiology, July 16, 2003).
A 5 year study by John Hopkins University of 4,740 people over 65 found that subjects taking both 400IU of Vitamin E and at least 500mcg (a miniscule dose) of Vitamin C reduced their risk of dementia and Alzheimer's disease by 64%. No effect occurred if only Vitamin C or only Vitamin E was taken, only when both vitamins were taken in combination.
In September 2003, Professor Tim Chambers and his team at St George's Medical School, University of London found that osteoporosis can be prevented by taking large doses of Vitamin C.
In April 2004, a University of California research team showed that taking 500mg of Vitamin C a day for 2 months results in a 24% drop in CRP levels (CRP may be a better predictor of heart disease than cholesterol levels).
In May 2004, Nobel prize winner Louis J. Ignaro and his team at UCLA found that the beneficial results of moderate exercise in heart patients were increased when they took a supplement containing Vitamin C, Vitamin E and the amino acid L-arginine.
A study by the Linus Pauling Institute at the Oregon State University, published in June 2004, found a reduction in LDL oxidation by users of 1000mg Vitamin C and 400IU of Vitamin E in combination. Vitamin E alone had no effect. The findings may indicate that this combination will be helpful to people suffering from Alzheimer's disease, diabetes, stroke and heart disease, as well as to smokers and the obese.

Medically, Vitamin C is used in the treatment of scurvy, anaemia, respiratory diseases, bleeding gums, psychiatric disorders, colds and flu, various forms of cancer, high levels of cholesterol in the blood, alcoholism, arthritis, leg cramps, and as an antihistamine.

Food sources

Losses in processing

Best food sources are acerola cherry juice and camu pulp.
Both contain 10 times more than rosehip syrup, the next best source.
Other sources, in order of importance: blackcurrants and guavas, parsley and kale, horseradish, broccoli tops, green peppers, Brussels sprouts, citrus fruits, watercress and cabbage, mustard tops.

Processing and storage of soft fruit	up to 60%
Refrigerated fruit juices	up to 50%*
Potatoes stored for 1-3 months	33%
Potatoes stored for 4-5 months	50%
Potatoes stored for 6-7 months	67%
Potatoes stored for 8-9 months	89%
Potatoes, peeled, boiled and mashed	30-50%
Potatoes, boiled in skins, steamed, baked or roast	20-40%
Chips (french fried potatoes)	25-35%
* Further loss occurs whenever the container is shaken.