DEFINITION

Vitamin C is a water-soluble vitamin that performs a wide variety of functions in the human body.

DESCRIPTION

Vitamin C is commonly found in 3 forms: sodium ascorbate, calcium ascorbate and ascorbic acid. Very high levels of Vitamin C are found in the pituitary and adrenal glands, the liver and skeletal muscles. Vitamin C is essential for the production of collagen, which is an important structural protein in the body that is found in tissues such as the skin and nails. Vitamin C is also important for the production of the chemicals that allow impulses to pass between nerves, for the breakdown of cholesterol, for the production of bile (which assists in the breakdown and absorption of fats), for the production of certain hormones as well as for the metabolism of metals in the body (e.g. the absorption of iron).

Vitamin C is also an antioxidant. This means that it protects the body from damaging chemicals such as free radicals, which are produced during infection and during the breakdown of certain chemicals in the body (e.g. alcohol and medications). Vitamin C may help protect the body against certain degenerative diseases like cataracts as well as cancer and cardiovascular disease.

INTERACTIONS

- Vitamin C may decrease the effects of the drug propranolol. Vitamin C should not be taken in excessive amounts (more than 500mg per day) by people taking propranolol.

MEDICAL USE

Always consult your Health Professional to advise you on dosages and any possible medical interactions. The chief medical use of Vitamin C is in the treatment and prevention of Vitamin C deficiency and scurvy. Vitamin C may have other health benefits, some of which are listed below, but most of these have not been proven. They include:

- The Common Cold. Vitamin C has been shown to be effective in reducing the length of the common cold.

- Sorbitol accumulation in the cells of people with Diabetes is considered to be a potential risk factor for developing complications such as retinopathy and neuropathy. This risk may be reduced by taking 1000 to 2000 mg of Vitamin C daily.

- Asthma. Vitamin C supplements may reduce wheezing symptoms associated with Asthma.

- Disease Prevention. The antioxidant properties of Vitamin C may help prevent certain types of cancers and cataracts. Vitamin C is just one of a number of antioxidants that probably work cooperatively to reduce the risks of these diseases.

- Osteoarthritis. Vitamin C can help to reduce the level of cartilage loss in the early stages of osteoarthritis. A recent clinical trial involving patients with osteoarthritis of the knee revealed that the patients taking moderate to high daily doses of Vitamin C had reduced incidence of knee pain and progression of the disease.

Heart Disease. Vitamin C and vitamin E, taken in combination, help to stabilise LDL cholesterol in the body. This may help to reduce the risk of atherosclerosis. Clinical studies indicate that this benefit may be greater in smokers than non-smokers. A recent clinical trial indicates that Vitamin C can improve blood circulation to the heart which can be impaired in smokers.

- Wound Healing. Vitamin C is required for the body to produce collagen, which is necessary for effective wound healing.

- High Blood Pressure. Vitamin C has been shown in clinical trials to reduce elevated systolic blood pressure. There is no evidence, however, to show that Vitamin C has any effect on elevated diastolic blood pressure. The antioxidant properties of Vitamin C help to enhance the synthesis of or prevent the breakdown of nitric oxide. This small molecule causes constricted blood vessels to relax thus helping to lower elevated blood pressure.

DEFICIENCY

Vitamin C deficiency can lead to a condition called scurvy. Scurvy causes loosening of the teeth, gum disease, anaemia, tender and painful extremities (hands and feet), bleeding into the joints, poor wound healing, weakness, fatigue and psychological disturbances.

SOURCES

The best sources of Vitamin C are citrus fruits (e.g. oranges and grapefruits), berries, melons, tomatoes, potatoes, green peppers and leafy green vegetables. Vitamin C is sensitive to air, heat and water and is easily destroyed by prolonged storage, overcooking and processing of foods.

DOSAGE

The recommended dietary intake (RDI) for Vitamin C is 40 mg per day for adult males and 30 mg per day for adult females, although females that are pregnant require 60 mg per day and those that are lactating require 75 mg per day. Many Vitamin C supplements contain significantly larger amount of Vitamin C than the recommended dietary allowance. Large doses of Vitamin C should be avoided by people with kidney stones, haemochromatosis or any other iron storage disease.

Vitamin C is available in powder or tablet form. The forms of Vitamin C that are gentle on the stomach are 'buffered'. These include calcium ascorbate and sodium ascorbate. Vitamin C has a rapid effect in the body and is excreted within four hours of ingestion. Divided doses throughout the day are recommended for optimum therapeutic value. Vitamin C is non-toxic and the body does not store excess amounts. Diarrhoea is a side effect that is seen in cases where massive doses of Vitamin C are ingested. It is advisable to reduce the intake of Vitamin C gradually over a 1 to 2 week period when reverting from high to low doses

NOTES

Many commercial formulae contain Vitamin C along with bioflavonoids. Bioflavonoids increase the absorption of Vitamin C and are commonly found in foods with naturally occurring, high Vitamin C levels such as citrus fruits and berries (especially blackcurrants and strawberries). High doses of Vitamin C can cause nausea, abdominal cramps and diarrhoea.

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