C (Vitamin C)
Vitamin C (ascorbic acid) is a ubiquitous compound, present in the physiologies of almost all plants and animals. Humans, other high primates, fruit bats and guinea pigs cannot produce their own bodily supply of vitamin C, and consequently require a regular dietary intake.
Vitamin C is an unstable water-soluble vitamin that is sensitive to heat, air, water (by leaching) and alkali (e.g. bicarbonate of soda). Certain metals, e.g. Copper also speed the oxidative destruction of vitamin C.
Vitamin C has very many functions in the body - some still not completely understood. Below are listed some of the processes in which it is involved:
- Formation of collagen - the bodyís intracellular "cement"
- Growth, tissue repair and Wound healing
- Formation of antibodies and stimulation of the white blood cells
- Formation of corticosteroid hormones in the adrenal gland
- Absorption of Iron and its necessary accumulation in the bone marrow, spleen and liver.
- As an antioxidant nutrient, it protects water-soluble substances from oxidation by allowing itself to be oxidised.
- As an anti-histamine, vitamin C reduces the effect of histamine produced by the Immune System. Histamine is responsible for many of the symptoms of allergies such as Hay Fever.
- Carnitine formation in vegetarians, together with lysine.
Vitamin C carries out most of its functions through acting as a powerful antioxidant. This also means that vitamin C is a very effective neutraliser of free radicals - destructive and highly reactive molecules that are thought to be the basis of many serious diseases including cancer and heart disease.
The classic vitamin C deficiency disease is scurvy, early symptoms of which are usually bleeding of the gums and loosening of the teeth, together with lassitude, weakness, irritability and muscle ache.
A prolonged marginal deficiency of vitamin C may not lead to clinical symptoms, but may predispose towards heart disease and lowered immunity.
Upper safe level for daily supplementation = 2000mg
Recommended Daily Allowance = 60mg
(Smokers requirements are increased by 80mg)
Controlled studies have shown that vitamin C levels become depleted during the course of an Infection (1). There is also evidence that large doses (at least 1g/day) can help symptoms of the Common Cold.
Surgery and Fracture:
Vitamin C helps in wound healing(2) after invasive surgery and is also vital for proper healing of Fractures.
Dental and Oral Conditions:
Vitamin C given before and after dental extraction may help in the healing of gums.
Anaemia and Haemorrhagic Disorders:
The use of vitamin C as an adjunct to Anaemia treatment is well accepted because of the vitaminís important connection with Iron metabolism (3). In haemorrhagic disorder, vitamin C may help to strengthen fragile capillaries, especially in conjunction with Bioflavonoids (substances that are often found naturally occurring alongside vitamin C).
Vitamin C (preferably in its buffered form) may be of benefit to sufferers from osteoarthritis (4), presumably through its role in collagen production. It seems to relieve the Pain and stiffness in some people.
Allergic conditions may be helped through vitamin C supplementation (5), presumably through an anti-histamine effect.
Stomach and Duodenal Ulcers:
Vitamin C is very important to the healing of Ulcers, but the "buffered" (non-acidic) form should be used.
Plasma vitamin C levels are lower in smokers compared to non-smokers due to oxidative Stress. As a result, smokers require increased intakes of this nutrient (6).
High Blood Pressure:
Vitamin C may have beneficial effects on blood pressure in those with Hypertension (7).
Asthmatics have reduced levels of vitamin C in their blood (8). Supplementation with vitamin C has been found to reduce Asthma attacks (9) and protect against attacks during exercise (10).
Types of Vitamin C Supplement
Ascorbic acid v Calcium ascorbate (buffered or low acid form)
Vitamin C supplements are generally available in different forms. Firstly, ascorbic acid (pure vitamin C), which is suitable for the majority of people. It provides a readily available substance at an affordable price. Secondly, as the buffered or low acid form, calcium ascorbate, which is more suitable for people with digestive disorders, sensitive stomachs or Ulcers, Candida albicans, Arthritis, or just getting older. It could be described as the kinder form of vitamin C.
Vitamin C is on the whole extremely safe, with no toxic effects even at dosages of grams per day. Transient Diarrhoea is the usual side-effect that is noted when excess levels are taken
The only other possibility of danger from high vitamin C intake occurs in people who have a family history of Kidney stones, as oxalate can combine with Calcium to form the stones. However, people who are not at high risk of kidney stones do not need to avoid vitamin C.
Taking very high doses of vitamin C - 5000 mg a day and up - and then suddenly stopping the supplementation has been thought to possibly cause "rebound scurvy". However a recent review has shown there is no real basis for this belief. Nevertheless it is perhaps advisable to come off high level vitamin C slowly.
INTERACTIONS AND CONTRA-INDICATIONS
It is not advisable for people with kidney stone to take high levels of vitamin C (above approx. 1g per day).
Vitamin C may possibly dilute the effect of tricyclic anti-depressants (e.g. amitriptyline, imipramine).
Various drugs may increase the need for vitamin C, including cortisones, aspirin and birth control pills.
Vitamin C supplements have been shown to overcome long-term tolerance to nitrovasodilators (11).
Pepper, green 100
Brussels sprouts 90
Sweet Potato 25
Potatoes: new 16; Oct-Dec 19; Jan-Feb 9; Mar-May 8
The main sources of vitamin C in the diet are potatoes, fruit juices, citrus fruit and green vegetables. The vitamin C content of foods varies very widely depending upon season, variety and freshness.
1. Pfitzenmeyer P et al. Vitamin B6 and vitamin C status in elderly patients with Infections during hospitalisation. Ann Nutr Metab, 41;6:344-352, 1997.
2. Thomas DR. Specific nutritional factors in wound healing. Adv Wound Care, 10;4:40-43, 1997.
3. Essien EU. Plasma levels of retinol, ascorbic acid and alpha-tocopherol in sickle cell Anaemia. Cent Afr J Med, 41;2:48-50, 1995.
4. McAlindin TE. Do antioxidant micronutrients protect against the development and progression of knee arthritis. Arthritis Rheum, 39;4:648-656, 1996.
5. Kodoma M et al. Automune disease and Allergy are controlled by vitamin C treatment. In Vivo, 8;2:251-257, 1994.
6. Lykkesfeldt J. et al. Ascorbic acid and dehydroascorbic acid as biomarkers of oxidative Stress caused by Smoking. Am J Clin Nutr,65;4:959-963, 1997.
7. "Handbook of Dietary Supplements", Pamela Mason, Blackwell Science, 1995.
8. "Healing Through Nutrition", Dr M Werbach, Thorsons, 1993.
9. Anah CO, Jarike LN and Baig HA> High dose ascorbic acid in Nigerian asthmatics. Trop Geograph Med, 32:132-137, 1980.
10. Schachter EN and Schlesinger A. The attenuation of exercise-induced bronchospasm by ascorbic acid.. Ann Allergy, 49:146-150, 1982.
11. Bassenge E et al. Dietary supplement with vitamin C prevents nitrate tolerance. J Clinical Investigation, 102:67-71, 1998.