C (Vitamin
C)
DESCRIPTION:
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
body’s 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)
Infections:
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 vitamin’s 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).
Osteoarthritis:
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.
Allergies:
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.
Smokers:
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).
Asthma:
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
Kidney stones:
It is not advisable for people with kidney stone to take high
levels of vitamin C (above approx. 1g per day).
Antidepressants:
Vitamin C may possibly dilute the effect of tricyclic
anti-depressants (e.g. amitriptyline, imipramine).
Other Drugs:
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).
Food (mg/100g)
Blackcurrants 200
Pepper, green 100
Brussels sprouts 90
Mango 80
Cauliflower 60
Cabbage 55
Oranges 50
Grapefruit 40
Sweet Potato 25
Tomatoes 20
Potatoes: new 16
Oct-Dec 19
Jan-Feb 9
Mar-May 8
Lettuce 15
Bananas 10
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.
REFERENCES:
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.
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