Vitamin C or ascorbic acid was first discovered in 1933, when Szent Gyorgyi isolated the molecule, thus gaining the Nobel Prize for Medicine.
Many discoveries in the medical field resemble the history of this vitamin. In 1747, a British physician who was serving in the navy noted the healing and preventive properties of lemon juice towards some pathologies the seamen often suffered from. The crew used to spend many months sailing, thus taking a diet with a total lack of fruits and vegetables. After a period af 2-3 months all of them showed some peculiar symptoms, such as gum bleeding, feableness, joint or muscle pains, depression, hair and nail loss, that quickly recovered after assuming lemon or citrus fruits juice. Scurvy was the name given to this syndrome.
It took however 40 years for doctor James Lind’s observations to be officially approved so that the lemon juice entered the equipment of the British Navy crews.
In 1921 the name Vitamin C was chosen to refer to the compound that succefully cured scurvy, even if not chemically detected yet. It was not until 1933 that Szent-Gyorgyi’s studies lead to the isolation of the chemical structure of the antiscorbutic factor.
Chemical characteristics
Vitamin C is a highly water soluble, sugar acid compound, isolated in odorless and flavourless crystals at a pH of 2.5.
Dietary vitamin C is absorbed in mouth, stomach but mainly in the gut. With regular intake the absorption rate varies between 70 to 95%. However, the degree of absorption decreases as intake increases, reaching even 16%.
It is stored in body’s tissues, adrenal glands and liver notably maintaining high concentrations. Ascorbate concentrations over renal re-absorption threshold pass freely into the urine and are excreted.
Ascorbic acid is also widely used as a food additive, to prevent oxidation. Many items’ packages refer to the corresponding initials (E300, E301, E302 etc.).
Most of these vitamin c based additives is inactivated by heat or by food exposion to light rays.
Systemic effects
It is a strong antioxidant agent and has a protective action against oxidation caused damages.
Vitamin C enhances many biological functions, mainly:
- synthesis of collagen, the main protein of connectival tissue which is an important structural component of skin, cartilage,
tendons, bone, cornea and teeth (periodontal ligament);
- conversion of dopamine into norepinephrine, a chemical mediator whose lack can account for depression;
- synthesis of carnitine, a compoud enhancing fatty acids metabolism. Decreasing levels of carnitine therefore cause
decreasing energy production and increasing adipose tissue,
- it modulates tyrosine metabolism, which is a precursor to neurotransmitters and hormones such as catecholamines, tyroxine,
melanine. Tyroxine is an hormon produced by the thyroid gland that stimulates the synthesis of proteins thus increasing
muscle tone and vigor. Melanine is an effective absorber of light: the pigment is able to dissipate over 99.9% of absorbed
UV radiation.Because of this property, melanin is thought to protect skin cells from UVB radiation damage reducing the risk
of cancer and the skin aging process,
- synthesis of some polypeptides hormones such as oxitocin, which increases estrogen production thus delaying the onset of
menopause and its related symptoms (anxiety, depression, irritation, sleep desorders, etc.),
- synthesis of bile acids that promote processing of dietary fat and of several important vitamins such as vitamin A,D,E and K
- enhances iron absorption. Its deficiency results in symptoms such as weakness, pallor, nausea, headache, faticability,
depression and irritability: iron deficiency anemia,
- exerts sparing effect on vitamin E. Vitamin E is a powerful antioxidant compound that acts as a peroxyl radical scavenger,
preventing the propagation of free radicals in tissues and slowing the skin aging process,
- acts as a natural anticoagulant factor: it prevents the development of atherosclerotic plaques, thrombosis and embolism,
which are risking factors for myocardial infarction and stroke,
- reduces the formation af nitrosamines, chemical compounds most of which are carcinogenic (stomach and esophagus cancer).
Nitrosamines are produced from nitrites used as preserving and flavoring agents. Significant levels of nitrosamines are
found in many foodstuffs, especially beer, fish and fish byproducts, and also in preserved meat and cheese products and
sausages,
- it interacts with the immune system increasing resistance to infectious viral deseases,
- it decreases the risk of smoking induced damages.
Vitamin C deficiency and its symptoms
A severe lack of vitamin C results in scurvy. The outstanding symptom of scurvy is the occurrence of bleeding from all mucous membranes due to the avitaminosis induced capillary fragility. In adults scurvy. The onset of scurvy is usually heralded by several other symptoms as weakness, fatigue, muscle and joint pains and wieght loss.
Common symptoms include gum bleeding and infection, teeth loss and, in advanced scurvy, gastric, nasal, conjunctival and urogenital bleeding. May be experienced occur shortness of brath, problems with digestion, coarseand fragile hair, enamel weakness, hematoma occurrance, slow recovery of wounds and fractures.
A correlation has been found between low blood levels of vitamin C and neuropsychiatric symptoms such as depression, hysteria and hypochondria.
Both smoking and alcohol are correlated to decreased blood levels of vitamin C. Vitamin C is a heat- and photo-sensitive compound, easily inactivated by cooking or light exposure. we eat mostly As our current diet generally lacks in raw foods and vegetables, it is some experts’ opinion that our society lives a sort of “perpetual” scurvy.
The mainstream medical community has assessed that a daily intake of 10 mg (compared to the recommended 30-100 mg/day) can prevent scurvy symptoms for months or even years. This amounts sounds ridiculous, as it is the equivalent of three grams fresh red peppers or 10 grams kiwi or 20 grams orange juice.
Recommended intake
There is continuing debate among the scientific community over the best dose schedule (daily reqirements). The National Health Organization recommends a daily intake of 30-100 mg, others rather suggest higher doses (100-300 mg) or even megadoses (10-20 gr) in order to benefit from both its therapeutical and preventive effects.
One of the most convinced and authoritative promoter of this theory is Linus Pauling, who was awarded the Nobel Prize in Chemistry in 1954 and the Nobel Peace Prime in 1962. The magazine New Scientists mentioned his among the top 20 scientists in history, he was a pioneer in molecular genetics thanks to his studies on sickle-cell anemia.
In fact, Pauling advocated tthe use of vitamin megadoses in the treatment of cancer and heart deseases, as well as in the prevention and tratment of the common cold. However, Pauling’s studies generated much controversy and the international medical community finally concluded that his claims on vitamin C properties were just quackery.
Side effects
Vitamin C exhibits remarkably low toxicity, expecially for daily intakes highly below the lethal dose, which , though still unknown in humans, in rats is generally accepted to be 11.9 grams per kilogram of body weight when orally given in one shot. According to these data, death from overdose should occur after a single assumption of 850 gr in a man of 70 kg.
Several side-effects are possibly caused by vitamin C megadoses:
- diarrhea, that can be significant,
- kidney stones formation, though infrequent, is due to an enhanced oxalate reabsorption from intestine or a conversion of
the vitamin itself into oxalate. A high daily intake (over 2 gr/day) could cause the formation of kidney oxalate stones in
patients with a history of nephro- or urolithiasis (presence of stones in the kidney or urinary tract),
- hemocromatosis is a rare genetic condition characterized by an increased pathological intestinal iron uptake that overloads
several internal organs such as liver, pancreas, skin and heart. An increased iron absorptionVitamin C linked may become an
issue for these patients,
- nausea and indigestion: since vitamin C is an acid (L-ascorbic acid) it is advisable not to take it on an empty stomach,
possibly splitting the total uptake throughout the day, thus avoiding an annoying heartburn.
Conclusions
In conclusion, it can be assessed that vitamin C supplementation exerts benefical effects. The debate over the best dose schedule determining the treatment and prevention of many deseases is still open. Beside the traditionally recommended assumption of 30-100 mg per day, some scientists suggest hgher doses (1000-3000 mg/day) or even megadoses (10-20 gr/day).
Comparing the scarce and mild side effects (together with the low cost) of megadoses to the health improvments they involve, it is probaly advisable to increase the traditional intake of 30-100 mg/day without exceeding the reasonable threshold of 2-5-gr/day.
The attendance of a medical doctor is nevertheless advisable, collecting an accurate medical history and correctly reading the specific blood tests, in order to evaluate the treatment with vitamin C supplementation in the medium- and long-term follow up.
dr Massimo Mazza
Bibliography
An historical compendium of 20th-Century medical & scientific literature attesting to the efficacy of Ascorbate (Vitamin C) in the treatment and prevention of human and animal illness and disease
Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C – Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases – Cochrane Database Syst Rev. 2012 Mar 14;3
Cameron, E., and Pauling, L. The Orthomolecular Treatment of Cancer. I. The Role of Ascorbic Acid in Host Resistance. Chem.-Biol. Interactions 9:273-283, 1974
Creagan FT, Moertel CG, O’FalIon JR et al. Failure of high-dose vitamin C (ascorbic acid) to benefit patients with advanced cancer: a controlled trial. N Eng J Med 1979; 301:687-690.
Ewan Cameron, Linus Pauling. Supplemental ascorbate in the supportive treatment of cancer: prolongation of survival times in terminal human cancer. Proceeding of the National Academy of Sciences 73:3685-3689, 1976.
Funk – Vitamine, il loro significato per la fisiologia e la patologia – 1922
Linus Pauling; Harvey Itano, S. J. Singer, Ibert Wells. Sickle Cell Anemia, a molecular Disease. Science, novembre1949. URL consultato in data 5 agosto 2007.
Linus Pauling – Come vivere più a lungo e sentirsi meglio
Harri Hemilä, Elizabeth Chalker, Bob Douglas – Vitamin C for preventing and treating the common cold – Cochrane Database Syst Rev. 2012 Mar 14;3 feb 2010
Wikipedia, l’enciclopedia libera
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