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Vitamin C
*** Shopping-Tip: Vitamin C
see
Vitamin C
:''This article is about the
nutrient. For the
musician known as 'Vitamin C' and her self-titled album, see
Colleen Fitzpatrick. For a general discussion on the chemical properties of the molecule, see
Ascorbic acid''
Image:Ascorbic_acid.png right|frame|Chemical structure of vitamin C.
'''Vitamin C''' is a
water (molecule) water-
soluble nutrient essential for life, used by the human body for many purposes. It is one of a number of such key nutrients called
vitamins.
To the best of
science scientific knowledge, all animals and plants synthesize their own vitamin C, except for
humans and a small number of other animals, including,
apes,
guinea pigs, the
red-vented bulbul, a
Megabat fruit-eating bat and a species of
trout. This has led a minority of scientists, most notably
Linus Pauling to conclude that failure to produce the chemical by an animal species is a
genetic defect and to
hypothesis hypothesize that if it were replaced in humans to the level found in animals better health would result.
Vitamin C was first isolated in
1928, and in
1932 it was proved to be the agent which prevents
scurvy. In 1937
Albert Szent-Györgyi was awarded the
Nobel Prize in Medicine for this feat.
Vitamin C is a
weak acid, called
ascorbic acid or
ascorbate (an
L-enantiomer L-enantiomer of
ascorbic acid; an
L-enantiomer is simply one of two mirror image forms of the same chemical molecular structure, see
optical isomerism optical isomers). The active part of the substance is the ascorbate ion, which can express itself as either an acid or a salt of ascorbate that is neutral or slightly basic. Commercial vitamin C is often a mix of ascorbic acid, sodium ascorbate and/or other ascorbates. Some supplements contain in part the
D-enantiomer, which is useless but harmless. See the '''
ascorbic acid''' article for a full description of the molecule's chemical properties.
Discovery and history
The need to include fresh plant food or raw animal flesh in the diet to prevent disease was known from ancient times. Native peoples living in marginal areas incorporated this into their medicinal lore. For example, infusions of spruce needles were used in the temperate zones, or the leaves from species of drought-resistant trees in desert areas. In 1536, the French explorer Jacques Cartier, exploring the
Saint Lawrence River St. Lawrence River, used the local natives' knowledge to save his men who were dying of scurvy. He boiled the needles of the
Thuja arbor vitae tree to make a tea that was later shown to contain 50 mg of vitamin C per 100 grams.
Through history the benefit of plant food for the survival of sieges and long sea voyages was recommended by enlightened authorities.
John Woodall, the first appointed surgeon to the
British East India Company, recommended the use of
lemon juice as a preventive and cure in his book "The Surgeon's Mate" of
1617. The
Netherlands Dutch writer,
Johann Bachstrom of Leyden, in
1734, gave the firm opinion that ''"scurvy is solely owing to a total abstinence from fresh vegetable food, and greens; which is alone the primary cause of the disease."''
Image:Ambersweet oranges.jpg right|thumb|[[Citrus fruits were one of the first sources of vitamin C available to ship's surgeons.]]
The first attempt to give scientific basis for the cause of scurvy was by a ship's surgeon in the British
Royal Navy,
James Lind. While at sea in May
1747, Lind provided some crew members with two oranges and one lemon per day, in addition to normal rations, while others continued on
cider,
vinegar or sea water, along with their normal rations. In the
history of science this is considered to be the first example of a controlled experiment comparing results on two populations of a factor applied to one group only with all other factors the same. The results conclusively showed that citrus fruits prevented the disease. Lind wrote up his work and published it in
1753, in ''
Treatise on the Scurvy''.
Lind's work was slow to be noticed, partly because he gave conflicting evidence within the book and partly because of social inertia in some elements at the British admiralty who saw care for the well-being of ships' crew as a sign of weakness. There was also the fact that fresh fruit was very expensive to keep on board, whereas boiling it down to juice allowed easy storage but destroyed the vitamin. Ships' captains assumed wrongly that it didn't work, because the juice failed to cure scurvy.
It was
1795 before the British navy adopted lemons or
Lime (fruit) lime as standard issue at sea. (This practice led to the nickname
Alternative words for British limey for British people, especially British sailors.) Captain James Cook had previously demonstrated and proven the principle of the advantages of fresh and preserved foods, such as
sauerkraut, by taking his crews to the Hawaiian islands and beyond without losing any of his men to scurvy. For this otherwise unheard of feat, he was awarded a medal by the British Admiralty. So the Navy was certainly well aware of the principle. The cost of providing fresh fruit on board was probably a factor in this long delay. Luxuries or non-standard supplies not provided by the Admiralty were usually provided by the Captains.
The name "antiscorbutic" was used in the eighteenth and nineteenth centuries as general term for those foods known to prevent scurvy, even though there was no understanding of the reason for this. These foods include lemons, limes, and oranges;
sauerkraut, salted cabbage, malt, and portable broth were employed with variable effect.
In
1907,
Axel Holst and
Theodor Frølich, two
Norway Norwegian biochemists studying
beriberi contracted aboard ship's crews in the Norwegian Fishing Fleet, wanted a small test mammal to substitute for the
pigeons they used. They fed
guinea pig guinea pigs the test diet, which had earlier produced beriberi in their pigeons, and were surprised when scurvy resulted instead. Until that time scurvy had not been observed in any organism apart from humans, and it was considered an exclusively human disease.
In the early
twentieth century, the
Polish-American scientist
Casimir Funk conducted research into deficiency diseases, and in
1912 Funk developed the concept of vitamins, for the elements in food which are essential to health. Then, from
1928 to
1933, the
Hungary Hungarian research team of
Joseph L Svirbely and
Albert Szent-Györgyi and, independently, the
United States American Charles Glen King, first isolated vitamin C and showed it to be ascorbic acid.
In
1928 the arctic anthropologist and adventurer
Vilhjalmur Stefansson attempted to prove his theory of how
Eskimo (
Inuit) people are able to avoid scurvy with almost no plant food in their diet. This had long been a puzzle because the disease had struck European Arctic explorers living on similar high-meat diets. Stefansson theorised that the native peoples of the Arctic got their vitamin C from fresh meat that was raw or minimally cooked. Starting in February 1928, for one year he and a colleague lived on an animal-flesh-only diet under medical supervision at
New York's
Bellevue Hospital; they remained healthy.
In
1933-
1934, the British chemists Sir
Walter Norman Haworth and Sir
Edmund Hirst and, independently, the
Poland Polish Tadeus Reichstein, succeeded in synthesizing the vitamin, the first to be artificially produced. This made possible the cheap mass production of vitamin C. Haworth was awarded the
1937 Nobel Prize for Chemistry largely for this work.
The synthetic form of the vitamin is identical to the natural form.
In
1959 the American
J.J. Burns showed that the reason some mammals were susceptible to scurvy was the inability of their
liver to produce the active
enzyme L-gulonolactone oxidase, which is the last of the chain of four enzymes which synthesize ascorbic acid.
American biochemist
Irwin Stone was the first to exploit Vitamin C for its food preservative properties and held patents on this. He developed the theory that vitamin C was an essential nutrient deficient in humans as a result of a genetic defect that afflicted the whole human race.
Sources of vitamin C
Plant sources
Image:Rosa canina hips.jpg right|thumb|[[Rose hips are a particularly rich source of vitamin C]]
Citrus fruits (
orange (fruit) orange,
lemon,
grapefruit,
Lime (Citrus aurantifolia) lime),
tomatoes, and
potatoes are good common sources of vitamin C. Other foods that are good sources of vitamin C include
papaya,
broccoli,
brussels sprouts,
black currants,
strawberry strawberries,
cauliflower,
spinach,
cantaloupe, and
kiwifruit. Also,
Cranberry cranberries and
Capsicum red peppers are good sources of the vitamin.
The amount of vitamin C in foods of plant origin depends on:
* the precise variety of the plant,
* the soil condition
* the climate in which it grew,
* the length of time since it was picked,
* the storage conditions,
* the method of preparation. Cooking in particular is often said to destroy vitamin C - but see the section on Food preparation.
The following table is approximate and shows the relative abundance in different raw plant sources. The amount is given in mg per 100 grams of fruit or vegetable:
Animal sources
Image:Goat.jpg thumb|250px|Goats and most animals make their own vitamin C
The overwhelming majority of species of animals and plants synthesise their own vitamin C. It is therefore not a vitamin for them. Synthesis is achieved through a sequence of 4
enzyme driven steps, which convert
glucose to ascorbic acid. It is carried out either in the
kidneys, in
reptiles and
birds, or the
liver, in
mammals and
perching birds. The last enzyme in the process, l-gulonolactone oxidase, cannot be made by humans because the gene for this enzyme is defective. The loss of an enzyme concerned with
ascorbic acid synthesis has occurred quite frequently in
evolution and has affected most
fish; many
birds; some
bats;
guinea pigs; and most
primates, including
humans. The
mutations have not been lethal because ascorbic acid is so prevalent in the surrounding food sources (it may be noted that many of these species feed, or fed, largely on fruit).
For example an adult
goat will manufacture more than 13,000 mg of vitamin C per day in normal health and as much as 100,000 mg daily when faced with life-threatening disease, trauma or stress.
Trauma or injury has been demonstrated to use up large quantities of vitamin C in animals, including humans.
It was only realised in the 1920s that some cuts of meat and fish are also a source of vitamin C for humans. The muscle and fat which make up the modern western diet are however poor sources. As with fruit and vegetables cooking degrades the vitamin C content.
The following table shows the relative abundance of vitamin C in various foods of animal origin, given in mg of vitamin C per 100 grams of food:
{| class="wikitable" border="1" cellpadding="2"
!Food
!Amount
|-
|
Calf liver (raw) || 36
|-
|
Beef liver (raw) || 31
|-
|
Oysters (raw) || 30
|-
|
Cod roe (fried) || 26
|-
|
Pork liver (raw) || 23
|-
|
Lamb brain (boiled) || 17
|-
|
Chicken liver (fried) || 13
|-
|Lamb liver (fried) || 12
|-
|Lamb
heart (roast) || 11
|}
{| class="wikitable" border="1" cellpadding="2"
!Food
!Amount
|-
|Lamb
tongue (stewed) || 6
|-
|
Breastfeeding Human milk (fresh) || 4
|-
|Goat milk (fresh) || 2
|-
|Cow milk (fresh) || 2
|-
|Beef
steak (fried) || 0
|-
|Hen's egg (raw) || 0
|-
|Pork
bacon (fried) || 0
|-
|Calf veal cutlet (fried) || 0
|-
|Chicken leg (roast) || 0
|}
Vitamin C is produced from
glucose by two main routes. The Reichstein process developed in the 1930s uses a single pre-fermentation followed by a purely chemical route. The more modern Two-Step fermentation process was originally developed in
China in the 1960s, uses additional fermentation to replace part of the later chemical stages. Both processes yield approximately 60% vitamin C from the glucose feed.
Research is underway to create yeast micro organisms that will synthesise ascorbic acid cheaply in large quantities in a single fermentation step.
[
[http://www.scri.sari.ac.uk/SCRI/Web/Site/home/ResearchAreas/Theme2~GenestoProducts/QHN/External/vitaminC.asp Scottish Crop Research Institute] -Development of a Yeast-Based Single-Step Process for the Manufacture of L-Ascorbic Acid (vitamin C)]
In 1934, the Swiss pharmaceutical company
Hoffmann-La Roche was the first to mass produce synthetic vitamin C, under the brand name of
Redoxon.
World production is currently estimated at approximately 110,000 tonnes annually.
Main producers today are
BASF/
Takeda Chemical Industries Takeda,
Hoffmann-La Roche Roche,
Merck KGaA Merck and the China Pharmaceutical Group Ltd. of the
People's Republic of China. China is slowly becoming the major world supplier as its prices undercut those of the US and European manufacturers. [http://www.nutraingredients.com/news/ng.asp?n=63349-dsm-vitamin-c].
Functions in the body
* As a participant in
hydroxylation, vitamin C is needed for the production of
collagen in the
connective tissue. These fibers are ubiquitous throughout the body; providing firm but flexible structure. Some
biological tissue tissues have a greater percentage of collagen, especially:
skin,
mucous membrane mucous membranes,
tooth teeth and
bone bones.
* Vitamin C is required for synthesis of
dopamine,
noradrenaline and
adrenaline in the
nervous system or in the
adrenal glands.
* Vitamin C is also needed to synthesize
carnitine, important in the transfer of energy to the cell
mitochondrion mitochondria.
* It is a strong
antioxidant.
* The
biological tissue tissues with greatest percentage of vitamin C — over 100 times the level in blood plasma — are the
adrenal glands,
pituitary,
thymus,
corpus luteum, and
retina.
* The
brain,
spleen,
lung,
testicle,
lymph nodes,
liver,
thyroid,
small intestine small intestinal mucous membrane mucosa,
leukocytes,
pancreas,
kidney and
salivary glands usually have 10 to 50 times the concentration present in plasma.
No bodily organ stores ascorbate as a primary function, and so the body soon depletes itself of ascorbate if fresh supplies do not continue to arrive through the digestive system, eventually leading to death if unresolved.
Vitamin C deficiency
Lack of ascorbic acid in the daily diet leads to a disease
called
scurvy, a form of
avitaminosis that is characterized by:
* loose teeth
* superficial bleeding
* fragility of
blood vessel blood vessels
* poor healing
* compromised
immunity
* mild
anemia
It is eventually fatal, and was a common condition among sailors and during winter. Scurvy is now very rare in industrialized countries. It should not be confused with "subclinical scurvy" or "chronic scurvy", both high-dose advocate terms for the normal human condition of blood levels lower than those typical among mammals.
Daily requirement
There is a continuing debate within the scientific community over the optimum amount of vitamin C for humans.
[British pharmacology professors debate with the US National Institutes of Health over the optimum vitamin c dose (''from PR Newswire - 6th July 2004'') [http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=109&STORY=/www/story/07-06-2004/0002204911&EDATE=]]
Recommended Intake Levels
A healthy person on a balanced diet should be able to get the vitamin C needed to prevent the symptoms of scurvy from their daily diet without supplementation. People who smoke, those under stress, and pregnant women have a slightly higher requirement.
Recommendations for vitamin C intake have been set by various national agencies as follows:
40 mg per day: Food Standards Agency (UK) [http://www.nutrition.org.uk/home.asp?siteId=43§ionId=414&subSectionId=320&parentSection=299&which=1 Reference Nutrient Intake (RNI)]
60–95 mg per day Food and Nutrition Board (US) 2001 [http://www.iom.edu/?id=12700 Recommended Dietary Allowance (RDA)].
Advocacy amounts
Some researchers have calculated the amount needed for an adult human to achieve similar blood serum levels as Vitamin C synthesising mammals as follows:
:400 mg per day –
Linus Pauling Institute & US National Institutes of Health (NIH) Recommendation.
:3000 mg per day or more during illness or pregnancy (up to 300g for some illnesses) – Vitamin C Foundation's recommendation. [http://www.vitamincfoundation.org/vitcrda.htm]
:6000-12000 mg per day – Thomas Levy, Colorado Integrative Medical Centre recommendation.
:6000-18000 mg per day –
Linus Pauling's daily recommendation
:from 3000 mg to 200,000 mg per day based on a protocol described by Robert Cathcart
[Robert F. Cathcart III M.D., ''[http://www.orthomed.com/titrate.htm Vitamin C, Titrating To Bowel Tolerance, Anascorbemia, and Acute Induced Scurvey]'', Allergy, Environmental, and Orthomolecular Medicine] knowns as a vitamin C flush wherin escalating doses of Vitamin C are given until diarrhea develops, then choosing the highest dose that does not cause diarrhea (bowel tolerance threshold). High doses (thousands of mg) may result in
diarrhea, which is harmless if the dose is reduced immediately. Some researchers
claim the onset of diarrhea to be an indication of where the body’s true vitamin C requirement lies. Both Cathcart
and Cameron have demonstrated that very sick patients with cancer or influenza do not display any evidence of diarrhea at all until ascorbate intake reaches levels as high as 200 grams (½ pound).
Food preparation
It is important to choose a suitable method of food preparation that conserves vitamin C content. When cooking vegetables, one should seek to minimize temperature and duration of cooking and not discard water used in preparation, e.g. by
steaming steam cooking or by making soup. Food source vitamin C is identical to that in supplements. The structure of vitamin C is well understood, see
ascorbic acid, and there is no difference in benefit between natural and synthetic forms (although fruits and vegetables contain various other nutrients, and Vitamin C is not their only health benefit).
Recent observations suggest that the impact of temperature and cooking on vitamin C may have been overestimated:
#Since it is water soluble, vitamin C will strongly leach into the cooking water while cooking most vegetables — but this doesn't necessarily mean the vitamin is destroyed — it's still there, but it's in the cooking water. (This may also suggest how the apparent misconception about the extent to which boiling temperatures destroy vitamin C might have been the result of flawed research: If the vitamin C content of vegetables (and not of the water) was measured subsequent to cooking them, then that content would have been much lower, though the vitamin has not actually been destroyed.)
#Not only the temperature, but also the exposure time is significant. Contrary to what was previously and is still commonly assumed, it can take much longer than two or three minutes to destroy vitamin C at boiling point.
It also appears that cooking doesn't necessarily leach vitamin C in all vegetables at the same rate; it has been suggested that the vitamin is not destroyed when boiling
broccoli[Combs GF. The Vitamins, Fundamental Aspects in Nutrition and Health. 2nd ed. San Diego, CA: Academic Press, 2001:245-272]. This may be a result of vitamin C leaching into the cooking water at a slower rate from this vegetable.
Copper pots will destroy the vitamin.
Vitamin C enriched teas and infusions have increasingly appeared on supermarket shelves. Such products would be nonsense if boiling temperatures did indeed destroy vitamin C at the rate it had previously been suggested. It should be noted however that as of
2004 most academics not directly involved in vitamin C research still teach that boiling temperatures will destroy vitamin C ''very'' rapidly.
Therapeutic uses
Vitamin C is needed in the diet to prevent
scurvy. From its ready availability in pure form in the
1930s however some practitioners experimented in using vitamin C as a treatment for diseases other than scurvy. Most notable was
Fred R. Klenner, a doctor in general practise in
Reidsville, North Carolina. He utilised both oral and intravenous vitamin C to treat a wide range of infections and poisons. He published a paper in
1949 that described how he had seen
poliomyelitis yield to vitamin C in sufficiently large doses.
Vitamin C also has a reputation for being useful in the treatment of
colds and
flu, owing to its recommendation by prominent biochemist
Linus Pauling. In the years since Pauling's popular books about vitamin C, general agreement by medical authorities about larger than RDA amounts of vitamin C in health and medicine has remained elusive. Ascorbate usage in studies of up to several grams per day, however, have been associated with decreased cold duration and severity of symptoms, possibly as a result of an
antihistamine effect [http://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/]. The highest dose treatments, published clinical results of specific orthomolecular therapy regimes pioneered by Drs. Klenner (repeated IV treatments, 400-700+ mg/kg/day [http://www.seanet.com/~alexs/ascorbate/197x/klenner-fr-j_int_assn_prev_med-1974-v1-n1-p45.htm][http://www.seanet.com/~alexs/ascorbate/197x/klenner-fr-j_appl_nutr-1971-v23-n3&4-p61.htm#appendix]) and Cathcart (oral use to bowel
tolerance
, up to ~150 grams ascorbate per day for flu, have remained experimentally unaddressed by conventional medical authorities for decades.
There is a strong advocacy movement for large doses of Vitamin C, although it should be noted not all purported benefits are as yet supported by medical backing. Many pro-Vitamin C organizations promote usage levels well beyond the current RDA. The Vitamin C Foundation, for example, recommends an initial usage of up to 8 grams of vitamin C every 20-30 minutes [http://www.vitamincfoundation.org/surefire.htm] in order to show an effect on the symptoms of a cold infection that is in progress. Most of the studies showing little or no effect employ doses of ascorbate such as 100 mg to 500 mg per day, considered "small" by the vitamin C advocates. Equally importantly, the plasma half life of high dose ascorbate is approximately 30 minutes, which implies that most high dose studies have been methodologically defective and would be expected to show a minimum benefit. Clinical studies of the divided dose supplementation, predicted on pharmacological grounds to be effective, have only rarely been reported in the
literature. Essentially all the claims for high dose vitamin C remain to be scientifically refuted. The clinical effectiveness of large and frequent doses of vitamin C is an open scientific question.
There is also evidence that Vitamin C is useful in preventing
lead poisoning, possibly helping to chelate the toxic heavy metal from the body. [http://www.seanet.com/~alexs/ascorbate/193x/holmes-hn-etal_j_lab_clin_med-1939-v23-n11-p1119.html]
In
2002 a
meta-study into all the published research on effectiveness of ascorbic acid in the treatment of infectious disease and toxins was conducted, by Thomas Levy, Medical Director of the Colorado Integrative Medical Centre in Denver. He claimed that evidence exists for its therapeutic role in a wide range of viral infections and for the treatment of snake bites.
Orthomolecular medicine and a minority of scientific opinion sees vitamin C as being a low cost and safe way to treat viral disease and to deal with a wide range of poisons.
In 2005
in vitro research by the
National Institutes of Health indicated that Vitamin C administered in pharmacological concentrations (i.e.
intravenous) was preferentially toxic to several strains of
cancer cells. The authors noted: "These findings give plausibility to intravenous ascorbic acid in cancer treatment, and have unexpected implications for treatment of infections where H
2O
2 may be beneficial." This research appeared to support Linus Pauling's claims that Vitamin C can be used to fight cancer
[ [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16157892&dopt=Abstract Qi Chen and others. Pharmacologic ascorbic acid concentrations selectively kill cancer cells: Action as a pro-drug to deliver hydrogen peroxide to tissues. Proceedings of the National Academy of Sciences of the United States of America (PNAS) | September 20, 2005 | vol. 102 | no. 38 | 13604-13609] ]
It has been also suggested that Vitamin C might prevent the formation of
cataracts.
[ Tessier, F., et al. Decrease in Vitamin C concentrations in human lenses during cataract progression. Int. J. Vitamino Nutr Res 1998;68:309-15 ]
Advocacy arguments
Since its discovery Vitamin C has been considered a universal panacea by some, although this led to suspicions of it being overhyped by others. It should be noted that many medical hypotheses proposed by scientists and researchers remain speculations and have yet to be proven by science.
The fact that man possesses three of the four enzymes that animals employ to manufacture ascorbates in relatively large amounts, has led researchers such as
Irwin Stone and
Linus Pauling to hypothesize that man's ancestors once manufactured this substance in the body millions of years ago in quantities roughly estimated at 3,000-4,000 mg daily, but later lost the ability to do this through a chance of evolution. If true, this would of course mean that vitamin C was misnamed as a
vitamin and is in fact a vital
macronutrient like fat or carbohydrate.
Dr. Hickey, of Manchester Metropolitan University, believes that man carries a mutated and ineffective form of the genetic machinery for manufacturing the fourth of the four enzymes used by all mammals to make ascorbic acid. Cosmic rays or a retro virus could have caused this mutation, millions of years ago. In humans the three surviving enzymes continue to produce the precursors to ascorbic acid but the process is incomplete and the body then disassembles them.
In the
1960s Nobel Prize Nobel-Prize winning chemist
Linus Pauling, after contact with
Irwin Stone, began actively promoting vitamin C as a means to greatly improve human health and resistance to disease. His book ''How to Live Longer and Feel Better'' was a bestseller and advocated taking more than 10,000 milligrams per day. It sold widely and many advocates today see its influence as the reason there was a marked downward trend in US
heart disease from the early
1980s onwards.
Stone's work also informed the practise of Dr.
Robert Cathcart Robert F. Cathcart III, in the
1970s and
1980s. He applied extremely large doses of ascorbate (300 grams = 0.66 pounds per day) to a wide range of viral diseases with successful results. Cathcart developed the concept of
Bowel tolerance, the use of the onset of
diarrhea as an indication of when the body's true requirement of ascorbic acid had been reached. He found that seriously ill people could often tolerate levels of tens of grams per day before their tolerance limit is reached.
In
2003 Steve Hickey and Hilary Roberts of the Manchester Metropolitan University published a fundamental criticism of the approach taken to fix the nutritional requirement of vitamin C. They argued in 2004 that the RDA which is based on blood plasma and white blood cell saturation data from the
National Institutes of Health (NIH) was based on flawed data
[ Hickey, Steve & Roberts, Hilary; (March, 2005), Ridiculous Dietary Allowance, Lulu Press, Inc. ISBN 1411622219.''(Note: [http://www.lulu.com Lulu] is a print on demand self-publishing house.)'']. According to these authors, the doses required to achieve blood, tissue and body "saturation" are much larger than previously believed. They allege that the
Institute of Medicine (IoM) and the NIH had ignored an open letter from a number of scientists and medical researchers notabley Drs Steve Hickey, Hilary Roberts, Ian Brighthope, Robert Cathcart,
Abram Hoffer,
Archie Kalokerinos, Tom Levy, Richard Passwater, Hugh Riordan, Andrew Saul and Patrick Holford, which called for revision of the RDA.
It has been suggested by some advocates that ascorbic acid is really a
food group in its own right like
carbohydrates or
protein and should not be seen as a pharmaceutical or vitamin at all.
Some vitamin C advocates hold that the wider adoption of vitamin C for therapeutic use is hindered by the fact that it cannot now be
patent patented and that pharmaceutical companies are unwilling to fund research or promotion of a substance in which they stand to make little profit and which advocates claim will compete with the companies' patented medicines in which they have invested large sums.
Some advocates have gone so far as to term the epidemic of heart disease and cancer resulting from low C doses a "genocide," implying that health care providers (and particularly cardiologists and pharmaceutical companies) are aware of its benefits and are deliberately seeking to block its acceptance as a therapeutic agent. [http://www.vitamincproject.com/]
Known harmful effects
Vitamin C is recognized to be one of the least toxic substances known to medicine. Its
LD50 for rats is 11 900 mg kg
-1 [http://ptcl.chem.ox.ac.uk/MSDS/AS/ascorbic_acid.html], [http://www.inchem.org/documents/jecfa/jecmono/v05je20.htm],
[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=DisplayFiltered&DB=pubmed].
* A primary concern is people with unusual or unaddressed iron overload conditions, including
hemochromatosis. Vitamin C enhances iron absorption. If sufferers of iron overload conditions take gram sized doses of Vitamin C, they may worsen the iron overload due to enhanced iron absorption.
* Vitamin C causes
diarrhea in everyone if taken in quantities beyond a limit which is variable to the individual. Cathcart
has called this limit the Bowel Tolerance Limit and observed that it is higher in people with serious illness than those in good health. It ranges from 5 grams per day in the healthy to 300 grams per day in the seriously ill, such as those with
AIDS and
cancer. The diarrhea will cease as soon as the dose is reduced, and without harmful effect.
* Inadequate
Glucose-6-phosphate dehydrogenase enzyme (G6PD) levels, a genetic condition, may predispose some individuals to
hemolytic anemia after intake of specific oxidizing substances present in some food and drugs. This includes repeated, very large intravenous or oral dosages of vitamin C. There is a test available for G6PD deficiency [http://brightspot.org/cresearch/intravenousc2.shtml]. High dose
Vitamin E has been proposed as a potential protective factor.
Other reports of harmful effects
Reports of harmful effects of vitamin C tend to receive great prominence in the world's media. As such, these reports tend to generate much debate and more research into Vitamin C. Some of the harmful effects described below have been proven to be unfounded in later studies, while other effects are still undergoing further analysis.
*In April
1998 the journal ''Nature'' reported alleged
carcinogenic and
teratogenic effects of excessive doses of vitamin C. The effects were noted in test tube experiments and on only two of the 20 markers of free radical damage to DNA. They have not been supported by further evidence from living organisms. [http://lpi.oregonstate.edu/new/vitamincancer2.html]
*In April
2000,
University of Southern California researchers reported a thickening of the arteries of the neck in persons taking high vitamin C doses. It was later pointed out by vitamin C advocates that this can be explained by vitamin C's collagen synthesising role leading to thicker and stronger artery walls. (ref.{{fn|6}} para 10)
*In June
2004,
Duke University researchers reported an increased susceptibility to osteo-arthritis in guinea pigs fed a diet high in vitamin C. However, a
2003 study at
Umeå University in
Sweden, found that "the plasma levels of vitamin C, retinol and uric acid were inversely correlated to variables related to rheumatoid arthritis disease activity."
*A speculated increased risk of
kidney stones may be a side effect of taking Vitamin C in larger than normal amounts. The potential mechanism of action is through the
metabolism of Vitamin C (
ascorbic acid) to
dehydroascorbic acid, which is then metabolized to
oxalic acid, a known constituent of kidney stones. However, this issue is still controversial, with evidence being presented for [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15987848&query_hl=11] and against [http://lpi.oregonstate.edu/f-w99/kidneystones.html] the possibility of this side effect.
Vitamin B6 may mitigate this risk by decreasing oxalate production [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10203369&query_hl=13]. Additionally,
thiamine may inhibit oxalate formation. Furthermore, correcting any magnesium deficiency
[[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16100850&query_hl=28 NCBI]] may decrease the risk of kidney stones by decreasing oxalate crystallization. Increasing one's fluid intake also helps to preventing oxalate crystallization in the kidney.
* "Rebound scurvy" is a theoretical, never observed, condition that could occur when daily intake of Vitamin C is rapidly reduced from a very large amount to a relatively low amount. Advocates suggest this an exaggeration of the ''rebound effect'' which occurs because ascorbate-dependent enzyme reactions continue for 24-48 hours after intake is lowered, and use up vitamin C which is not being replenished. The effect is to lower one's serum vitamin C blood concentration to less than normal for a short amount of time. During this period of time there is a slight risk of cold or flu infection through reduced resistance. Within a couple of days the enzyme reactions shut down and blood serum returns to the normal level of someone not taking large supplements. This is not scurvy, which takes weeks of zero vitamin C consumption to produce symptoms. It is something people who take large vitamin C supplements need to be aware of in order to manage phased rather than sudden changes to the amount taken. (ref.{{fn|6}} para 4) This is a theoretical risk for those taking supplements - e.g. if they find themselves severely ill, and in a hospital without the supplements, at a time when they need normal or better levels of vitamin C to fight the disease
(ref..
*Some writers
[[http://www.acu-cell.com/vitc.html acu-cell]] have identified a theoretical risk of poor
Copper absorption from high doses of Vitamin C, although little experimental evidence supports this. However,
ceruloplasmin levels seem specifically lowered by high vitamin C intake. In one study, 600 milligrams of Vitamin C daily did not decrease copper absorption or overall body copper status in young men, but led to lower
ceruloplasmin levels similar to those caused by copper deficiency
[[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3694287&query_hl=11 NCBI]]. In another, ceruloplasmin levels were significantly reduced
[[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6837490&dopt=Abstract NCBI]].
*There are stories circulating among some folk remedy proponants that doses of around 12 grams per day of Vitamin C can induce an abortion in women under 4 weeks of pregnancy.
[ [http://www.sisterzeus.com/Hsp1shlp.htm Home Abortion Remedy - Vitamin C, 8 March 2006]
] This is not supported by scientific reseach however.
[ [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=988001&dopt=Abstract ''Vitamins C and E in spontaneous abortion''] Int J Vitam Nutr Res. 1976;46(3):291-6.]
Sources
* Pauling, Linus (1986) ''How to Live Longer and Feel Better'' W. H. Freeman and Company, ISBN 0-380-70289-4
* Thomas Levy (September 2002) ''Vitamin C, Infectious Diseases, and Toxins'', Xlibris Corporation (Paperback). ISBN 1401069630 ''(Note: [http://www.xlibris.com Xlibris] is a
print on demand self-publishing house.)''
* Hickey, Steve; Roberts, Hilary (May, 2004) ''Ascorbate: The Science of Vitamin C'', Lulu Press, Inc. ISBN 1411607244 ''(Note: [http://www.lulu.com Lulu] is a
print on demand self-publishing house.)''
References
External links
-
United Kingdom Foods Standards Agency Official UK view on vitamin C.
-
The Vitamin C Foundation Vitamin C high dosage advocacy organisation with links to research supporting their view.
** {{fnb|6}} [http://www.vitamincfoundation.org/faq.htm FAQ] provided by The Vitamin C Foundation.
-
Vitamin C in human health and disease is still a mystery? An overview among all time most-viewed articles published by BioMed Central (free access)
-
AscorbateWeb "An historical review of the medical & scientific literature attesting to the efficacy of Ascorbate (Ascorbic Acid, Cevitamic Acid, Sodium Ascorbate etc. a.k.a. “Vitamin C�) in the treatment and prevention of human and animal ills, conditions and diseases."
-
Vitamin C May Not Have Much Effect on Colds health.dailynewscentral.com Finding that 200mg per day has little effect on colds but a single dose of 8 grams does.
-
Ascorbate and cancer Discussion of both historical and current uses of Vitamin C in cancer treatment
-
Vitamin C Requirements: Optimal Health Benefits vs Overdose A moderately high dose advocacy supporting site .
-
Vitamin C toxicity data at University of Oxford
-
Natural food-Fruit Vitamin C Content
-
Clinical Guide to the Use of Vitamin C, The Clinical Experiences of
Fred R. Klenner Frederick R. Klenner, M.D., abbreviated, sumarized and annotated by Lendon H. Smith, M.D.
-
The Healing Factor: Vitamin C Against Disease By
Irwin Stone
-
Vitamin C Therapeutics, [http://www.doctoryourself.com/vitaminc2.html Mega-vitamin C and Babies], and [http://www.doctoryourself.com/vitciv.html For Doctors: Preparation of Vitamin C IV's] -- information gathered and presented by Andrew W. Saul, PhD.
-
Information regarding treatment of the Bird Flu with massive doses of ascorbate. by
Robert Cathcart ROBERT F. CATHCART III, M.D.
-
United States Patent 5,278,189 Prevention and treatment of occlusive cardiovascular disease with ascorbate and substances that inhibit the binding of lipoprotein (A), Inventors: Matthias W. Rath and
Linus Pauling Linus C. Pauling
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