Talk:Vitamin C

Removed during Big Cleanup

Image:Ascorbic_acid.png|right|frame|Chemical structure of vitamin C

Image:Ascorbic-acid-3D-vdW.png|thumb|right|200px|Model of the vitamin C (L-ascorbic acid) molecule. Black is carbon, red is Oxygen and white is Hydrogen

Image:GyorgyiNIH.jpg|thumb|200px|right|Albert Szent-Györgyi, pictured here in 1948, was awarded the 1937 Nobel Prize in Medicine for the discovery of vitamin C

Image:Rosa canina hips.jpg|right|thumb|Rose hips are a particularly rich source of vitamin C

Image:Goat.jpg|thumb|250px|Goats, like almost all animals, make their own vitamin C. 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.

Image:RedoxonVitaminC.jpg|thumb||right|Vitamin C is widely available in the form of tablets and powders. The Redoxon brand, produced by Hoffmann-La Roche was the first mass-produce synthetic vitamin C and was launched in 1934.

Pierre-Alain Gouanvic 00:05, 20 November 2007 (CST)Image:Ambersweet oranges.jpg|right|thumb|Citrus fruits were one of the first sources of vitamin C available to ship's surgeons. Pierre-Alain Gouanvic 04:38, 21 November 2007 (CST) Image:James lind.jpg|180px|right|thumb|James Lind (1716 – 1794), a British Royal Navy surgeon who, in 1774, identified that a quality in fruit prevented the disease of scurvy in what was the first recorded controlled experiment.

Image:Pauling Vit C Book Cover.jpg|right|thumb|250px|Linus Pauling's popular and influential book How to Live Longer and Feel Better, first published in 1986, advocated very high doses of vitamin C.

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Serum and plasma vitamin C measurements do not correlate well with tissue levels while lymphocyte vitamin C levels provide the most accurate assessment of the true status of vitamin C stores and are not affected acutely by circadian rhythm or dietary changes.”

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I don't see any real reason for having a seperate article on ascorbic acid, because vitamin C and ascborbic acid are one and the same, as pointed out in this article. Also, a bunch of chemical properties are already included, so I suggest removing sentences aluding to a non-existent ascorbic acid article. I'll leave that to the original authors though. I don't know how to wrap text around images, so the image I added is centered with nothing around it: a waste of space. Feel free to fix this. David E. Volk 16:37, 31 July 2007 (CDT)

Proposition: creation of the "Discovery of vitamin C"/"Discovery and history of vitamin C" page

The lengthy explanations on the history of vitamin c are interesting but could be displayed in a separate article. CZ has the article : "Discovery of pennicilin". I consider that "Discovery of vitamin C" would be an interesting page in its own right and could be the place to explore those problems surrounding vit. C's discovery and patenting and related issues (e.g. how scurvy was gradually accepted, how nascent globalisation of trade enabled the provision of never before seen amounts of vit. C in the northern latitudes, etc.). The page could also be more accurately called : "Discovery and history of vitamin C". A redirect from "Discovery of vitamin C" to "Discovery and history of vitamin C" or "History of vitamin C" could be used. Pierre-Alain Gouanvic 16:57, 13 November 2007 (CST)

Go for it. Chris Day (talk) 03:17, 19 November 2007 (CST)

The basic structure

The whole debate about recommended intakes is one thing, and of course Linus Pauling (and his 1971 paper) is at the center of the debate. Keeping an historical perspective is logical and useful. The fact that bowel tolerance varies in function of disease pertains to another logic, and to another section. Finally, the therapeutic uses are another section. No info will be suppressed in the process of structuring this article. Pierre-Alain Gouanvic 03:29, 19 November 2007 (CST)

...the 1974 paper. The reference has been included. Pierre-Alain Gouanvic 18:04, 19 November 2007 (CST)

The "Politics of Vitamin C" section

Was this a part of the original WP article? Because saying there is a conspiracy against Vitamin C seems awfully absurd (unless it actually is the case). Is it actually something that goes on? Also some things about the "Hypothesis" section seem equally dubious. --Robert W King 16:45, 19 November 2007 (CST)

It comes from WP. I agree. I'll work on that and will try to be constructive. Thanks for the input; I'll send you a notice when I it is done. Pierre-Alain Gouanvic 17:32, 19 November 2007 (CST)

A description of a nutrient includes its distribution in tissues and organs. This section will necessarily cover (part of) the debate on vitamin C requirements. Putting this in a separate "controversial" section would be biased.Pierre-Alain Gouanvic 21:08, 19 November 2007 (CST)

The "Vitamin C hypothesis" section

Many things in this section reflect a lack of understanding of who said what, etc. They will be moved in their respective sections on biosynthesis. Pierre-Alain Gouanvic 00:05, 20 November 2007 (CST)

In the following, all parts that are in italics are false, as we can judge by reading the biosynthesis section:

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 mean that vitamin C was misnamed as a vitamin and is in fact a vital macronutrient like fat or carbohydrate. {Irwin Stone: "The Healing Factor"}

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 retrovirus could have caused this mutation, millions of years ago. {Hickey: "Ascorbate"} 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.

To be kept for future inclusion: the retrovirus hypothesis deserves its place; Irwin Stone's work, quoted in OMIM, too. Pierre-Alain Gouanvic 01:30, 20 November 2007 (CST)

Not useful in the intro, as it is in the chem box on its side

But the references will be useful:

also known by the chemical name of its principal form, L-ascorbic acid or simply ascorbic acid. Pierre-Alain Gouanvic 00:57, 21 November 2007 (CST)

Idem: The guidance provided by the United States of America and Canada for Dietary Reference Intake (DRI) recommends 90mg per day and no more than 2g per day (2000mg/day). Pierre-Alain Gouanvic 04:20, 21 November 2007 (CST)

Misplaced in the pharmacokinetics debate

Of course the following has to do with the debate:

Testing for ascorbate levels in the body Simple tests exist which measure levels of ascorbate ion in urine, serum or blood plasma. However, these tests do not accurately reflect actual tissue ascorbate levels. Reverse-phase high-performance liquid chromatography (HPLC) is used for determining vitamin C levels within lymphocytes and other tissue. It has been observed that while serum or blood plasma levels follow the circadian rhythm or short term dietary changes, levels within tissues are more stable and give a better determination of ascorbate availability within the organism. However, very few hospital laboratories are adequately equipped and trained to carry out such detailed analyses, and require samples to be analyzed in specialized laboratories.

... but this clearly deserves to be in the Distribution section. It will be important to provide a properly phrased link to the Distribution section. In +, the style doesn't have to be so colloquial. The example taken from diabetes is not especially useful: the article as it is now explains very clearly where, in the body, vitamin C is concentrated. Pierre-Alain Gouanvic 04:15, 21 November 2007 (CST)

General discussion on the acceptance of supplements

This burdens the page (see below, after the quote in italics). It's valid info, but it belongs to the "dietary supplement" page, some of it should really go in "consumer protection laws", "labelling", etc.

It will be possible to formulate concise and well referenced statements to replace this (there's only one ref, and its the conspiracy documentary. Worse than nothing, if it's not well supported (cf the comment by Robert W King, above)).

There exists research on the bias against Vitamin C in research, quoted by the famous Cochrane reviewer and researcher Harri Hemila: (http://www.cmaj.ca/cgi/eletters/174/7/937#4039)

Goodwin and Tangum (10) provided several examples to support the conclusion that there has been systematic bias against the concept that vitamins might be beneficial in levels higher than the minimum required to avoid classic deficiency diseases. Also, bias against vitamin C was documented by Richards (11,12) who compared the attitudes and arguments of physicians to three putative cancer medicines: 5-fluorouracil, interferon, and vitamin C. It seems that Pauling’s conclusions were dismissed because of the fundamental divergence with the traditional notion that the only purpose of vitamin C is to prevent scurvy (3) and not because of experimental findings. Evidently, carefully planned trials should be carried out to evaluate the potential role of high-dose therapeutic vitamin C on the common cold and cancer.

Removed section:

Advocacy arguments

Vitamin C advocates argue that there is a large body of scientific evidence that the vitamin has a wide range of health and therapeutic benefits but which they claim have been ignored. They claim the following factors affect the marketing and distribution of vitamin C, and the dissemination of information concerning the nutrient:

• There is increasing evidence of the applications and efficacy of vitamin C, but governmental agency dose and frequency of intake recommendations have remained relatively fixed. This has lead some researchers to challenge the recommendations.

• Research and the treatment approval process are so expensive, pharmaceutical companies rarely apply for approval of an unpatentable product. To do so without the protection of a patent would allow competitors to manufacture the product too, which would drive the price (and profit margin) down to a point much less desirable than the price point (and profit margin) of patentable products. The lower price would also reduce the likelihood of recuperating the company's exorbitant research funding and treatment approval costs. Vitamin C is not eligible for patenting because it is a natural substance, and because it has already been marketed to the public for some time. As of yet, no company has applied to the FDA (nor paid) for approval of vitamin C as a treatment for any disease.

• Companies selling a treatment product are not required to inform consumers or patients of other treatments, even if those treatments are more effective, less expensive, and have fewer side-effects. Medical practitioners are not required to inform their patients of treatments for which treatment approval has not been granted. This situation, coupled with the label censorship explained above makes it more difficult to keep the public informed about the benefits of and new discoveries concerning the applications and effective dosage levels of vitamin C.

• Matthias Rath and others point to low doses of vitamin C as the cause of the current epidemics of heart disease and cancer, and have termed the situation "a genocide", implying that health care providers (and particularly cardiologists and pharmaceutical companies) are aware of vitamin C's benefits and are deliberately seeking to block its acceptance as a therapeutic agent for financial gain.[111] He claims that governments have also colluded in this technology blockade by their expensive and bureaucratic systems of treatment approval which place barriers to new, inexpensive but not patentable approaches.

Reference 111:

1. ↑ http://www.vitamincproject.com/ A conspiracy against vitamin C supplements has been underway for over three decades

(the end)

Pierre-Alain Gouanvic 04:38, 21 November 2007 (CST)

Scurvy

In parallel with the redefinition of vitamin C ("it is not simply the antiscorbutic vitamin"; Cf section 2 on allowances, in particular), the redifinition of scurvy was also suggested, by more researchers than one would imagine (I guess). In other words, some have adopted the point of view that there's more than scurvy, while others have developped the point of view that scurvy is more than what James Lind described (and that we don't really have a non-arbitrary definition for scurvy). "Subclinical scurvy" and other paraphrases are not so uncommon amongst clinicians.

It would probably be wise to develop an article on scurvy that would account for this evolution of the term and of the notion. A practical benefit: it would make the vitamin C article more concise and more about vitamin C. A methodological advantage: it would allow for more detailed pathophysiological considerations : low vitamin C associated with

- high histamine (cf the article on Barlow's disease)

- capillary fragility (in many tissues)

- bone fragility

- weakness and fatigue (carnitine deficiency; cf article)

- etc.

... an article with direct clinical implications.

Then, the vitamin C article would more easily welcome even more useful informations on its physiological roles, and better explanations for the layperson.

Of course, both articles would link to each other.

Pierre-Alain Gouanvic 10:47, 21 November 2007 (CST)

Fact check

In the description: "The D-enantiomer shows no biological activity." ambiguous. It can't be used as an enzyme cofactor, but it can be an electron donor (an antioxidant). It is not present in living things, if that's what it was supposed to mean. Pierre-Alain Gouanvic 11:44, 21 November 2007 (CST) "The active part of the substance is the ascorbate ion." Not a part. Pierre-Alain Gouanvic 11:46, 21 November 2007 (CST)

To do list

Section on evolution (biosynthesis)

At present, there are three considerations on the role and the impact of the inability to produce vit. C (in the article, Biosynthesis section). There exists other, possibly complementary, hypotheses (or "very suggestive observations") :

• 1. Retroviruses, Ascorbate, and Mutations, in the Evolution of Homo sapiens Jack J. ChallemA, * and E. Will Taylor.

high oxidative stress =) high DNA mutation rate =)high evolution rate

and :

retroviruses=)DNA mutations=)including GLO deficiency (hypoascorbemia)

Pierre-Alain Gouanvic 17:15, 22 November 2007 (CST)

• 2. Evolutionary significance of vitamin C biosynthesis in terrestrial vertebrates.

A Nandi, CK Mukhopadhyay, MK Ghosh, DJ … - Free Radic Biol Med, 1997

Evolution of vertebrates from aquatic medium to the terrestrial atmosphere containing high concentration of environmental oxygen was accompanied by tissue-specific expression of the gene for L-gulonolactone oxidase (LGO). ...

also see Ascorbic Acid: Biochemistry and Biomedical Cell Biology, James R. Harris, p. 157 (Dabrowski, 1994)

• 3. Vitamin C: the primate fertility factor? J MILLAR - Medical hypotheses, 1992
• 4. l-gulonolactone oxidase, a microsomal enzyme that catalyzes the terminal step in the biosynthesis of l-ascorbic acid is missing in most primates. Consequently, these organisms are prone to scurvy if the concentration of vitamin C in the diet falls. Paleopathological markers for the diagnosis of scurvy in ancient human skeletons have been described (22), but there is no paleopathological evidence of scurvy (or any other vitamin-specific dietary deficiency) among the Neanderthals or other fossil hominids. A molecule of l-ascorbic acid is consumed for each hydroxylation event (23). With an omnivorous dietary adaptation, especially a shift toward greater carnivory, there are periods when dietary vitamin C would either not be available or present only in reduced amounts. Recent humans, chimpanzees, and orangutans are omnivores; therefore, this difference in the posttranslational hydroxylation of osteocalcin compared to the herbivorous gorilla may relate to increased selective pressure to limit hydroxylation to counteract periods of low dietary vitamin C.

Osteocalcin protein sequences of Neanderthals and modern primates http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15753298

• Z. "the primate L-gulono-gamma-lactone oxidase genes are a typical example of pseudogene" Random nucleotide substitutions in primate nonfunctional gene for L-gulono-gamma-lactone oxidase, the missing enzyme in L-ascorbic acid biosynthesis.Biochim Biophys Acta. 1999 Oct 18;1472(1-2):408-11. Ohta Y, Nishikimi M.

Section on "as an enzyme cofactor"

"Unlike other water-soluble vitamins, ascorbate is not specifically required for the functioning of ANY enzyme, and its exact physiological role is unkown" (then follows a rather long list of enzymes which use ascorbate). p158 (ibid) Pierre-Alain Gouanvic 17:56, 22 November 2007 (CST)