Vitamin C

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Vitamin C

• Ascorbic Acid

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Ascorbic Acid

• A simple substance, similar to glucose in
  chemical formula
• Destroyed by oxidation and hastened by heat, air
  and alkaline environment
• Deficiency disease scurvy written about as
  early as 1550 B.C.

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Ascorbic Acid

• Chemistry mapped in 1928 by two scientists at
  almost the exact time working in two separate
  laboratories and two separate countries.

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Ascorbic Acid

• Active in the body
• As dehydroascorbic acid

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Vitamin E helps prevent oxidation of Vitamin C
thus preserving it for further biochemical uses
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Oxalic Acid

• A pathway that some molecules of vitamin C
  undergoes produces oxalic acid. Because many
  kidney stones are composed of oxalic acid some
  have stated large doses of vitamin C causes
  kidney stones.

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• A weakness of this claim is that studies of
  kidney stone patients have shown a very low
  percentage take any form of vitamins as well as
  claims that large numbers of people who take a
  lot of Vitamin C do not develop kidney stones.

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• Still, to prevent this occurrence, be sure
  patients who take Vitamin C also take Vitamin B6
  it blocks the accumulation of oxalic acid.

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Functions

• Collagen Synthesis
• Collagen represents 30 of bodys protein.
• To manufacture it, the amino acid proline must be
  hydroxylated to hydroxyproline.

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Oxygen is required for this transaction. Vitamin
C is the only substrate that can accomplish this
reaction and forms the basis for scurvy (i.e.)
breakdown of collagen in vessel walls with
massive bleeding.
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• The disease scurvy can be reversed (cured) with
  as little as 50 mg. of Vitamin C administered
  which is how the RDA was computed.
• This may not be a rational way to determine
  Vitamin C requirements

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Functions (continued)

• Hydroxylation of Dopamine
• Necessary for the formation of norepinephrine
  from dopamine.

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• Iron Metabolism
• Ascorbic acid aids the absorption of iron in the
  gut by reducing ferric iron to ferrous the
  absorptive form

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• Tyrosine metabolism
• Required for breakdown of tyrosine for excretion

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• Interactions with other vitamins
• Protects Vitamin A from peroxidation
• Protects PUFAs from peroxidation
• Required in folacin and B-12 utilization at the
  cellular level
• Protects Vitamin E from peroxidation

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• Required for multiple hydrogen transfer
  mechanisms
• Required in several amino acid metabolic
  functions
• Performs redox reactions
• Forms tightly bound complexes with metals and can
  aid in their excretion. This forms the basis for
  claims as a detoxification agent.

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Antagonists

• Alcohol
• Anticonvulsives
• Tetracycline
• Aspirin
• Oral contraceptive agents

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• Large, oral doses of Vitamin C will cause
  diarrhea.
• Some nutritionists believe that the way to
  determine an individuals Vitamin C requirement
  is to take increasing doses until the patient
  gets diarrhea then recommend the amount per day
  just before the level causing diarrhea.

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• Many people who take large amounts of Vitamin C
  claim that whatever their level of intake that
  will cause diarrhea is if they are catching a
  cold or virus they can take many, many times
  more than this without diarrhea during those
  times. Implication is that when the body needs
  extra vitamin C, it will not dump it.

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High C Intake

• It is well known that if a patient is on high
  doses of vitamin C it is preferable to reduce
  their dosage gradually. There is a condition
  called rebound scurvy that occurs when large
  amounts of vitamin C are abruptly stopped. This
  is true also for pregnant women who take high
  amounts during pregnancy and may cause rebound
  scurvy in their newborn. Breast feeding prevents
  this.

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• An enzyme, monodehydroascorbate transhydrogenase
  is induced in large amounts in the mitochondria
  when someone takes large amounts of C for an
  extended time. This enzyme is plentiful when C is
  taken if the C is withdrawn, the enzyme will
  shunt the remaining C into electron transport
  and it will not be available for collagen
  synthesis causing the rebound scurvy.

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Deficiency

• Early Signs
• Anorexia
• Muscle weakness
• Fatigue
• Follicular hyperkeratosis
• Pain in joints
• Increased bruising

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• Later signs
• Petechiae
• Joint Hemorrhage
• G.I. Bleeding
• Water retention
• Bleeding gums
• Final stage is scurvy bleed to death through
  blood vessel walls

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Linus Pauling

• Two-time Nobel Prize winner lost credibility by
  hyper-promotion of Vitamin C. He took
  correlational data and made claims that required
  experimental data.
• He claimed Vitamin C would prevent colds, when
  all he had was some data showing that people who
  took high Vitamin C had fewer colds than the
  general public.

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Cause Versus Related

• Very important difference between relational
  matters and causative matters.
• Pauling later made similar claims for preventing
  even curing cancer so really became
  ostracized from the scientific community.

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Claims that make sense

• Pauling discovered an enzyme gluconolactone
  oxidase absent in humans but present in
  almost all other animals. This enzyme
  manufacturers vitamin C from glucose.
• Pauling went on to suggest man once had this
  enzyme, but lost it.

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Claims

• But, if one looks at the animals that manufacture
  vitamin C by pathway of this enzyme and
  extrapolated the amounts made in most animals,
  the amount a 150 pound human male would
  manufacture if possible would be 1500 mgs.
• Pauling started at this level to study Vitamin C
  effects.

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Claims (continued)

• He further suggested that since Vitamin C comes
  from glucose our inability to manufacture it
  causes craving for high sugar foods in an attempt
  to secure enough vitamin C for our bodies.
• May be some anecdotal support for this.

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Sources

• Citrus
• Nuts
• Legumes
• Green and yellow vegetables

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Pauling and Cameron

• Cancer study conducted in the 70s in Scotland.
• 100 terminally ill cancer patients matched with
  another 100 of terminally ill cancer patients.
• One group given 10 grams of vitamin C per day

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Study

• The Vitamin C group lived an average of 10 months
  longer than other group and claimed to have a
  greatly improved quality of life.
• Two of the 100 had a spontaneous remission,
  according to the study
• The American Cancer Society called the report
  quackery.

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Study

• Pauling was finally successful, after long years
  of trying, to get the ACS to conduct a similar
  study in the U.S. They did and the Vitamin C
  group did no better than the control patients.
  Pauling criticized the study on the basis that
  the US study supplemented orally, while he had
  supplemented intravenously in the Scotland study.

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Pauling died at 92

• After his death, the controversy is fairly over.
  However, many nutritionists still recommend 1000
  to 1500 mg. per day as well as up to 10X this
  during stress times such as when catching a virus.