From: Bonnie MacEvoy <bonmom@humboldt1.com>
Subject: Re: Vitamin C
>What about the fact that megadoses of ascorbic acid inhibit copper
>absorption. How does this compromise health?
>Ngoldbeck@aol.com
Mega doses of vit C interfere with copper and other trace mineral
absorption, which can increase heart size, cause hair loss, and affect the
red blood cells. It is assumed this interaction is from reduction and
chelation of the metal in the gut. Overall body copper status may not be
affected. This issue is unclear. Of interest, high fiber diets are also
claimed to decrease copper absorption (you just can't win!).
Copper deficiency in general can involve anemia, bone defects, nervous
system problems, infertility, and decrease in arterial elasticity. RDA
about 1.6 mg/day for men. Sources - meats, seafoods, nuts, and seeds.
Some of the party-line complaints about high doses of vit. C are these:
- it is nearly impossible to plan a balanced diet providing 2g or more of
vit.C without using supplements. Not all brands of Vit C pills are closely
scrutinized or regulated.
- large blood levels will exceed the renal threshold and thereby spill into
the urine.
- increasing ascorbic acid intake can increase its breakdown by accelerating
the enzymes that break it down (this mentioned in the infant rebound scurvy
issue), a kind of tolerance.
- it interferes with heparin and coumadin, 2 life saving drugs used to slow
blood coagulation in patients with blood clotting problems.
- as vit C breaks down, it forms oxalates, which have been implicated in
urinary tract stone formation.
- some studies in animals claim infertility, abortion, mutagenic and
diabetic effects from large doses.
On the pro side, it has been offered (Anderson) that vitamin C (but not in
mega doses) can decrease the number of days of disability secondary to a
cold. I haven't seen this article, so I do not know the criteria used.
The most current publication from the RDA summarizes the issue well - "Many
persons habitually ingest 1g or more of ascorbic acid without developing
apparent toxic manifestations. A number of adverse effects have, however
been reported, and the risk of sustained ingestion of such amounts is
unknown. Routine use of large doses of ascorbic acid is therefore not
recommended." (RDA, 10th edition, p. 121). Scientific agencies cannot
recommend something that is still in question. Does not mean the
possibility of benefit or usefulness does not exist; rather, it has not been
convincingly shown.
There is an ascorbic acid pool of 1500 mg in the body, beyond which amounts
are excreted. This in healthy volunteers; not much good science on RDAs for
disease states.
Many responses about presence of vitamin C in animals. Body needs
L-gulonolactone oxidase, an enzyme, to manufacture ascorbic acid. This
enzyme is known to be missing in humans, cat fish, monkeys, guinea pigs, and
others. Consensus seems to be it is present in most mammals except the above.
Thanks,
Bonnie MacEvoy, MD