From: Bonnie MacEvoy <>

Subject: Re: Vitamin C


>What about the fact that megadoses of ascorbic acid inhibit copper

>absorption. How does this compromise health?



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.



Bonnie MacEvoy, MD