What could be Less Toxic than Water?


Vitamin C (ascorbic acid) is one of the least toxic substances.  Obviously water is less toxic in terms of the weight of it that is required to be harmful when ingested.  However if the criterion for the least toxic is the multiple of the desirable dose that is still nontoxic, vitamin C is much less toxic than water.  Forty mg. daily is required for health.  Four thousand mg.is still harmless---100 times 40.   


Some substantial fraction of a gallon of water per day is healthy.  Five to ten times that amount taken orally in a short time might be fatal because of exceeding the kidney’s ability to excrete it and the resulting dilution and excess volume of the blood.   Compare with 100 times too much vitamin C being harmless. 


It is interesting that as toxic doses of vitamin C are approached, it starts to be destroyed in the body instead of merely excreted.  A major portion of the destroyed vitamin C is converted to oxalic acid.  Fatal doses of oxalic acid could easily be consumed based on this mechanism.  Don’t worry too much---it hasn’t happened yet.  Mild chronic oxalate poisoning would lead almost inevitably to kidney stones.  


A possibility, short of fatality, that also has not been reported: could induction of the destruction of vitamin C by enormous doses result in temporary deficiency if the enormous dose were abruptly reduced to 40 mg. daily?  It could well be that the destruction could not be so immediately curtailed.  Food for thought


Bottom line: this is a logical rebuttal to the error in thinking, “If a little is good, more is better.”  


PS Google told me that the dose of vitamin C that kills 50% of rats is 11,900,000,000 nanograms.per kilogram (11.9 grams per kg).  14,000,000,000 ng (14 grams) has been given to adult humans in a single dose.  This is 200 mg. per kg.  A discussant said that twice that amount would probably not have been fatal.  The doses of toxic materials on Wikipedia were all in nonograms presumably to emphasize the unique toxicity of Clostridium botulinum toxin, 1ng/kg (0.000,000,001 gm/kg).


John A. Frantz, MD  

January 13, 2010