High doses of vitamin C can lead to renal, bone, hematolog-ical, and gastrointestinal effects.46 Renal calculi because of oxalate or urate result from enhanced renal excretion of these compounds in the presence of high doses of vitamin C. Increased release of calcium and phosphorus from bone have been observed. Hematological effects include increased absorption of nonheme iron without significant increases in total body iron stores. Diarrhea, likely resulting from an osmotic effect, has been reported following large doses, and ascorbic acid tablets that lodge in the esophagus can cause local erosion. Finally, ascorbic acid has been shown to interfere with several colorimetric redox assays because of its ability to act as a reducing agent.
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