This is a good question, and I will forward to Dr. Levy for his comment, but I hesitate to even read the study because of the following logical inconsistency
The predialysis levels of vitamin C showed extremely good correlation to the serum oxalate levels. Overingestion of vitamin C in food or as supplementation may lead to excessive serum levels of vitamin C, resulting in hyperoxalemia that may contribute to vascular disease in patients on chronic hemodialysis.
In short the study finds one thing (which we know is bogus anyway, at least in normal people with properly functioning kidneys - the maxium blood level is 15 mg/dl at roughly 200 mg. The rest is excreted by a properly functioning kidney
It then extrapolates outside the bounds of the study to something else - in this case, hperoxalemia that "may contribute to vascular disease". This is speculation, on top of speculation, and I'll bet a dime that this finding is not what the study was designed to investigate.
This is the same erroneous reasoning that causes medical text books to warn prospective medical students that vitamin C causes kidney stones, when all the clinical evidence demonstrates the opposite. Some kidney stones contain oxalate. Vitamin C increases oxaltes. Ergo, Vitamin C "may" increase the frequency of kidney stones. (Well, kidney stones contain calcium too. So calcium may increase the frequency of kidney stones. The point is that you design a study to find out) The studies that have investigated the right question, at least the ones we know of, have found no relationship between vitamin C intake and kidney stones, at least not a negative relationship. These studies have noticed that people with low vitamin B6 levels are more likely to suffer kidney stones.
Getting back to whether vitamin C is contraindicated for people on dialysis - hard question, but under any scenario/argument - 200 mg daily can not cause any harm since there would be NO excess for the kidney to excrete. But if dialysis indeed works like a kidney, then there would be no problem with even more vitamin C, which in theory, might help the kidney repair itself through the "vitamin C effect" on stem cells.
Oh, and I "love" that title - Vitamin C Intoxification... he he he
Owen R. Fonorow, Orthomolecular Naturopath
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