First, I am not sure why the Toxicity forum is locked. Are we supposed to post here and let the forum admin move the thread into that forum for archiving purposes?
I was just reading yet another book that claims vitamin C causes kidney stones. I decided to check for the very newest research. In the process, I found something that isn't the newest, but it sounds more conclusive than other studies I have seen:
(see abstract below)
It states, based on the Tiselius index, that
These data suggest that vitamin C supplementation may increase ... the risk of calcium oxalate crystallization ....
I checked the existing threads in this forum and didn't see this study mentioned. I didn't see any responses on this forum that would directly refute the study, so I would like to ask about it specifically. If anyone can comment on it, I would appreciate it. I do note that they didn't actually find kidney stone formation, but the study was too short for that and it wasn't designed for that. They did look specifically at oxalate crystallization
, however. Can anyone comment on the Tiselius index? Thanks.
Here are the existing threads on this topic in this forum:
Here is the abstract of the study:
Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients
Background. The contribution of ascorbate to urinary oxalate is controversial. The present study aimed to determine whether urinary oxalate and pH may be affected by vitamin C supplementation in calcium stone-forming patients. Methods. Forty-seven adult calcium stone-forming patients received either 1 g (N = 23) or 2 g (N = 24) of vitamin C supplement for 3 days and 20 healthy subjects received 1 g. A 24-hour urine sample was obtained both before and after vitamin C for calcium, oxalate, magnesium, citrate, sodium, potassium, and creatinine determination. The Tiselius index was used as a calcium oxalate crystallization index. A spot fasting morning urine sample was also obtained to determine the urinary pH before and after vitamin C. Results. Fasting urinary pH did not change after 1 g (5.8 ± 0.6 vs. 5.8 ± 0.7) or 2 g vitamin C (5.8 ± 0.8 vs. 5.8 ± 0.7). A significant increase in mean urinary oxalate was observed in calcium stone-forming patients receiving either 1 g (50 ± 16 vs. 31 ± 12 mg/24 hours) or 2 g (48 ± 21 vs. 34 ± 12 mg/24 hours) of vitamin C and in healthy subjects (25 ± 12 vs. 39 ± 13 mg/24 hours). A significant increase in mean Tiselius index was observed in calcium stone-forming patients after 1 g (1.43 ± 0.70 vs. 0.92 ± 0.65) or 2 g vitamin C (1.61 ± 1.05 vs. 0.99 ± 0.55) and in healthy subjects (1.50 ± 0.69 vs. 0.91 ± 0.46). Ancillary analyses of spot urine obtained after vitamin C were performed in 15 control subjects in vessels with or without ethylenediaminetetraacetic acid (EDTA) with no difference in urinary oxalate between them (28 ± 23 vs. 26 ± 21 mg/L), suggesting that the in vitro conversion of ascorbate to oxalate did not occur. Conclusion. These data suggest that vitamin C supplementation may increase urinary oxalate excretion and the risk of calcium oxalate crystallization in calcium stone-forming patients.
Kidney international (Kidney int.) ISSN 0085-2538 CODEN KDYIA5
2003, vol. 63, no3, pp. 1066-1071 [6 page(s) (article)] (43 ref.)