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:
http://cat.inist.fr/?aModele=afficheN&cpsidt=15144143 (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:
http://vitamincfoundation.org/forum/viewtopic.php?t=194
http://vitamincfoundation.org/forum/viewtopic.php?t=807
Here is the abstract of the study:
Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients
Abstract
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.
Journal Title
Kidney international (Kidney int.) ISSN 0085-2538 CODEN KDYIA5
Source
2003, vol. 63, no3, pp. 1066-1071 [6 page(s) (article)] (43 ref.)