Vitamin C/Kidney Stones

[Guest guest]

http://www.vitamincfoundation.org/news.htm#KIDNEY

May 2002

Megadose Vitamin C consumption does not cause kidney stones.

Intake of vitamins B6 and C and the risk of kidney stones in women

Curhan, G. C., Willett, W. C., Speizer, F. E., Stampfer, M. J.

J Am Soc Nephrol 10:4:840-845, Apr 1999

Abstract

Urinary oxalate is an important determinant of calcium oxalate kidney stone

formation. High doses of vitamin B6 may decrease oxalate production, whereas

vitamin C can be metabolized to oxalate. This study was conducted to examine the

association between the intakes of vitamins B6 and C and risk of kidney stone

formation in women. The relation between the intake of vitamins B6 and C and

the risk of symptomatic kidney stones were prospectively studied in a cohort

of 85,557 women with no history of kidney stones. Semiquantitative

food-frequency questionnaires were used to assess vitamin consumption from both

foods and

supplements. A total of 1078 incident cases of kidney stones was documented

during the 14-yr follow-up period. A high intake of vitamin B6 was inversely

associated with risk of stone formation. After adjusting for other dietary

factors, the relative risk of incident stone formation for women in the highest

category of B6 intake (> or =40 mg/d) compared with the lowest category (<3

mg/d)

was 0.66 (95% confidence interval, 0.44 to 0.98). In contrast, vitamin C

intake was not associated with risk. The multivariate relative risk for women in

the highest category of vitamin C intake (> or =1500 mg/d) compared with the

lowest category (<250 mg/d) was 1.06 (95% confidence interval, 0.69 to 1.64).

Large doses of vitamin B6 may reduce the risk of kidney stone formation in

women.

Routine restriction of vitamin C to prevent stone formation appears

unwarranted.