Table 4.

Relative risk of symptomatic kidney stones, according to category of energy-adjusted vitamin C intake among 85,557 women (the Nurses' Health Study)

ParameterVitamin C Category (mg/d)χ (P for trend)
<250250 to 499500 to 9991000 to 14991500+
aThe multivariate model included age (in 5-yr age categories), body mass index (seven categories), alcohol (six categories), vitamin B6 (five categories), supplemental calcium (four categories), and dietary intake of calcium, animal protein, sodium, potassium, sucrose, caffeine, and total fluid (quintile groups).
No. of cases7391501214424
No. of person-years659,783152,494102,77043,50321,758
Age-adjusted relative risk1.000.871.050.900.98-0.46 (0.64)
95% CIReferent0.73 to 1.040.87 to 1.270.67 to 1.220.65 to 1.47
Multivariate relative riska1.000.891.080.951.060.79 (0.43)
95% CIReferent0.74 to 1.080.87 to 1.340.69 to 1.310.69 to 1.63