PURPOSE: Because of high correlations between dairy intake and total dietary 
calcium, previously reported associations between lower calcium intake and 
increased kidney stone risk represent de facto associations between milk 
products and risk. We examined associations between dietary calcium from 
nondairy and dairy sources, and symptomatic nephrolithiasis.
MATERIALS AND METHODS: We performed prospective studies in the Health 
Professionals Follow-up Study (HPFS) in 30,762 men, and in the Nurses' Health 
Study (NHS) I and II in 94,164 and 101,701 women, respectively. We excluded men 
60 years old or older because we previously reported inverse associations 
between calcium intake and risk only in men younger than 60 years. Food 
frequency questionnaires were used to assess calcium intake every 4 years. We 
used Cox proportional hazards regression to adjust for age, body mass index, 
supplemental calcium, diet and other factors.
RESULTS: We documented 5,270 incident kidney stones during the combined 56 years 
of followup. In participants in the highest vs the lowest quintile of nondairy 
dietary calcium the multivariate relative risk of kidney stones was 0.71 (95% CI 
0.56-0.92, p for trend 0.007) in HPFS, 0.82 (95% CI 0.69-0.98, p trend 0.08) in 
NHS I and 0.74 (95% CI 0.63-0.87, p trend 0.002) in NHS II. When comparing the 
highest to the lowest quintile of dairy calcium, the multivariate relative risk 
was 0.77 (95% CI 0.63-0.95, p trend 0.01) for HPFS, 0.83 (95% CI 0.69-0.99, p 
trend 0.05) for NHS I and 0.76 (95% CI 0.65-0.88, p trend 0.001) for NHS II.
CONCLUSIONS: Higher dietary calcium from nondairy or dairy sources is 
independently associated with a lower kidney stone risk.