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 sought to examine associations between dietary calcium from non-dairy and dairy sources and symptomatic nephrolithiasis.
Materials and Methods: We conducted prospective studies in the Health Professionals Follow-up Study (HPFS; N=30,762 men), the Nurses' Health Study I (NHS I; N=94,164 women), and the Nurses' Health Study II (NHS II; N=101,701 women). We excluded men ≥ 60 years old because we previously reported inverse associations between calcium intake and risk only in men < 60. Food frequency questionnaires assessed calcium intake every four years. We used Cox proportional hazards regression to adjust for age, BMI, supplemental calcium, diet, and other factors.
Results: We documented 5,270 incident kidney stones over a combined 56 years of follow-up. For participants in the highest compared to lowest quintile of non-dairy dietary calcium, the multivariable relative risks of kidney stones were 0.71 (95% CI 0.56-0.92; P for trend 0.007) for HPFS, 0.82 (0.69-0.98; P trend 0.08) for NHS I, and 0.74 (0.63-0.87; P trend 0.002) for NHS II. The multivariable relative risks comparing highest to lowest quintile of dairy calcium were 0.77 (0.63-0.95; P trend 0.01) for HPFS, 0.83 (0.69-0.99; P trend 0.05) for NHS I, and 0.76 (0.65-0.88; P trend 0.001) for NHS II.
Conclusions: Higher dietary calcium from either non-dairy or dairy sources is independently associated with lower kidney stone risk.
Written by:
Taylor EN, Curhan GC Are you the author?
Channing Division of Network Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA; Division of Nephrology and Transplantation, Maine Medical Center, Portland, ME.
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Reference: J Urol. 2013 Mar 24. (Epub ahead of print)
doi: 10.1016/j.juro.2013.03.074
PubMed Abstract
PMID: 23535174
