| BACKGROUND. A high dietary calcium intake is strongly suspected of
increasing the risk of kidney stones. However, a high intake of
calcium can reduce the urinary excretion of oxalate, which is thought
to lower the risk. The concept that a higher dietary calcium intake
increases the risk of kidney stones therefore requires examination.
METHODS. We conducted a prospective study of the relation between
dietary calcium intake and the risk of symptomatic kidney stones in a
cohort of 45,619 men, 40 to 75 years of age, who had no history of
kidney stones. Dietary calcium was measured by means of a
semiquantitative food-frequency questionnaire in 1986. During four
years of follow-up, 505 cases of kidney stones were documented.
RESULTS. After adjustment for age, dietary calcium intake was
inversely associated with the risk of kidney stones; the relative
risk of kidney stones for men in the highest as compared with the
lowest quintile group for calcium intake was 0.56 (95 percent
confidence interval, 0.43 to 0.73; P for trend, < 0.001). This
reduction in risk decreased only slightly (relative risk, 0.66; 95
percent confidence interval, 0.49 to 0.90) after further adjustment
for other potential risk factors, including alcohol consumption and
dietary intake of animal protein, potassium, and fluid. Intake of
animal protein was directly associated with the risk of stone
formation (relative risk for men with the highest intake as compared
with those with the lowest, 1.33; 95 percent confidence interval,
1.00 to 1.77); potassium intake (relative risk, 0.49; 95 percent
confidence interval, 0.35 to 0.68) and fluid intake (relative risk,
0.71; 95 percent confidence interval, 0.52 to 0.97) were inversely
related to the risk of kidney stones. CONCLUSIONS. A high dietary
calcium intake decreases the risk of symptomatic kidney stones.
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