K. Sakhaee et al., LIMITED RISK OF KIDNEY-STONE FORMATION DURING LONG-TERM CALCIUM CITRATE SUPPLEMENTATION IN NONSTONE FORMING SUBJECTS, The Journal of urology, 152(2), 1994, pp. 324-327
The physiological and physicochemical effects of long-term calcium cit
rate supplementation (25 mmol. calcium per day) were assessed in 7 nor
mal premenopausal women. Calcium citrate increased urinary calcium fro
m 3.27 +/- 0.42 mmol. per day (standard deviation) before treatment to
5.16 +/- 0.75 mmol. per day after 1-month of treatment (p <0.0125). A
fter 3 months of treatment urinary calcium decreased from the 1-month
value to 4.54 +/- 0.67 mmol. per day (p <0.0125) but remained higher t
han the pretreatment value (p <0.0125). Fractional intestinal calcium
absorption and serum 1,25-dihydroxyvitamin D levels decreased marginal
ly at 1 month of calcium citrate therapy, from 0.457 +/- 0.092 to 0.37
4 +/- 0.035 (p <0.05) and from 103 +/- 7 to 77 +/- 14 pmol./l. (p <0.0
5), respectively. After 3 months of treatment fractional intestinal ca
lcium absorption decreased further to 0.341 +/- 0.061 (p <0.0125 compa
red to pretreatment), whereas serum 1,25-dihydroxyvitamin D remained u
nchanged at 82 +/- 14 pmol./l. Calcium citrate treatment decreased uri
nary phosphorus levels significantly from 18.9 +/- 3.3 to 15.0 +/- 2.5
mmol. per day (p <0.0125) and 14.0 +/- 2.5 mmol. per day (p <0.05) at
1 and 3 months, respectively. Mean urinary oxalate decreased by 15 to
20% and urinary citrate increased marginally during treatment. Urinar
y saturation of calcium oxalate and brushite did not change during cal
cium citrate therapy, except at 1 month when the saturation of calcium
oxalate increased marginally. The inhibitory activity of urine agains
t spontaneous nucleation of calcium oxalate and brushite (formation pr
oduct) did not change during treatment. In conclusion, long-term calci
um citrate supplementation in normal subjects does not increase the pr
opensity for crystallization of calcium salts in the urine. This prote
ctive effect is probably due to the attenuated increase in urinary cal
cium excretion (from a decrease in fractional intestinal calcium absor
ption), a decrease in urinary phosphorus and an increase in urinary ci
trate.