Benefits
Urinary citrate and urine pH
In people who form calcium stones and have low urinary citrate, 30 to 60 mEq a day raised urinary citrate and pH and lowered new stone formation versus placebo over 3 years. A Cochrane review of 7 trials found citrate salts lowered new stone formation (risk ratio 0.26), but rated study quality moderate to poor. These are prescription-strength doses, far above a supplement serving.
Urine alkalinizing effect
In 18 people with uric acid stones treated for an average of almost 3 years with 30 to 80 mEq a day, urine pH rose from about 5.3 to 6.2 to 6.5 and the amount of poorly soluble uric acid in urine fell into the normal range. This was an uncontrolled case series at prescription doses that needed medical monitoring.
Bone mineral density support
In 161 postmenopausal women with low bone mass, 30 mEq a day for 12 months raised spine and hip bone density versus potassium chloride. In 201 healthy adults over 65 also taking calcium and vitamin D, 60 mEq a day raised spine bone density by 1.7% versus placebo over 2 years. Neither trial measured actual fractures.
Blood pressure
In a randomized crossover trial in adults with early-stage high blood pressure, 40 mmol a day of potassium citrate for 6 weeks did not significantly change 24-hour blood pressure, arterial stiffness or endothelial function compared with placebo. A blood pressure benefit is not established for this form.
Mechanism of action
Citrate to Bicarbonate Conversion
Absorbed citrate is turned into bicarbonate in the liver. This offsets part of the body's acid load, raises urine pH and increases the amount of citrate passed in urine.
Urinary citrate and calcium binding
Citrate in urine binds calcium, which lowers calcium oxalate supersaturation, a measure of how readily these crystals can form. Repeat stones are more common in people with low urinary citrate, which is why urinary citrate is a common target in stone research.
Urinary pH Elevation
Citrate raises urine pH. Uric acid dissolves better in less acidic urine, so a higher urine pH lowers the amount of poorly soluble uric acid. In a long-term case series, prescription doses raised urine pH from about 5.3 to between 6.2 and 6.5.
Acid-Base Buffering
Bicarbonate generation buffers chronic mild metabolic acidosis from typical Western diets — proposed mechanism for bone-sparing effects.
Clinical trials
Randomized, double-blind, placebo-controlled trial of 30 to 60 mEq/day potassium citrate for 3 years in 57 adults with 2 or more stones in the previous 2 years and low urinary citrate (Barcelo et al. 1993, J Urol)
57 adults with active calcium stone disease and low urinary citrate; 18 on potassium citrate and 20 on placebo were followed for 3 years.
Stone formation fell from 1.2 to 0.1 stones per patient-year on potassium citrate and stayed at 1.1 on placebo; 72% versus 20% were in remission. Urinary citrate, pH and potassium rose only with potassium citrate. Two people on potassium citrate and one on placebo withdrew because of side effects.
Randomized, double-blind trial of 30 mEq/day potassium citrate versus 30 mEq/day potassium chloride for 12 months in 161 postmenopausal women with low bone mass (Jehle et al. 2006, J Am Soc Nephrol)
161 postmenopausal women, average age about 59, with low bone mass.
Compared with potassium chloride, spine bone density rose by about 1.9%, femoral neck by 1.4% and total hip by 2.0% (all p<0.001). Distal radius and total body did not differ. Urinary calcium fell and a bone breakdown marker dropped. Fractures were not measured.