Malic acid raises urinary citrate and pH in healthy people
What it found
In eight healthy people, taking 1200 mg of malic acid daily for 7 days raised urinary pH and citrate.
Lab modelling suggested malate itself would not change calcium salt saturation.
What they found
Studies in people
Urinary pH and citrate
After 7 days of malic acid, urinary pH and citrate excretion rose significantly compared with before supplementation.
Calcium oxalate saturation
The calculated amount of free calcium and the saturation of calcium oxalate fell after supplementation, but the change was not statistically significant.
Calcium phosphate saturation
Saturation of hydroxyapatite and tricalcium phosphate rose significantly as pH increased. Brushite and octacalcium phosphate saturation did not change significantly.
Animal and lab studies
Lab modelling of malate
Computer modelling showed that malate binding to calcium at normal body levels would not affect calcium salt saturation.
What the authors conclude
“We conclude that malic acid supplementation may be useful for conservative treatment of calcium renal stone disease by virtue of its capacity to induce these effects.”
Also in their conclusions
- They speculate that malic acid caused a shift in body acid-base balance, which reduced the kidney's reabsorption and breakdown of citrate, leading to more citrate in the urine.
- They say the fall in calcium oxalate saturation was due to citrate binding more calcium.
- They conclude that malic acid supplementation may be useful for conservative treatment of calcium kidney stone disease because of these effects.
How it was done
Raising urinary pH and citrate is a common treatment for calcium kidney stones, and citrate-rich fruit juices have been suggested as a gentler option. The authors wanted to see whether malate, a similar compound, could do the same job.
Eight healthy people took 1200 mg of malic acid per day for 7 days. Their 24-hour urine was collected before and on day 7 and tested for pH, citrate and other stone-related components. A computer program modelled how malate affects calcium and calcium salt saturation.
What it can’t tell you
- We summarised it from the abstract only.
- This was a small study of eight healthy people over 7 days, so it cannot show whether malic acid prevents kidney stones or helps people who already have them.
- The study did not test whether the changes in urine actually reduce stone formation.
Who paid
- Authors work at
- University of Cape Town, South Africa
The paper
- Title
- Malic acid supplementation increases urinary citrate excretion and urinary pH: implications for the potential treatment of calcium oxalate stone disease
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Abstract only
- Cite
- Rodgers AL, Webber D, de Charmoy R, Jackson GE, Ravenscroft N (2014). Malic acid supplementation increases urinary citrate excretion and urinary pH: implications for the potential treatment of calcium oxalate stone disease. Journal of endourology. doi:10.1089/end.2013.0477PubMed 24059642DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error