Malic acid supplements and urine changes in eight healthy people
What it found
Taking malic acid for a week raised urine pH and citrate levels in eight healthy people.
The authors suggest it might help prevent calcium kidney stones.
What they found
Studies in people
Urine pH and citrate
After seven days of taking malic acid, the eight people had higher urine pH and more citrate in their urine. Both changes were clear enough to be unlikely due to chance.
Other calcium salts
The rise in urine pH led to a clear increase in two other types of calcium phosphate crystals in the urine. Two further types did not change significantly.
Studies in people and animals
Calcium oxalate stone risk
Computer models showed that malic acid binding directly to calcium would not change crystal formation. However, after people took the supplement, calculated calcium levels and calcium oxalate crystal risk dropped slightly, though not by a statistically clear amount.
What the authors conclude
- They suggest that taking malic acid makes the body more alkaline, which leads the kidneys to release more citrate into the urine.
- They conclude that the extra citrate then binds calcium and lowers the chance of calcium oxalate crystals forming.
- The authors propose that malic acid supplements could be a useful natural option for treating calcium kidney stones.
How it was done
Raising urine pH and citrate is a common way to treat calcium kidney stones. Citrate binds calcium and stops crystals from forming, so the researchers wanted to see if malic acid could do the same thing.
Eight healthy people took 1200 mg of malic acid each day for seven days. Researchers collected their urine over 24 hours before starting and on the final day. They also used computer models to predict how malic acid would affect calcium in urine.
What it can’t tell you
- We summarised it from the abstract only.
- This was a small study of only eight healthy people over one week.
- It cannot show whether malic acid actually prevents kidney stones in people who are prone to them.
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 1 Oct 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error