Phosphoric acid and infection urinary stone minerals in artificial urine
What it found
In artificial urine, phosphoric acid made the minerals that make up infection urinary stones form earlier, at lower pH, and in smaller amounts.
The effect only happened when the urine contained urease-positive bacteria or their simulated activity.
What they found
Animal and lab studies
Earlier mineral formation
In artificial urine, phosphoric acid shifted the start of carbonate apatite and hydroxyapatite formation to lower pH values. This happened both with Proteus mirabilis bacteria and when bacterial urease was simulated with ammonia solution.
Smaller amount of solid
The higher the phosphoric acid concentration, the smaller the amount of solid phases formed. In the bacteria-free tests, the weighed sediment was smaller than in the control for most concentrations. With bacteria, the calcium content, which indicates the amount of solid, was also lower at higher phosphoric acid levels.
No straight-line relationship
The drop in the pH at which minerals started to form was not proportional to the phosphoric acid concentration. The highest concentration did not lower the starting pH much more than the next highest.
More clumping
Microscopic images suggested that phosphoric acid made the solid particles clump together more, especially at higher concentrations. The authors say this needs more objective study, such as zeta potential measurements.
Infection is required
The authors state that these effects of phosphoric acid only happen when the urinary tract is infected with urease-positive bacteria. Without infection, phosphoric acid will not cause these solid phases to form.
Other findings
Which mineral is responsible
A computer analysis of chemical complexes showed that the shift to lower pH was linked to the earlier appearance of the complex that forms hydroxyapatite, not the one that forms carbonate apatite. The hydroxyapatite-forming complex was present at levels 10,000 times higher than the carbonate apatite one.
What the authors conclude
“It should be remembered that all these effects of phosphoric acid are possible in the case of urinary tract infection with urease‐positive bacteria.”
Also in their conclusions
- They conclude that the higher the concentration of phosphoric acid, the earlier the formation of these solid phases begins, which they call not a favourable effect.
- They also note that the amount of solid formed is lower with more phosphoric acid, which they call a positive effect.
- They advise that the increased clumping they saw needs more objective study, such as zeta potential measurements.
How it was done
The authors note that infection urinary stones are becoming more common in highly developed countries, and they wanted to check whether food and drink containing large amounts of phosphoric acid might be a risk factor for this type of stone.
They studied artificial urine that matched the average daily mineral levels in a healthy person's urine. They tested four phosphoric acid concentrations, both with the urease-positive bacterium Proteus mirabilis and without bacteria, where ammonia solution was added to mimic bacterial urease. They tracked pH, turbidity, the amount of solid formed, and ran a computer analysis of the chemical complexes.
What it can’t tell you
- This was a lab study using artificial urine, not people. It cannot show what happens in the human urinary tract.
- The experiments ran for up to 24 hours in still conditions, without the flow of urine that happens in a real urinary tract.
- The authors say the effect on stone formation only applies when a urinary tract infection with urease-positive bacteria is already present.
Who paid
- Conflicts
- The authors have declared that no competing interests exist.
- Authors work at
- Lodz University of Technology, Poland; Jan Długosz University of Czestochowa, Poland; University of Lodz, Poland
The paper
- Title
- Phosphoric Acid Versus Biogenic Mineralization of Hydroxyapatite and Carbonate Apatite in Relation to Infection-Induced Urinary Stones: Physical, Chemical and Microbiological Aspects
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Prywer J, Mielniczek-Brzóska E, Torzewska A (2025). Phosphoric Acid Versus Biogenic Mineralization of Hydroxyapatite and Carbonate Apatite in Relation to Infection-Induced Urinary Stones: Physical, Chemical and Microbiological Aspects. ChemPlusChem. doi:10.1002/cplu.202400712Free full textPubMed 40028826DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error