Review scope

This summary is based on the published abstract. We have not appraised the full methods, tables or supplementary material. Details absent from the abstract remain unverified.

Question and design

Two studies involving 48 and 50 healthy adult cats. Diets with higher total and inorganic phosphorus and lower calcium:phosphorus ratios. Comparator: Lower-phosphorus control foods.

What was measured?

Kidney filtration, ultrasound, health markers and mineral balance.

Main findings

The first study stopped after four weeks because of adverse kidney findings. In the second, mean filtration did not change, but ultrasound changes occurred in 36% of test cats; stones in both groups complicated interpretation.

Study strengths

Controlled feeding with functional and structural kidney measurements.

Limitations

Phosphorus amount, source and calcium ratio changed together. A universal safe limit cannot be isolated from these comparisons.

Researchers’ conclusion

The authors called for further investigation of phosphorus sources and calcium balance.

Evidence.pet interpretation

The study warrants formulation-specific scrutiny. An ingredient list alone cannot reveal the exposure tested here.

Funding and conflicts

The source identifies Mars Petcare funding. Full conflict declarations and methods were not appraised for this abstract-based summary.

Source and review date

Alexander J et al. Effects of the long-term feeding of diets enriched with inorganic phosphorus on the adult feline kidney and phosphorus metabolism. British Journal of Nutrition. 2019. PMCID: PMC6390406.

Read the primary source

STU-041. Reviewed 25 September 2026. Next review 25 December 2026.