Abstract-only review · 2021
Phosphorus source and calcium balance: a 30-week cat study
No adverse health effects were reported for these specific diets over 30 weeks; this is not a universal phosphorus limit.
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
75 healthy adult cats, 25 per group. Foods with total phosphorus of 4 or 5 g/1,000 kcal, including 1 g phosphorus from sodium tripolyphosphate; calcium:phosphorus ratios above one. Comparator: Lower-phosphorus control food.
What was measured?
Blood and urine markers, kidney filtration, ultrasound and bone density.
Main findings
The abstract reports no adverse kidney, bone or general-health effects. Several mineral and biochemical measurements changed.
Study strengths
Randomised parallel groups and repeated functional measurements.
Limitations
Results depend on phosphate source, calcium balance, population and duration. They do not establish safety for all formulations or cats with kidney disease.
Researchers’ conclusion
The authors proposed a no-observed-adverse-effect level for the tested STPP formulations.
Ingredients investigated
Multi-ingredient formulations
Calcium
Multi ingredient · cat. 75 healthy adult cats, 25 per group.
Tested form: Complete foods with calcium:phosphorus ratios above one; exact calcium source and inclusion not reported in the reviewed abstract. Dose: Calcium:phosphorus ratios above one; exact calcium amount not reported (Dietary mineral ratio). Duration: Seven months. Comparator: Lower-phosphorus control food.
Measured finding: The abstract reports no adverse kidney, bone, or general-health effects. Several mineral and biochemical measurements changed.
Limitations: Results depend on phosphate source, calcium balance, population, and duration. They do not establish safety for all formulations or cats with kidney disease.
This ingredient was part of a combined formulation; the study does not isolate its contribution.
Phosphorus
Multi ingredient · cat. 75 healthy adult cats, 25 per group.
Tested form: Foods with total phosphorus of 4 or 5 g/1,000 kcal, including 1 g phosphorus from sodium tripolyphosphate; calcium:phosphorus ratios above one. Dose: Total phosphorus 4 or 5 g/1,000 kcal; 1 g phosphorus from sodium tripolyphosphate (Grams of phosphorus per 1,000 kcal). Duration: Seven months. Comparator: Lower-phosphorus control food.
Measured finding: The abstract reports no adverse kidney, bone, or general-health effects. Several mineral and biochemical measurements changed.
Limitations: Results depend on phosphate source, calcium balance, population, and duration. They do not establish safety for all formulations or cats with kidney disease.
This ingredient was part of a combined formulation; the study does not isolate its contribution.
Evidence.pet interpretation
Read alongside higher-phosphorus studies with different salts and calcium ratios. Total phosphorus alone does not explain the comparison.
Funding and conflicts
Full funding and conflict declarations were not appraised for this abstract-based summary.
Source and review date
Coltherd JC et al. Seven-month feeding study investigating no observed adverse effect levels for phosphorus in adult-cat diets. British Journal of Nutrition. 2021;126(11):1626–1641. Title shortened; DOI identifies the paper.
Read the primary source · DOI record
STU-042. Reviewed 25 September 2026. Next review 25 December 2026.