- Design
- Randomised 2x3 factorial trial, secondary complete-case analysis
- Population
- 83 of 108 women aged 40-77 doing resistance or concurrent training
- Primary outcome
- Lipid, kidney and liver biomarkers at 12 weeks by protein intake
- Effect
- Creatinine and cystatin C rose, eGFR fell, mainly 0.8 vs 1.6 or 2.2 g/kg/day
This randomised factorial trial assigned 108 women aged 40 to 77 to resistance training alone or with cycling, and to protein intakes of 0.8, 1.6 or 2.2 g/kg/day for 12 weeks. This secondary analysis of 83 completers examined blood lipids, kidney markers and liver enzymes.
Urea, blood urea nitrogen, creatinine and cystatin C rose and three eGFR estimates fell, with differences mainly between 0.8 g/kg and the two higher intakes and little between 1.6 and 2.2 g/kg. Lipids improved in all groups.
The authors state plainly that the changes in eGFR do not establish kidney injury or long-term harm, and that energy and food composition were not fully matched. The practical point is interpretive: a falling eGFR in someone who has sharply raised protein intake may reflect diet as much as kidney function.
- Ask about recent changes in protein intake and supplements when interpreting a new fall in eGFR.
- Remember that cystatin C also moved here, so switching markers may not remove the effect.
- Recheck kidney function after a period of usual intake before labelling CKD on one result.
- Advise patients with established CKD to discuss high-protein diets with their clinician or dietitian.
Why it matters
High-protein diets and supplements are common, and their effect on routine kidney markers can mislead.
Don't overread it
The changes in eGFR do not show kidney injury or long-term harm.
The statistics, in plain English
This was a secondary analysis of completers, which can introduce bias, and the trial was not designed to test kidney safety. The changes were in laboratory estimates over 12 weeks, not clinical outcomes.
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