TOPLINE

Over 10 years, higher habitual dietary protein intake was not associated with a faster decline in iohexol-measured GFR (mGFR) among middle-aged and older adults.

METHODOLOGY

• Researchers conducted a prospective cohort study, analyzing data from the Renal Iohexol Clearance Survey, a population-based cohort with repeated mGFR measurements in Norway.
• A total of 1324 participants (mean age, 63.6 years; 50.4% women) were included; most were without chronic kidney disease (CKD), diabetes, or cardiovascular disease; the median follow-up was 10 years.
• GFR was measured directly using single-sample plasma iohexol clearance.
• Baseline protein intake was estimated using a validated 261-item food frequency questionnaire; mean reported protein intake was 1.2 g/kg/d.
• Outcomes assessed were annual mGFR decline rate, accelerated GFR decline (top 10% with steepest annual reductions), and incident mGFR <60 mL/min/1.73 m²; analysis was adjusted for several confounders.

TAKEAWAY

• Protein intake was not associated with mGFR decline rate; the annual change was −0.01 mL/min/1.73 m² (95% CI, −0.04 to 0.02) per 0.1 g/kg/d increase in protein intake in the fully adjusted model.
• Higher protein intake was not associated with accelerated GFR decline, with an odds ratio of 0.97 (95% CI, 0.86-1.10) per 0.1 g/kg/d increase.
• Among 1064 participants with baseline mGFR ≥60 mL/min/1.73 m², 118 (11.1%) developed incident mGFR <60 mL/min/1.73 m² during follow-up; baseline protein intake was not associated with this outcome, with a hazard ratio of 1.09 (95% CI, 0.96-1.21) per 0.1 g/kg/d increase.

IN PRACTICE

"Our findings from a population-based cohort with repeated iohexol-based GFR measurements over 10 years suggest that higher self-reported protein intake is not associated with GFR decline. These findings indicate that protein restriction may not be a lifestyle strategy for preventing CKD," wrote the authors of the study.

SOURCE

The study was led by Ludvig Balteskard Rinde, Metabolic and Renal Research Group, Department of Clinical Medicine, UiT The Arctic University of Norway in Tromsø, Norway. It was published online on July 11 in Clinical Kidney Journal.

LIMITATIONS

Protein intake was assessed using a food frequency questionnaire, which may introduce misclassification, and the absence of 24-hour urinary urea nitrogen measurements limited objective validation of total protein intake. The questionnaire and iohexol measurements were taken at different times (median interval 20.5 months). Data on specific protein sources (plant-based vs animal-based) were not available. The cohort consisted of relatively healthy, middle-aged Norwegian adults, which may limit generalizability to populations with different dietary patterns or higher CKD prevalence.

DISCLOSURES

The Renal Iohexol Clearance Survey studies were supported by grants from the Northern Norway Regional Health Authorities. One author reported support from the Swedish Research Council and the Swedish Heart and Lung Foundation. The authors reported no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.