Sodium Intake and Six-Month Kidney Function in Adults with Diabetic Kidney Disease: An Observational Study

Abstract

Dietary management is an important component of diabetic kidney disease (DKD) care, although evidence linking habitual nutrient intake with short-term kidney-function trajectories remains limited. We examined the associations of protein, fat, carbohydrate, and sodium intake with six-month kidney function in adults with DKD. This observational analytic study included 50 adults with type 2 diabetes and chronic kidney disease. Habitual dietary intake was assessed using a semiquantitative food-frequency questionnaire supported by 24-hour dietary recall. Six-month estimated glomerular filtration rate (eGFR) was modeled with adjustment for baseline eGFR. Separate linear regression models evaluated continuous dietary exposures, while sodium intake was additionally examined using a predefined threshold of <2300 versus ≥2300 mg/day. The cohort predominantly had advanced CKD, with 76.0% classified as G4–G5 and 96.0% having urinary albumin-to-creatinine ratio ≥30 mg/g. Mean sodium intake was 2541±742 mg/day. Continuous protein, fat, carbohydrate, and sodium intake were not associated with six-month eGFR. In contrast, sodium intake ≥2300 mg/day was associated with a lower six-month eGFR after adjustment for baseline eGFR, age, sex, HbA1c, and systolic blood pressure (B=−8.82 mL/min/1.73 m²; 95% CI −16.22 to −1.43; p=0.021). Adjusted mean six-month eGFR was 31.57 mL/min/1.73 m² for sodium intake <2300 mg/day and 22.75 mL/min/1.73 m² for intake ≥2300 mg/day. The association was attenuated but remained directionally consistent after exclusion of influential observations (B=−5.46; 95% CI −10.89 to −0.02; p=0.049). These findings identify a clinically relevant categorical association between sodium intake and short-term kidney function in DKD, while not supporting a linear dose-response relationship. Larger prospective studies with repeated dietary and objective sodium assessment are warranted.