Abstract
OBJECTIVE: Recently, the Japan Diabetes Society changed its nutrition recommendations and now recognizes a low-carbohydrate diet as an effective dietary approach. There has been controversy regarding low-carbohydrate diets in relation to renal function. That is, high protein intake may lead to renal damage through hyperfiltration. Global nutritional therapy for diabetic kidney disease (DKD) recommends a protein intake of 0.8 g/kg body weight (BW)/day. In Japan, the recommended protein intake is precisely determined based on the chronic kidney disease stage. However, evidence supporting the positive health impact of such protein restriction is scarce. Therefore, we aimed to investigate the effect of a low-carbohydrate diet without protein restriction on the estimated glomerular filtration rate (eGFR) decline rate. METHODS: Clinical data of patients with DKD in Tokyo Saiseikai Central Hospital and Kitasato Institute Hospital in Japan were retrospectively analyzed between February 2019 and December 2023. Sixty-eight participants were classified into two groups based on their diet: the energy-restricted and low-carbohydrate groups. RESULTS: The protein intake of the low-carbohydrate group was significantly higher than that of the energy-restricted group (1.2 ± 0.4 and 1.0 ± 0.2 g/kg BW/day, respectively). No significant differences were observed in the baseline, endpoint, or slope of eGFR between the two groups. CONCLUSIONS: This study suggests that among Japanese adults with DKD, the protein intake difference between energy-restricted and low-carbohydrate diets does not form any gap in eGFR decline rates. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13340-025-00808-y.