Impact of water consumption on renal function in the general population: a cross-sectional analysis of KNHANES data (2008–2017)

Background: The renoprotective effect of water intake remains unclear. We aimed to investigate the relationship between water intake and renal impairment in the Korean general population, focusing on individual differences in body fluid distribution and risk of chronic dehydration. Methods: We conducted a cross-sectional analysis of the 2008–2017 Korea National Health and Nutrition Examination Survey (KNHANES). Adult participants who had body weight and serum creatinine data and had answered 24-h recall nutritional survey were included. Four water intake groups were defined by daily total water intake per body weight: lowest (< 20 mL/kg/day), low-moderate (20–29.9 mL/kg/day), high-moderate (30–49.9 mL/kg/day), and highest (≥ 50 mL/kg/day). We assessed the risk of renal impairment (estimated glomerular filtration rate ≤ 60 mL/min/1.73 m²) according to water intake. Results: In total of 50,113 participants, 3.9% had renal impairment. The risk of renal impairment gradually decreased as water intake increased. After adjustment of sodium intake, the trend of renoprotective effect was remained in low-moderate and high-moderate water intake group compared to low intake group, whereas no significant impact was observed with the highest water intake due to concurrent intake of high sodium. In subgroup analysis, the renoprotective effect of water intake was significant in the participants with elderly, male and daily sodium intake over 2 g/day. Conclusions: High daily water intake is renoprotective. Our data may provide an important basis for determining the amount of water intake needed to prevent renal impairment, considering variations in body weight, body composition and risk of chronic dehydration.