Fluid and nutrient intake and risk of chronic kidney disease

Aim: We evaluated the association between fluid and nutrient intake and chronic kidney disease (CKD). Methods: Two cross-sectional population-based studies. Validated nutrition food frequency questionnaires (FFQ) administered to people >50 years, identified in a door-to-door census of a well-defined suburban area. Based upon nutrition tables we calculated intakes of over 40 nutrients (factors) and total daily energy intake. Primary outcome was CKD. Fluid (total content of fluid and drinks assessed in the FFQ) and nutrient intake was stratified in quintiles and association with CKD analysed by logistic regression, expressed as unadjusted and adjusted odds ratios, with testing for linear trend. Results: The proportion of participants who completed the FFQ and had glomerular filtration rate (GFR) measures was 2744/3654 (75.0%) for the first and 2476/3508 (70.6%) for the second survey. CKD was present in 12.4-23.5% men and 14.9-28.7% women (mean ages 66.4-65.4 years), respectively. Participants who had the highest quintile of fluid intake (3.2 L/day) had a significantly lower risk of CKD (odds ratio 0.5, 95% CI 0.32 to 0.77, P for trend = 0.003). These findings were consistent across both study periods, both equations to calculate GFR and both GFR thresholds. Conclusion: Higher intakes of fluid appear to protect against CKD. CKD may be preventable at a population level with low-cost increased fluid intake.