Dietary total antioxidant capacity and its association with renal function and kidney stones: Results of a RaNCD cohort study.

There is evidence to support the hypothesis that dietary antioxidants have shown protective effects against chronic kidney disease (CKD). The purpose of this study was to determine the association between the dietary total antioxidant capacity (DTAC), renal function, and development of CKD and kidney stones in Ravansar Non-Communicable Diseases (RaNCD) cohort study, Kermanshah, Iran. This cross-sectional study was conducted using the recruitment baseline data of the RaNCD cohort study on 9,777 individuals aged 35-65 years. Food frequency questionnaire (FFQ) was performed to assess diet. DTAC scores were calculated using the ferric reducing antioxidant power (FRAP) of selected foods. Renal function was assessed by the estimated glomerular filtration rate (eGFR), blood urea nitrogen, and serum creatinine concentration. Prevalent CKD was based on an eGFR less than <60 ml/min per 1.73 m. Incidence of kidney stones was also assessed by self-reporting. Out of 9,777 participants, 1,747 subjects (eGFR: 18.50 ml/min per 1.73 m; 95% confidence interval (CI): 17.72-19.30) had CKD. The mean DTAC score in this study was 0.24 ± 0.16 µmol TE/100 g (micromole of Trolox Equivalents). We showed a significant trend for eGFR across quartiles of DTAC, i.e., participants in the fourth quartile had a higher glomerular filtration rate (GFR) than those in the first one (DTAC  = 82.20 versus 72.20 ml/min per 1.73 m,  < .001). Another finding is that high DTAC scores were not associated with having kidney stones after adjusting for confounders. We revealed that higher DTAC scores have positive effects on the renal function. Interestingly, our findings showed that a high DTAC score had nonsignificant correlation with odds of kidney stones.