The Major Source of Antioxidants Intake From Typical Diet Among Rural Farmers in North-eastern Japan in the 1990s

Association between an Antioxidant-Rich Japanese Diet and Chronic Kidney Disease: The Ohasama Study

AIMS

Although physiological effects of hydrophilic- (H-) and lipophilic- (L-) antioxidant capacities (AOCs) are suggested to differ, the association of an antioxidant-rich diet and chronic kidney disease (CKD) incidence has not been examined. We therefore explored the association between the H- or L-AOC of a whole Japanese diet and CKD risk in a general population.

METHODS

A total of 922 individuals without CKD (69.2% women; mean age, 59.5 years old) from Ohasama Town, Japan, were examined. CKD incidence was defined as the presence of proteinuria and/or an estimated glomerular filtration rate (eGFR) of ＜60 ml/min/1.73 m2. Consumption of H-/L-AOC was determined based on the oxygen radical absorbance capacity in a specially developed Japanese food AOC database. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for new-onset CKD using a Cox proportional hazards model.

RESULTS

During the median follow-up of 9.7 years, 137 CKD incidents were recorded. After adjusting for potential confounding variables, the highest quartile of L-AOC was significantly associated with a 51% reduced CKD risk among only women. An increased L-AOC intake was more effective in preventing eGFR reduction than in preventing proteinuria in women. These associations were not seen for H-AOC intake in both sexes and L-AOC intake in men.

CONCLUSIONS

A high intake of lipophilic antioxidants may be associated with a reduced CKD risk. The balance between dietary antioxidant intake and pro-oxidants induced by unhealthy lifestyles may be crucial for preventing future kidney deterioration.

Hydrophilic oxygen radical absorbance capacity values of low-molecular-weight phenolic compounds containing carbon, hydrogen, and oxygen

The antioxidant capacity of an antioxidant reflects its ability to remove reactive oxygen species (ROS). In this study, the hydrophilic oxygen radical absorbance capacity (H-ORAC) method was used to quantitatively evaluate the antioxidant capacities of natural phenols and their derivatives against peroxyl radicals. This method was comprehensively applied to low-molecular-weight phenols to construct a database. Although no macroscopic correlation was observed for values related to the antioxidant capacity expression, we observed a difference in the trend of the H-ORAC values for each functional group. Thus, this database will serve as a new benchmark and tool for molecular design.

The hydrophilic oxygen radical absorbance capacity (H-OARC) assay measures the antioxidant capacity of compounds against the peroxyl radical, a reactive oxygen species.