Changes in Urine Osmolar Composition seen in Different Age Groups in the Local Korean Population

Due to their unique living conditions and dietary habits, the Koreans' renal function model may be different from that of the Western people. About 40 years ago, a researcher reported that two thirds of the urine osmolality in Koreans was contributed by NaCl, while less than 1/3 by urea. It is known that the Koreans' daily consumption of NaCl is higher while their protein intake is lower, compared to that of the Westerners. Now-a-days, the Korean's dietary habit is changing to a westernized life style. In this study, we investigated whether there were changes in urine composition and osmolality according to age. The subject of study were 215 Koreans (128 male, 142 female, age 7-68 years) living in the Chonbuk and Chonnam province in Korea. We performed routine physical examinations and analyses of the urine Na(+), K(+), Cl(-), urea, NH3, creatinine, and osmolality on their 24 hour urine samples. In the case of the male, total body water, Na and Cl excretion, urine ammonia excretion were significantly changed between groups. In the case of the female, total body water and urine creatinine excretion were significantly changed between groups. We calculated the urine osmolar contribution of NaCl and urea. Our results showed that NaCl composed 63.6% of total urine osmolality and Urea composed 36.4% of total urine osmolality. In conclusion, urine osmolar composition is similar to the 1960's, but further studies are required to elucidate the change of urine composition in this population for another 50 years.