Japanese preschool children's normal range of urinary sodium (Na) level is higher and potassium (K) level lower than those of WHO, resulting in high urinary sodium/potassium ratio (U-Na/K).
The aim of this study is to investigate the dietary factors that influence U-Na/K and to create a basis for salt-reduction education.
Study Design, Setting, Participants
The target population was four to five-year-old preschool children attending collaborating kindergartens, whose parents agreed to their participating after a briefing of informed consent.
We asked the parents to take two samples of their child's first urination on two consecutive days and to answer a dietary questionnaire called BDHQ3y (Brief-type Self-administered Diet History Questionnaire for Japanese children aged three to six years). U-Na/K was calculated by the target child's Na (mEq/L) /g Cr and K (mEq/L) /g Cr. The results of the dietary questionnaire were corrected by the density method (g/1000 kcal). The correlation of two groups of values was calculated by Spearman rank correlation coefficient. Multiple regression analysis was performed where differences were significant.
Out of the 452 parents who attended the informed consent briefing: 87 did not agree; 27 did not hand in data. The remaining 338 were registered as final target population. They were an average of 58 months old; 103.0cm tall; 16.7kg by weight, with a U-Na/K value of 4.47. Concerning U-Na/K and nutrients, positive correlation was found with sodium, potassium, calcium, and phosphorus intake, and only sodium (β = 0.189) was a significant predictor when assessed by multiple regression analysis. For food: positive significant correlation was found with noodles, pickles, soft drinks, and seasoning·splices; negative significant correlation with fruits and milk products. Multiple regression analysis showed, noodles (β = 0.132), fruits (β = -0.154), soft drinks (β = 0.155), and seasoning·splices (β = 0.113) as significant predictors. There was no correlation with sex or region.
The urinary sodium to potassium ratio correlated positively with noodles, soft drinks, and seasoning·spice, and correlated negatively with fruits, in Japanese preschool children.