Urinary sodium-to-potassium ratios are known to be high in preschoolers, but there are no reports comparing these ratios with those of the children’s mothers. The aim of this study was to investigate the association between the urinary sodium-to-potassium ratios of mothers and their preschool children under the hypothesis that the ratio is equivalent between the two. We evaluated 297 preschoolers aged four to five attending six kindergartens (four in northern Japan, two in southern Japan), and we also evaluated the children’s mothers. We asked the participants to take morning first urine samples for 2 consecutive days in the spring and autumn of the same year (four samples per participant) and to fill out a dietary questionnaire. There was a correlation between the urinary sodium-to-potassium ratios of preschoolers and those of their mothers. However, in a comparison between the preschoolers and their mothers overall, higher values were found in the preschoolers [preschoolers: 4.6 (3.5–6.3) mmol/L/g·Cr; mothers: 4.3 (3.9–4.7) mmol/L/g·Cr, p = 0.003]. These results correlated with the urinary sodium-to-potassium ratios estimated from the dietary questionnaire. The preschoolers showed high sodium and low potassium intake consumption compared to the mothers. Interestingly, these were found to differ by region and gender. In conclusion, the urinary sodium-to-potassium ratio in Japanese preschoolers is related to and higher than that of their mothers. It is important to educate children, their parents, childcare professionals, and society as a whole about proper salt restriction and potassium supplementation, as well as to improve the food environment.

众所周知，学龄前儿童的尿钠钾比例很高，但没有报告将这些比例与孩子母亲的比例进行比较。本研究的目的是在假设两者之间的比率相等的假设下，调查母亲及其学龄前儿童的尿钠钾比率之间的关联。我们评估了 297 名 4 至 5 岁的学龄前儿童，他们在 6 所幼儿园（日本北部 4 所，日本南部 2 所），我们还评估了孩子的母亲。我们要求参与者在同年春季和秋季连续两天采集晨尿样本（每个参与者四个样本）并填写一份饮食问卷。学龄前儿童的尿钠钾比率与其母亲的尿钠钾比率之间存在相关性。然而，在学龄前儿童与其母亲的总体比较中，发现学龄前儿童的值更高[学龄前儿童：4.6（3.5-6.3）mmol/L/g Cr；母亲：4.3 (3.9–4.7) mmol/L/g Cr，p  = 0.003]。这些结果与从膳食问卷估计的尿钠钾比率相关。与母亲相比，学龄前儿童的钠摄入量高，钾摄入量低。有趣的是，这些发现因地区和性别而异。综上所述，日本学龄前儿童的尿钠钾比与其母亲相关且高于其母亲。对儿童、他们的父母、育儿专业人员和整个社会进行适当的限盐和补钾以及改善食物环境的教育非常重要。