Necessity of salt intake reduction education beginning in youth: a cross-sectional survey of sodium-to-potassium ratios in mothers and their preschool children.

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.