Salt intake in 3-year-old Japanese children

Salt restriction is widely recommended for the prevention and management of hypertension. It is very important to reduce salt intake during childhood. This survey was conducted to investigate salt intake in Japanese children. The study subjects, totalling 1,424, comprised 3-year-old children who received health checkups conducted by a public health center. Using first-morning urine samples, urinary concentrations of sodium, potassium and creatinine were measured. Additionally, the participants' parents filled out a questionnaire regarding their children's dietary habits. Urinary sodium and potassium concentrations were 140 ± 67 and 67 ± 41 mmol l(-1), respectively. The estimated urinary sodium excretion values had a wide distribution, with a mean value of 75 ± 47 mmol per day (4.4 g per day of salt). Sodium excretion exceeded 100 and 200 mmol per day in 336 (24%) and 32 (2.2%) subjects, respectively. Urinary sodium excretion was significantly higher in children who had older siblings than in firstborn children (78 ± 49 vs. 72 ± 45 mmol per day, P < 0.05). The urinary sodium/potassium ratio was also higher in the former group (3.0 ± 2.7 vs. 2.7 ± 2.2, P < 0.01). Sodium excretion tended to be higher in children who ate daily snacks than in those who did not (76 ± 48 vs. 71 ± 44 mmol per day, P=0.07). In contrast, potassium excretion was significantly higher and the sodium/potassium ratio was lower in children who ate fruits daily than those who did not (39 ± 29 vs. 33 ± 23 mmol per day and 2.6 ± 2.0 vs. 3.2 ± 2.7, P < 0.01, respectively). These results suggest that excess salt intake occurs in a significant number of 3-year-old Japanese children. The presence of older siblings and dietary habits of eating snacks or fruits influence their sodium and potassium intake.