Abstract
Objectives: To determine the sodium, potassium and iodine excretion and blood pressure (BP) of New Zealand (NZ) school children 8–13 years old and compare to recommended guidelines.
Methods: A cross-sectional study was undertaken in Auckland and Dunedin schools between July 2022 and February 2023. Sodium and potassium excretion were assessed using 24-hour urine, iodine using urine concentration and BP using standard methods; all values were compared with relevant international guidelines.
Results: 75 children from five schools took part (n=37 boys, 29 girls and 9 not stating gender). Mean (SD) 24-hour sodium excretion (n=59 complete samples) was 2420 (1025) mg, potassium excretion was 1567 (733) mg and the sodium-to-potassium molar ratio was 3.0 (1.6). 32% (19/59) of children met the WHO sodium guideline (<2000 mg/day), 2% (1/59) met the potassium guideline (≥3500 mg/day) and none met the sodium-to-potassium molar ratio guideline (<1:0). Median (25th, 75th percentile) urinary iodine concentration (n=55 complete samples) was 129 (90, 163) µg/L with 65% (36/55) above the WHO criteria for adequate iodine nutrition (≥99 µg/L). Mean (SD) systolic and diastolic BP (n=74) were 105 (10) mm Hg and 67 (9) mm Hg, respectively; 32% (21/65) of boys and girls with age and height measures had a systolic and diastolic BP measure >90th percentile for their gender, age and height.
Conclusions: This is the largest cross-sectional study using gold-standard methods to assess sodium and potassium excretion in NZ children. Findings suggest many NZ children could be at risk of developing cardiovascular disease later in life, and some are at risk of complications from low iodine intake.
Implications for public health: A national sodium reduction strategy and policies to increase potassium intake in NZ children are urgently needed, alongside adequate monitoring and a review of bread fortification as the only strategy for increasing children’s iodine intake in NZ.