BackgroundHigh sodium (Na) and low potassium (K) intakes in childhood have health effects across the life course. The objective was to estimate global, regional and national Na and K intakes in children since 1990.MethodsA systematic search of cross-sectional and longitudinal studies measuring Na or K intake in children aged 0–18 years of age since 1990 was conducted. Random effects multilevel meta-analyses and meta-regressions were performed to investigate age and time trends, country and regional differences, and to derive a worldwide average intake.ResultsA total of 259 studies with 520 630 children aged 0–18 years of age (mean 9.7 years) conducted between 1990 and 2021 in 79 different countries (mostly high-income countries) were included. The pooled Na and K intakes were 2.5 g/d (95% CI 2.4, 2.6) and 2.0 g/d (95% CI 1.9, 2.1), respectively. An estimated 73% of children had high Na intake (≥2 g/d/2000 kcal) and 89% had low K intake (<3.5 g/d/2000 kcal). Na intake was the lowest in Sub-Saharan Africa and the highest in North Africa and the Middle East. K intake was the lowest in South Asia and the highest in Central-Eastern Europe and Central Asia. Na and K intakes tended to decrease slightly linearly between 1990 and 2021 and increased logarithmically with age.ConclusionGlobally, children’s Na intake was too high, while K intake was too low. Data were lacking in many countries. Interventions are needed to reduce Na and increase K from childhood, and monitoring should be improved.