Effect of a school-based salt reduction health education program on urinary sodium, potassium, and KAP among primary school students and their parents: a quasi-experimental study

Background Excessive sodium intake in childhood is a key modifiable risk factor for cardiovascular disease, yet school-based salt reduction programs targeting the school food environment have not been evaluated in eastern China. Methods We conducted a quasi-experimental cluster-controlled trial in 20 primary schools across two cities in Jiangsu Province, China. Ten intervention schools received a one-year multi-component program comprising digital health education (WeChat mini-program), classroom activities, school cafeteria sodium reduction, and campus health promotion; ten control schools received routine health education. Outcomes were assessed in 487 student–parent pairs at baseline and follow-up, including 24-hour urinary sodium, potassium, Na/K ratio, and salt-related knowledge, attitudes, and practices (KAP). Intervention effects were estimated using linear mixed models under an intention-to-treat framework. Results KAP scores improved significantly in both students (net difference 16.55, P < 0.001) and parents (net difference 4.60, P < 0.001). Parent 24-hour NaCl excretion decreased by 0.63 g/day (95% CI : −1.11, − 0.14; P = 0.012). Student 24-hour potassium excretion increased by 0.17 g/day (95% CI : 0.10, 0.25; P < 0.001), while student sodium excretion did not change significantly. Cafeteria sodium content fell by 38% in intervention schools at follow-up, significantly lower than in control schools ( P < 0.001). Among intervention-group students, greater school lunch attendance was associated with larger reductions in urinary sodium and Na/K ratio, though interaction terms did not reach conventional significance. Conclusions This multi-component school-based intervention improved KAP, reduced parental sodium intake, increased children’s potassium excretion, and objectively modified the school food environment, but did not reduce children’s overall sodium excretion. School-based strategies may need to be combined with direct engagement of household meal preparers to achieve meaningful reductions in children’s dietary sodium.