Estimation of salt intake assessed by urinary excretion of sodium over 24 h in Spanish subjects aged 7-11 years

Abstract

Purpose: High intake of salt is associated with early development of cardiovascular risk factors (e.g., hypertension, obesity). In "developed" countries, individuals frequently exceed dietary recommendations for salt intake. Taking into account the limited data on sodium intake by 24-h excretion in urine in schoolchildren, we wished to determine baseline salt intake in Spanish subjects aged 7-11 years.

Methods: The present study was an observational study involving 205 schoolchildren (109 boys and 96 girls) selected from various Spanish provinces. Sodium intake was ascertained by measuring sodium excretion in urine over 24 h. Creatinine was used to validate completeness of urine collections. The correlation between fat-free mass determined by anthropometry and that determined via urinary excretion of creatinine was calculated (r = 0.651; p < 0.001).

Results: Mean 24-h urinary excretion of sodium was 132.7 ± 51.4 mmol/24 h (salt equivalent: 7.8 ± 3.1 g/day). Hence, 84.5 % of subjects aged ≤10 years had intakes of >4 g salt/day, and 66.7 % of those aged >10 years had intakes of >5 g salt/day. Urinary excretion of sodium was correlated with systolic blood pressure and diastolic blood pressure (r = 0.1574 and r = 0.1400, respectively). Logistic regression analyses, adjusted by sex, showed that a high body mass index (odds ratio = 1.159; 95 % CI 1.041-1.290; p < 0.05) was associated with an increased likelihood of high urinary excretion of sodium.

Conclusions: Sodium intake, as estimated by 24-h urinary excretion, was (on average) higher than recommended. Reducing the sodium content children's diet is a sound policy to reduce cardiovascular risk.

Keywords: Salt intake; Schoolchildren; Spain; Urinary sodium excretion.