Estimation of salt intake by 24 h urinary sodium excretion in a representative sample of Spanish adults

The present study reports the Na intake of a representative sample of Spanish young and middle-aged adults aged 18-60 years (n 418, 53.1 % women, selected from the capitals of fifteen provinces and the surrounding semi-urban/rural area), measured with a 24 h urinary Na excretion method. To validate the paper collection of 24 h urine, the correlation between fat-free mass determined by electrical bioimpedance (50.8 (SD 11.3) kg) and that determined via urinary creatinine excretion (51.5 (SD 18.8) kg) was calculated (r 0.633, P<0.001). Urinary Na excretion correlated with systolic and dyastolic blood pressure data (r 0.243 and 0.153, respectively). Assuming that all urinary Na (168.0 (SD 78.6) mmol/d) comes from the diet, Na excretion would correspond with a dietary salt intake of 9.8 (SD 4.6) g/d, and it would mean that 88.2% of the subjects had salt intakes above the recommended 5 g/d. Logistic regression analysis, adjusted for sex, age and BMI, showed male sex (OR 3.678, 95% CI 2.336, 5.791) and increasing BMI (OR 1.069, 95% CI 1.009, 1.132) (P<0.001) to be associated with excreting >200 mmol/d urinary Na - a consequence of the higher salt intake in men and in participants with higher BMI. The present results help us to know the baseline salt intake in the Spanish young and middle-aged adult population, and can be used as the baseline to design policies to reduce salt consumption.