Validation of salt intake measurements: comparisons of a food record checklist and spot-urine collection to 24-h urine collection.

OBJECTIVE: Monitoring population salt intake is operationally and economically challenging. We explored whether a questionnaire assessment and a prediction of Na intake from spot-urine could replace or complement the recommended measurement of Na in 24-h urine (24-h U). DESIGN: Compare the agreement of a Na-specific food record checklist (FRCL) and a late-afternoon spot-urine measurement (PM-spot) with 24-h U measurement in estimating Na intake at group level. Each participant's use of these methods extended over 3 d. Agreement was assessed using mean (95 % CI) differences, linear regression models and Bland-Altman plots. SETTING: The validation study was part of a 1-year workplace intervention trial to lower salt intake in Switzerland. PARTICIPANTS: Seventy women and 71 men, aged 21-61 years, completed three FRCL, and acceptable PM-spot and 24-h U samples at baseline (April-October 2015). RESULTS: Mean Na intake estimates varied slightly across methods (3·5-3·9 g/d). Mean Na intake differences from 24-h U were 0·2 (95 % CI (0, 0·5)) g/d for FRCL and 0·4 (95 % CI (0·2, 0·6)) g/d for PM-spot. Linear regression models and Bland-Altmann plots more clearly depicted differences by sex and discretionary salt use. CONCLUSIONS: Although 24-h U remains the best reference method for monitoring Na intake at the population level, PM-spot and FRCL might be more practical instruments for frequent, periodic Na intake assessments. Population-specific prediction models to estimate 24-h U could be developed and evaluated.

A short food literacy questionnaire (SFLQ) for adults: Findings from a Swiss validation study.

The short food literacy questionnaire (SFLQ) was developed to measure a broad range of skills including functional, interactive, and critical elements of FL. This study evaluated SFLQ measurement properties. We used a workplace intervention trial to reduce salt intake in Switzerland to explore the underlying structure of the questionnaire with 350 respondents and identify the ideal number of SFLQ items to capture the different elements of FL. Exploratory factor analysis showed a unidimensional structure of the final 12-item questionnaire. A sum score based on all 12 items (Cronbach's α = 0.82) showed expected positive associations with health literacy and knowledge of recommended salt intake. The findings indicate the SFLQ is a feasible and reliable tool to assess FL among adults that can be helpful in public health practices focusing on FL.