title: Cross-Sectional Study of 24-Hour Urinary Electrolyte Excretion and Associated Health Outcomes in a Convenience Sample of Australian Primary Schoolchildren: The Salt and Other Nutrients in Children (SONIC) Study Protocol.
abstract: BACKGROUND
  Dietary sodium and potassium are involved in the pathogenesis of cardiovascular disease. Data exploring the cardiovascular outcomes associated with these electrolytes within Australian children is sparse. Furthermore, an objective measure of sodium and potassium intake within this group is lacking.
  
  
  OBJECTIVE
  The primary aim of the Salt and Other Nutrient Intakes in Children ("SONIC") study was to measure sodium and potassium intakes in a sample of primary schoolchildren located in Victoria, Australia, using 24-hour urine collections. Secondary aims were to identify the dietary sources of sodium and potassium, examine the association between these electrolytes and cardiovascular risk factors, and assess children's taste preferences and saltiness perception of manufactured foods.
  
  
  METHODS
  A cross-sectional study was conducted in a convenience sample of schoolchildren attending primary schools in Victoria, Australia. Participants completed one 24-hour urine collection, which was analyzed for sodium, potassium, and creatinine. Completeness of collections was assessed using collection time, total volume, and urinary creatinine. One 24-hour dietary recall was completed to assess dietary intake. Other data collected included blood pressure, body weight, height, waist and hip circumference. Children were also presented with high and low sodium variants of food products and asked to discriminate salt level and choose their preferred variant. Parents provided demographic information and information on use of discretionary salt. Descriptive statistics will be used to describe sodium and potassium intakes. Linear and logistic regression models with clustered robust standard errors will be used to assess the association between electrolyte intake and health outcomes (blood pressure and body mass index/BMI z-score and waist circumference) and to assess differences in taste preference and discrimination between high and low sodium foods, and correlations between preference, sodium intake, and covariates.
  
  
  RESULTS
  A total of 780 children across 43 schools participated. The results from this study are expected at the end of 2015.
  
  
  CONCLUSIONS
  This study will provide the first objective measure of sodium and potassium intake in Australian schoolchildren and improve our understanding of the relationship of these electrolytes to cardiovascular risk factors. Furthermore, this study will provide insight into child taste preferences and explore related factors. Given the cardiovascular implications of consuming too much sodium and too little potassium, monitoring of these nutrients during childhood is an important public health initiative.
authors.affiliation: Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Research Sciences, Deakin University, Melbourne, Australia. carley.grimes@deakin.edu.au.
authors.forename: Carley A
authors.identifier: http://orcid.org/0000-0002-9123-1888
authors.initials: CA
authors.lastname: Grimes
authors.forename: Janet R
authors.identifier: http://orcid.org/0000-0002-9745-461X
authors.initials: JR
authors.lastname: Baxter
authors.forename: Karen J
authors.identifier: http://orcid.org/0000-0002-4499-3396
authors.initials: KJ
authors.lastname: Campbell
authors.forename: Lynn J
authors.identifier: http://orcid.org/0000-0002-0688-2134
authors.initials: LJ
authors.lastname: Riddell
authors.forename: Manuela
authors.identifier: http://orcid.org/0000-0002-5195-4272
authors.initials: M
authors.lastname: Rigo
authors.forename: Djin Gie
authors.identifier: http://orcid.org/0000-0002-6619-6101
authors.initials: DG
authors.lastname: Liem
authors.forename: Russell S
authors.identifier: http://orcid.org/0000-0003-2147-7687
authors.initials: RS
authors.lastname: Keast
authors.forename: Feng J
authors.identifier: http://orcid.org/0000-0003-2807-4119
authors.initials: FJ
authors.lastname: He
authors.forename: Caryl A
authors.identifier: http://orcid.org/0000-0001-6586-7965
authors.initials: CA
authors.lastname: Nowson
keywords: Australia; blood pressure; child; obesity; potassium, dietary; sodium chloride, dietary; sodium, dietary; taste; urine specimen collection