title: Sodium and potassium intake estimated using two methods in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).
abstract: OBJECTIVE
  Sodium and potassium intake from different food sources is an important issue regarding cardiovascular physiology. Epidemiological assessment of the intake of these electrolytes intake is done through food frequency questionnaires or urinary excretion measurements. Our aim was to compare these methods using a sample of Brazilian civil servants.
  
  
  METHODS
  Cross-sectional baseline evaluation from the Brazilian Longitudinal Study of Adult Health.
  
  
  METHODS
  Sodium and potassium intake was obtained using two methods: a semi-quantitative questionnaire including 114 food items; and overnight 12-hour urinary excretion measurement. Sodium and potassium estimates obtained through the questionnaire were adjusted for energy intake using the residual method. Urinary excretion measurements were considered valid if they met three adequacy criteria: collection time, volume and total creatinine excretion. Mean nutrients were estimated, and Spearman correlations were calculated. Sodium and potassium intake was categorized into quintiles, and weighted kappa coefficients and percentage agreement were calculated. The significance level for all tests was 0.05.
  
  
  RESULTS
  Data from 15,105 participants were analyzed, and significant differences between mean intakes of sodium (questionnaire: 4.5 ± 1.7 g; urine: 4.2 ± 2.1 g) and potassium (questionnaire: 4.7 ± 1.8 g; urine: 2.4 ± 1 g) were found. Weak agreement was found for sodium (K = 0.18) and potassium (K = 0.16). The percentage disagreement between methods ranged from 41.8 to 44.5%, while exact concordance ranged from 22.1% to 23.9%.
  
  
  CONCLUSIONS
  The agreement between the food frequency questionnaire and urinary excretion measurements for assessment of sodium and potassium intakes was modest.
authors.affiliation: Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Taísa Sabrina Silva
authors.initials: TS
authors.lastname: Pereira
authors.affiliation: Department of Internal Medicine, School of Medicine, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Isabela Judith Martins
authors.initials: IJ
authors.lastname: Benseñor
authors.affiliation: Department of Maternal and Child Nursing and Public Health, School of Nursing, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Jorge Gustavo Velásquez
authors.initials: JG
authors.lastname: Meléndez
authors.affiliation: Department of Integrated Health Education, Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Carolina Perim de
authors.initials: CP
authors.lastname: Faria
authors.affiliation: Department of Nursing, Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Nágela Valadão
authors.initials: NV
authors.lastname: Cade
authors.affiliation: Department of Physiology, Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: José Geraldo
authors.initials: JG
authors.lastname: Mill
authors.affiliation: Department of Integrated Health Education, Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Maria del Carmen Bisi
authors.initials: Mdel C
authors.lastname: Molina
mesh_terms: D000328:Adult; D000368:Aged; D001938:Brazil; D003404:Creatinine / Q000652:urine; D003430:Cross-Sectional Studies; D004034:Diet Surveys / Q000592:standards* / Q000706:statistics & numerical data*; D002149:Energy Intake; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D017419:Potassium, Dietary / Q000008:administration & dosage / Q000652:urine*; D012016:Reference Values; D015203:Reproducibility of Results; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000652:urine*; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires / Q000592:standards*; D013997:Time Factors
chemical_list: D017419:Potassium, Dietary; D012982:Sodium, Dietary; D003404:Creatinine