ABSTRACT
ABSTRACT CONTEXT AND 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. DESIGN AND SETTING: 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.
RESUMO CONTEXTO E OBJETIVO: O consumo de sódio e potássio de diferentes fontes alimentares é uma questão importante para a fisiologia cardiovascular. A avaliação epidemiológica do consumo desses eletrólitos é feita pelo questionário de frequência alimentar ou pela excreção urinária. O objetivo deste estudo é comparar esses métodos em uma amostra de servidores públicos brasileiros. TIPO DE ESTUDO E LOCAL: Avaliação transversal da linha de base do Estudo Longitudinal de Saúde do Adulto. MÉTODOS: O consumo de sódio e potássio foi obtido por dois métodos: questionário semi-quantitativo com 114 itens alimentares e excreção urinária de 12 horas noturnas. Estimativas de sódio e potássio obtidas pelo questionário foram ajustadas pela energia utilizando o método residual. A excreção urinária foi considerada válida se atendesse a três critérios: tempo de coleta, volume e excreção total de creatinina adequados. Foram estimadas médias dos nutrientes e calculada a correlação de Spearman. O consumo de sódio e potássio foi categorizado em quintis e foram calculados o kappa ponderado e o percentual de concordância. O nível de significância para todos os testes foi de 0,05. RESULTADOS: Foram analisados dados de 15,105 participantes e encontradas diferenças significativas entre médias de sódio (questionário: 4,5 ± 1,7 g; urina: 4,2 ± 2,1 g) e potássio (questionário: 4,7 ± 1,8 g; urina: 2,4 ± 1 g). Foi encontrada fraca concordância para sódio (K = 0,18) e potássio (K = 0,16). Percentuais de discordância entre métodos variaram de 41,8-44,5%; concordâncias exatas de 22,1-23,9%. CONCLUSÃO: A concordância entre o questionário de frequência alimentar e excreção urinária para avaliação do consumo de sódio e potássio foi modesta.
Subject(s)
Adult , Aged , Female , Humans , Male , Middle Aged , Diet Surveys/standards , Diet Surveys/statistics & numerical data , Potassium, Dietary/urine , Sodium, Dietary/urine , Surveys and Questionnaires/standards , Brazil , Creatinine/urine , Cross-Sectional Studies , Energy Intake , Longitudinal Studies , Potassium, Dietary/administration & dosage , Reference Values , Reproducibility of Results , Sodium, Dietary/administration & dosage , Statistics, Nonparametric , Time FactorsABSTRACT
Background: Hypertension is associated with elevated sodium and low potassium intakes. The determination of sodium and potassium intake by dietary records is inaccurate, being its measurement from 24-h urine collection the reference method. Aim: To determine urinary sodium and potassium excretion in adults. To compare dietary sodium and potassium intake and their excretion from an isolated urine sample against the reference method. Material and Methods: Seventy healthy adults aged 35 ± 8 years with a body mass index 25 ± 2 kg/m² (36 women) were studied. Urine was collected over 24 h, including an isolated urine sample taken in fasting conditions. Additionally, three 24-h dietary records were performed. Results: Reported sodium and potassium intake was 2,720 ± 567 and 1,068 ± 433 mg/day, respectively. In turn, urinary excretion of sodium and potassium was 4,770 ± 1,532 and 1,852 ± 559 mg/day, respectively. These latter values were significantly higher than those obtained by dietary records. Furthermore, the urinary sodium and potassium excretion estimated from an isolated urine sample was 4,839 ± 1,355 and 1,845 ± 494 mg/day, respectively. These values were similar to those obtained with a 24 h urine collection. Conclusions: Dietary records underestimated electrolyte intake when compared with the reference method. Using an isolated urine sample to estimate electrolyte intake may be a reliable alternative.