Hydration status and fluid intakes in Dunedin residents: A pilot study testing the use of an objective measure of hydration status for future population studies

Abstract

Background: Hydration is important for cognition, and the prevention of disease such as kidney stones. The current fluid recommendations (Adequate Intakes (AI)) for New Zealand adults from food and beverages combined are 2.8 L/day for women and 3.4 L/day for men. No population studies in New Zealand have assessed whether New Zealanders are achieving these levels. International studies have focused on self-reported fluid intake, while the measurement of hydration status using a biomarker such as urine specific gravity (USG) is less common.

Objective: The aim of this study is to determine the hydration status of a small sample of Dunedin adult residents by measuring both fluid intake and USG. Design: Thirty-three participants (16 women and 17 men) provided spot urine samples, taken in the morning, for the measurement of USG. They also completed a 3-day diet record to assess self-reported fluid intake from food and beverages. Participants were also asked if they perceived they consumed adequate fluid to remain hydrated. Results: Self-reported fluid intake ranged from 0.7-3.8 L/day, with a mean of 2.2 L/day in males and 1.9 L/day among females. Half of the participants appeared to be hypohydrated based on the USG results. Of the 50% who were hypohydrated, over two-thirds perceived they were consuming sufficient fluid. Conclusion: The mean reported intakes of fluid among this population were low compared to the AI, suggesting that the prevalence of inadequacy is likely to be high. This is in agreement with the objective measure of hydration status, indicating that half the sample was hypohydrated. It appears that the majority of those who are hypohydrated are not aware they are consuming insufficient fluids. Future larger studies using representative samples should measure both fluid intake and USG to determine whether hydration status is compromised in the New Zealand population.