Underhydration is prevalent across education levels and associated with low intake of water but not sugar-sweetened beverages: A cross-sectional study from the UK

Abstract Purpose Adequate hydration is vital for health, yet many people do not meet fluid recommendations. This study aimed to characterise the role of water and sugar-sweetened beverages in hydration across different levels of socioeconomic status (SES) in the UK. Methods In a pre-registered cross-sectional study, participants ( N = 1,112) recalled beverages consumed on the previous day and reported urine colour as an indicator of their hydration status. We analysed water intake (H1), sugar-sweetened beverage (SSB) intake (H2), and SES (education; H3) as predictors of hydration status using stepwise binomial logistic regression adjusted for health, demographic, and lifestyle covariates. Results Forty percent of participants were classified as underhydrated. Higher water intake was associated with a greater likelihood of adequate hydration: Drinking one extra glass of water per day (250 ml) increased the odds of being adequately hydrated by about 16%. However, SSB intake was not associated with hydration unless intake from other drink sources was held constant. Having a higher versus lower level of education was not significantly associated with hydration status, although finer-grained and income-based analyses suggested modest socioeconomic differences. Conclusion Water intake—rather than SSB intake—is the primary correlate of adequate hydration in this UK sample. Public health initiatives should emphasise the importance of water for hydration, invest in ways to make water more appealing, and promote the use of urine colour as a marker of hydration status.