Plain water consumption in relation to energy intake and diet quality among US adults, 2005-2012

Objective: The present study examined plain water consumption in relation to energy intake and diet quality among US adults. Methods: A nationally representative sample of 18 311 adults aged >= 18 years, from the National Health and Nutrition Examination Survey 2005-2012, was analysed. The first-difference estimator approach addressed confounding bias from time-invariant unobservables (e.g. eating habits, taste preferences) by using within-individual variations in diet and plain water consumption between two nonconsecutive 24-h dietary recalls. Results: One percentage point increase in the proportion of daily plain water in total dietary water consumption was associated with a reduction in mean (95% confidence interval) daily total energy intake of 8.58 (7.87-9.29) kcal, energy intake from sugar-sweetened beverages of 1.43 (1.27-1.59) kcal, energy intake from discretionary foods of 0.88 (0.44-1.32) kcal, total fat intake of 0.21 (0.17-0.25) g, saturated fat intake of 0.07 (0.06-0.09) g, sugar intake of 0.74 (0.67-0.82) g, sodium intake of 9.80 (8.20-11.39) mg and cholesterol intake of 0.88 (0.64-1.13) g. The effects of plain water intake on diet were similar across race/ethnicity, education attainment, income level and body weight status, whereas they were larger among males and young/middle-aged adults than among females and older adults, respectively. Daily overall diet quality measured by the Healthy Eating Index-2010 was not found to be associated with the proportion of daily plain water in total dietary water consumption. Conclusions: Promoting plain water intake could be a useful public health strategy for reducing energy and targeted nutrient consumption in US adults, which warrants confirmation in future controlled interventions.