Abstract
PurposeUrine colour (UCol) is simple to measure, differs between low-volume and high-volume drinkers, and is responsive to changes in daily total fluid intake (TFI). However, to date, no study has quantified the relationship between a change in TFI and the resultant change in UCol. This analysis aimed to determine the change in TFI needed to adjust 24-h UCol by 2 shades on an 8-colour scale, and to evaluate whether starting UCol altered the relationship between the change in TFI and change in UCol.MethodsWe performed a pooled analysis on data from 238 healthy American and European adults (50 % male; age, 28 (sd 6) years; BMI 22.9 (sd 2.6) kg/m2), and evaluated the change in TFI, urine volume (UVol), and specific gravity (USG) associated with a change in UCol of 2 shades.ResultsThe mean [95 % CI] change in TFI and UVol associated with a decrease in UCol by 2 shades (lighter) was 1110 [914;1306] and 1011 [851;1172] mL/day, respectively, while increasing UCol by 2 shades (darker) required a reduction in TFI and UVol of −1114 [−885;−1343] and −977 [−787;−1166] mL/day. The change in UCol was accompanied by changes in USG (lighter urine: −.008 [−.007;−.010]; darker urine: +.008 [.006;.009]). Starting UCol did not significantly impact the TFI change required to modify UCol by 2 shades.ConclusionsOur results suggest a quantifiable relationship between a change in daily TFI and the resultant change in UCol, providing individuals with a practical means for evaluating and adjusting hydration behaviours.
Highlights
Water is fundamental to sustaining life and has been referred to as the most essential nutrient [1, 2]
Adults in the highest percentiles of daily fluid intake [5] and urine volume [6] have lower risk for developing chronic kidney disease (CKD), and low urine volume is linked to the recurrence of kidney stone disease [7, 8]
Recent studies of adults in normal daily living conditions with ad libitum access to water have shown that habitual lowvolume drinkers excrete low volumes of concentrated urine that correspond with the highest categories of CKD risk [6, 9]
Summary
Water is fundamental to sustaining life and has been referred to as the most essential nutrient [1, 2]. Consuming a larger volume of water, enabling production of a greater volume of dilute urine is beneficial for the kidneys, urinary tract, and potentially other physiological systems [6, 8, 11, 12]. In this context, measures of urine concentration, including osmolality, specific gravity, and colour, are becoming increasingly relevant as biomarkers of acute hydration, and of sufficient fluid intake for long-term health
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