How different fluids affect hydration: a new study

First published December 23, 2015, doi: 10.3945/​ajcn.115.114769
Am J Clin Nutr

A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index 1

Ronald J Maughan2,*, Phillip Watson2, Philip AA Cordery2, Neil P Walsh3, Samuel J Oliver3, Alberto Dolci3, Nidia Rodriguez-Sanchez4, and Stuart DR Galloway4

Author Affiliations

2School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, United Kingdom;
3School of Sport, Health and Exercise Sciences, Bangor University, Bangor, United Kingdom; and
4School of Sport, University of Stirling, Stirling, United Kingdom

Author Notes

↵1 Supported by a grant from the European Hydration Institute.

↵*To whom correspondence should be addressed. E-mail:


Background: The identification of beverages that promote longer-term fluid retention and maintenance of fluid balance is of real clinical and practical benefit in situations in which free access to fluids is limited or when frequent breaks for urination are not desirable. The postingestion diuretic response is likely to be influenced by several beverage characteristics, including the volume ingested, energy density, electrolyte content, and the presence of diuretic agents.

Objective: This study investigated the effects of 13 different commonly consumed drinks on urine output and fluid balance when ingested in a euhydrated state, with a view to establishing a beverage hydration index (BHI), i.e., the volume of urine produced after drinking expressed relative to a standard treatment (still water) for each beverage.

Design: Each subject (n = 72, euhydrated and fasted male subjects) ingested 1 L still water or 1 of 3 other commercially available beverages over a period of 30 min. Urine output was then collected for the subsequent 4 h. The BHI was corrected for the water content of drinks and was calculated as the amount of water retained at 2 h after ingestion relative to that observed after the ingestion of still water.

Results: Total urine masses (mean ± SD) over 4 h were smaller than the still-water control (1337 ± 330 g) after an oral rehydration solution (ORS) (1038 ± 333 g, P < 0.001), full-fat milk (1052 ± 267 g, P < 0.001), and skimmed milk (1049 ± 334 g, P < 0.001). Cumulative urine output at 4 h after ingestion of cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water, and a sports drink were not different from the response to water ingestion. The mean BHI at 2 h was 1.54 ± 0.74 for the ORS, 1.50 ± 0.58 for full-fat milk, and 1.58 ± 0.60 for skimmed milk.

Conclusions: BHI may be a useful measure to identify the short-term hydration potential of different beverages when ingested in a euhydrated state. This trial was registered at as ISRCTN13014105.


This entry was posted in Sports Medicine, Nutrition: Hydration, Nutrition: Food: Tea, Nutrition: Food: Soft Drinks, Nutrition: Food: Milk, Nutrition: Beer. Bookmark the permalink.

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