REF-058 · Maughan et al., 2016 · American Journal of Clinical Nutrition, Vol. · Paper

Beverage Hydration Index: Milk and Oral Rehydration Solution Retain More Fluid Than Water

B+moderate evidenceMeasured on recreational peopleWritten before October 2026, being re-checked

Participants

n=72 euhydrated, fasted male subjects. Each ingested 1 L of still water or 1 of 3 other commercially available beverages over 30 min (13 beverages tested across the cohort); urine was collected for 4 h. The beverage hydration index (BHI) = water retained at 2 h relative to still water, corrected for the drinks' water content.

Protocol

Randomized trial (registered ISRCTN13014105): 72 euhydrated and fasted male subjects; 13 commonly consumed drinks were tested (from the abstract).
Each subject ingested 1 L of still water or 1 of 3 other commercially available beverages over 30 min.
Urine output was collected for the subsequent 4 h; the beverage hydration index (BHI) = water retained at 2 h after ingestion relative to still water, corrected for the water content of the drinks.

Overview

Maughan et al. built a beverage hydration index to rank common drinks by how much of their fluid is still retained after ingestion in a rested, euhydrated state. Against still water (4-h urine output 1337 ± 330 g), urine output was lower after an oral rehydration solution (ORS; 1038 ± 333 g), full-fat milk (1052 ± 267 g) and skimmed milk (1049 ± 334 g), all P < 0.001.

Cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water and a sports drink were NOT different from water. The BHI at 2 h was 1.54 ± 0.74 for ORS, 1.50 ± 0.58 for full-fat milk and 1.58 ± 0.60 for skimmed milk. The authors propose BHI as a measure of short-term hydration potential when drinks are taken in a euhydrated state.

Key Findings

Milk (full-fat and skimmed) and ORS: ~50% more fluid retained at 2 h than still water (BHI 1.50, 1.58, 1.54)
4-h urine output: water 1337 ± 330 g vs ORS 1038 ± 333, full-fat milk 1052 ± 267, skimmed milk 1049 ± 334 g (all P < 0.001)
A commercial sports drink, cola, diet cola, tea, coffee, lager, orange juice and sparkling water: no different from water
Study state: rested and euhydrated, not post-exercise dehydration

Practical Application

In 72 euhydrated men drinking 1 L, milk (full-fat or skimmed) and an oral rehydration solution left about 50% more fluid in the body at 2 h than still water (BHI 1.50-1.58), while a sports drink, cola, tea, coffee, juice and lager retained no more than water — when fluid has to stay on board (travel, long gaps between drinks), milk or an ORS beats both water and an ordinary sports drink.
Not from this paper; the base's own practice: after a sweaty session, drink beyond the measured loss and include sodium (an ORS, milk, or salted food with water) rather than plain water alone; the exact volume follows the athlete's weighed sweat loss.
Inference, not tested here: the retention advantage of milk and ORS most plausibly comes from their energy and electrolyte content; the sports drink tested did not carry enough of either to differ from water.

Limitations

Euhydrated, fasted men at rest: the ranking was not tested after exercise-induced dehydration or during exercise.
1 L bolus; other volumes and repeated drinking were not tested; only one sports drink and one ORS were included.
n=72 total, but each beverage was tested in a subset of the cohort.
How this entry was checked and changed
Content correction 2026-09-27
"Milk 137%, ORS 130% hydration index" -> the abstract's BHI at 2 h: full-fat milk 1.50, skimmed milk 1.58, ORS 1.54 (~150-158%); added the urine-mass results.
The entry recommended "electrolyte sports drink" over water — the abstract reports the tested sports drink was NOT different from water; corrected.
Removed unsourced "sodium 20-40 mmol/L optimal", "150% of body weight loss over 4 h", "sodium 25 mmol/L, glucose 60 g/L, amino acids", "<60 min / >90 min"; rehydration practice labelled as the base's own.
2026-09-28: added Protocol from the abstract (Europe PMC PMID 26702122).