A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.
Level 2 - randomized trial
Individual randomized trial evaluating fluid retention across multiple beverages.
PubMed 26702122 · doi:10.3945/ajcn.115.114769
What was done
In a randomized trial, 72 euhydrated and fasted male subjects consumed 1 L of still water or 1 of 3 other commercially available beverages over 30 minutes, evaluating 13 drinks in total. Urine output was collected for 4 hours post-ingestion. A Beverage Hydration Index (BHI) was calculated as fluid retained at 2 hours relative to still water, corrected for beverage water content.
What was found
Total 4-hour urine mass for still water was 1337 ± 330 g. Urine mass was significantly lower for oral rehydration solution (1038 ± 333 g, P < 0.001), full-fat milk (1052 ± 267 g, P < 0.001), and skimmed milk (1049 ± 334 g, P < 0.001). Urine output after cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water, and sports drink did not differ from water. The mean BHI at 2 hours was 1.54 ± 0.74 for oral rehydration solution, 1.50 ± 0.58 for full-fat milk, and 1.58 ± 0.60 for skimmed milk.
Why it matters
This study provides a standardized index showing that drinks containing electrolytes and macronutrients retain fluid longer than water, while moderate caffeine or low alcohol content does not impair short-term hydration.
Limits
The study was conducted exclusively in resting, euhydrated, fasted young adult males, limiting generalizability to females, dehydrated states, or exercise conditions. Ingesting a large 1-liter fluid volume within 30 minutes may not reflect natural drinking behaviors.
Cited by
- supports Drinking mineralized liquid, such as electrolyte water or salted tea, causes less frequent urination than drinking plain, unmineralized water.