The Beverage Hydration Index: What Hydrates Better Than Water
A landmark randomized trial measured how 13 drinks are retained versus still water. Milk, ORS and orange juice topped water; coffee, tea, cola and beer matched it. None scored below water.
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The Beverage Hydration Index: What Hydrates Better Than Water
The Beverage Hydration Index (Maughan 2016, Am J Clin Nutr, PMID 26702122) ranks how well drinks are retained versus still water, set at 1.00. Skim milk (1.58), oral rehydration solution (1.54), whole milk (1.50) and orange juice all beat water at 2 hours. Coffee, tea, cola, beer and a sports drink matched water (BHI approximately 1.0); none scored below water.
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The Beverage Hydration Index (BHI) was created by Maughan and colleagues in a 2016 randomized trial published in the American Journal of Clinical Nutrition (PMID 26702122). Seventy-two euhydrated, fasted healthy men each drank 1 litre of still water or one of 12 other beverages over 30 minutes, and all urine was collected for 4 hours afterward. BHI is calculated as the urine output after still water divided by the urine output after the test drink, with still water anchored at 1.00. A BHI above 1.0 means the body retained that beverage better than plain water. At 2 hours, skim milk (1.58), oral rehydration solution (1.54) and whole milk (1.50) all retained significantly more fluid than water, and orange juice was also significantly above water at this point (P < 0.05). Coffee, tea, cola, diet cola, sparkling water, lager beer and a sports drink were all statistically the same as water (BHI approximately 1.0). Critically, no beverage tested scored significantly below water, meaning none caused net dehydration at this single 1 litre dose.
The Beverage Hydration Index, Ranked (2-Hour BHI)
| Beverage | 2-Hour BHI | Hydration vs Water | Source |
|---|---|---|---|
| Skim (skimmed) milk | 1.58 ± 0.60 Significantly better retained than water (P < 0.05 at 2 h; water-corrected P < 0.01). Electrolytes, protein and 350 kcal/L slow fluid loss. | ||
| Oral rehydration solution (ORS) | 1.54 ± 0.74 Significantly better retained than water (P < 0.05; water-corrected P = 0.01). Designed sodium/glucose content maximizes retention. | ||
| Whole (full-fat) milk | 1.50 ± 0.58 Significantly better retained than water (P < 0.05; water-corrected P = 0.02). Highest energy density at 640 kcal/L slows gastric emptying. | ||
| Orange juice | > 1.0 at 2 h Significantly higher than water at 2 h (P < 0.05) but lost significance by 4 h (P = 0.06) and after water-content correction (P = 0.11). Energy density 470 kcal/L. | ||
| Cola | ≈ 1.0 4 h urine output not significantly different from water. Energy density 420 kcal/L. | ||
| Diet cola | ≈ 1.0 4 h urine output not significantly different from water. | ||
| Hot tea | ≈ 1.0 4 h urine output not significantly different from water; the caffeine did not cause net fluid loss at this dose. | ||
| Cold / iced tea | ≈ 1.0 4 h urine output not significantly different from water. | ||
| Coffee | ≈ 1.0 4 h urine output not significantly different from water; at 1 L it neither dehydrated nor super-hydrated participants. | ||
| Sports drink | ≈ 1.0 4 h urine output not significantly different from water — contrast with ORS (1.54), which has higher sodium content. | ||
| Lager beer | ≈ 1.0 4 h urine output not significantly different from water; not below water. Energy density 330 kcal/L. | ||
| Sparkling water | ≈ 1.0 4 h urine output not significantly different from water. | ||
| Still water (reference) | 1.00 The reference beverage. All other drinks are scored relative to this baseline of 1.00. |
What the Index Tells You
Why Milk and ORS Win
Skim milk (1.58), ORS (1.54) and whole milk (1.50) stayed ahead of water through the full 4 hours. Their sodium, potassium, protein and energy content slow gastric emptying and reduce urine output. After water-content correction, only these three remained significantly above water (skim milk P < 0.01, ORS P = 0.01, whole milk P = 0.02). See our milk and ORS deep-dives.
Orange Juice: Strong, Then Fades
Orange juice was significantly above water at 2 hours — but the edge disappeared by 4 hours (P = 0.06) and after adjusting for its water content (P = 0.11). It hydrates well in the short term thanks to 470 kcal/L of carbohydrate, but it is not in the same durable tier as milk.
Coffee and Tea Do Not Dehydrate
Coffee, hot tea and iced tea all produced 4-hour urine output statistically indistinguishable from water (BHI approximately 1.0). At a 1 litre dose, the caffeine did not trigger net fluid loss — the 'coffee dehydrates you' claim does not hold here. Read the full coffee and tea breakdowns.
Beer, Cola and Sports Drinks Match Water
Lager beer, cola, diet cola, sparkling water and a sports drink all matched water (BHI approximately 1.0). Notably, the sports drink did not beat water, unlike the much saltier ORS. No beverage in the study scored below water — none caused net dehydration at 1 litre.
How to Use the Hydration Index
- For everyday hydration, plain water (BHI 1.00) is perfectly effective — no beverage in the study scored below it, so your usual drinks are not 'dehydrating' you.
- For maximum fluid retention after heavy sweating or illness, reach for skim milk (1.58), oral rehydration solution (1.54) or whole milk (1.50) — the only drinks that beat water through a full 4 hours.
- Orange juice is a good short-term rehydrator (significantly above water at 2 hours) but loses its edge over water by the 4-hour mark, so do not rely on it alone for sustained recovery.
- Do not assume a sports drink out-hydrates water — the one tested matched water (BHI approximately 1.0), while the saltier ORS reached 1.54.
- Enjoy coffee and tea without worry: at a 1 litre dose their hydration index was the same as water, so they still count toward your daily fluids.
- Remember the BHI was measured at rest with a single 1 litre dose in healthy men — use it to compare drinks, not as an exact prescription for athletes or sick days.
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- water = 1.00 (reference) — The BHI compares fluid retention of a drink versus still water, which is anchored at 1.00; a BHI above 1.0 means the beverage is retained better than plain water.[1]
- n=72; 1 L; 30 min; 4 h collection; 13 beverages — 72 euhydrated, fasted healthy men each ingested 1 litre of still water or one of 12 other beverages over 30 minutes, with urine collected for 4 hours (13 beverages total).[1]
- 1.58 ± 0.60 — Skim (skimmed) milk had the highest 2-hour Beverage Hydration Index, significantly above water.[1]
- 1.54 ± 0.74 — Oral rehydration solution (ORS, Dioralyte) had a 2-hour Beverage Hydration Index significantly above water.[1]
- 1.50 ± 0.58 — Full-fat (whole) milk had a 2-hour Beverage Hydration Index significantly above water.[1]
- 2 h significant (P < 0.05); 4 h P = 0.06; water-corrected P = 0.11 — Orange juice was significantly above water at 2 hours but lost significance by 4 hours (P = 0.06) and after water-content correction (P = 0.11).[1]
- BHI ≈ 1.0 (not different from water) — Cumulative 4-hour urine output after cola, diet cola, hot tea, cold/iced tea, coffee, lager, orange juice, sparkling water and the sports drink was not significantly different from water.[1]
- 0 beverages below water — No beverage tested — including coffee, tea and lager beer — had a BHI significantly lower than water; none caused net dehydration at 1 litre.[1]
- whole milk P = 0.02; skim milk P < 0.01; ORS P = 0.01 — After water-content correction, the 2-hour BHI remained significantly above water only for full-fat milk, skim milk and ORS.[2]
- whole milk 640; orange juice 470; cola 420; skim milk 350; lager 330 kcal/L — Energy density of the higher-energy beverages tested.[2]
- coffee BHI ≈ 1.0 (n.s. vs water) — Coffee's 4-hour urine output was not different from water; coffee did not cause dehydration at the dose tested.[4]
- water baseline = 1.0; none below water — Water set at 1.0 as the baseline and no beverage (including coffee) had a BHI significantly lower than water.[3]
- [1]Maughan 2016 (Am J Clin Nutr) — Maughan RJ, Watson P, Cordery PA, Walsh NP, Oliver SJ, Dolci A, Rodriguez-Sanchez N, Galloway SD. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. Am J Clin Nutr. 2016 Mar;103(3):717-23.PMID: 26702122DOI: 10.3945/ajcn.115.114769
- [2]Maughan 2016 accepted manuscript (LJMU repository) — Maughan RJ, Watson P, Cordery PA, Walsh NP, Oliver SJ, Dolci A, Rodriguez-Sanchez N, Galloway SD. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index (final accepted manuscript). Am J Clin Nutr. 2016;103(3):717-23.PMID: 26702122DOI: 10.3945/ajcn.115.114769
- [3]ACE ProSource 2016 (Hydration Index summary) — American Council on Exercise (ACE) ProSource, April 2016. The Newest Index on the Block: The Hydration Index (summary of Maughan et al. 2016).
- [4]National Coffee Association (AboutCoffee.org) — National Coffee Association, AboutCoffee.org research summary of Maughan et al. 2016. Confirms coffee's 4-hour urine output was not different from water at the dose tested.
Last reviewed: 2026-06-20. Every figure on this page is sourced to the named primary references above.
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Frequently Asked Questions
What is the Beverage Hydration Index (BHI)?
The BHI, created by Maughan et al. in 2016 (Am J Clin Nutr, PMID 26702122), compares how well a drink is retained versus still water, which is anchored at 1.00. It is calculated as the urine output after water divided by the urine output after the test drink. A BHI above 1.0 means the beverage is retained better than plain water over the 4-hour measurement window. The study tested 72 men, each drinking 1 litre of a beverage.
Which drinks hydrate better than water?
In Maughan et al. (2016), only skim milk (BHI 1.58), oral rehydration solution (1.54) and whole milk (1.50) hydrated significantly better than water through the full 4 hours. Orange juice was significantly higher at 2 hours but lost significance by 4 hours (P = 0.06). Their electrolyte, protein and energy content slows fluid loss, keeping more fluid in the body than plain water.
Does coffee dehydrate you?
No. In the 2016 Beverage Hydration Index study (Maughan et al., Am J Clin Nutr), 72 men drank 1 litre of coffee and produced no more urine over 4 hours than after drinking water. Coffee's hydration index was statistically the same as water (approximately 1.0) — at this dose it neither dehydrated nor super-hydrated participants.
Does beer dehydrate you?
Not at the amount tested. In Maughan et al. (2016), 1 litre of lager produced 4-hour urine output statistically indistinguishable from water, giving a hydration index of about 1.0. No beverage in the study — including beer, coffee or tea — had a BHI significantly below water, so none caused net dehydration at this single 1 litre dose.
Is milk more hydrating than a sports drink?
Yes, in this study. Skim milk (BHI 1.58) and whole milk (1.50) hydrated significantly better than water, while the sports drink tested produced urine output not different from water (BHI approximately 1.0). Milk's protein, electrolytes and energy density (350–640 kcal/L) slow gastric emptying and improve fluid retention more than the sports drink did.
Can any drink dehydrate you compared to water?
Not in this trial. None of the 13 beverages tested by Maughan et al. (2016) — including coffee, tea, cola and lager beer — had a Beverage Hydration Index significantly below 1.00. Every drink was either equal to or better than water at retaining fluid when consumed as a single 1 litre dose in healthy, rested men.
Why is orange juice not ranked as high as milk?
Orange juice was significantly above water at 2 hours, but the advantage disappeared by 4 hours (P = 0.06) and after correcting for its water content (P = 0.11). Skim milk, ORS and whole milk kept their lead through all 4 hours and after correction, so orange juice is a strong short-term rehydrator but sits below the top tier (Maughan 2016).
How was the Beverage Hydration Index measured?
Maughan et al. (2016) recruited 72 euhydrated, fasted healthy men. Each drank 1 litre of still water or one of 12 other beverages over 30 minutes, then had all urine collected for 4 hours. The urine mass after water was divided by the urine mass after each test drink to produce the index, with still water set at 1.00 as the reference (PMID 26702122).
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