Drinking to Thirst, Programmed Drinking and Beverage Choice: What the Sources Compared
Drinking to thirst and programmed drinking similarly affected 1–2 h endurance performance in a meta-analysis, with any advantage of drinking to thirst likely trivial (Goulet 2019); cool drinks below 22 °C increased fluid consumption and hydration during exercise (Burdon 2012); hypotonic drinks better maintained plasma volume than isotonic drinks (Rowlands 2021); post-exercise rehydration volume needs to exceed the deficit by about 150% with sodium (Sharp 2006); and caffeine up to 400 mg a day did not produce dehydration (Ruxton 2008).
Fluid-restriction conditions (heart/kidney failure) require clinician-set targets
- Signs of disordered eating (food/weight preoccupation, restriction, bingeing, purging, compulsive exercise): see a qualified eating-disorder professional
- Diagnosed medical condition (diabetes, chronic kidney disease, heart failure, GI disease): see a registered dietitian or physician
- Pregnancy or breastfeeding: see a prenatal provider or registered dietitian
- Unintentional weight loss, difficulty swallowing, or persistent GI symptoms: seek medical evaluation
- Fluid-restriction orders or heart/kidney failure: follow clinician's targets
What the evidence says
The sources on this entry are meta-analyses, trials and reviews comparing drinking strategies and beverage types during and after exercise. Goulet 2019 (meta-analysis of 7 crossover publications, 82 subjects) reports that drinking to thirst improved endurance performance by 0.98% over programmed drinking despite half the fluid intake rate and greater dehydration (−2.1% versus −1.0% body mass), and concludes that both strategies similarly affect 1–2 h cycling and running performance in temperate to warm conditions, with the advantage of drinking to thirst likely trivial. Backes 2016 (randomised trial) reports exercise performance significantly better under voluntary than dictated drinking, and concludes that when dehydration is likely, drinking to guidelines may protect against it, while when it is not likely, voluntary drinking is preferable for performance; Perreault-Briere 2019 (crossover trial) reports that neither programmed nor thirst-driven fluid intake offered an advantage over no fluid intake in a 1 h cycling time-trial. On beverage temperature, Burdon 2012 (meta-analysis of 14 studies) reports that cool beverages below 22 °C were preferred, that participants consumed about 50% more of them, and that dehydration was reduced by 1.3% of body weight. On formulation, Rowlands 2021 (meta-analysis of 28 studies) reports that hypotonic drinks better maintained plasma volume during continuous exercise than isotonic drinks; Sharp 2006 (narrative review) reports that post-exercise rehydration volume needs to exceed the fluid deficit by about 150% because of urinary losses, with sodium chloride reducing urinary water loss; Leiper 2015 (narrative review) reports that rehydration volume must exceed water lost and that formulation affects gastric emptying and absorption. On other drinks, Słyś 2025 (systematic review) reports that alkaline water consistently elevated urine pH but gave only minor changes in acid-base markers and anaerobic performance, the same as neutral water or sports drinks for performance; Ruxton 2016 (systematic review of 6 trials) reports that tea performed similarly to plain water up to six servings daily; Wynne 2021 (systematic review) reports that a low-alcohol beer (under 4%) may be more effective for post-exercise rehydration than higher-alcohol beer. On caffeine, Ruxton 2008 (narrative review) reports that intakes up to 400 mg a day did not produce dehydration, and Zhang 2014 (meta-analysis of 16 studies) reports a minor diuretic effect of caffeine that was negated by exercise, concluding that concerns about caffeine-related fluid loss are unwarranted, especially before exercise.
- 'Everyone needs eight glasses.' Thirst is largely an adequate guide.
- 'Coffee/tea don't count and dehydrate you.' Tea hydrates comparably to water in specified ranges, and caffeine at up to 400 mg a day does not cause meaningful dehydration.
- Do not claim any food, diet, or supplement cures, treats, or prevents any disease
- Do not diagnose nutrient deficiencies or medical conditions
- Do not promise specific weight-loss amounts or timelines
- Do not deliver individualized medical nutrition therapy or replace clinical care
- Do not claim water intake alone causes weight loss or detoxification
- Agreement
- Direction recorded for 0 of 12 sources; not yet recorded for the rest.
- The claim's outcome
- Outcome not yet recorded
- Certainty
- No source states a certainty rating.
- Authors
- Sources share authors: C. Ruxton (first author of 2 sources); C. Ruxton (senior author of 2 sources).
- How the sources were read
- Some sources are based on abstracts, not full texts.
What each source measured and concluded (12)
- What it measured
- Endurance performance (ad libitum vs programmed drinking)
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Systematic review with meta-analysis of crossover controlled trials
- Studies and participants, as stated
- 7 publications; 8 effect estimates; 82 subjects
- What it measured
- Beverage palatability and fluid intake during exercise
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Systematic review with meta-analysis
- Studies and participants, as stated
- N=14 studies (10 palatability, 5 fluid consumption, 4 hydration)
- What it measured
- Cognitive function, mood, physical performance, and hydration effects of caffeine
- How it was read
- based on the abstract, not the full text
- What it measured
- Impact of tea consumption on validated markers of hydration
- How it was read
- based on the abstract, not the full text
- What the review says it includes
- Systematic review (of intervention trials)
- Studies and participants, as stated
- N=6 trials
- What it measured
- Urinary pH and acid-base balance.
- How it measured it
- Urine pH and specific gravity (objective).
- How it was read
- read in full text
- What the review says it includes
- Systematic review
- Heterogeneity, as stated
- Limitations: Small sample sizes, short intervention durations, lack of blinding, heterogeneity in study designs and participant demographics.
- What it measured
- Exercise performance (duration and speed).
- How it measured it
- Elapsed time and terminal speed (objective).
- Its conclusion, in its own words
- “In situations where dehydration is likely, drinking to recommended guidelines may protect individuals from dehydration and its negative effects. However, when dehydration is not likely, allowing an individual to follow voluntary drinking behavior is preferable for exercise performance.”
- How it was read
- read in full text
- What it measured
- Hydration (fluid balance, body mass, plasma Na+ or K+, urine specific gravity).
- How it measured it
- Objective measures (body mass, plasma Na+ or K+, urine specific gravity).
- How it was read
- read in full text
- What it measured
- Effects of hypertonic, isotonic, hypotonic sports drinks and water on delta percent plasma volume (dPV) during exercise
- How it was read
- screened only, not extracted
- What the review says it includes
- Systematic review and meta-analysis (random-effects, Bayesian)
- Studies and participants, as stated
- 28 studies; 68 drink treatment effects
- What it measured
- Effect of acute caffeine ingestion on diuresis/urine volume
- How it was read
- screened only, not extracted
- What the review says it includes
- Meta-analysis
- Studies and participants, as stated
- 16 studies; 28 effect sizes
- What it measured
- 1 h cycling time-trial performance (distance/power output)
- How it was read
- screened only, not extracted
- What it measured
- Factors affecting gastric emptying and intestinal absorption of beverages
- How it was read
- screened only, not extracted
- What it measured
- Fluid and sodium replacement for fluid homeostasis
- How it was read
- screened only, not extracted
Each source below is shown with its study design and a link to the original study, or, where it is not a completed research paper, with what kind of record it is; those are not counted. This is the audit trail.
Why do some records show a record type instead of a study design?
A study design is shown for a completed, peer-reviewed paper. A registered protocol, a preprint, a conference abstract, a referee report or a book chapter has not been through peer review as a finished paper, so it is labelled for what it is, and it is counted in no source count. Where a record could not be confirmed as a completed paper at all, it says so rather than guessing. They all stay in the list, and their DOI still resolves, because the count of what was screened is part of the audit trail.
- Protocol / registration A registered plan for a review or trial, not its results.
- Preprint Posted by its authors before peer review.
- Conference abstract A conference summary rather than a peer-reviewed paper.
- Peer-review report A referee's report on a paper, not the paper itself.
- Guideline / position stand A recommendation derived from evidence, which is a step further from the data than the evidence itself.
- Book chapter A chapter in a scholarly book rather than a journal paper.
- Type not recorded Our record does not say what kind of publication this is, so it is counted in no source count. That is a gap in our data, not a judgement about the research.
“Abstract only” means the review read that paper’s abstract, not its full text; “screened only” means it was included at re-screening and not extracted. Both stay in the trail with their DOI, because how a source was read is part of the audit.