Hydrate Sensibly
Drinking to thirst, keeping water handy and adjusting for heat and exercise: one way to carry out what the sources on drinking strategy compared. Goulet 2019 reports that drinking to thirst and programmed drinking similarly affected 1–2 h endurance performance, with any advantage of drinking to thirst likely trivial.
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
How to do it
What the evidence says
This practice is one way to carry out what the sources on the concept entry (phys.nutrition.drinking-to-thirst) studied: drinking strategy and beverage choice during and after exercise. Goulet 2019 (meta-analysis of crossover trials) reports that drinking to thirst and programmed drinking similarly affected 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) concludes that when dehydration is likely, drinking to guidelines may protect against it, and when it is not, voluntary drinking is preferable for performance; Burdon 2012 (meta-analysis) reports that cool beverages below 22 °C increased fluid consumption and hydration during exercise; Sharp 2006 (narrative review) reports that post-exercise rehydration volume needs to exceed the deficit by about 150% because of urinary losses, with sodium reducing urinary water loss; Ruxton 2008 reports caffeine intakes up to 400 mg a day did not produce dehydration, and Zhang 2014 (meta-analysis) reports a minor diuretic effect negated by exercise. The full account, source by source, is on the concept entry this practice links to (phys.nutrition.drinking-to-thirst).
- '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.