Drink water only when thirsty; there is no need to force a fixed daily amount.
Original statement
اشرب الماء حين تعطش فقط — لا داعي لإجبار نفسك على شرب كميات محددة يومياً.
verbatim according to source. Translation by the project; the Arabic wording is authoritative.
Translation
Drink water only when thirsty; there is no need to force a fixed daily amount.
Origin
- Source status
- Third-party site (unofficial)
- Attribution
- Third-party site (unofficial; states it is not affiliated with Elawady)
- Origin
- https://altayybat.com/ar/
- Attribution uncertainty
- Lowest attribution level; no source video given.
- Claimed mechanism
Thirst accurately signals water needs.
- Claimed health effect
Avoiding overload of body systems with water
- Population concerned
General population
- Geographic restriction by Elawady
none found
Diverging source versions
- Source status
- Video transcript (own words)
- Attribution
- Elawady (machine transcript)
- Video
- Dr Diaa Al Awady د ضياء العوضي is live!لايف مش مهم خالص (Open source)
- Published
- 11 February 2026
- Timestamp
- not available (transcript has no timings)
- Attribution uncertainty
- Archive transcript (YouTube CC or AI-generated); no timestamps; 'published' is the date listed by the archive and may be the upload date. Live-stream transcripts can contain viewer comments read aloud; the quoted passage was checked in context to be spoken by Elawady.
- Source status
- Video transcript (own words)
- Attribution
- Elawady (machine transcript)
- Video
- الجزء الرابع من الندوة (Open source)
- Published
- 2 March 2024
- Timestamp
- not available (transcript has no timings)
- Attribution uncertainty
- Archive transcript (YouTube CC or AI-generated); no timestamps; 'published' is the date listed by the archive and may be the upload date. Live-stream transcripts can contain viewer comments read aloud; the quoted passage was checked in context to be spoken by Elawady.
Scientific assessment
Potentially true – Some evidence points in favour of the statement, but it is not sufficient for a clear judgement.
Certainty of evidence: low – Further research is likely to change the assessment considerably.
1. What was claimed?
Thirst alone should guide drinking.
2. What is demonstrably correct?
'No scientific studies were found in support of 8 x 8'; the osmoregulatory system maintains water balance in healthy adults (I-FAST-08).
3. What is wrong or exaggerated?
The same review emphasises that higher intakes are advisable for prevention of some diseases and in hot climates and vigorous work (I-FAST-08). In an RCT, high water intake reduced kidney stone recurrence (12/99 vs 27/100 over 5 years) (I-FAST-09).
4. What remains unclear?
Optimal intake in hot climates.
5. Which studies support it?
I-FAST-08; I-FAST-123 (few trials; no proof that everyone needs a fixed amount).
6. Which studies contradict it?
I-FAST-09 and Cochrane review of the same trial (I-FAST-122): increased water intake reduced stone recurrence (12/99 vs 27/100 over 5 years).
7. What applies to Germany and Europe?
EFSA adequate intakes for total water: 2.0 L/day women, 2.5 L/day men from all sources, for moderate temperature and activity (I-FAST-124; abstract verified via Crossref/OpenAlex).
8. What is known about Egypt?
Hot climate and kidney stone prevalence in Egypt make the exceptions practically important.
9. What practical conclusion is appropriate?
For healthy adults in moderate conditions thirst is a reasonable guide; in heat, with stones, in old age or illness people need to drink more deliberately.
Assessment details
- Rationale for certainty of evidence
For healthy adults in temperate conditions there is no evidence for '8 glasses a day' (narrative review, I-FAST-08) and only 18 RCTs on changing water intake exist (I-FAST-123). Extra water helps defined groups: stone recurrence RR 0.45 with higher intake (Cochrane, one RCT, low certainty; I-FAST-122). EFSA adequate intakes (2.0 L women, 2.5 L men, including food water) apply to moderate climate and activity (I-FAST-124); hot climates, heavy work, older age, fever and diarrhoea raise needs.
- Source quality
Third-party site plus own words.
- Regional transferability
Egypt's hot climate increases water needs; transfer from temperate-climate evidence is limited.
- Individual exceptions
Kidney stones, hot climate, heavy exercise, elderly, children, illness with fluid loss, people on SGLT2 inhibitors or diuretics.
- Regional scope of the claim
- general (biological/medical)
- Last reviewed
- 26 October 2026 provisional
Scientific evidence in detail
True only under certain conditions – The claim holds only for certain doses, groups of people, preparations or circumstances.
Research question: In healthy adults, is drinking according to thirst sufficient, without a fixed daily amount?
Research question in detail (PICO)
- Population
- Healthy adults; subgroups (stone formers, older adults, hot climate, heavy work)
- Intervention or exposure
- Thirst-guided drinking
- Comparison
- Fixed or increased intake
- Geographic scope
- climate-dependent (hot climate in Egypt)
- Outcomes
- Hydration status
- Kidney stones
- Weight, other outcomes
Study results as reported by the authors. Our assessment follows below.
What speaks for the claim?
Do we need eight glasses of water a day?
Valtin H. Am J Physiol Regul Integr Comp Physiol 2002 · PMID 12376390 · DOI 10.1152/ajpregu.00365.2002 Narrative reviewabstract checkedNo scientific studies support '8 x 8'; osmoregulation is precise in healthy adults in temperate climate.
- Actual result
- Narrative review.
- Methodological quality
- low (narrative review)
- Relevance
- direct
- Limitations
- Old; temperate climate.
Trials of drinking more water
Hakam N et al.. JAMA Netw Open 2024 · PMID 39585691 · DOI 10.1001/jamanetworkopen.2024.47621 Systematic reviewabstract checkednewly addedFew RCTs exist on changing water intake; benefits shown mainly for stones and weight loss.
- Actual result
- 18 RCTs; 55% at least one positive result.
- Methodological quality
- moderate (systematic review)
- Relevance
- direct: no proof that a fixed amount is needed for everyone
- Limitations
- No meta-analysis.
What speaks against the claim?
Drinking more water to prevent kidney stones
Bao Y et al.. Cochrane Database Syst Rev 2020 · PMID 32045491 · DOI 10.1002/14651858.CD004292.pub4 Systematic reviewabstract checkednewly addedFor people with previous kidney stones, drinking enough to pass >=2 L urine/day reduces recurrence.
- Actual result
- RR 0.45 (0.24-0.84); 149 fewer per 1000 over 5 years; low certainty.
- Methodological quality
- high-quality review, low-certainty evidence (1 RCT)
- Relevance
- direct for stone formers
- Limitations
- Single trial (same as I-FAST-09).
What does the overall evidence say?
Editorial assessment based on the studies above – not itself a study result.
Which position is better supported?
Healthy adults in moderate conditions can generally rely on thirst; there is no proof that everyone must drink a fixed amount. People with kidney stones, in hot climates, doing heavy work, older people (blunted thirst), children and the ill need deliberate, often higher intake.
Why some studies weigh more
Evidence is thin in both directions; Cochrane evidence for stone formers is the most rigorous.
Is a causal relationship established? Possible, not established Causal benefit of extra water shown only for stone recurrence (single RCT).
Remaining uncertainty
Optimal intake in hot climates.
Justified conclusion
Conditionally true.
Why do studies seem to disagree?
Valtin (no need for 8x8) and Cochrane (more water for stone formers) address different populations; no true conflict.
Does this depend on the country?
- General biological effects
- Universal osmoregulation.
- Eating habits
- Hot Egyptian summers and outdoor work increase water needs; temperate-climate reference values (EFSA) underestimate needs in heat.
- Origin of the food
- Not applicable.
- Contaminants
- Not applicable.
- National production conditions
- Not applicable.
- Legal rules
- Not applicable.
- Actual monitoring data
- No Egyptian hydration surveillance data assessed.
A regional difference that changes the conclusion is not supported by robust data.
Statistical re-check
- Absolute effect and NNT from Borghi counts; independence of evidence – 12/99 vs 27/100: RR 0.45, ARR 14.9 points, NNT about 7; Cochrane and Borghi are the same trial (not independent). recalculated
Certainty of the overall evidence (GRADE, simplified)
- Main outcome
- Adequacy of thirst-guided drinking for health in healthy adults
- Starting level
- low (observational studies)
- Reasons for downgrading
- indirectness (temperate settings)
- Result
- low
Simplified assessment by a single reviewer, following the GRADE approach; not a formal GRADE panel. GRADE rates the body of evidence for one outcome, not individual studies.
Clinical guidelines and official statements checked
- EFSA NDA Panel: Scientific Opinion on Dietary Reference Values for water (2010) · Original publication
Adequate total water intake (drinks plus food moisture) 2.0 L/day women, 2.5 L/day men, valid for moderate temperature and activity; more in pregnancy (+300 mL) and lactation (+about 700 mL). Abstract read via OpenAlex; EFSA page blocked (403).
Search strategy
Documented literature searches for this review (search strings in the original database syntax).
| Database | Date | Search | Looking for | Hits | Included |
|---|---|---|---|---|---|
| Europe PMC | 26 October 2026 | JOURNAL:"Cochrane Database Syst Rev" AND TITLE:(water OR fluid) AND (stones OR nephrolithiasis OR urolithiasis) | contradicting evidence | 6 | |
| Europe PMC | 26 October 2026 | ("water intake" OR hydration) AND (health outcomes OR mortality OR "chronic kidney disease" OR weight) AND ("systematic review" OR "umbrella review") AND TITLE:(water) | both directions | 191 | |
| Europe PMC | 26 October 2026 | ("ad libitum drinking" OR "drinking to thirst" OR "thirst-guided" OR "thirst") AND (hydration OR "fluid balance") AND (adequate OR sufficient) AND (healthy adults OR older adults) | supporting evidence | 927 | |
| Crossref + OpenAlex | 26 October 2026 | DOI 10.2903/j.efsa.2010.1459 (EFSA DRV water); EFSA/Wiley page returned 403 | guidelines | 1 |
Open questions
Evidence on thirst-guided drinking in hot climates.
How deeply was this checked?
5 linked studies: 0 checked in full text (0 of them with a structured risk-of-bias assessment), 5 on the basis of the abstract, 0 bibliographically only. No formal assessment with two independent reviewers and no independent human expert review has taken place yet.
Last scientific review: 26 October 2026
History of the verdict
- 25 October 2026 · Phase 1 · Initial assessment: Potentially true (moderate)
- 26 October 2026 · Phase 4 (systematic evidence review) · Verdict changed: Potentially true (moderate) → Potentially true (low)
Verdict unchanged. Certainty lowered: the supporting evidence is a narrative review and the 2024 systematic review shows the trial base on water intake is thin in both directions; 'moderate' overstated it.
New sources: I-FAST-122 I-FAST-123 I-FAST-124
In plain language
There is no proof that everyone must drink eight glasses of water a day; healthy adults in a cool climate can usually rely on thirst. But in hot weather, during hard work, in old age, or for people who have had kidney stones, drinking more than thirst suggests is important.
Studies on this claim
Studies supporting the claim (1)
-
Do we need eight glasses of water a day?
Valtin H. Am J Physiol Regul Integr Comp Physiol 2002 · PMID 12376390 · DOI 10.1152/ajpregu.00365.2002Narrative reviewindependent cross-checkabstract checkedNo proof for 8 glasses in healthy adults in mild climates, but more is needed in heat, hard work and some diseases.
Does the study support the specific claim? Partly · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Is there evidence for '8 x 8' glasses of water a day?
- How was the study done?
Narrative review
- How many people, animals or samples were studied?
not applicable; Healthy adults
- What was actually found?
No evidence for 8 x 8.
- How large was the observed effect?
not applicable
- What do the results mean in everyday life?
Thirst usually suffices if healthy and in mild climate.
- What are the study's limitations?
Narrative; Old
- What does it say about Elawady's specific claim?
Supports C-FAST-09; partly C-FAST-10 (no fixed high intake), with stated exceptions.
- Do the results apply to Germany and Europe?
Temperate climate applies to Germany.
- What can explicitly not be concluded from this study?
Advice for hot climates or patients.
No study in this group is marked as key.
Studies contradicting or limiting the claim (2)
-
Drinking more water to prevent kidney stones
Borghi L et al.. J Urol 1996 · PMID 8583588Randomised controlled trialindependent cross-checkabstract checkedOver five years, stones came back in 12% of those drinking a lot vs 27% without advice.
Does the study support the specific claim? No · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
High water intake and calcium stone recurrence
- How was the study done?
Randomised prospective 5-year study
- How many people, animals or samples were studied?
199 patients; First-episode idiopathic calcium stone formers (plus 101 controls)
- What was actually found?
Recurrence halved.
- How large was the observed effect?
12% vs 27%
- What do the results mean in everyday life?
Stone formers should drink more.
- What are the study's limitations?
Not blinded; Single centre
- What does it say about Elawady's specific claim?
- Do the results apply to Germany and Europe?
Italian; directly applicable.
- What can explicitly not be concluded from this study?
Benefits in people without stones.
-
Drinking more water to prevent kidney stones
Bao Y et al.. Cochrane Database Syst Rev 2020 · PMID 32045491 · DOI 10.1002/14651858.CD004292.pub4Systematic reviewindependent cross-checkabstract checked★ key studyPeople who had kidney stones and drank enough to pass 2 litres of urine a day had fewer new stones.
For people with previous stones, increased water intake (urine >=2 L/day) reduces recurrence (low certainty).
Does the study support the specific claim? No · Methodological quality: high · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Assess water for stone prevention.
- How was the study done?
Cochrane review.
- How many people, animals or samples were studied?
1 RCT, 220 people.
- What was actually found?
RR 0.45 for recurrence.
- How large was the observed effect?
149 fewer recurrences per 1000.
- What do the results mean in everyday life?
Stone formers should drink more than thirst alone suggests.
- What are the study's limitations?
Only one trial.
- What does it say about Elawady's specific claim?
Limits the thirst-only rule; contradicts water restriction.
- Do the results apply to Germany and Europe?
Applicable; stone disease common in Egypt's hot climate.
- What can explicitly not be concluded from this study?
Primary prevention.
No study in this group is marked as key.
Studies with mixed or unclear results (2)
-
Trials of drinking more water
Hakam N et al.. JAMA Netw Open 2024 · PMID 39585691 · DOI 10.1001/jamanetworkopen.2024.47621Systematic reviewindependent cross-checkabstract checked★ key studyOnly 18 trials exist; drinking more water helped with kidney stones and weight loss in some.
Few RCTs; benefits of extra water shown mainly for stones and weight loss; no proof that everyone needs a fixed amount.
Does the study support the specific claim? Partly · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Summarise RCTs of water intake.
- How was the study done?
Systematic review.
- How many people, animals or samples were studied?
18 RCTs.
- What was actually found?
Benefits for stones and weight in some trials.
- How large was the observed effect?
15 fewer stones per 100 over 5 years.
- What do the results mean in everyday life?
No strong proof that everyone must drink a set amount; some people benefit from drinking more.
- What are the study's limitations?
Few, heterogeneous trials.
- What does it say about Elawady's specific claim?
Partly supports thirst-guided drinking; limits it for specific groups.
- Do the results apply to Germany and Europe?
Applies; same physiology.
- What can explicitly not be concluded from this study?
Optimal intake in hot climates.
-
EU reference values for water
EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). EFSA Journal 2010 · DOI 10.2903/j.efsa.2010.1459Guideline / position statementindependent cross-checkabstract checked★ key studyEuropean experts set adequate total water intake at 2.0 L/day for women and 2.5 L/day for men, including water in food.
AIs include water from food and apply to moderate conditions; they do not require forced drinking but define normal total intake.
Does the study support the specific claim? Partly · Methodological quality: moderate · Certainty of evidence: see overall assessment of the claim
Original publication · Scientific details
Study explained simply
- What did the researchers want to find out?
Set reference values for water.
- How was the study done?
Expert review of intake and urine data.
- How many people, animals or samples were studied?
not applicable
- What was actually found?
AIs by age and sex.
- How large was the observed effect?
not applicable
- What do the results mean in everyday life?
Normal water needs are substantial; heat increases them.
- What are the study's limitations?
Only for moderate climate and activity.
- What does it say about Elawady's specific claim?
Contradicts water restriction; neutral on thirst-guided drinking.
- Do the results apply to Germany and Europe?
EU reference; Egypt's hotter climate implies higher needs.
- What can explicitly not be concluded from this study?
Needs in hot climates.
No study in this group is marked as key.
Regional context
Germany / EU
EFSA adequate intakes for total water: 2.0 L/day women, 2.5 L/day men from all sources, for moderate temperature and activity (I-FAST-124; abstract verified via Crossref/OpenAlex).
Egypt
Hot climate and kidney stone prevalence in Egypt make the exceptions practically important.
What applies in my country?
General scientific assessment
Potentially true Reasonable for healthy adults in moderate conditions, with important exceptions.
This statement concerns biological or medical relationships. The scientific assessment above applies regardless of the country; country-specific food data do not change it.
References
- "Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 x 8"?. Valtin H. Am J Physiol Regul Integr Comp Physiol 2002 · PMID 12376390 · DOI 10.1152/ajpregu.00365.2002
- Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study.. Borghi L et al.. J Urol 1996 · PMID 8583588
- Water for preventing urinary stones.. Bao Y et al.. Cochrane Database Syst Rev 2020 · PMID 32045491 · DOI 10.1002/14651858.CD004292.pub4
- Outcomes in Randomized Clinical Trials Testing Changes in Daily Water Intake: A Systematic Review.. Hakam N et al.. JAMA Netw Open 2024 · PMID 39585691 · DOI 10.1001/jamanetworkopen.2024.47621
- Scientific Opinion on Dietary Reference Values for water.. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). EFSA Journal 2010 · DOI 10.2903/j.efsa.2010.1459