His taxi was air-conditioned.
I was in that rare moment when you almost enjoy traffic jams, simply because outside, the air had decided to become soup.
Hot soup.
Thick soup.
Urban soup made of asphalt, car horns, burning metal, fine particles and that very specific feeling that you have become a vegetable inside a giant couscoussier.
He, however, was fully launched.
Hot rhetoric.
Burning certainty.
Professor-like tone.
According to him, Bedouins drink very hot tea, even almost boiling tea, to fight heat.
Everybody knows that.
Therefore, it must be true.
I asked him whether he had Bedouins in his family or among his friends.
He burst out laughing. A magnificent laugh. The laugh of a man for whom my question was already proof of my naivety.
“No, but everybody knows that! Very hot tea makes you sweat more!”
The sentence had just entered the taxi with the confidence of a guest who does not need to knock before opening the door.
Obviously, everybody knows that.
I did not.
And that is precisely when my brain started scratching.
When an obvious truth starts sweating
I like these moments.
They look tiny. A conversation in a taxi. A sentence thrown with confidence. A belief passed from mouth to mouth. An “everybody knows that” planted like a flag on a hill.
And suddenly, there is a crack.
Not a major intellectual revolution.
Just a cognitive itch.
What if the sentence was true?
What if it was false?
What if it was true in a specific context, then absurd in another?
That is often where subjects become interesting.
The problem with obvious truths is that they travel very well. They move from one country to another, from one generation to another, from one office to another, from one executive committee to another. They rarely change clothes. They keep the same sentence, the same posture, the same certainty.
But they sometimes lose their original environment.
The boiling tea of desert peoples then becomes the approximate health advice of an air-conditioned taxi.
And I, trapped somewhere between a train station, a heatwave and a teapot-shaped certainty, decided to investigate.
Science does not always reward confidence
The scientific answer is far more interesting than the popular belief.
Yes, drinking a hot beverage can increase sweating.
Yes, this sweating can help cool the body.
But only if that sweat actually evaporates.
This is where the taxi driver’s sentence begins to lose its arrogance.
A study published in Acta Physiologica by Bain, Lesperance and Jay tested beverages at different temperatures during physical activity. Participants drank water at 1.5°C, 10°C, 37°C or 50°C. Under conditions allowing full sweat evaporation, the hot drink was associated with lower body heat storage. The proposed explanation: warm-sensitive thermoreceptors in the esophagus and stomach trigger increased sweating. If that sweat evaporates, it removes heat from the body (Acta Physiologica).
There it is.
The driver was not completely wrong.
But he had forgotten the most important word in the whole story: if.
If the sweat evaporates.
If the air is dry enough.
If air circulates.
If clothing allows evaporation.
If the body can use that sweating as a cooling system.
Otherwise, sweat does not cool much. It runs. It sticks. It soaks the shirt. It makes social interaction more delicate, but it does not remove enough heat.
Sweat that does not evaporate is an unkept promise.
The desert is not the subway
This is probably where folklore and physiology got mixed together.
In a desert environment, the air is often very dry. When air is dry, evaporation can be highly effective. If you wear loose clothing, if the air circulates, if sweat can leave the skin and enter the air, then drinking hot liquids may trigger a useful mechanism.
In that context, the idea can make sense.
But in a humid city, a packed subway, a poorly ventilated room, an office with no airflow or a street trapped between concrete walls, the body does not play by the same rules.
Research published in Environmental Health Perspectives notes that humidity worsens heat stress by reducing the evaporation of sweat. In simple terms: the more water the air already contains, the harder it becomes for your own sweat to evaporate. The body may produce more sweat, but that sweat cools less effectively (Environmental Health Perspectives).
That is why a practice can be intelligent in a desert and ridiculous in a subway carriage.
The problem is not tea.
The problem is context transfer.
When the body becomes a poorly managed company
We could stop here.
We could say: “Thank you, science, I will take fresh water instead.”
But that would miss what truly interests me.
This small exchange with my taxi driver says something much larger than the temperature of a beverage.
It says something about our relationship with certainty.
It says something about the way we copy a practice without copying the conditions that make it effective.
It says something about a very common error in organizations.
A company observes another company succeeding. It takes a method. It copies a ritual. It installs a tool. It borrows a fashionable word. It launches design thinking, lean startup, agile, generative AI, a four-day week, hackathons, OKRs, cultural transformation or standing meetings.
Then it wonders why the result is not the same.
Why?
Because it copied the teapot.
Not the desert.
It copied the visible gesture.
Not the invisible ecosystem.
It copied the practice.
Not the conditions for success.
This is exactly one of the traps I address in my book, chapter 6: the lived experience of the individual directly influences how that person perceives, interprets and reacts to a situation. An individual belief can become a collective decision when it is expressed with enough confidence. And sometimes, confidence replaces evidence.
Sweating is not enough
The human body does not cool down simply because it sweats.
It cools down mainly when that sweat evaporates.
A synthesis on human thermoregulation reminds us that sweat evaporation is an essential mechanism for heat loss, especially during exercise or heat exposure (PubMed).
This detail changes everything.
It turns a simple sentence into a conditional system.
Popular sentence: “Drinking hot makes you sweat, so it cools you down.”
Physiological version: “Drinking hot can increase sweating; this sweating can cool the body if it evaporates; this evaporation depends on humidity, ventilation, clothing, physical activity and the person’s condition.”
The popular version fits inside a taxi.
The scientific version needs a little more room.
That is often why the first one wins.
It is simpler.
It is easier to remember.
It is more comfortable.
It gives the impression of understanding.
What about cold water?
Studies on cold beverages add another interesting nuance.
A 2018 study by Barwood, Goodall and Bateman, published in European Journal of Applied Physiology, observed that cold drinks improved thermal comfort during exercise in hot, dry conditions. In other words, even when the overall physiological effect is more complex, perceived comfort matters too (PubMed).
Another review published in Sports Medicine indicates that cold water or ice slurry ingestion can improve endurance performance in the heat in certain sports contexts, while also noting that the effect depends on environmental conditions, because cold drinks can reduce sweating in some cases (Sports Medicine).
Again, context decides.
There is no magical beverage.
There is an interaction between your body, your environment, your activity, your clothing, your airflow, your humidity level, your hydration status and your personal vulnerability.
A heatwave is not a café debate. It is a systemic problem.
Public health: the teapot is not the emergency plan
Public health recommendations are more sober than folklore.
Santé publique France recommends, during a heatwave or period of high heat, drinking water regularly, wetting the body and using ventilation, eating enough, avoiding physical exertion and not drinking alcohol (Santé publique France).
Service-Public.fr also recommends avoiding beverages with a high caffeine content, such as coffee or tea, as well as very sugary drinks, and prioritizing water (Service-Public.fr).
This does not mean that a cup of lukewarm tea is a crime against thermoregulation.
It means that the central reflex remains regular hydration, shade, ventilation, rest, body cooling and vigilance toward vulnerable people.
And if we are talking about very hot drinks, another issue appears.
The International Agency for Research on Cancer, part of the World Health Organization, classified the consumption of very hot beverages above 65°C as probably carcinogenic to the esophagus. The risk concerns the temperature, not tea itself (IARC).
So between “drinking hot” and “drinking scalding hot,” there is a boundary.
A physiological boundary.
A health boundary.
And sometimes a common-sense boundary.
Beliefs love to travel light
What fascinates me in this story is the way a belief circulates.
It travels without its footnotes.
It travels without the humidity level.
It travels without the wind.
It travels without loose clothing.
It travels without the actual temperature of the beverage.
It travels without health limits.
It travels in a far more seductive form: “Bedouins do it, so it must be smart.”
The formula is perfect.
It is short.
It is exotic.
It feels ancient.
It gives the person repeating it a small sense of intellectual superiority.
It turns a cultural anecdote into a scientific argument.
In the taxi, my driver was not only defending a beverage.
He was defending his membership in the camp of those who know.
And I understand that mechanism very well, because we all fall into it.
I do.
You do.
Leaders do.
Experts do.
Consultants do.
Executive committees do.
Organizations have their own boiling teas
In companies, “boiling teas” are everywhere.
“In our company, innovation must go through a committee.”
“In our industry, customers are not ready.”
“Employees dislike change.”
“We already tried.”
“AI will automate everything.”
“Agile works at Spotify, so let’s copy Spotify.”
“Creativity appears when we put sticky notes on a wall.”
“Startups succeed because they take risks.”
Some of these sentences contain a fragment of truth.
That is what makes them dangerous.
A completely absurd sentence is easy to reject. A partially true sentence is much more resistant. It sticks to the skin like a damp shirt in the middle of a heatwave.
A leader’s role is not to destroy all beliefs.
A leader’s role is to examine the conditions under which a belief becomes useful, false, dangerous or simply unsuitable.
The right reflex: ask “under what conditions?”
Since that taxi exchange, I keep one simple question in mind.
Not “is it true?”
Rather: “under what conditions is it true?”
This formulation changes everything.
It does not ridicule the other person.
It does not close the conversation.
It opens the system.
Under what conditions can hot tea help?
Under what conditions does an innovation method work?
Under what conditions does a managerial ritual become effective?
Under what conditions can a startup practice work in a large group?
Under what conditions does an AI solution create value?
Under what conditions does a brilliant idea become a useful innovation?
This question is a gentle weapon against certainty.
It forces us to leave the slogan and return to reality.
My conclusion on hot tea
So, should you drink hot tea during a heatwave?
Useful answer: a hot beverage can promote sweating, but the benefit depends on the evaporation of that sweat. In a dry, ventilated environment, it may make sense. In a humid, closed, crowded or poorly ventilated environment, the benefit becomes much less obvious, and fresh or room-temperature water is often more pleasant and more pragmatic.
Avoid scalding beverages.
Drink water regularly.
Wet your body.
Use ventilation.
Reduce physical effort.
Avoid alcohol.
Check on vulnerable people.
And above all, be careful with sentences that begin with “everybody knows that.”
Because often, behind “everybody knows that,” there is a teapot, a belief, a fragment of badly transported science and a forgotten context left on the side of the road.
The next time an obvious truth enters your inner taxi with too much confidence, ask it one simple question:
Under what conditions?
That is sometimes the beginning of science.
It is often the beginning of innovation.
References
- (Acta Physiologica) = https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1748-1716.2012.02452.x
- (PubMed – Bain, Lesperance, Jay) = https://pubmed.ncbi.nlm.nih.gov/22574769/
- (Environmental Health Perspectives) = https://pmc.ncbi.nlm.nih.gov/articles/PMC10231239/
- (PubMed – Sweat evaporation in humans) = https://pubmed.ncbi.nlm.nih.gov/40719527/
- (PubMed – Barwood, Goodall, Bateman) = https://pubmed.ncbi.nlm.nih.gov/30203296/
- (Sports Medicine) = https://pmc.ncbi.nlm.nih.gov/articles/PMC5790850/
- (Santé publique France) = https://www.santepubliquefrance.fr/fortes-chaleurs-canicule/quelles-mesures-pour-prevenir-les-risques-lies-a-la-chaleur
- (Service-Public.fr) = https://www.service-public.gouv.fr/particuliers/actualites/A14978
- (IARC) = https://www.iarc.who.int/wp-content/uploads/2018/07/pr244_E.pdf
