Cooler Than You Actually Are

Why Some Drinks Work in Summer and Others Do Not

Thirty-four degrees, midday, a lounge chair, a glass beaded with condensation. What follows is the paragraph you've read a hundred times: alcohol suppresses antidiuretic hormone, the body loses fluid, dehydration, heat stroke. Drink water. All of it is true.

In September 2024, the journal Environmental Health published a systematic review consolidating every controlled study in which people were given alcohol in heat above twenty-eight degrees and compared against a placebo of equal volume. Out of more than seven thousand papers, very few made it through the screening - the subject turned out to be studied far less thoroughly than you'd expect.

The results contradict the conventional picture.

Sweating under the influence of alcohol barely changed. Neither did hydration markers, in most of the studies. Body temperature - and this is the most unexpected part - didn't rise but fell: alcohol dilates the blood vessels in the skin, and the body genuinely sheds heat more efficiently.

Physiologically, a moderate dose of alcohol in the heat doesn't do what we assume it does.

But the review documented two other things.

First: heart rate went up, and blood pressure went down.

Second, and most importantly: the perception of temperature changed. People felt cooler than they actually were.

This is where the real danger lies. It isn't in the kidneys. It's in the sensor.

Why a Broken Sensor Is Worse Than Dehydration

The body defends itself against overheating not just through physiology, but through behaviour.

Discomfort is an interface. It gets hot, unpleasant, difficult - you move into the shade, take off your cap, get into the water, pour a glass of water, sit down. It's this chain of responses that saves people in the heat far more often than any physiological mechanism does. Overheating almost always warns you in advance.

Alcohol mutes the warning.

You sit in the sun longer than you should have. You think about water less often. You don't notice that you haven't sweated in forty minutes - which is one of the early signs that things are going wrong. You agree to a volleyball game at two in the afternoon. You decide you can drive home yourself.

Layer onto that an elevated heart rate and lowered blood pressure - exactly what heat is already doing to the cardiovascular system without any alcohol involved - and you get the actual mechanism by which people end up in hospital on hot weekends. Not through gradual dehydration. Through a sharp drop in blood pressure on standing, through dizziness, through a decision made by the wrong person.

One caveat, without which the picture is incomplete. All of this laboratory data concerns moderate single doses in healthy adults under controlled conditions. Mortality statistics during extreme heat events describe a different scenario: a lot of alcohol, many hours, often alone, often in an apartment without air conditioning. There, dehydration and everything else are very much in play.

The Rule That Explains All the Others

Now the main point. If you take one thing away from this piece, let it be this one.

There are no "dehydrating" and "refreshing" alcoholic drinks.

There is a ratio of alcohol to liquid.

The diuretic effect depends on the amount of ethanol. The compensating effect depends on the amount of water that came with it. The outcome is determined by which one outweighs the other.

Do the math yourself.

A double whisky is roughly 60 ml of liquid and about 19 grams of pure alcohol. Almost no water, a lot of alcohol. The balance is sharply negative.

Half a litre of 5% beer is 500 ml of liquid and roughly those same 19 grams of alcohol. The same alcohol, but in ten times the volume of water.

This is exactly what a study by Ronald Maughan and colleagues, published in 2016 in the American Journal of Clinical Nutrition, demonstrated. Seventy-two volunteers each drank a litre of one of thirteen beverages, after which urine output was measured over several hours. From this, a "beverage hydration index" was built - how much fluid actually stayed in the body compared to plain water.

The leaders were rehydration solutions and milk, both full-fat and skim - they were retained better than water.

And 4% lager was statistically indistinguishable from water.

Not "almost indistinguishable" - indistinguishable. Same as coffee, tea, soda, orange juice, and sports drinks.

This doesn't mean beer is a source of hydration and can be drunk instead of water. It means the common phrase "beer dehydrates you" describes alcohol, not beer, and that in a given beer there simply isn't much alcohol per unit of volume. That same litre, but of whisky, is an entirely different story.

Everything else follows from this rule, including the answer to the question of what to drink in summer.

Spirits: The Question Isn't "What" but "How"

Whisky, vodka, gin, rum, tequila, cognac - taken neat, this is the worst ratio in existence. Maximum alcohol, minimum water, rapid absorption, and a vascular response layered on top of the one heat has already triggered.

But spirits turn into their own opposite with a single motion of the hand.

A highball is that same whisky, but in a tall glass, filled to the brim with ice and soda. The alcohol-to-liquid ratio changes several times over. Ice adds still more water as it melts and physically cools the drink. Drinking it quickly is impossible - there's simply too much of it.

In Japan, where summer combines thirty-five degrees with humidity approaching ninety percent, the highball isn't a cocktail but a foundational summer category. That's no accident, but a rational solution a culture arrived at empirically.

What it works for: a long hot day, a terrace, a conversation lasting several hours. Gin and tonic, vodka soda with lime, and a tequila paloma with grapefruit soda all work on the same principle.

What it doesn't work for: a shot on the beach at two in the afternoon. Whisky by the pool. Anything where spirits are drunk undiluted and in the sun.

Beer: Rehabilitated, with Two Caveats

By alcohol-to-liquid ratio, beer is one of the more sensible summer options, and the data supports that.

The first caveat is volume. Beer isn't drunk by the glass but by the litre. Three pints of a strong IPA (7%) contain more alcohol than four servings of whisky. A "light" drink stops being light by the third bottle.

The second caveat is almost never discussed, and it's more serious than the first.

When a person sweats for several hours in the heat, they lose not just water but sodium. And if they're simultaneously pouring large volumes of fluid into themselves that contains almost no sodium - and beer contains practically none - blood sodium concentration falls.

This condition is called hyponatremia, and its symptoms are deceptively similar to those of dehydration and ordinary intoxication: headache, nausea, weakness, confusion, and in severe cases, seizures. Medicine even has a specific term for the extreme form of this scenario in people who live primarily on beer.

The practical conclusion is simple, and it's also the single genuinely important piece of advice in this entire piece: if you're sweating heavily, you need to replace not just water but salt. Olives, salted nuts, a proper meal, mineral water with high mineral content, an electrolyte mix. This is precisely why Mediterranean culture serves something salty with an aperitif - that isn't table decoration, it's physiology.

What it works for: a long day outdoors, a barbecue, the beach - provided moderate strengths (4-5%) and food alongside.

What it doesn't work for: high-alcohol craft varieties in the sun. Beer as a substitute for water during physical exertion.

Sparkling Wine: The Effect Is Real, but More Modest Than the Legend

The idea that champagne gets you drunk faster has a basis in reality - just a weaker one than commonly assumed.

The first study appeared in 2003 in Alcohol and Alcoholism: twelve participants were given identical amounts of alcohol as champagne, and as the same champagne with the carbonation removed. The group with bubbles showed higher blood alcohol concentration and noticeably worse results on a divided-attention test.

The experiment was later repeated more rigorously in Manchester: twenty-one participants, vodka with still and with carbonated water. Initial absorption rate with carbonation rose by roughly half on average.

But "on average" is the key phrase here. In three of the twenty-one participants, the carbonated version was absorbed more slowly. In another four, there was no difference at all. And in the first study, the difference between groups disappeared after roughly half an hour.

The mechanism is thought to work like this: carbon dioxide accelerates gastric emptying, and the bulk of alcohol absorption happens in the small intestine, where the surface area is orders of magnitude greater.

The honest conclusion: the effect is real, small, highly individual, and confined to the first twenty to thirty minutes. In the heat, this matters for exactly one reason - those first twenty minutes are ones you're most likely spending standing in the sun with a glass in your hand, and that's precisely when you decide whether to pour a second.

What it works for: an aperitif in the shade, small pours, the start of an evening. A well-chilled dry sparkling wine is one of the best summer aperitifs there is.

What it doesn't work for: on an empty stomach in open sun. Especially at weddings and daytime events, where your glass gets topped up unnoticed and you lose count.

White and Rosé: The Correct Answer to "Wine in Summer"

Here, everything lines up.

Dry whites and dry rosés are typically lower in alcohol than reds - often 11-12.5% versus 13.5-15%. They're served chilled to 8-12 degrees, meaning the drink physically absorbs heat. Their acidity delivers the very sensation of refreshment we're actually reaching for in the heat.

And they're also traditionally drunk with food, and more slowly than cocktails.

One category deserves separate mention, one North America barely understands: dry sherry. Fino and manzanilla run 15% alcohol, but are served ice-cold, in small glasses, with olives, almonds, and jamón. Andalusia has been drinking them at forty degrees for several centuries running. That isn't a paradox but a precisely calibrated system: a small pour, a low temperature, and a salty snack compensating for sodium loss.

What it works for: lunch, dinner, the second half of the day, any situation involving food.

What it doesn't work for: nothing, except the case where the bottle sits in the sun and by the third glass the wine is warm - at which point the entire reason it was a good choice disappears.

Red Wine: And, Incidentally, What We Got Wrong for Twenty Years

Red is harder to tolerate in the heat. There are two reasons, and the second is more interesting than the first.

The first is serving temperature. Red is served at 16-18 degrees, and on a terrace at thirty-five, it reaches air temperature within ten minutes. Not the slightest cooling effect.

The second is the headache some people get from one or two glasses of red, even though they tolerate other alcohol without trouble.

Tannins and sulfites have traditionally been assigned the blame. Both explanations appear to be wrong - white wine generally contains even more sulfites.

In November 2023, Scientific Reports published work from researchers at the University of California, Davis and San Francisco proposing a different mechanism. It concerns quercetin - a flavonol present in noticeably higher amounts in red wine than in white, beer, or spirits, because it's found in grape skins, and in red wine production the skins stay in contact with the must for longer.

Once in the bloodstream, quercetin converts into a metabolite that inhibits the enzyme ALDH2. And that enzyme is precisely what breaks down acetaldehyde - the toxic intermediate product of alcohol metabolism. Acetaldehyde accumulates, and the person experiences exactly what people with a genetically weakened ALDH2 variant experience: facial flushing, tachycardia, nausea, and headache. Roughly 40% of the East Asian population has a less effective version of this enzyme for genetic reasons - hence the "Asian flush."

The hypothesis hasn't yet been tested in human clinical trials, and the authors say so explicitly. But it's the first explanation that offers a mechanism rather than simply naming a suspect.

In the heat, all of this works against you: dehydration intensifies headaches as it is.

What it works for: an evening after sunset, a cool room, food. Light reds - Gamay, Pinot Noir, Schiava, Frappato - can be served lightly chilled, and in summer that's the right call.

What it doesn't work for: daytime heat in any form.

Sweet Cocktails: The Problem Isn't the Sugar

Piña colada, frozen margarita, daiquiri, pitcher sangria, "fruity" poolside cocktails.

They're usually criticized for their sugar. The sugar is genuinely there - some servings contain as much as a couple of cans of soda. But the real problem is something else.

In a sweet, cold cocktail, you can't taste the alcohol.

A frozen margarita the size of a vase contains two or three standard servings of tequila, and tastes like lemonade. It goes down fast because it's cold and sweet, and in the heat you're thirsty. The drinker doesn't track the quantity, because the taste signal they normally rely on to do that simply isn't there.

Add in the non-alcoholic versions sitting next to them on the same table, plus caffeinated cocktails, and you get a situation where intoxication arrives without warning.

What it works for: one, slowly, with food, in the evening. As a dessert - because that's essentially what it is.

What it doesn't work for: three in a row in the sun. Anything served in a vessel larger than a glass.

Spritzes and the Low-Alcohol Category: Where All of This Leads

If you take the ratio rule and follow it to its logical conclusion, you arrive at exactly what southern Europe drinks in summer without any science at all.

An Aperol spritz: bitter, prosecco, soda, ice, orange - final strength around 8%, in a tall glass, over ice. Vermouth with soda and ice is lower still. Shandy (beer with lemonade), beer with grapefruit juice, wine diluted with water and ice, which nobody in France or Spain finds remotely embarrassing.

This isn't a compromise or a "light version." It's a construction engineered for heat: lots of liquid, little alcohol, low temperature, bitterness and acidity instead of sugar, and food alongside as a requirement.

The non-alcoholic category deserves its own mention. Over the past several years it has stopped being dreary: decent non-alcoholic aperitifs, vermouths, beers, and sparkling wines are now available in any major North American store. Alternating is the simplest strategy that actually works, and it doesn't require giving up anything.

Medications: A Section That Applies to More People Than You'd Think

This is the part summer articles usually skip, and it matters more than everything listed above.

A whole range of medications independently impairs heat tolerance - through diuretic action, reduced sweating, or effects on thermoregulation or blood pressure. Alcohol adds to every one of these mechanisms.

Diuretics cause direct loss of fluid and electrolytes; combined with ACE inhibitors or ARBs, the risk in heat rises especially noticeably. Beta blockers affect vascular response and the ability to shed heat. SSRI antidepressants can increase sweating; tricyclics, conversely, suppress it. Antihistamines and other medications with anticholinergic effects - including ordinary allergy remedies - reduce sweating. Antipsychotics affect central thermoregulation.

If you take any of the above, the question of "how much can I drink in the heat" has a different answer than it does for the person in the next lounge chair, and it's a question for a doctor or pharmacist, not the internet.

A separate risk group: older adults, whose sense of thirst is diminished, along with people with cardiovascular disease and diabetes.

The Practical Version, Briefly

Not on an empty stomach. Food slows absorption, and salty food simultaneously handles the sodium question.

Not during peak hours. Between eleven and four, the sun does all the work for you.

A glass of water between drinks. Not because it neutralizes the alcohol - it doesn't - but because you physically won't be able to drink more than you planned, and because water restores that broken sensor.

Salt, not just water, if you're sweating for hours on end.

Shade, a hat, and no physical activity afterward - that isn't about alcohol, that's simply about heat, but alcohol makes breaking these rules more likely.

And the signs at which the conversation about drinks ends: dizziness, nausea, confusion, headache, sweating stopping while the heat continues, skin temperature above normal with dry skin. This isn't "had too much." This is possible heat exhaustion, and the person needs to be moved into the cool immediately, cooled down, and, if their condition worsens, given emergency help.

The most inconvenient thing about this subject is that the physiology turned out to be more forgiving than we were warned, and the behaviour more dangerous than we thought.

A glass of cold rosé on a shaded terrace, with olives and a glass of water alongside, isn't a crime against your health and never was.

But the sensation that you're not hot at all, when you actually are, is something worth taking seriously.

The body usually tells you when it's time to move into the shade. We just sometimes turn the sound off ourselves.