Hangovers and what the science says about beer

A hangover starts as the alcohol leaves

A hangover usually peaks when blood alcohol has fallen back to around zero, often the morning after. Headache, tiredness, thirst, nausea, poor concentration and a low mood are the familiar set. The odd part is that the alcohol itself is mostly gone by then. The hangover is the body dealing with what the alcohol did on the way through.

The size of the hangover tracks the amount of alcohol more than anything else. Four 500 ml glasses of 6% IPA put 120 ml of pure alcohol through your body, about 12 UK units. That is the main reason the morning feels the way it does.

Several things contribute

Researchers point to a mix of causes rather than one:

• Acetaldehyde. The liver breaks alcohol down into acetaldehyde, a toxic compound, before turning it into acetate. While it lingers it contributes to nausea and flushing.
• Inflammation. Heavy drinking appears to trigger an immune response, which may explain the aches and general unwell feeling.
• Poor sleep. Alcohol helps people fall asleep but disrupts sleep later in the night, cutting deeper, restful sleep.
• Fluid loss. Alcohol suppresses vasopressin, so you pass more urine. It contributes to thirst and headache but is not the whole explanation.
• Low blood sugar. Alcohol can interfere with how the body regulates blood sugar, adding to shakiness and fatigue.

Congeners and why some drinks feel worse

Congeners are the other compounds produced during fermentation and ageing: fusel alcohols, esters, aldehydes and others. Dark spirits like bourbon and brandy tend to contain more of them than clear spirits like vodka. Studies comparing the two have found worse hangovers with the high congener drinks at the same alcohol dose.

Beer has congeners too. Fusel alcohols are the most relevant. A well run fermentation keeps them low. A beer fermented too warm, often in a hot climate without proper temperature control, can carry far more. You can sometimes taste them as a hot, solvent-like note. Our guide to solvent and hot alcohol notes explains how to spot that fault. The amount of alcohol still matters far more than the congeners.

Myths that do not hold up

Some popular beliefs have little support:

• "Beer before wine and you'll feel fine." There is little evidence the order of drinks matters. Total alcohol does.
• "Hazy or unfiltered beer gives worse hangovers." Yeast and protein haze are not a known cause. Strength matters more. Our guide to hazy versus clear beer explains what haze actually is.
• "Hair of the dog cures it." Another drink only delays the hangover while adding more alcohol.
• "Coffee sobers you up." It may help you feel more alert. It does not change blood alcohol.

Time is the only proven remedy

No product reliably cures a hangover. Plenty claim to. Time is the only certain remedy. Water, rest and a light meal can make the hours more bearable but they do not speed up recovery in any proven way.

Be careful with painkillers. Paracetamol is processed by the liver, which has just worked through a lot of alcohol. If you are unsure what is safe for you, ask a pharmacist rather than guessing.

The same goes for the many hangover drinks, powders and pills sold in shops and online. Some contain vitamins or electrolytes that do no harm. None has strong evidence that it prevents or cures a hangover. Their marketing usually works by suggesting you can drink more without paying for it, which is the opposite of what helps.

Prevention is about the night before

The only reliable prevention is drinking less. A few habits help:

• Eat a proper meal before you start.
• Drink a glass of water with every beer. Our guide to water between beers explains why it slows your pace.
• Choose lower strength beers and smaller glasses.
• Stop an hour or two before bed so the alcohol does less damage to your sleep.

A night of three 330 ml session beers at 4.5% puts about 45 ml of alcohol through your body. A night of three 650 ml strong lagers at 8% puts 156 ml through. The mornings feel as different as those numbers suggest.

Count your next evening

Next time you go out, note each beer, its size and its ABV on your phone. Add up the millilitres of alcohol the next morning and compare it with how you feel. After two or three nights you will know your own limit far better than any rule of thumb.

Common questions

What causes a hangover?

A mix of factors: acetaldehyde from breaking down alcohol, inflammation, disrupted sleep, fluid loss and low blood sugar. The amount of alcohol drunk matters most.

Do some beers give worse hangovers?

Stronger beers do, simply because they carry more alcohol. Badly fermented beers with high fusel alcohols may add to it.

Does the order of drinks matter for a hangover?

There is little evidence that it does. Total alcohol is what counts.

Is there a cure for a hangover?

No proven cure exists. Time is the only certain remedy. Drinking less is the only reliable prevention.