The science of hangovers: everything you need to know

Hangovers explained: Everything you need to know

What is a hangover?

Sure, we all know a hangover is what you get after drinking too much alcohol, but in terms of scientific definitions, Sarah says “it’s complicated” doesn’t even begin to explain it.

“By definition, the hangover state occurs [after drinking to excess] when your body doesn’t have alcohol in it,” she says. “That means the hangover will begin when your blood alcohol concentration (BAC) returns to zero.”

Depending on how much alcohol you’ve had to drink, that could happen six hours later or 12, with the symptoms starting when your BAC is approaching zero.

The general malaise and unpleasantness of a hangover can generally be attributed to a combination of three things: dehydration, toxic byproducts of alcohol metabolism and toxic compounds (congenas) found within certain alcoholic beverages. But the effects and symptoms of a hangover are different from those of residual alcohol, which may be present the morning after when BAC is still above zero.

Why do we get hangovers?

Though the science of hangovers is still cloudy at best, Sarah says when it comes to why we feel sick after drinking, the answer is simple. Ethanol.

“Alcohol is metabolised in the liver by an enzyme called alcohol dehydrogenase, which converts ethanol [alcohol] into acetaldehyde,” she says. “Acetaldehyde is a toxic substance, so your body tries to get rid of it as quickly as possible. To do this, it uses aldehyde dehydrogenase to convert toxic acetaldehyde into acetate. It’s this process that is capable of metabolising roughly one standard drink per hour.”

If someone is to drink more than that, Sarah explains, that’s when you see BAC rise and, as BAC rises, your body becomes less efficient at removing the acetaldehyde. (More: What is a standard drink?)

“It is hypothesised that, as the acetaldehyde builds up in the body, this is what results in the hangover – leading to headaches, dehydration and nausea.”

In simple terms, Sarah says, you’re basically poisoning yourself.

Does sleep help to reduce a hangover?

While sleep itself isn’t a hangover cure, Sarah says getting more of it can change subjective feelings of hangover.

“One of the factors that can contribute to the feeling of being hung over is a lack of sleep,” she says. "This is because if you drink excessively it can change your sleeping patterns. Alcohol can interfere with your sleep stages, which means people will often fall into a deep sleep really quickly, but then they’ll wake up during the night and find it difficult to get back to sleep. Given fatigue is a big component of feeling hung over, getting fewer hours of good sleep can increase or exacerbate the hangover state.”

Why are hangovers worse as you get older?

If you’re reading this while you sit on the couch, you might want to put down the chocolate bar or bowl of ice-cream. Scientists believe one of the reasons hangovers feel more severe as you get older is because people’s body composition changes as they age, which is a polite way of saying that as our waistlines increase, so too does the severity of our hangovers.

“People often start getting a higher proportion of body fat as they age,” Sarah says. “Fatty tissue has a lower water content than muscle and, given alcohol is water-soluble, the higher body fat a person has, the less alcohol can be absorbed.”

This leads to a quicker increase in BAC and therefore intoxication, ergo, could explain why people suffer from more extreme hangovers as they get older.

“There are a couple of studies looking at the [physiological markers] of hangovers, but they don’t show any convincing differences between hangovers at 18 or 48,” Sarah says. “But anecdotally, people experience a worse hangover as they get older."

Other reasons for this might be that people’s drinking behaviours change as they get older, they have different responsibilities or other lifestyle factors as they age – such as increased stress or children waking them up early in the morning (no sleep ins here) – which make the hangover feel worse.

Is there such as think as a hangover cure?

When it comes to hangover cures, Sarah says the promises of repercussion-free boozing are just empty marketing hype.

Most of the over-the-counter hangover helpers focus on treating different physiological aspects of a hangover. She says some of the common areas to focus on are alcohol metabolism and vitamin replacement.

“There are so many supposed hangover cures available,” she says. “The idea is that if you can improve the metabolism of alcohol, the hangover will be less severe, or that by replacing lost vitamins, you will feel better. But, at the moment, we don’t have any empirical evidence that they work. The only thing that is proven to reduce your hangover is drinking less alcohol.”

Why do some people throw up?

There are two kinds of people in this world. Those who spew after drinking too much alcohol, and those who don’t. “Some people are spewers and some aren’t,” Sarah says. “Alcohol is toxic and it can affect the lining of the stomach so, during intoxication, if you have a more sensitive stomach, you might be more likely to be sick.”

Why are some hangovers worse than others?

While scientists have long believed that drinking alcohol impacts the immune system, Dr Benson says we still have limited understanding about how. What we do know is that there is a correlation between cytokines (biomarkers of immune function) in the blood and alcohol consumption. One study found that people with hangovers have elevated cytokines, which has been associated with nausea, headaches, fatigue and even disrupted memory formation.

“There has been a lot of research done on this and researchers aren’t able to find exactly what it is that alcohol does to the immune system,” she says, “They aren’t able to replicate findings. One study will find one thing and, when they try to replicate it, the findings will be different. I suspect this is because there is a lot of individual variation in the presence and severity of hangover symptoms – not only between people but also within people. Everything from how much sleep you’ve had and what you’ve eaten on any given day to what you drank and how quickly, can scientifically assess hangovers.”

Are there ingredients in alcohol that can exacerbate hangover symptoms?

Though we don’t know exactly why some hangovers are worse than others, what we do know is that drinking certain types of alcohol can lead to more severe hangover symptoms because of the toxic impurities found within them. 

Congenas

Congenas are compounds that are produced during fermentation and have been shown to increase the frequency and severity of hangovers. Most alcoholic drinks contain varying levels of congeners, with darker alcohols (rum, red wine, whisky) containing the highest levels. 

Bubbles

There’s a reason they say champagne hangovers are the worst: bubbles. “Carbonated drinks may be absorbed quicker in the stomach,” Dr Benson explains. “This leads to a higher overall BAC and, therefore, a worse hangover.”

What should you drink to avoid a hangover?

While drinking anything to excess is likely to result in a hangover, choosing white spirits or still wines with a lower ABV may help to lessen the alcoholic blow to the system.

If you do wake up with a hangover, is there anything you can take to help you feel better?

Over-the-counter products won't necessarily cure a hangover, but they may help to alleviate some of the symptoms.

NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen and naproxen, have been shown to provide effective relief from headaches and muscle aches. "Anti-inflammatories are the most effective over-the counter medications to treat hangover symptoms because they can reduce inflammation, headache and body pain," Sarah says. "However, they should be used with caution as they may irritate the stomach lining and should be taken with food."

Vitamins

There's a reason people reach for the Berocca or hydralytes when they wake up feeling a little seedy. Drinking excessive alcohol can leave you dehydrated, which means your body is also lacking in water-soluble vitamins. The theory is that taking a vitamin or hydration supplement can help to replace these lost fluids. But whether or not this actually helps with your hangover symptoms is still unclear. 

Hangover cure myths 

Caffeine  

While many people swear by their post-binge caffeine hit, there is no evidence to suggest drinking coffee will help your hangover symptoms. In fact, it may even make things worse. Caffeine narrows your blood vessels and boosts blood pressure, both of which could serve to make that pounding headache seem more severe. Add to that the fact that caffeine can often have a mild diuretic effect on the body, which could further exacerbate hangover dehydration. 

Hair of the dog 

A Bloody Mary with brunch might seem like a good idea at the time but Sarah says having another drink is one of the worst things you can do if you're hungover. "It might slightly take the edge off your symptoms," she says. "But all you're really doing is adding to the toxic load."

Greasy food

The midnight Maccas run or next-day Drive-Thru dash might be a rite of drinking passage but Sarah says there is no evidence to suggest greasy food is a hangover helper. She recommends sticking to easy-to-digest foods such as toast and making sure you stay hydrated.

Australian Drinking Guidelines

The Australian Guidelines recommend healthy adults should drink no more than two standard drinks on any day to cut the lifetime risk of harm from alcohol-related disease or injury. They also recommend consuming a maximum of four standard drinks on a single occasion to reduce the risk of alcohol-related injury. Visit health.gov.au for more information.