“Alcohol is a ‘dirty drug’,” says Emily Palmer, a researcher at Imperial College London, who studies hangovers. “It impacts multiple systems in the brain.”

Scientists are not exactly sure what is going on in our bodies during a hangover, but they do know it is caused by a variety of biochemical and neurochemical changes. “It doesn’t just affect the liver or the brain,” says Palmer, “it affects almost every organ.”

This Christmas, many of us will be celebrating with a drink or two or three. So is it possible to get through the morning after the night before unscathed?

The slippery slope

“You have your first drink and a neurotransmitter called gamma-aminobutyric acid – or Gaba – is released in the brain,” says Rayyan Zafar, a neuropsychopharmacologist at Imperial College London and researcher for the charity Drug Science.

“Gaba slows the brain,” he continues. “It works on receptors in the cortex, specifically parts involved in the thinking processes and control.”

Gaba reduces a nerve cell’s ability to send and receive chemical messages throughout the central nervous system. So, for the first one to three drinks, as Gaba is released you feel relaxed, says Zafar.

At the same time, you get a rush of dopamine. “You feel good, you feel relaxed, and you want more,” says Zafar. But as you continue to drink the alcohol binds to glutamate receptors in the brain – which are important for memory formation. Their electrical activity is suppressed, “essentially blocking the formation of memories,” says Zafar.

The alcohol moves from your cortex, which controls behaviour, to the cerebellum, which is in charge of movement, motor coordination and balance.

Next, alcohol intoxication hits the medulla, right in the middle of the brain. It controls autonomic systems including heartbeat, breathing and blood pressure. “The brain just shuts down,” says Zafar. “That’s why people call alcohol a depressant; not because it makes you feel depressed, but because it depresses the whole central nervous system.”

Can I get drunk on non-alcoholic beer?

“Probably not,” reassures Zafar. “Say the average pint of beer is 5% alcohol, you’d need to have 10 0.5% low-alcoholic beers to have the same effect as a pint. I don’t think your body would be able to hold on to that much liquid.”

The aftermath

The liver eliminates around one unit of alcohol an hour, then the hangover kicks in. Vomiting, explains Zafar, is an evolutionary survival tactic that has developed as a way of ejecting harmful substances from the body. Perhaps a small comfort when your head is hanging over the toilet bowl.

Alcohol is metabolised by the enzyme alcohol dehydrogenase (ADH). As ADH breaks down the ethanol, it forms acetaldehyde, a poison and carcinogen. When blood alcohol content reaches zero, hangover symptoms are usually at their worst, as at that point all of the alcohol has been converted to acetaldehyde, which changes the way DNA functions,” says Zafar.

Alcohol damages mitochondrial DNA. Mitochondria are the energy-producing machines in our cells, and even slight damage can lead to toxicity in the brain.

“If you regularly drink enough to cause a hangover, we think that damage may build up,” says Palmer, “resulting in cognitive decline and early memory loss.”

Alcohol also suppresses the release of vasopressin, a hormone that tells the kidneys to retain fluid, so urination increases. The resulting dehydration can leave you feeling thirsty, tired and headachy.

“We think hydration is super-important,” adds Zafar. “And by hydration, we don’t just mean water. We also mean sodium, chloride and potassium.”

When your body is damaged, your immune system is activated. It sends out inflammatory cells which attack bacteria or heal damaged tissue.

“When you drink alcohol, the gut signals that it has a poison inside it,” says Zafar. “In response, your immune system ramps up to try and reverse the toxicity. This can lead to too much inflammation.”

The body has turned on itself. The inflammatory response can cause nausea, vomiting, headache, confusion, mood changes, cognitive impairment, and learning and memory deficits. Regularly drinking to excess can also lead to chronic inflammation, which is linked to diabetes, cancer and heart disease.

Do hangovers get worse with age?

Metabolism is a word we might associate with digestion of food, but the term actually describes all the chemical processes that take place in the body. “As you get older, your metabolism slows, so it takes longer to recover,” says Zafar.

Palmer suggests it may also be down to reduced tolerance due to less heavy drinking as we age, and changing our drink preferences. “When we’re younger, we might drink something like vodka tonics,” he says. “Later, we might drink wine or whisky.”

Congeners, found in darker drinks, are a byproduct of the fermentation process. They are complex organic molecules with toxic effects including acetone, acetaldehyde, fusel oil, tannins and furfural. Whisky has been found to have 37 times the amount of congeners as vodka, and studies show that drinks with more congeners causes a worse hangover.

How can I prevent a hangover?

Drink less, obviously. If you do want to have a few drinks, however, there are some tactics that can help you avoid the hangover.

Pace yourself
Dilute alcohol by adding ice, soda, lemonade or other mixers. You’ll consume alcohol more slowly so your body will have a greater chance to process alcohol and your blood alcohol peak won’t be as high.

Choose your drinks
Avoid dark-coloured drinks such as red wine or whisky as they contain more congeners than clear drinks such as vodka or gin.

Eat eggs
Eggs, says Zafar, contain the amino acid cysteine, which slows the metabolism of alcohol.

Can I cure my hangover?

Unfortunately not. According to researchers from King’s College London there is no convincing evidence that any so-called hangover cures work.

Their recent review assessed clove extract, red ginseng, Korean pear juice and other supposed hangover cures, and concluded that there isn’t enough high-quality evidence for any of them.

However, ibuprofen can help reduce inflammation, and rehydrating with isotonic drinks, such as sports drinks, can help replace lost fluid and ions and may give you some relief.

Are some people immune to hangovers?

Some people are able to rapidly make alcohol dehydrogenase to break down alcohol, and some people can’t do it quite so quickly. It all depends on your genes.

“Those who are able to rapidly regulate this enzyme and break down alcohol … probably don’t have hangovers,” says Zafar. “But they are more likely to develop alcohol addiction, because they can drink more without the negative effects.”

Restraint might be easier knowing the discomfort that follows. “We want to try to prevent the damage we’re causing to our bodies,” says Palmer, “rather than sticking plaster on it.”