Hangovers: how your body is affected
A hangover is the unpleasant consequence of having overindulged or had ‘one too many’ alcoholic drinks. Symptoms usually appear several hours after stopping drinking when your blood alcohol content has dropped considerably and is near to zero. This is usually the morning after a big night out.
Hangover symptoms may include:
- nausea and vomiting;
- disturbed sleep and fatigue;
- anxiety and irritability;
- decreased concentration;
- tremor or shaking; and
Symptoms can last up to 24 hours.
Doctors believe that there are many things that contribute to these unpleasant symptoms, including dehydration and the way alcohol is processed (metabolised) in your body – that is the way your liver breaks down alcohol. Inflammation also seems to play a role.
Metabolism of alcohol
Your liver processes alcohol in two steps. Firstly, an enzyme in your liver cells — alcohol dehydrogenase (ADH) — converts alcohol to a toxic substance called acetaldehyde. Acetaldehyde is then converted to acetate (a non-toxic substance) by another enzyme, aldehyde dehydrogenase (ALDH).
Normally, acetaldehyde is quickly converted to acetate and excreted from your body. But when you have had a lot of alcohol to drink, your liver may not convert the acetaldehyde as quickly as usual, and it may build up enough to contribute to the nausea, vomiting and sweating of a hangover.
Direct effects of alcohol
Alcohol dilates the blood vessels in your brain, which can trigger a headache — one of the most common symptoms of a hangover. Dehydration also contributes to the throbbing type of headache that many people associate with hangovers.
While many people find that they fall asleep more easily after drinking alcohol, they often report sleeping less soundly. This is because your body is rebounding from the depressive effect of alcohol, disturbing your normal sleep rhythm, so you won’t get as much deep sleep.
3. Low blood sugar
Alcohol can prevent your body from maintaining its usual tight control on blood sugar levels, causing a low blood sugar concentration. Low blood sugar is one of the main causes of fatigue and weakness that people experience as part of a hangover.
Alcohol is a diuretic, meaning that it stimulates your body to increase urine production, depleting your body of fluid. This can cause dehydration if you have consumed a lot of alcohol. Symptoms of dehydration may include dry mouth, thirst, dizziness and headache.
5. Gastrointestinal effects
Alcohol can cause inflammation of your stomach lining (gastritis), leading to nausea, vomiting and stomach pain. It also stimulates your stomach to produce excess acid and delays movement of your stomach contents into the small bowel, further contributing to nausea and vomiting.
Some people also have diarrhoea because alcohol causes less water to be absorbed from the small bowel, meaning its contents are propelled along more quickly.
Alcohol and inflammation
Recent research has found that drinking too much can trigger your immune system to release chemicals called cytokines. Increased levels of cytokines have been found to affect memory and concentration, as well as causing symptoms of nausea, headache, chills and tiredness.
The release of cytokines is part of an inflammatory response – similar to when you have an infection. This response may be related to the microbes in your gut. Alcohol may increase the numbers of pro-inflammatory bacteria and stimulate the microbes to release toxins. Good bacteria in the gut may also be reduced, which can lead to ‘leaky gut’ – meaning that toxins can escape the gut and enter the bloodstream.
Some experts believe that at least some of the symptoms of a hangover, such as sweating, anxiety, tremors and increased heart rate, are due to the effects of withdrawing from alcohol. Your nervous system may need to re-adjust as your blood alcohol level returns to zero.
How to avoid a hangover
It’s no secret that the more alcohol you drink, the more likely it is that you’ll have a hangover. So limiting yourself to the recommended number of standard drinks is the best way of avoiding a hangover.
Other tips to decrease your risk of a hangover include the following.
- Don’t drink on an empty stomach. Make sure you have something to eat before you have a drink, and enjoy a meal or some snacks while you are drinking.
- Avoid drinking quickly. Try to avoid drinking in ‘rounds’ so that you can drink at your own pace. Have no more than one drink an hour, and drink water between drinks.
- Minimise drinking carbonated (bubbly or fizzy) alcoholic drinks, such as champagne. These tend to raise your blood alcohol level more quickly than other drinks.
- Steer clear of bourbon, whiskey, brandy and red wine, which all contain high concentrations of compounds called congeners, which tend to cause more severe hangovers. Congeners are found in most alcoholic drinks, but their concentration varies. Gin and vodka tend to contain fewer congeners than other alcoholic drinks. However, all types of alcohol can cause a hangover.
- Don’t smoke while drinking, as smoking makes hangovers worse.
What can make a hangover better?
In general you’ll just have to wait it out – there are no simple hangover cures. But there are some things that can help you feel better after overindulging. Keep your fluids up – regularly sipping water will ease symptoms of dehydration and should improve a headache. And having a snack can help settle your stomach and increase your blood sugar levels.
Also, it’s important to realise that if you are hungover, there is a chance that your blood alcohol concentration is still too high to be able to drive safely. It may also not be safe for you to work if you are over the limit. Even if your blood alcohol level has returned to normal, when your concentration is affected you should avoid driving, work and other tasks that could be dangerous if you are impaired.
Last Reviewed: 18/09/2018
1. National Health and Medical Research Council (NHMRC). https://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/ds10-alcohol.pdf Australian guidelines to reduce health risks from drinking alcohol, 2009. https://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/ds10-alcohol.pdf (accessed Sep 2018).
2. Mackus M, Adams S, Barzilay A, et al. Proceeding of the 8th Alcohol Hangover Research Group Meeting. Current drug abuse reviews. 2017;9(2):106-112. doi:10.2174/1874473709666161229121527.
3. Alcohol and Drug Foundation. Alcohol (updated 20 Aug 2018). https://adf.org.au/drug-facts/alcohol/ (accessed Sep 2018).