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The science of alcohol
The science of alcohol

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2 What is a hangover?

Ethanol can have both acute (short duration) and chronic (persisting for a long time or constantly recurring) effects on the body. You will look at the chronic effects in Week 7. The acute effects increase as more alcohol is consumed, and are short-lived. These effects arise through the immediate actions of ethanol on different parts of the body.

For example, ethanol has the effect of irritating the stomach and intestinal lining which can result in inflammation of these areas. Ethanol also increases the production of gastric acid and intestinal secretions, and the after-effects of these processes include abdominal pain, nausea and vomiting, all of which can be associated with hangovers. A hangover is the term used to describe the collection of signs and symptoms that someone usually experiences on the day following a heavy drinking session.

  • Can you list some typical signs and symptoms of a hangover?

  • The causes of a hangover are not well understood, but typical signs and symptoms are: headache, nausea, dry mouth and thirst, flushing on the skin, abdominal pain, diarrhoea, anorexia (lack of appetite), tremor (dizziness), fatigue and a poor sense of well-being.

Some of these are related to dehydration. An imbalance in electrolytes (your body’s salt levels) is generated which has knock-on effects causing nausea, dizziness, dry mouth, high levels of thirst and fatigue. Alterations in salt and water levels can lead to diarrhoea as the body adjusts to the environment.

Fatigue is also caused by a decrease in blood sugar levels. At its most severe, hypoglycaemia can lead to a coma state and death, similar to a diabetic situation. Sadly, while drinking a lot of water can help with these symptoms they will not fully stop the effects.

  • What was the product of the first enzymatic reaction for the breakdown of ethanol in the liver?

  • In the first enzymatic reaction in the liver, ethanol forms acetaldehyde.

Acetaldehyde is significantly toxic itself and, combined with the genetic factors you briefly read about earlier, its concentration can be elevated in the bloodstream for a significant amount of time. This causes the flushing of the skin (redness). It can also cause cellular stress by affecting a number of other receptors in cells.

Ethanol also has an effect on a group of chemicals in the body called cytokines. These play a highly important part in cell signalling (how cells talk to each other) and the immune system. Alcohol causes changes in their concentration with some of these compounds exhibiting higher levels. These have been implicated in nausea, headache and fatigue as the immune system is activated.

In addition to ethanol, a significant number of alcoholic beverages contain congeners. These are substances produced during the production process that contribute to the taste and smell of a drink. These are a mix of small organic compounds, some of which are harmless, but others such as methanol are highly toxic. Methanol (CH3OH) breaks down in a similar fashion to ethanol in the body but the products of this reaction are highly toxic (formaldehyde and formic acid). Congeners have been shown to mitigate or aggravate the hangover effect.

  • Which do you think has more congeners in? Whisky or vodka?

  • Whisky has significant amounts of congeners, which aid with the complex taste and smell that is associated with these drinks, whereas the clear vodka has hardly any, hence its ‘pure’ status among beverages.

Several scientific studies have explored the severity of hangovers with respect to the type of alcohol consumed. It is considered that dark drinks (such as whisky, dark rum, red wine, ale) will give a greater hangover than clear ones (vodka, gin, white wine, lager). One such study found an average of fourteen standard units of beer was needed to produce a hangover, but only seven to eight units was required for wine or liquor.