Hangovers are caused by drinking too much alcohol, although exactly what constitutes “too much” varies from person to person. The symptoms for a hangover typically start once the blood alcohol level drops significantly and has reached, or is close to, zero.
According to a study, the headache which comes with the condition - one of the most common types of headache - is caused by acetate. This conclusion is supported by the observation that acetate provided during kidney dialysis also causes similar head pain. The claim challenges the common belief that dehydration, impurities and congeners alone are the cause of a hangover headache.
The research – which was conducted on rats – found that the animals exhibited signs of a headache within 4 to 6 hours of being given alcohol. In the case of rats, this included the area around the eye becoming sensitive to touch.
Next, acetate alone was given, and was also found to cause typical hangover symptoms. However, an enzyme to inhibit the buildup of acetaldehyde added later on had little effect, pointing towards acetate as being the cause of the hangover.
This provided insight into the mechanism of hangovers and challenged the common notion that acetaldehyde – formed in the liver after the alcohol is metabolized – is to blame for the condition. The researchers suggested acetate instead to be culpable, contesting further that acetate increases to much higher levels in the circulation, even in the case of moderate drinking, compared to acetaldehyde levels.
The common claim that coffee should be avoided during a hangover due to its dehydrating effect was also put to the test. It was found that a mixture of caffeine and anti-inflammatory drugs actually gave the best results in the experiment when it came to providing relief from hangover symptoms. This led to the suggestion that caffeine and painkillers might in fact be the best cure for the condition.
The research, however, could not completely exclude the role of acetaldehyde. Acetaldehyde might still play a role in causing hangover symptoms in humans, but the study was able to fully demonstrate that acetate also contributes to that role, particularly in the case of a headache.
Since the study has come out, there has been some criticism against the methodology used by it to implicate acetate in causing hangovers. Particularly, the usage of rats for the research has scrutinized. Dan Levy at Harvard University noted that he would be wary of calling the rat’s headache a hangover. He went on to add, however, that he still felt that the study was an important step towards understanding alcohol-triggered headache.