Asked by: Amanda Tully, London
Hangovers are caused by three main processes. Alcohol dehydrates you by causing your kidneys to remove more water from your bloodstream. This shrinks your brain slightly, pulling on the surrounding membrane and giving you a headache. Then there’s the alcohol itself. This is broken down by the liver through several intermediate stages. The chemical pyruvate is used as ‘fuel’ for one of these reactions and this diverts pyruvate from other reactions, one of which is to supply glucose to the brain. Finally, there are the impurities present in the drink. Known collectively as congeners, these include tannins and propanone and breaking these toxins down also places more stress on the liver.
Dark drinks, like red wine and bourbon, have more congeners than light ones and there are several studies to show that for a given level of blood alcohol, dark drinks produce worse hangovers. But outside of the laboratory, the worst hangover will come from whatever causes you to drink the most. For some people that’ll be tequila slammers, for others it might be fine brandy.