The Consensus: Darker Alcohol Is More Likely to Cause Worse Hangovers

The dreaded hangover. Headache, nausea, dizziness, tiredness, thirst and most of all: regret for the drinking sins of the night before. Many of these symptoms are directly attributed to alcohol. Alcohol is a diuretic (promotes urination) which helps explain the dehydration. Then there is the tiredness from alcohol causing poor sleep. Alcohol is also a stomach irritant so there is the queasy feeling. Effects on blood sugar and dilation of blood vessels help explain moodiness and headaches.

Apart from not drinking, is there any way to reduce the nasty effects of overindulgence? One theory is that darker coloured alcoholic drinks can lead to worse hangovers. And it is substances in these drinks called congeners that could be to blame. Congeners are a by-product of fermentation and distillation during the alcohol production process.

All distilled spirits start off clear or light. When it is aged in barrels or through similar processes, it ferments and takes on a darker appearance. Spirits can also absorb some of the substances that are present in the container such as oak barrels. These organic compounds then end up in the liquor. Congeners are found in larger amounts in dark liquors, such as brandy, rum, whiskey, darker beer and red wine.

It’s all about the congeners

Congeners are complex organic molecules made up of toxic chemicals including acetone, acetaldehyde, fusel oil, tannins and furfural. Bourbon, for instance, has 37-times the amount of congeners compared to vodka.

“There has been a substantial amount of research to support the idea that drinking alcohol high in congeners, which tend to be higher in darker alcohol, increases the likelihood and severity of hangover symptoms experienced the next day” writes alcohol expert Dr Kelly Courtney from University of California, San Diego.

As Dr Richard Stephens from Keele University wrote, darker drinks tend to cause worse hangovers because of their higher concentration of congeners. Dr Stephens references a Brown University controlled study  that tested the darker spirits theory. Over two nights, 95 healthy volunteers drank bourbon or vodka on one evening. On the other evening, they drank placebo beverages consisting of chilled caffeine-free cola mixed with de-carbonated tonic water with a few drops of vodka or bourbon floated on top. The amount of alcohol they had was 1.2 grams per kilogram of body weight, which is equivalent to 6 bottles of beer for a person weighing 70 kg. The next morning participants completed a hangover symptom questionnaire. Not surprisingly, hangover symptoms were greater after drinking alcohol compared with the placebo drinks. But crucially, they people reported higher hangover symptom scores after the congener-rich bourbon compared with the vodka.

Jacob Peter Harmann from the University of Copenhagen also agreed with this and noted that the higher amount of methanol in darker alcohols might be the culprit in upping the severity of a hangover. Methanol can be metabolised into formaldehyde and formic acid which are both very toxic to the body. “Additional research suggests that at least some of the commonly experienced hangover symptoms may be attributed to other mechanisms such as the effects of alcohol itself or alcohol metabolites. [Congeners] are definitely not the whole story” writes alcohol expert Dr Kelly Courtney from University of California, San Diego.

Although it is likely drinking darker alcoholic drinks will increase your chances of having a more severe hangover the next day, it is not the whole story. Even light-coloured alcoholic drinks, thanks to their alcohol content, can put you in a severe state of hangover when binge drinking.