Ah, congeners. What are congeners, you may ask? They are the impurities created from the fermentation process of alcohol production. A few of these impurities include acetone, acetaldehyde, and tannins – all of which are toxic at high doses. So, if you love your dark liquors and red wine, boy, do we have some bad news for you!

Or maybe, from personal experience, you already have a clue to their effect on hangovers.  Congeners are found in their greatest amount in these particular alcoholic beverages, so before imbibing on that whiskey or cabernet, be cautious! We've heard it too: "drink clear liquors to prevent a hangover." Y'all might be on to something... Or are you?

One study investigated the effects of heavy drinking between bourbon and vodka. Although equal blood alcohol concentrations were targeted, the study found that bourbon elicits significantly greater hangover severity than vodka. That is individuals felt far worse after drinking bourbon. This is due to the fact that vodka virtually contains no more congeners than pure ethanol, while bourbon contains the highest congener content – 37 times more than vodka! Shocking, we know. But this is not to say that vodka doesn’t cause hangovers; it does! Alcohol, no matter the type, is the strongest cause of hangovers (duh!).

Congeners and Hangovers: Takeaways

Not only does it make you feel worse, it can cause or make your alcohol flush even worse! If you're known to get cherry red when you drink, stay away from the dark liquors and wines and maybe, just maybe, you can help reduce or prevent asian flush.

References for Congeners

Rohsenow, D., Howland, J., Arnedt, J.T., Almeida, A.B., Greece, J., Minsky, S., Kemple, C.S., and Sales, S. (2010). Intoxication with Bourbon vs Vodka: effects on hangover, sleep, and next-day neurocognitive performance in young adults. Alcohol Clin Exp Res, 34(3), 509-518. doi:10.1111/j.1530-0277.2009.01116.x.

Rohsenow, D.J. and Howland, J. (2010). The role of beverage congeners in hangover and other residual effects of alcohol intoxication: a review. Current Drug Abuse Reviews, 3:37-79.