How Do Congeners in Alcohol Affect Hangovers?
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It’s a morning-after mystery: you go out and have a few drinks, nothing too crazy or out of the ordinary, but then, out of nowhere, you wake up the next day with a killer hangover. If you’re wondering what’s up (and how to avoid this unpleasant surprise in the future), there are several suspects you need to know about — congeners.
You may have heard of them, but what are congeners exactly? Well, for one thing, these sneaky compounds might be the secret culprits behind our hangover woes. Which types of alcoholic drinks have them, and how did they get there in the first place? And if we’re sensitive to congeners, what’s the best alcohol for no hangover effects? Or, if “no hangover” isn’t an option, what’s the alcohol with the least hangover-inducing properties? Let’s find out!
Congeners, meaning “same kind,” are compounds in alcoholic beverages that add to the flavor and aroma of alcohol (and, yes, hangovers). They result from fermentation — the process by which yeast converts sugars into alcohol. Congeners are another byproduct of this reaction.
The amount of congeners depends on a few different factors:
Each type of congener is built a little differently, and there are actually lots of different types with different molecular structures:
The amount and types of congeners in alcohol types tends to be unique. In a way, congeners act as a particular drink’s molecular “fingerprint!”
In fact, analysis of the congeners present in a particular drink has been used as part of the so-called “hip flask defense.” Originating in Germany, this defense is an assertion that the alcohol a defendant was intoxicated with at the time of arrest was consumed after an accident rather than before it (i.e., “When the accident happened, the booze was still in my hip flask — I didn’t drink it until later, I promise!”).
Backing this claim up hinges on calculating blood alcohol levels and comparing the exact congener profile in the defendant’s system with that of the alleged drink in order to prove the timing and the type of alcohol consumed. Of course, there are several obvious holes in this type of defense. For one thing, just because our suspect had a gin and tonic 10 minutes after a crash didn’t mean they didn’t also throw one back half an hour before. Plus, if they consumed a mixture of different drinks — and let’s be honest, this isn’t such a stretch — there would be too many compounds in the “congener cocktail” to make sense of which ones corresponded to a particular drink.
Still, the fact that the “hip flask defense” exists at all is testament to the unique nature of a particular drink’s congener profile. But what does any of this have to do with hangovers?
Hangovers — those unfortunate reminders of the night before — come with a characteristic set of symptoms, including headaches, nausea, shakiness, fatigue, and overall malaise (Ugh!). To find out more about the timeline of hangovers and what causes them, check out our blog The Science Behind Hangovers: Why They Last as Long as They Do.
So where do congeners come in? In general, the reason congeners make hangovers worse has to do with the fact that the body has to break down the congeners in addition to the alcohol. Both processes release toxic byproducts. However, since the liver can only do so much at a time, the result is a buildup of toxins that are partially responsible for those oh-so-familiar hangover symptoms.
According to a Current Drug Abuse Reviews article, methanol in particular is a congener that can wreak the most havoc on the body. Methanol metabolism releases formic acid and formaldehyde — two highly toxic byproducts that will continue to cause damage in our system even hours later.
Here’s the breakdown of methanol in various alcohol types, according to “Alcohol Congener Analysis and the Source of Alcohol: A Review”:
However, the authors also point out a crucial fact to keep in mind: while it may be true that brandy or rum has more congeners than vodka, the latter is still very high in alcohol content. And when it comes to the intensity of a hangover, the amount of alcohol we consume — no matter what the levels of congeners it may have — is what ultimately makes the biggest difference.
Likewise, while congeners may play a role in hangovers, they don't seem to affect the level of impairment we experience as a result of drinking. The authors mention that “safety-sensitive performance that was affected by alcohol intoxication the previous night (vigilance with reaction time; ataxia) was not differentially affected by bourbon versus vodka.”
That said, if we’re sensitive to congeners, we might want to know exactly which types of alcohol have the most.
The following have the highest levels of congeners:
The following alcohol types rank somewhere in the middle:
These are the “winners,” as far as “least hangover-inducing” alcohol types are concerned:
So what can you do to stay smart about congeners and lower your chances of ending up with a nasty hangover? Here are some ideas:
In the end, it can be helpful to see a frustrating experience like a hangover (whether or not congeners are to blame) as an opportunity. It’s easy to go about our routine on autopilot and forget to listen to our own intuition — specifically, what our body is trying to tell us. Try to see the unpleasant effects as a sign that maybe it’s time to shift gears a bit and change up your weekend routine. Do this in the spirit of curiosity, not judgment — it’s an opportunity to discover what works best for you!
1. What are congeners?
Congeners are compounds that get added to different types of alcohol through the fermentation process. They are responsible for the unique flavor profiles of many alcoholic drinks, but they can also lead to problems such as hangovers.
2. How do congeners cause hangovers?
Congeners can make hangovers worse due to the buildup of toxins that get released during their metabolism. Processing these in addition to the alcohol itself can overload our system more quickly, leading to unpleasant physical effects.
3. Which types of alcohol have the most congeners (and cause the worst hangovers)?
Dark liquors (especially bourbon, which has the most methanol congeners) and red wines have the most congeners and can make hangover symptoms worse.
4. Which types of alcohol are “best” for hangovers?
Vodka, sake, and beer have the least congeners and are technically “best” in terms of congener-related hangover symptoms. However, since the main contributor to hangovers is the amount of alcohol itself, they can still cause severe symptoms. Vodka is very high in ABV, so it’s especially important to be careful.
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