If you break down alcohol into smaller compounds, you’d have mostly ethyl alcohol. But further still are compounds researchers call congeners. Researchers think these compounds may have something to do with why you get a hangover.

Keep reading to find out what congeners are and why doctors think they may make hangovers worse.

A spirits manufacturer produces congeners during the fermentation or distillation process.

During this process, a spirits producer will convert sugars into alcohol using different strains of yeasts. The yeasts convert sugars to ethyl alcohol, also known as ethanol.

But ethanol isn’t the only byproduct of the fermentation process. Congeners are there, too.

The amount of congeners the manufacturer produces can depend upon the original sugar, or carbohydrate, sources used to make alcohol. Examples include cereal grains for beer or grapes for wine.

Researchers currently think congeners can give beverages a certain taste and flavor. Some manufacturers even test for the amount of congeners to make sure their product has a consistent taste profile.

Examples of congeners the distillation process makes include:

  • acids
  • alcohols, such as isobutylene alcohol, which smells sweet
  • aldehydes, such as acetaldehyde, which often has a fruity smell present in bourbons and rums
  • esters
  • ketones

The amount of congeners present in alcohol can vary. As a general rule, the more distilled a spirit is, the lower the congeners.

This is why some people may find that “top shelf” liquors that are highly distilled don’t give them a hangover as much as a lower-priced alternative.

Research suggests congener content may play a role in the occurrence of a hangover, but it probably isn’t the only factor.

According to an article in the journal Alcohol and Alcoholism, drinking alcoholic beverages that have more congeners usually causes a worse hangover than drinks with fewer congeners.

Doctors still don’t have all the answers when it comes to hangovers, including why they occur in some people and not others. They don’t have all the answers for congeners and alcohol consumption, either.

One of the current theories about alcohol and congeners related to hangovers is that the body has to break down congeners, according to a 2013 article.

Sometimes breaking down congeners competes with breaking down ethanol in the body. As a result, alcohol and its byproducts may linger for longer in the body, contributing to hangover symptoms.

In addition, congeners may stimulate the body to release stress hormones, such as norepinephrine and epinephrine. These can cause inflammatory responses in the body that lead to fatigue and other hangover symptoms.

Scientists have found lots of different congeners in alcohol. They haven’t connected one specific one with causing a hangover, just that their increased presence may worsen one.

According to an article in the journal Alcohol and Alcoholism, the following are drinks in order from most to least congeners:

High congenersbrandy
red wine
Medium congenerswhiskey
white wine
Low congenersvodka
ethanol (like vodka) diluted in orange juice

Scientists have also tested alcohol for the amount of individual congeners. For example, the 2013 article reports brandy has as much as 4,766 milligrams per liter of methanol, while beer has 27 milligrams per liter. Rum has as much as 3,633 milligrams per liter of the congener 1-propanol, while vodka has anywhere from none to 102 milligrams per liter.

This supports the concept that vodka is a low congener drink. According to a 2010 study, vodka is a beverage that contains some of the least congeners of any drink. Mixing it with orange juice also helps neutralize some of the congeners present.

Another 2010 study asked participants to consume either bourbon, vodka, or a placebo in similar amounts. The participants were then asked questions about their hangover, if they said they had a hangover.

The researchers found that participants had a more severe hangover after consuming bourbon, which has a higher amount of congeners, compared to vodka. They concluded that increased presence of congeners contributed to hangover severity.

While researchers have connected increased presence of congeners with hangover severity, people still get hangovers when they drink too much of any kind of alcoholic beverage.

If you’re worried about reducing hangover symptoms, you could try low congener drinks to see if you feel better the next day.

According to a 2013 article, people who make their own alcohol at home, such as home-brewed beers, have less control over the fermentation process as a manufacturer.

As a result, alcoholic beverages made at home usually have more congeners, sometimes as much as 10 times the usual amount. You may want to skip these if you’re trying to avoiding a hangover.

Researchers currently believe a hangover is the result of many contributing factors, including:

  • how much a person drank
  • sleep duration
  • sleep quality

Alcohol consumption may also contribute to dehydration, which can cause unpleasant symptoms, including nausea, weakness, and dry mouth.

In addition to avoiding congener-rich beverages, here are some more tips to avoid a hangover:

  • Don’t drink on an empty stomach. Food can help slow how fast the body absorbs alcohol, so the body has more time to break it down.
  • Drink water along with the alcohol you consume. Alternating an alcoholic beverage with a glass of water can help prevent dehydration, which makes you feel worse.
  • Get plenty of sleep the night after drinking. More sleep can help you feel better.
  • Take an over-the-counter pain reliever like ibuprofen to reduce body aches and headache after drinking.

Of course, there’s always the advice to drink in moderation. Drinking less can usually guarantee you’ll have less (to no) hangover.

Researchers have linked congeners with worse hangovers. Current theories are that congeners affect the body’s abilities to break down ethanol as fast and trigger stress responses in the body.

The next time you have a night of drinking, you could try drinking a low congener spirit and see if you feel better than usual the next morning.

If you find yourself wanting to stop drinking but can’t, call the Substance Abuse and Mental Health Services Administration’s National Helpline at 800-662-HELP (4357).

The 24/7 service can help you find information on how to quit and resources in your area that can help.