Hangovers are probably one of the most widespread negative experiences worldwide. If you drink, chances are that you've experienced this misery at least once in your life. The technical term for your Saturday morning misery is veisalgia, and it has many symptoms, from vomiting to lethargy to headaches that feel like an army tap-dancing in your skull. The pain typically subsides after a few hours, but hangovers an also affect your gut health in ways that you might not expect, and it doesn't just have to do with nausea.
"Typically, a hangover begins within several hours after the cessation of drinking, when a person’s blood alcohol concentration (BAC) is falling," the National Institute on Alcohol Abuse & Alcoholism wrote. "Symptoms usually peak about the time BAC is zero and may continue for up to 24 hours thereafter," When you're drinking alcohol, the composition of your gut microbes changes, adapting to what's coming into the body. This process is called dysbiosis, and it does some intriguing things.
Numerous studies have looked at the effects of alcohol on the gut microbiome, and found that some moderate drinking of alcohol — specifically red wine, which contains polyphenol — is actually helpful to gut bacteria, though excessive consumption harms it. Alcoholism harms gut microbial diversity (the amount of different bacteria in the gut), but a little bit of good Cabernet seems to raise levels of healthy bacteria like Enterococcus and Prevotella. So what happens to the gut when the party's over?
Gut changes during drinking appear to be part and parcel of the misery of hangovers. According to Professor Tim Spector, writing in the Guardian in 2015, microbial changes on a night out on the town can cause gut microbes to 'leak' toxins called LPS. A study of 25 non-heavy drinkers, he explained, found that those with the worst hangover symptoms also had the highest levels of LPS and a spike in microbes that attack invading cells. The attacking microbes set off an immune response, "stimulating the immune system as if it were under attack and contributing to the general sick-feeling so typical of hangovers."
When we're hungover, inflammation in our guts seems to go into overdrive. This "increased abundance of pro-inflammatory bacteria and [...] decrease in anti-inflammatory bacteria," according to the proceedings of the 8th Alcohol Hangover Research Meeting, can also lead to something more serious than hangovers — "disruption of intestinal barrier integrity," or leaky gut syndrome, which allows bacteria and other microbes to leave your gut and get into your bloodstream. It's reported to be behind a lot of immune conditions and inflammation-linked health problems.
However, that's not the full story on the gut and hangovers. A fellow researcher, Spector told the Guardian, had another theory: while observing her own gut microbiota following five days of beer-drinking, she noted a rise in levels of a bacteria called Erysipelotrichia. Spector told Shaughnessy Bishop-Stall in 2018's Hungover: The Morning After that this Erysipelotrichia experiment may be the key to understanding the gut's role in hangovers.
Erysipelotrichia, he noted, is essential to the process that breaks alcohol down into acetadelhyde. Acetadelhyde is a toxic by-product of alcohol that may, according to a study in 2014, be the culprit behind serious hangover symptoms; it builds up in the body on 'the morning after' before being broken down further into something more harmless. If you have a headache and vomiting the day after a binge, higher levels of Erysipelotrichia in your gut might be to blame.
The Alcohol Research Group had another perspective on how gut microbes might affect hangovers — and it has to do with your circadian rhythms. They explained that when mice were given alcohol and had their circadian rhythms disrupted, they were more likely to experience dysbiosis and gut leakiness. Circadian rhythms are the body's 24-hour clock, its pattern of sleeping and waking. It's regulated by the brain but backed up by numerous other systems — and the gut microbiome has a big role in helping keep it regular. Alcohol is known to disrupt circadian rhythms, and sticking to a 24-hour clock (rather than laying in darkness till 3 p.m.) has been shown to help cure hangover symptoms. It's possible that drinking can change your gut microbes in ways that interrupt your natural 24-hour clock, and that in turn makes hangover symptoms more intense.
Gut microbiome research about alcohol is often focused on the long-term; for instance, alcohol abuse over time causes changes in the gut microbiome that can increase the likelihood of liver disease, according to research reported in Scientific American in 2016. However, if you just want a short-term solution to the hell of the morning after, the answer may be in your microbiome. A probiotic company announced in 2018 that it was formulating a probiotic "hangover cure" that could help beat hangover symptoms by boosting various microbes in the gut, though it hasn't been tested yet.
In the meantime, you might be able to lessen hangover symptoms by cultivating a healthy gut. Keep your gut microbiome healthy by eating a diverse range of foods and getting enough sleep, and try to focus on red wine in moderation the next time you're out on the town.