Does Drinking Alcohol Kill Your Gut Bacteria?

From the hand sanitizer at your favorite food
truck to those single-use wipes at the doctor’s office, alcohols are used to disinfect things
all the time. So every time you have an alcoholic drink,
it’s basically like microbe-killing juice… which doesn’t sound so great for the helpful
critters in your gut. But, turns out, drinking in moderation could
actually kill the microbes that cause food poisoning and diarrhea, while helping the
bacteria that help you. It’s been known for centuries that alcohols
can kill microscopic germs—the Greek physician Galen used wine to clean gladiatorial wounds
way back in 150 CE. But the ethanol in beer and wine is just one
type of alcohol. Chemically, alcohols are compounds with at
least one hydroxyl group, which is just a hydrogen and an oxygen, bound to a chain of
at least one carbon . High concentrations of alcohol—like the
70% isopropanol in antibacterial wipes—dissolve cell membranes, killing bacteria and viruses
on contact. But a straight shot of vodka is only about
40% ethanol, while the average glass of wine is 12%, and beer is 5%. Even though they’re below membrane-nuking
concentrations, lots of drinks can kill bacteria and viruses. But exactly how is less clear. We know that lower concentrations of ethanol
can still make cell membranes unstable. And they can promote the production of reactive
oxygen metabolites, which can damage important cell parts. So alcohol can knock out some unwelcome microbes
in your stomach and upper intestine before they become harmful. For example, there’s pretty good evidence
that beer and wine take out Vibrio cholerae—the bacterium that causes cholera, a disease where
you’re attacked by uncontrollable diarrhea. That could be part of why alcohol was so popular
on long sea voyages, and not just for Captain Jack Sparrow-types: it was safer to drink
rum or beer than probably-contaminated water. Booze doesn’t just kill cholera, either. Case studies have shown that wine, in particular,
might be able to kill the nasty bugs that cause food poisoning like Salmonella and Norovirus,
before they set up shop in your bowels. And one study on around 80 people found that
drinking wine and other beverages with more than 10% alcohol kept people from being infected
with hepatitis A from contaminated oysters, which can cause liver disease. Of course, we now know that there are also
beneficial bacteria that live on and inside us, and you wouldn’t want to kill a bunch
of them with every shot of tequila. So it’s a good thing that doesn’t really
happen, partially because a lot of the microbes that matter are in your colon, not your stomach. By the time your drink mixes with stomach
acid and makes its way through your upper intestines, most of the alcohol is already
absorbed. That said, some scientists think a glass of
wine every night could affect your lower intestines—in a good way. Some of the non-alcoholic compounds in wine
called polyphenols feed helpful bacteria, and get broken into smaller useful molecules. Some scientists think these molecules can
bind to the cell membranes of disease-causing bacteria, like those in the genus Clostridium,
and kill them off. Or they might even boost your health. One study suggested that polyphenol byproducts
could explain why regular wine drinkers seem to have fewer heart problems. And another found that they might help counteract
some of the metabolic problems caused by obesity. But don’t go tapping that keg in celebration
just yet. These potential benefits aren’t a sure thing,
and they refer to moderate drinking—so, like, a glass of wine or a couple beers a
day. Binge drinking and alcoholism are a totally
different ballgame. For example, a fairly large study published
in 2001 found that regularly drinking a little alcohol seemed to reduce the chance of being
infected with Helicobacter pylori, a bacterium that causes severe stomach ulcers. But the researchers found that drinking more
wasn’t better. After a certain point, as alcohol consumption
increased, so did the chance of infection. In fact, the upper intestines in both short
and long term heavy drinkers tend to have too much bacteria. Scientists think that large doses of alcohol
could slow down intestinal movement and take a toll on helpful bacteria, which could give
harmful microbes the time and space to gain a foothold. Alcohol can also mess with the genes in cells
that line your intestines and stomach, which can lead to things like producing too much
or almost no stomach acid after long term abuse. And this isn’t great because stomach acid
is one of the most effective defenses against disease-causing bacteria. Chronic alcohol abuse also cripples your immune
system, making you much more vulnerable to pathogens in general. Not to mention the whole “destroying your
liver” bit. If you picture your gut lining as a sturdy
trash bag made of cells, alcohols and their byproducts can punch a ton of little holes
in it. This lets junk like bacterial toxins leak
out, which your liver has to clean up. And the harder it has to work, the more damaged
it becomes. So a glass of red wine with dinner might actually
help you resist some food poisoning. But if you go overboard, hangovers will be
the least of your concerns. Thanks for watching this episode of SciShow,
which was brought to you by our patrons on Patreon. If you want to help keep the science shots
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