.png){kind=small}
The Science of… Being Drunk
- Dan Gill
- Jul 12
- 3 min read
Every alcoholic drink contains a percentage of ethanol—the type of alcohol that’s safe to drink (in small doses!). When you see ABV (alcohol by volume) on a label, that’s telling you what percentage of the drink is pure ethanol. So a drink with 12% ABV (like wine) means 12% of what’s in your glass is alcohol.
Fun Fact: Even some naturally occurring fruit juices can contain a tiny amount of ethanol – up to 0.11% ABV! Orange and grape juices, in particular, can experience a bit of early fermentation, leading to this bonus alcoholic content.
Your body mainly absorbs ethanol through your stomach and small intestine. Surprisingly, the speed at which you absorb it depends on the strength of the drink. Alcohol is absorbed fastest when the ABV is around 20–30%—like many spirits diluted with mixers. But go higher than that, and absorption actually slows down.
That’s because stronger drinks delay the stomach from emptying into the small intestine, where ethanol is more rapidly taken up into the bloodstream.
Once ethanol is absorbed, the liver gets to work, breaking the alcohol down using a cast of somewhat intimidating-sounding enzymes.
First up is alcohol dehydrogenase (ADH), which breaks down ethanol into a compound called acetaldehyde. The acetaldehyde then meets its match in aldehyde dehydrogenase 2 (ALDH2), which further metabolises it into acetate, with the acetate slowly breaking down into carbon dioxide and water.
You’ve likely felt the wrath of that last chemical, acetate—it’s believed to be behind hangover headaches. Ethanol dulls pain while you're drinking, but it clears out of your system faster than acetate does. So once the ethanol is gone, you're left with a heightened sensitivity to pain... and that familiar pounding head.
But it's not just the by-products of alcohol metabolism that affect you; ethanol itself has a profound and direct impact on your central nervous system. Your brain coordinates a whole range of signals, some excitatory (telling things to speed up) and some inhibitory (telling them to slow down).
When ethanol is in the body, it enhances the function of those inhibitory signals, essentially putting the brakes on. At the same time, it dials down the function of excitatory signals, reducing the overall number of signals flying around. The result? That classic combo of feeling relaxed and confident while also becoming less coordinated, slower to respond, and a bit clumsy. You lose your filter and your balance, all at once.
On the feel-good side, alcohol triggers the release of dopamine and serotonin—brain chemicals linked to pleasure, motivation, and mood. That’s part of why the first couple of drinks can feel so good.
This delicate dance between inhibition and excitation can be disrupted by long-term alcohol abuse. Your brain doesn’t like being out of balance, so in an attempt to maintain its equilibrium, it can start to compensate by boosting the effect of excitation on its functioning. Without the dampening effect of alcohol, the brain's excitation becomes excessive, potentially leading to severe symptoms like anxiety, delirium, and even seizures.
This elaborate interaction between alcohol and our brain signals is a complex area of ongoing research, offering a glimpse into the ways this widely used substance shapes our experiences.
Sources:
Fernando Valenzuela, C. (1997) ‘Alcohol and Neurotransmitter Interactions’, Alcohol Health and Research World 21, no. 2: 144–48.
Gorgus, E., Hittinger, M., and Schrenk, D. (2016) ‘Estimates of Ethanol Exposure in Children from Food Not Labeled as Alcohol-Containing’, Journal of Analytical Toxicology 40, no. 7: 537–42, https://doi.org/10.1093/jat/bkw046.
Maxwell, C. R., et al. (2010) ‘Acetate Causes Alcohol Hangover Headache in Rats’, PLoS ONE 5, no. 12: e15963, https://doi.org/10.1371/journal.pone.0015963.
Mercier, C. (1912) ‘DRUNKENNESS AND THE PHYSIOLOGICAL EFFECT OF ALCOHOL’, The Lancet, 1492–96.
Find your science tribe.
Sign up to the Lit Lab London Science and Sip mailing list for the weekly blog series, 'the Science of…', Science and Sip events and experiments to try at home!
Comments