Let’s not beat around the bush here – a lot of people reading this are probably going to be drinking at some point during the next week or two. With that in mind, I thought today we would explore the fascinating mechanisms behind one of the world’s oldest and most popular intoxicants.
To start, “alcohol” as it’s referred to in drinking contexts usually refers to ethanol (C2H6O), as opposed to isopropanol, or rubbing alcohol (C3H8O), as well as the general subclass of chemicals that both belong to. Most alcohols, including ethanol, are colourless liquids at room temperature, and tend to be flammable, volatile and toxic.
Ethanol is produced naturally by the metabolic processes of yeasts (a class of single-celled microorganisms in the fungi kingdom) in a process called fermentation; yeast processes simple sugars like glucose, sucrose and fructose into cellular energy, producing both ethanol and carbon dioxide as a side effect. All alcoholic beverages are produced through various methods of fermentation (wine from fermented grapes, beer from fermented grains etc.), and most alcoholic beverages contain only a small percentage of ethanol (typically 5% for beer, 12% for wine, and 35-45% for spirits), though potable concentrations of up to 95.6% alcohol by volume can be achieved via distillation (ex. Everclear).
When consumed by humans, ethanol acts as a depressant on the central nervous system when it builds up in the bloodstream faster than it can be metabolized by the liver. Ethanol is partially broken down by an enzyme called alcohol dehydrogenase which is found in high concentrations in the liver and gastric lining of the stomach – without this enzyme, ethanol could not be metabolized, and would thus act as a literal poison when consumed, much like methanol, or wood alcohol (CH4O). Because of this however, alcohol can be oxidized into a chemical called acetaldehyde, which through a similar series of steps is further broken down and metabolized by the liver – using this process it takes a healthy liver roughly 90 minutes to metabolize around 30mL of pure ethanol, about the amount in a standard serving of beer, wine or mixed drinks.
As the concentration of alcohol in the blood increases, its physical effects (i.e. drunkenness) become apparent. At lower levels this includes a mild but pleasant sense of euphoria and decreased social inhibitions resulting from its biochemical interactions with the brain (which, indecently, classifies alcohol as a psychotropic drug in the same vein as LSD and peyote), but as the concentration builds, less pleasant effects set in, such as impairment of decision-making ability and a lack of balance & muscle coordination, as well as possible nausea and vomiting caused by the disruptive effects of alcohol on the canals of the inner ear and the mucus lining of the stomach.
The processes which lead to hangovers are not as well understood, but are thought to be correlated with increased levels of dehydration, low blood sugar, and lack of sleep. Genetics is also a factor – some people are less tolerant to alcohol and more prone to hangovers, while conversely about 25% of heavy drinkers report that they’ve never had a hangover. Acetaldehyde, the first byproduct of ethanol metabolization, is thought to play a part as well – it is between 10 and 30 times as toxic as alcohol itself, and can remain at elevated levels for hours after consumption while interfering with normal biochemical processes. Now one thing to note about is that acetaldehyde absorption levels increase when one smokes cigarettes while consuming alcohol – thus, combining smoking with drinking is thought to lead to a worse hangover in the morning. Just something to think about dart lovers.
For more alcohol-related science tips, check out my article from a few years ago titled “The science of better drinking: the orientation week article you’ve all been waiting for” online at themuse.ca.