How does alcohol cause hangovers? - Judy Grisel

1,367,480 views ・ 2022-07-05

TED-Ed


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In a 1973 study, 20 volunteers got drunk once a week for 8 consecutive weeks,
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each time on a different alcoholic beverage,
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and each time with precisely the same dosage—
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this was science, after all.
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The goal of this experiment was to find out which alcoholic drinks
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cause worse hangovers.
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Of course, it takes much more than one small study to answer such a question.
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Since then, science has learned a lot about hangovers—
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though some mysteries remain.
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The molecule responsible for hangovers is ethanol,
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which we colloquially refer to as alcohol.
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Ethanol is present in all alcoholic beverages, and generally speaking,
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the more ethanol, the greater the potential for a hangover.
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The symptoms and severity can vary depending on weight, age,
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genetics, and other factors.
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But still, hangovers generally share some common— and unpleasant— features.
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So how exactly does alcohol cause a hangover?
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And is there any way to reliably prevent one?
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Alcohol slows down the communication between neural cells.
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After someone has had their last drink,
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as the concentration of alcohol in the blood drops back to zero,
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the brain rebounds from sedation and swings in the other direction,
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entering a hyperactive state.
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This may lead to the tremors or rapid heartbeat associated with hangovers.
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It also makes sleep shorter and less restful than normal.
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But these effects are just the beginning—
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alcohol impacts so many of the body’s processes,
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throwing delicate balances off-kilter.
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And even the most familiar hangover symptoms have surprising contributors.
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For example, alcohol disrupts levels of many hormones.
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One of those hormones is cortisol.
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Normally, fluctuating cortisol levels help regulate wakefulness
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throughout the day and night.
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So the disruption in cortisol during a hangover
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may cause people to feel groggy or disoriented.
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Another hormone alcohol interferes with is vasopressin,
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which normally decreases the volume of urine made by the kidneys.
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By decreasing levels of vasopressin,
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alcohol causes people to pee more and become dehydrated.
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Dehydration can lead to thirst, dry mouth, weakness, lightheadedness, and headache,
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one of the most common hangover symptoms.
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In addition to dehydration, hangover headaches can result
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from alcohol’s influence on chemical signaling in the brain,
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especially on neurotransmitters involved in pain signaling.
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Alcohol can also damage mitochondria,
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which are responsible for producing the ATP that gives us energy.
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This may contribute to the fatigue, weakness, and mood disturbances
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experienced during a hangover.
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Meanwhile, alcohol stimulates the immune system,
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leading to inflammation that can damage cells within the brain,
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affect mood, and impair memory.
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And it can irritate the gastrointestinal tract
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and inflame the lining of the stomach and intestines.
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Alcohol may also slow down stomach emptying,
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which could lead to increased production of gastric acid.
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This is why alcohol can cause stomach pain, nausea, and vomiting.
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Alcoholic drinks also contain other substances that are produced
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during the fermentation process that give the drink its specific flavor.
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Some evidence suggests that one of these, methanol,
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is particularly bad for hangovers.
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The body doesn’t start metabolizing methanol
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until it’s done processing ethanol.
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And when it does, the toxic metabolites of methanol
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may potentially worsen the hangover symptoms.
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Beverages that are closer to pure ethanol, such as gin and vodka,
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may cause fewer hangover effects.
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Meanwhile, the presence of flavoring ingredients in beverages
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like whiskey, brandy, and red wine,
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may make these kinds of alcohol cause more hangover symptoms.
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So, the choice of alcoholic beverage matters,
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but any of them can cause hangovers, simply because they all contain alcohol.
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So, do common hangover remedies actually work?
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Drinking water and electrolyte beverages can help reduce symptoms
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related to dehydration.
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And eating— especially carbs— can help replenish the glucose levels
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alcohol reduces.
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But ultimately, the only sure way to prevent a hangover
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is to drink alcohol in moderation or not at all.
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