Does Drinking Alcohol Kill Brain Cells?

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Watch someone after they’ve had a few drinks, and you’ll find clear evidence that alcohol does something to their brain. They stumble, slur their words, lose control of their emotions, and forget things. 

Some people have tried to explain this behavior as the aftermath of cell death caused by alcohol. Often, it’s packaged as a neat factoid like “Three beers kill 10,000 brain cells.”

But is this true? No. But alcohol does damage some of your 86 billion brain cells, or neurons, which send electrical and chemical messages within the brain and between it and other parts of the body. 

Ethyl alcohol (the kind found in boozy beverages, also known as ethanol) can kill cells and microorganisms. That’s what makes it an effective antiseptic. Fortunately, when you drink alcoholic beverages, your body tries not to let all of that ethanol roam around unchecked. Enzymes in your liver convert it first info acetaldehyde (which is highly toxic) and then into acetate, which is broken down into water and carbon dioxide and eliminated by your body.

The liver can only work so fast, though, processing about 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of distilled spirits per hour. If you’re knocking drinks back fast enough that your liver can’t keep up, the excess alcohol hangs out in the blood and travels through the body until it can be processed. 

When this alcohol reaches the brain, it doesn’t kill the cells. What it does is inhibit the communication between dendrites, or branching connections at the ends of neurons that send and receive information between neurons, in the cerebellum, a part of the brain involved in motor coordination. This poor communication results in some of the typical impairments of intoxication. 

Researchers at Washington University in St. Louis found that alcohol, even when applied directly to neurons, didn’t kill them. It just interfered with the way they transmit information. Specifically, the researchers showed that alcohol causes certain receptors on neurons to manufacture steroids that inhibit memory formation. 

Some alcoholics can experience neuron death as part of a brain disorder called Wernicke-Korsakoff syndrome. In these cases, the evidence again suggests that the disease and cell death aren’t caused by the alcohol itself, but a B1 (or thiamine) deficiency and general malnutrition that often go hand in hand with alcoholism. 

For moderate drinkers, a number of studies from the last 15 years suggest that, far from killing brain cells, a little tipple is actually associated with a reduced risk of cognitive decline and dementia. 

Why Does Hand Sanitizer Have an Expiration Date?

Hand sanitizer does expire. Here's why.
Hand sanitizer does expire. Here's why.
galitskaya/iStock via Getty Images

The coronavirus pandemic has turned hand sanitizer from something that was once idly tossed into cars and drawers into a bit of a national obsession. Shortages persist, and people are trying to make their own, often to little avail. (DIY sanitizer may not be sterile or contain the proper concentration of ingredients.)

If you do manage to get your hands on a bottle of Purell or other name-brand sanitizer, you may notice it typically has an expiration date. Can it really go “bad” and be rendered less effective?

The short answer: yes. Hand sanitizer is typically made up of at least 60 percent alcohol, which is enough to provide germicidal benefit when applied to your hands. According to Insider, that crucial percentage of alcohol can be affected over time once it begins to evaporate after the bottle has been opened. As the volume is reduced, so is the effectiveness of the solution.

Though there’s no hard rule on how long it takes a bottle of sanitizer to lose alcohol content, manufacturers usually set the expiration date three years from the time of production. (Because the product is regulated by the Food and Drug Administration, it has to have an expiration date.)

Let's assume you’ve found a bottle of old and forgotten sanitizer in your house somewhere. It expired in 2018. Should you still use it? It’s not ideal, but if you have no other options, even a reduced amount of alcohol will still have some germ-fighting effectiveness. If it’s never been opened, you’re in better shape, as more of the alcohol will have remained.

Remember that sanitizer of any potency is best left to times when soap and water isn’t available. Consider it a bridge until you’re able to get your hands under a faucet. There’s no substitution for a good scrub.

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Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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