Science debunks a deadly summer food myth

The arrival of summer is an assault on all your senses — the brush of tall grass on bare legs, the whistle of a far-off lifeguard, and if you’re a kid (or a kid at heart) lots, and lots of ice cream and grilled treats.

Every fiber in your being screams that you should forget your worries, load up your burger with all the toppings, and cannonball into the closest body of water.

But as nostalgic as this time of year can be, it can also bring with memories of a nagging voice and a threat geared to ruin a good time: “Don’t swim after eating!”

But while your elders may be wiser than you about many things, this is one cultural hang-up that we really can afford to just put back on the shelf.

Linda Quan, an emergency attending physician at Seattle Children’s Hospital, tells Inverse that one of the most frustrating health myths she has to contend with in summer is the idea that eating and then swimming can spell certain doom.

Quan, who has researched drowning and how to prevent it for much of her career, sets the record straight:

“The bottom line is: there is no science, no basis to this issue,” she says.

“You may drown and it will be your own fault!”

For more than a century, it has been ingrained in western culture that if you plan to swim and eat, then you better either eat after you swim or eat and then set a timer for 30 minutes before you get in the water to avoid potentially deadly cramps. This is just untrue, Quan says. So where did the myth even come from?

Misinformation in the troops

It’s notoriously difficult to track down the exact origin of culturally pervasive myths like these, but fact check website Snopes points to a 1908 edition of the British Boy Scout handbook as a potential genesis.

The exact phrasing and placement of the advice in the handbook aren’t clear according to historian Ben Jordan, who was speaking in an interview with WBUR radio station. But according to Snopes, the warning goes something like this:

If you bathe within an hour and a half after taking a meal — that is, before your food is digested — you are very likely to get cramp. Cramp doubles you up in extreme pain so that you cannot move your arms or legs — and down you go.

You may drown... and it will be your own fault.

The meme seems to have crossed the pond in 1911 when it made its way into the handbook for the American Boy Scouts. It then remained in the handbook in some shape or form until 1967 — more than 50 years.

Essentially, like any meme, the myth that eating + swimming = drowning went viral. And, similarly to other pseudoscience memes, the spread didn’t come from an actual physician or scientist at all, Quan says. Instead, it was indoctrinated into the cultural psyche by camp counselors, parents, and children themselves. A classic case of misinformation moving like wildfire in the face of evolving science.

“It came from a non-science source and it just takes hold,” says Quan. “But you know, that happens so much. This is, unfortunately, the usual not the rare.”

Scientists in the 1960s actually decided to fact-check the idea themselves. They did a number of human trials to test the effect of swimming after eating on the body and a person’s swimming abilities. It made no difference.

Nevertheless, the myth persisted in the Scout handbook until 1967, and it still gets bandied around today — more than fifty years after that.

“It is very hard to unlearn [things],” Quan says. “We have to unlearn people. And it takes constant repetition.”

What causes cramps while swimming

It sounds sciencey — eating causes your body to have cramps in the water. Quan says the theory is driven by the idea that our bodies reroute blood to our stomachs to aid digestion after a big meal. In theory, this slight increase in blood flow to the stomach will create a slight decrease in blood flow elsewhere in the body (such as our legs), which could put strain on our muscles if we are in water.

But Quan says it’s simply not enough of a problem to cause a deadly cramp or for our appendages to just stop working.

“All you have to do is flip over and float like a lily pad.”

In fact, eating food before swimming could actually have the opposite effect, explains Quan.

When competing in long endurance events like the Tour de France or a mountain climb, Quans says athletes will consume food throughout their event like bananas to actually prevent their muscles from cramping up — the same goes for those odd little gel packs that smell like fake food essences you see marathon runners downing as they toil on to the finish line.

“You can live on a gel,” when you’re exercising says Quan, “but you can also eat real food.”

Swimming, either for competition or just for fun, is no different.

Can you swim after eating?

So, can you swim after eating? Quan says there’s absolutely no risk if you want to jump right back in the water after chowing down on a seaside picnic.

But like any sport, too much vigorous activity right after eating a big meal could cause stomach discomfort or even vomiting. So listen to your body and ask yourself if you need a minute before you do a 500-meter fly sprint.

That said, it’s very, very unlikely swimming after eating would cause cramping specifically.

And even if you do experience a body cramp in the water, Quan says the quickest and easiest way to stay safe and stay in the water is to turn over on your back and just float until it passes.

“All you have to do is flip over and float like a lily pad,” she says.

What swimmers should really worry about

But just because eating while swimming has the doctor’s seal of approval that doesn’t mean there aren’t other serious risks to consider when swimming this summer — like drinking.

Throwing back one too many hard seltzers or getting distracted by a new TikTok trend on your phone are far more dangerous than chowing down on a hotdog or two.

If Quan could leave you with one takeaway, it is this: Drinking and swimming don’t mix. Booze is a leading cause of drowning deaths among adults. Men are especially at risk, it seems. The CDC says men account for 80 percent of annual drowning deaths.

Another good way to practice waterside safety is to ensure that either a swim buddy, lifeguard, or floatation device is always available to you. And no, that doesn’t mean a flamingo-shaped pool float, says Quan.

“Swim around someone who can save you,” says Quan. And, less gravely, it is nice to have friends.

CHECK, PLEASE is an Inverse series that uses biology, chemistry, and physics to debunk the biggest food myths and assumptions.

Now read this: Food scientist debunks a dangerous myth about chicken