Why You Might Not Need to Wait 30 Minutes After Eating Before You Swim

There are a few commonalities across childhood swimming experiences in the United States that I’d venture to guess you might be familiar with. Did you ever play Marco Polo? Perhaps you rode around on foam pool noodles with your friends? Did you drink Capri Suns and snack on Cheetos Puffs around the perimeter of the water as I did? 

Even if none of the above rings true for you, I’m almost certain you’ve heard of the widely accepted pool wisdom that many parents share with their kids: Don’t swim for at least 30 minutes (or sometimes an hour, depending on which adult you’re asking) after you’ve eaten.

I heard this old adage throughout my childhood, and like many others, I’ve long accepted it as true. But when you reflect on this “fact” for a minute or two, it raises the question: Why can’t you swim for at least 30 minutes after eating? In a recent episode of the podcast ScienceStuff, host and former roboticist Jorge Cham takes listeners on a deep dive into this possible myth, exploring what it means exactly, if there’s any degree of truth to it, and whether we can start eating more snacks right before we hop in the pool.

Where did this myth come from?

Even the source of this age-old wisdom is somewhat shrouded in mystery. Cham explains that neither he nor anyone he consulted could definitively determine where the recommendation to wait 30 minutes before swimming originated. However, the earliest documented mention of this advice that he can find comes from a somewhat unexpected source: the original Boy Scout manual from 1908, Scouting for Boys by Robert Baden-Powell. 

This book — which was wildly popular in the early 20th century — offers a wide range of advice, from practical skills such as how to use a compass to wisdom that doesn’t endure, like weather predictions such as “a yellow sunset means wind.”

The latter is unsurprising, considering this is a text from over a hundred years ago. Yet, hidden within its pages is a piece of counsel that’s still passed on today: “Never bathe in deep water very soon after a meal, it is very likely to cause cramp, which doubles you up, and so you get drowned.” And here is where the 30-minute myth begins — at least to the best of our knowledge.

Is swimming after eating dangerous?

As the language in this archival Boy Scout manual indicates, the “rule” that you shouldn’t swim for at least 30 minutes after eating arises from a fear that doing so could lead to a cramp severe enough to cause drowning.

To determine whether this concern is justified, Cham consults an ideal source: Dr. Matthew Badgett, a physician specializing in internal medicine and pediatric primary care at the Cleveland Clinic, who also happened to be a competitive swimmer in high school. (Badgett has also spoken about the relationship between swimming and eating before.)

To start, Badgett highlights the contradiction in parents advising children against eating right before swimming, while simultaneously encouraging them to eat and drink just before other activities — such as soccer — to prevent cramps.

Recalling his own childhood, he says, “I always had a strong barometer for hypocrisy, but I always thought this rule really made no sense to me.” He also notes that “I could physically tell the difference if I had two pieces of toast and then went and swam an hour at 5:30, 6 a.m. in high school, versus if I didn’t eat it, I would be dragging.”

Overall, the doctor emphasizes that for strenuous activities such as biking and running, you need calories to fuel your body; this also applies to competitive swimming.

Although most people aren’t exercising vigorously while swimming in a pool, Badgett explains that during his pediatric training, he never learned anything indicating whether you should or shouldn’t eat before swimming in any scenario. He has also never had a parent approach him with an issue caused by their child eating shortly after swimming.

In addition to Badgett’s experience as a doctor and his logical argument against the archaic rule against eating and swimming, Cham also examines published scientific evidence confirming that there is nothing to worry about.

In 2011, the American Red Cross Scientific Advisory Committee (SAC)  published a comprehensive review of existing studies on the effects of eating before swimming. It ultimately concluded that, “Currently available information suggests that eating before swimming is not a contributing risk for drowning and can be dismissed as a myth.”

Even more importantly, the American Red Cross has published guidance as recently as 2024 stating that “Swimming within one hour of eating food in adult and child recreational or competitive swimmers does not increase the risk of drowning.” 

Can swimming after eating make you feel sick?

While evidence shows there’s no inherent danger in swimming soon after eating, there remains the possibility that it could cause nausea or discomfort. In fact, Cham notes that several studies reviewed by the SAC found “that the swimmers who went swimming [in] thirty minutes or less reported a significant amount of discomfort and nausea. It was not a good swimming experience for them.”

To understand why this occurs requires a brief biology lesson. Dr. Stephen Ives, an associate professor of health and human physiological sciences at Skidmore College, explains that when you’re at rest, your heart pumps the appropriate amount of blood to all the systems in your body based on their needs.

This includes your digestive system, and Ives details that “Your brain’s getting what’s needed, the heart’s getting what it needs, the muscles are getting some, the gut is getting what it needs.”

When you exercise, your cardiac output — the amount of blood your heart pumps per minute — increases. At the same time, the priority of blood flow to different bodily systems shifts, as certain areas require nutrients, energy, and oxygen from the blood while you exert yourself. “There’s a high demand for blood flow, for the nutrients, for the oxygen to support energy production so the muscles can keep doing their thing and contracting.

“That can come at [the] cost of some of the other organs. So on a percentage basis, the gut goes from getting maybe 25% of the blood that’s pumped out by the heart per minute to maybe a couple percent. It gets cut dramatically,” Ives explains.

This means your digestive process will likely be slower. If you’ve just eaten a very large and calorically dense meal — or something high in fat, which can be harder to digest — it might sit in your stomach for longer and cause discomfort. You can imagine this as a sensation very similar to if you went for a run right after a big meal. You could do it and be fine, but your stomach might feel a little unsettled.

But blood flow isn’t the only factor contributing to possible slow digestion while swimming. Ives points out that gastric emptying, the process of food moving from your stomach to your small intestine, occurs more quickly when you’re standing or sitting upright compared to lying down. When you swim, you’re technically horizontal, which could also lead to slower digestion and discomfort.

Ives points out that a common cause of muscle cramps is a lack of electrolytes, which can be obtained from foods like bananas, spinach, milk, dill pickles, and many others. If it has been too long since you consumed a good source of electrolytes, it could lead to cramps while swimming. Cham summarizes this by saying, “It sounds like you don’t want to eat too close to swimming, but you do want to eat something beforehand at some point,” to ensure you have fuel and electrolytes.

What does this mean for you?

According to the Red Cross’ guidance, you need not worry about any serious danger from eating within 30 minutes of swimming. As Ives concludes, “It’s not really a safety issue. I would say under-nutrition is probably more of a safety issue. It’s more of a comfort issue.”

You can definitely swim right after eating, but if you’ve had a large meal, it might be wise to wait for about 30 minutes to avoid feeling nauseous. If you’ve only had a light snack, you likely don’t need to worry at all, which is great news for those of us who love snacking and swimming.