Eating before swimming: Is it safe to go back in the water?


    For generations, our parents and grandparents have warned against the perils of swimming within an hour or two of eating.

    While the rulebook seems to vary between households, the rationale is usually much the same; that our blood gets diverted to the stomach for digestion, and this leaves us susceptible to a range of aquatic difficulties, including a cramp or stitch, insufficient blood flow to the arms and legs, or even drowning.

    On the surface, this may sound like a plausible explanation. But let’s dive a little deeper to explore where this theory came from, and whether it holds water!

    How it started

    Published in 1908, the original British version of the Scouting for Boys handbook offered some pretty abrupt advice on the matter, stating: ‘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.’ A few years later, this advice crossed the Atlantic, and similar instructions appeared in the first Boy Scouts of America handbook in 1911.

    A little closer to home, a book written by Annette Kellerman in 1918 titled How to Swim is thought to be the first published record of such advice in Australia. The book states that ‘A period of at least two hours should elapse between eating and entering the water, in order to give the digestive processes time to get their work well under way. If the water is entered too soon after eating, especially when it is at a low temperature, the digestive process is immediately arrested, and this in itself is likely to produce a severe case of cramps, and perhaps result in acute indigestion which may prove serious.’

    On a side note, it’s worth pausing for a moment to recognise Annette Kellerman’s many achievements beyond this questionable advice. At age 15 she set her first swimming world record over one mile and then proceeded to complete her first 10-mile swim, in the Yarra River. Also known as the ‘Million Dollar Mermaid’, she went on to star in 14 films, including one of the first films to take one million dollars at the box office. She also blazed a trail by wearing one-piece bathers at a time when other women were still swimming in pantaloons.

    Fact versus fiction

    Circling back to the science, it’s true that eating a meal increases blood flow to the stomach and digestive system. The medical name for this phenomenon is postprandial hyperaemia (postprandial = after a meal; hyperaemia = increased blood flow). 

    However, our bodies are constantly directing and redirecting blood to where it’s needed, and we have more than enough blood to digest food and stay afloat at the same time. In fact, some would argue that eating before swimming provides our bodies with additional fuel, which would actually be more of a help than a hindrance during an emergency.

    Another factor to consider is that it can take our bodies more than two days to fully digest a meal, particularly if that meal is high in protein and fat. So, if the goal is to stay high and dry until digestion passes, it could be quite a long wait!

    Given the persistence of this advice, it would be reasonable to assume that perhaps the matter is still up for scientific debate. But in fact, a number of studies dating back to the 1960s have conclusively shown that eating before swimming has very minimal side effects. A study published in 1968 also showed that eating a small meal before a freestyle time trial had no impact on swimming performance. The result was the same regardless of whether the swimmers waited 30 minutes, one hour or two hours before getting in the pool.

    In 2011, the American Red Cross put the matter to rest once and for all with the publication of a scientific review paper examining all available evidence over a period of 50 years. The review concluded that ‘Eating before swimming is not a contributing risk for drowning and can be dismissed as a myth.’ A similar scientific review published by the International Life Saving Federation in 2014 came to the same conclusion.

    Across both these reviews, the authors were unable to find a single reported case of drowning linked to eating before swimming. Similarly, the Royal Life Saving Society of Australia makes no mention of eating before swimming in its annual drowning reports, and offers no recommendations on the topic in its Australian Water Safety Strategy.

    So, there you have it folks! From this day forward, we can all blaze a trail of our own by telling our kids (and grandmas) that it is indeed safe to go back in the water after eating.

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    Human Interest
    Human Interest
    Welcome to your regular column on the science of human beings…and being human. Brought to you by Lauren Donley, an unashamed science nerd who never misses an opportunity to share a story about bodily functions. Please note that this article is for general interest and is not a replacement for medical care. If you have any questions or concerns about your health, please contact your doctor.

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