Deep Dive: How Swimming Affects Your Gut Microbiome

Who wants to go swimming? *raises hand* Well grab your bathing suit and adjust your goggles, because today we’re talking about how swimming impacts your gut microbiome. From public pools to lakes to oceans, we’re diving into the bacteria—the good, the bad, and the microbial balance of it all…

Public pools: a microbial melting pot

Public pools are the go-to swimming spot for many people. They offer a refreshing escape from the scorching heat, but they also provide a unique environment for your gut microbiome to interact with different bacterial strains. Bad news first: scientists calculated that one 220,000-gallon, commercial-size swimming pool contains almost 20 gallons of urine on average. Yikes! Alongside urine, public pools also harbor various bacteria, including Pseudomonas aeruginosa, which can cause skin rashes and ear infections, and Escherichia coli, a common indicator of fecal contamination. But don’t get out of the pool just yet! The CDC states that chlorine kills most bacteria, such as E. coli, in less than a minute if its concentration and pH are maintained.

Despite these less-than-pleasant findings, swimming in chlorinated pools has its benefits. Chlorine, a common disinfectant used in pools, helps control the spread of harmful microorganisms. Additionally, studies have shown that exposure to chlorinated water can boost the diversity of beneficial bacteria in the gut. So while you might encounter some unwelcome bacteria, the overall effect on your gut microbiome might be positive.

Lakes: nature's microbiome buffet

Unlike the controlled environment of a pool, lakes offer a more diverse ecosystem, both above and below the water's surface. Freshwater lakes are home to a multitude of bacterial strains, some of which can influence gut health. These bacterial strains look pretty cool—you might notice large blooms of blue-green algae in lakes. These harmful blooms of algae are most commonly caused by cyanobacteria, which are a kind of single-celled organism called phytoplankton. The CDC warns that some cyanobacteria produce toxins (poisons) called cyanotoxins. Exposure to cyanotoxins can cause gastrointestinal illness. In fact, according to the CDC, untreated bodies of water such as lakes, rivers, and reservoirs can harbor other contagions including norovirus, E. coli and bacteria in the Shigella family, all of which can cause illnesses when ingested.

So what’s a sweaty person supposed to do when standing next to a beautiful lake on a hot summer afternoon? Glad you asked. If the water looks stagnant, cloudy, oily, or it smells bad, don’t go in. Obvious, right? Also, if you have any open wounds, stay out. If the water looks fine but you’re still nervous, the CDC advises cautious swimmers to use nose clips to help keep from ingesting harmful bacteria. And once you’re done swimming, remember to wash your hands before eating.
That seems like a lot of bad bacteria backlash for lake swimming, but on the flip side, studies suggest that exposure to lake water can increase the diversity of the gut microbiome, fostering a more robust and resilient community of microorganisms.

The ocean: a marine microbial wonderland

We don’t want to play favorites here, but there’s truly nothing like the salty embrace of the ocean. The ocean is teeming with an astonishing array of bacteria, both good and bad. Unfortunately, recreational beaches and the water surrounding them are often contaminated by wastewater and stormwater runoff. The presence of a variety of pathogens, such as Salmonella, Shigella, Campylobacter, Vibrio cholerae, Staphylococcus aureus, intestinal parasites, viruses and other organisms in sewage and runoff can cause illness in swimmers and surfers..

Despite the presence of potentially harmful bacteria, the ocean is also a bountiful source of beneficial bacteria, including various species of the genus Bacillus, which have shown potential probiotic properties. Plus, the salty seawater is packed with minerals, such as magnesium and potassium, which can support a healthy gut environment. Moreover, exposure to the diverse microbial communities of the ocean can contribute to the overall diversity of your gut microbiome. As Isak Dinesen once wrote, “The cure for anything is salt water: sweat, tears, or the sea.”

Summertime and the swimming’s easy

Look, it’s summer, or so close we can almost taste the watermelon. We want to end on a high note, so let’s recap the gut-happy benefits of swimming: 

Immune system boost

Swimming can enhance immune function, leading to a healthier gut microbiome. Regular exercise, including swimming, has been linked to increased microbial diversity and improved immune responses.

Stress reduction

Taking a dip in the water can help alleviate stress. Stress has a significant impact on the gut microbiome, so swimming can indirectly contribute to a more balanced and diverse microbial community.

Probiotic potential

Some bacteria found in aquatic environments, such as certain strains of Bacillus, have shown probiotic properties, potentially aiding digestion and overall gut health.

So there we have it—from chlorinated pools packed with people to the serene depths of a freshwater lake and the briny churn of the ocean, bacteria is everywhere, good, bad, and indifferent. Dive in or tread lightly, but above all, have a happy and healthy summer.

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