Supplements and the Gut
From probiotics to ginger, here’s how to assess the supplements that can help you manage gut woes.
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When it comes to optimizing performance, recovery, and health, many of us are naturally attracted to quick remedies. The use of dietary supplements is one of the best examples of this quick fix culture. In the United States today, people spend more than $30 billion annually on supplements that promise to do everything from extend longevity to get you shredded at the gym. It’s not clear-cut why we so often turn to pills when we wish to dull an ache, boost our mood, or get stronger in the gym, but to some extent this predilection to instant remedies seems to be a part of our DNA.
As someone who has written extensively on gut issues in athletes, I often get questions about which supplements hold promise when it comes to improving gut function and reducing the chances of gut distress during exercise. To the disappointment of many of these answer seekers, I usually point out that most supplements have little scientific weight behind them, and for the handful that do work, the actual benefits are often smaller than what people hope for.
Still, dietary supplements are just one of many tools that an athlete can pull out of the toolbox to attempt to manage gut issues, so long as they are used smartly and for the right reasons. In this article, we’ll take a closer look at the scientific oomph behind some of the supplements that are commonly used to influence gut function in the context of exercise.
The gut (particularly the colon) is home to trillions of bacteria that come from perhaps 500 to 1000 different species. In fact, the number of bacterial cells colonizing the human body slightly outnumber human cells. Over the past couple of decades, literally hundreds of studies have documented undeniable links between this collection of microbes—called the microbiome—and different aspects of human health and function. Recent research has even tied different gut microbiome profiles to levels of physical fitness. It comes as no surprise, then, that probiotics—live microorganisms taken to manipulate the gut microbiome and health—are one of the trendiest supplements used by athletes.
Although it’s intuitive to think that probiotics can prevent or manage gut woes, the science on this topic is frustratingly inconsistent, at least when it comes to gut troubles in athletes. A few studies have found modest reductions in gut symptoms among athletes taking probiotics, but others have not, and one even found likely increases in the number and duration of GI symptom episodes with a Lactobacillus fermentum probiotic. It’s also important to recognize that the magnitude of benefit observed in the positive studies has generally been pretty small. In other words, even if a probiotic does work, you shouldn’t expect that it will completely ameliorate all your gut problems, or even reduce them by half in most cases.
Even though probiotics likely have minor effects on the severity of gut symptoms in most athletes, there is more positive data when it comes to their impact on the respiratory system. Placebo-controlled experiments in both athletes and non-athletes show that probiotics boost immune defenses in the respiratory tract, which, for athletes, may help keep their training regimens on track by reducing the odds of catching infections. (In case you’re wondering about the risk of SARS-CoV-2 infection and probiotics, we don’t currently know if they offer any protection.)
If you do decide to take a probiotic, be aware that varieties from the Lactobacillus and Bifidobacterium genera have the strongest records of benefit across a variety of applications. Fermented foods like yogurt, kefir, and kombucha are potential sources of probiotics, but supplements are probably a better route when it comes to targeting specific dosages and strains. There is no minimum dosage that applies to all probiotic supplements but using one that provides at least one billion colony-forming units is often recommended as a starting point.
Ginger has been used as an antidote for a queasy stomach for hundreds, if not thousands, of years. Ancient Chinese sailors purportedly used ginger during voyages on the high seas to ward off seasickness. In more contemporary times, its anti-barf properties have been trialed for everything from motion sickness to chemotherapy-induced nausea. The mega-popular TV show MythBusters even put ginger to the test in one of its episodes. For host Adam Savage and sidekick Grant Imahara, ginger prevented motion sickness even though they each spent half an hour in a slowly rotating chair. And among a few experiments that have evaluated ginger as a motion sickness therapy, the results have generally been favorable. Ginger is thought to work as an anti-nausea remedy by blocking the activation of receptors in the gut that bind with serotonin. This is the same pathway by which some prescription antinausea medications work (e.g., ondansetron, brand name Zofran).
Of all athletes, ultrarunners are especially well-acquainted with nausea. In a study of competitors from the Western States 100-mile Endurance Race (WSER), six out of 10 reported some queasiness. The WSER is often held in sweltering conditions, which may contribute to the remarkably high rates of nausea there; regardless, practically every ultrarunner has dealt with nausea at some point while training or competing.
So, what do we know about ginger’s potential as a nausea remedy for ultrarunners and other athletes? Unfortunately, direct evidence that ginger prevents nausea during exercise is lacking, so we’re largely left in the dark on this issue. Ginger is generally recognized as safe by the Food and Drug Administration and has a pretty solid safety record, though it can trigger other gut symptoms like heartburn, belching, and mild burning sensations in the stomach and affect blood clotting, meaning those who have clotting disorders or who take blood thinners should be extra-cautious. In terms of dosage, 1–2 grams an hour before an expected nausea-provoking event could be a starting point. For many runners, though, nausea doesn’t rear its ugly head until hours into competition, so ingesting some at the midway point of a race could be more effective. Many foods containing ginger (ales, snaps, etc.) probably don’t contain enough active compounds to quell nausea; if you’re looking to get a real physiological effect, it’s probably best to go with a supplement or to make your own beverage or food.
Your gut has a hearty appetite for the amino acid glutamine. After getting absorbed in the gut, most amino acids—the building blocks of protein—enter the blood, but half or more of glutamine never enters systemic blood circulation, meaning it gets locked up by gut tissue. Much of this sequestered glutamine, it turns out, is used by the gut for energy production. For this reason—as well as its effects on immune cell function—glutamine is often touted as a gut health promoter.
Exercise—especially when it’s intense or prolonged—poses a challenge to gut function. Blood, oxygen, and nutrient delivery to the gut can all become compromised as these precious resources are redirected to the skeletal muscle and skin (for cooling purposes). As a consequence, the normal gut barrier that prevents outside stuff from entering your body can become leaky and dysfunctional. This gut leakiness can lead to bacterial translocation inside the body. In turn, your body identifies these trespassers and releases inflammatory molecules to help keep the invasion at bay.
It’s been hypothesized that these changes in gut barrier integrity contribute to gut symptoms like nausea and perhaps even heat illnesses, though scientists still debate to what extent this theory is true. Regardless, glutamine supplementation has been tested in several studies to lessen gut leakiness during exercise (see here, here, and here for examples). In one representative study, glutamine ingested two hours before a 60-minute run in the heat (86℉) likely attenuated the typical rise in gut leakiness observed with exercise. While sports scientists like to geek out over changes in physiological biomarkers, most athletes are more interested in actual performance and perceptual improvements. Somewhat disappointingly, the studies cited above either did not measure gut symptoms or failed to find any clear improvements with glutamine when they did assess said perceptions. Perhaps more importantly, plain old carbohydrate is known to reduce gut leakiness with exercise, which begs the question as to whether the extra expense of supplementing with glutamine is largely redundant. As an added benefit, carbohydrate ingestion can improve performance when exercise lasts longer than 60 to 90 minutes.
I’m hopeful that future research will help clarify what advantages, if any, glutamine offers over carbohydrate ingestion, but at this juncture, I tend to favor focusing on other strategies for dealing with gut issues instead of turning to glutamine supplements. If you decide you still want to give glutamine a try, bear in mind that doses used in research range substantially but often fall somewhere between 15 and 50 grams. To minimize the likelihood of any stomach upset, it’s usually taken at least one hour before starting exercise.
Although dietary supplements are inherently an attractive means of easing gut problems (what’s easier than taking a pill?), the honest truth is that they are unlikely to be a home run for most athletes. Most of the time, taking supplements to fix the gut is more akin to hitting a slap single in the ninth inning when your team is down by five runs. If you do decide to use any of the supplements discussed in this article (or other supplements), it’s most definitely worth your effort to do some research on the company selling the product to make sure they are serious about quality and safety (for some resources on this process, see here and here). Oftentimes, however, people can achieve better outcomes with managing gut problems through changing their diet, getting sufficient sleep, and managing life stress and anxiety. Plus, improving these other aspects of your life are much more likely to extend to other aspects of your health and performance than taking a pill.