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Inside our intestines is our gut microbiome, home to trillions of microorganisms, including bacteria, viruses, fungi, and other microbes. Researchers say they are just beginning to understand all the ways our biodiverse guts impact our health. So far evidence suggests the microorganisms in our gut, when diverse and healthy, can aid digestion, regulate our immune system, help protect against certain diseases, and boost mood.
Plenty of data suggests exercise is part of the equation, too.
There’s a lot going on when we exercise — we allow more oxygen to reach our brain and bloodstream, our core body temperature heats up, and there’s a redistribution of our blood flow. Researchers suspect these conditions are great for the bacteria in our microbiomes to flourish, though the exact mechanisms are still unknown, says Taylor Valentino, PhD, a postdoctoral researcher at the University of Utah in Salt Lake City, where he studies the relationship between muscle development and the microbiome.
“Exercising causes important changes that help gut microbes to bloom and convert, and, coinciding with that, we get molecules our bodies can utilize,” Dr. Valentino says.
That means a regular exercise routine may help support a healthy gut ⎯ and still more research suggests that a healthier gut may be linked to improved performance, too.
Science Says Exercise Makes for a Healthy Gut
In a nutshell, most bacteria in our gut have a symbiotic relationship with our bodies, meaning they support body function and our bodies support the health and growth of these microorganisms. They produce vitamins, fatty acids, and amino acids that are used for things like immune functioning, digestion, mood regulation, and more.
Regular exercise accelerates the process, increasing the different kinds of microbial species in the gut, and encouraging bacteria to flourish, says Jacob Allen, PhD, an assistant professor of exercise physiology at the University of Illinois at Urbana-Champaign.
And there is a growing body of research to suggest that exercise does indeed promote a diverse gut microbiome.
In research published in 2018 in the journal Medicine and Science in Sports and Exercise, Dr. Allen’s team recruited 32 adults who were not regular exercisers at the start of the study; half the group were obese, and half were normal weight.
Both groups were assigned to six weeks of supervised workouts that gradually became more intense, starting with 30 minutes of brisk walking working up to an hour of spin class three times per week. (The researchers didn’t adjust participants’ diet or eating habits.) Then both groups were asked to stop exercising for the following six weeks.
Blood and fecal samples, as well as measures of aerobic fitness, were recorded at the start of the study, after the six weeks of exercise, and after the six weeks of no exercise. Across the board, participants had higher levels of short-chain fatty acids (the cornerstone to reducing inflammation in the body and regulating blood sugar levels) and the gut microbes that produce them after the six weeks of exercise. After the following six weeks of no exercise, their guts returned to looking like they did at the start of the study.
The microbiome is continuously active and reacting, not only to the food you fuel it with, but also how you move throughout the day, Allen says. “With this study, we saw how exercise is changing that ecosystem,” he explains, as well as the result of those changes (meaning the increase or decrease in healthy short-chain fatty acid production).
A study published in 2017 in PLoS One that followed 40 women ages 18 to 40 also showed that found that exercise helped improve composition of gut microbiota. Half the group exercised for at least three hours over a seven-day period; the other half exercised less than 1.5 hours per week. Stool samples and DNA genetic sequencing revealed stark differences in levels of 11 types of bacteria. The women who exercised had higher levels of health-promoting bacteria (like Roseburia hominis and Akkermansia muciniphila).
In a mouse study published in 2016 in Immunology and Cell Biology, Marc Cook, PhD, assistant professor at North Carolina Agricultural and Technical State University in Greensville, and an American College of Sports Medicine–certified clinical exercise physiologist, and his group found that exercise may increase numbers of Lactobacillus (a bacteria linked to lower cholesterol and one that helps with symptoms of irritable bowel syndrome and reducing diarrhea and loose stools) in the colon.
“This may be one way that exercise strengthens intestinal barrier function and reduces inflammation to improve health,” Dr. Cook says.
Does a Healthier Gut Help Boost Your Workouts?
Valentino points to a study published in 2019 in Nature Medicine (PDF) that found marathon runners’ stool samples have higher levels of another bacteria, called Veillonella, compared with nonrunners. The concentration of this microbe was higher after workouts and even more heightened after completing a marathon.
Veillonella is a microbe that eats up lactate — which our bodies produce during a hard workout — and turns it into propionate, a short-chain fatty acid that boost our energy levels. The Harvard Medical School scientists behind the research suggest that exercising triggers Veillonella microbes to increase in the gut for that extra energy boost needed for endurance running.
5 Ways to Make Your Exercise Routine a Gut-Friendly One
Are specific types of exercise good for the gut? Here’s what experts say:
1. Focus on Cardio
For now, the research connecting exercise to improved gut health has focused on aerobic exercise, and less so on resistance training like weightlifting. That doesn’t mean pumping iron won’t help your gut health, it’s just that the scientific community hasn’t explored this area yet, Allen says.
Allen had participants in the aforementioned study doing aerobic or cardiovascular exercise (like jogging or cycling) three days a week for 30 to 60 minutes at a target heart rate of 60 percent of their maximum heart rate, working up to 75 percent. At 60 percent, you should be able to talk comfortably and maintain regular breathing, while 75 percent is classified as “vigorous exercise,” where you may be breaking a sweat and your breathing speeds up, Cook says.
Other exercises, like rowing, swimming, or skipping, are ways to get your cardio in, too, Cook says.
2. Be Consistent
To keep the production of good microbes in your gut going, you’re going to have to keep exercising, making it part of your overall lifestyle.
“Consistency is number one because you can lose the beneficial effects if you don’t keep exercising,” Cook says. Note: in Allen’s study, participants’ gut microbiomes changed within six weeks of exercise, but then reverted back within six weeks once they stopped working out, too.
Just like you’ll lose your stamina if you quit running for a few weeks, your gut microbiome will lose out on the production of good microbes once you stop exercising, Cook warns.
3. Start Small
If you’re starting at square one and aren’t used to exercising, ease your way in, Valentino says. “Don’t go from couch to marathon,” he warns. For starters, you don’t want injuries, and you want to build a long-lasting habit.
“The goal is giving your microbiome a constant fuel source through exercise,” he says.
4. Get Outdoors
Exposure to nature increases our exposure to diverse ecosystems, and the bacteria within them. “If we’re outdoors, running in a park, or along the ocean, we’re breathing in very diverse communities of bacteria that are in the air,” says Christopher Lowry, PhD, a behavioral neuroscientist and assistant professor at the University of Colorado in Boulder, where his researches focuses on the gut microbiome and anxiety-related disorders.
He points to a Finnish study that found that children playing outside on the forest floor, in the dirt and among plants and flowers, had a richer, more diverse gut microbiome and a less inflammatory immune system compared with their peers who were in an urban daycare setting.
5. Don’t Forget Nutrition
What you put on your plate on the daily has just as much impact on your gut health as your exercise regime, Cook says. Before you go grocery shopping and meal planning, take note: the gut microbiome loves fermented foods, which are packed with bacteria and yeast.
Natural probiotics include:
Your gut microbiome thrives on plant diversity, too. That means you ought to load up on vegetables, fruits, nuts, and seeds. Research published in the American Society for Microbiology in May 2018 called for eating 30 different plants per week to bolster the diversity of your microbiome and optimize gut health.