Your Microbes Are Part of Your Training
Training changes your gut, and your gut bacteria may help you run longer.
You know training changes your muscles, heart and lungs. But you may not know that it also changes the microbes in your gut, and that effect may run in both directions.
In 2014, researchers compared the gut microbiomes of professional rugby players with those of healthy non-athletes. The players had noticeably more diverse microbial communities (Clarke et al., Gut, 2014). They also ate differently, with more protein and more food overall, so it was hard to separate the effects of exercise from those of diet. A later study helped sort that out. Researchers put sedentary adults on a six-week endurance program while keeping their diets steady. Their gut bacteria shifted toward species that produce short-chain fatty acids like butyrate. When they stopped training, most of those changes reversed (Allen et al., Medicine & Science in Sports & Exercise, 2018).
Your microbiome responds to training much like the rest of your body does. Stay consistent and it adapts. Stop, and it drifts back.
The part that gets athletes’ attention is the other direction. In 2019, a Harvard team collected stool samples from Boston Marathon runners in the week before and after the race (Scheiman et al., Nature Medicine, 2019). After the race, the prevalence of a bacterium called Veillonella jumped. What makes Veillonella interesting is what it eats: lactate, the byproduct your muscles pump out when you push hard. Veillonella converts lactate into propionate, a short-chain fatty acid.
When the researchers gave Veillonella to mice, the mice ran longer on a treadmill than mice given a different bacterium.
That’s mice, not people, and nobody should go looking for a Veillonella supplement any time soon. But it points to something anyone who trains regularly should find interesting: the microbes in your gut take an active part in how your body handles and tolerates exercise.
Dr. Emeran Mayer’s research adds another layer. He has spent more than 45 years studying what he calls the brain-gut-microbiome system, and it runs both ways. Your brain signals your gut through hormones and the autonomic nervous system, and your gut and its microbes signal back to the brain via the vagus nerves, microbial signaling molecules and the immune system.
Another factor that affects how your gut works is stress. Stress changes gut signaling, and those signals feed back to the brain, shaping mood and how you handle the next stressor. Movement is part of that loop.
What to do with this
- Stay consistent. The changes in the Allen study faded within weeks of stopping. Regular training beats occasional hard efforts.
- Feed the adaptation. The microbes that respond to training make short-chain fatty acids from fiber. Train hard on a low-fiber diet and you leave them without raw material. Feed them with a diverse high fiber diet, and they will thrive. Last week’s plant count is a good place to start.
- Recover well. Sleep and stress both act on the same system., but in opposite ways. Hard training on too little sleep adds strain everywhere and compromises the health of your gut microbiome.
- Train with people. Community is one of the seven pillars of Dr. Mayer’s new book, The Mayer Model. A group keeps you showing up, and showing up is what the microbiome rewards.
You’ve already got that last one handled.
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Some content in this article may have used AI-assisted tools for research, grammar, or outlining. All articles are reviewed and approved by our human editorial team.
Emeran Mayer, MD Is a Distinguished Research Professor in the Departments of Medicine, Physiology and Psychiatry at the David Geffen School of Medicine at UCLA, the Executive Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience and the Founding Director of the Goodman-Luskin Microbiome Center at UCLA.