Performance-Enhancing Gut Bacteria? 🦠
We have known for some time that exercise influences the composition of the gut microbiota. For instance, in 2014, Irish researchers published an analysis revealing that professional rugby players had a more diverse gut microbiome and a higher abundance of health-promoting genera compared to sedentary controls.
But could this relationship be bi-directional? Meaning, could certain gut microbes enhance exercise performance?
It is biologically plausible. Exercise requires energy, and the gut microbiota actually provides energy to us in the form of metabolites, which may meet up to 10% of our daily caloric requirements. These metabolites can enter the blood and skeletal muscle, where they enhance energy utilization and spare glycogen, potentially leading to boosted exercise performance.
Of course, you need the right microbes in order for this to happen. One of the research teams cited below has launched a company that is developing novel probiotics for exercise performance, but as you’ll see, you may also be able to cultivate a fitter gut microbiota through your diet.
This Week's Research Highlights
To explore how the microbiome might influence exercise performance, Japanese researchers administered either antibiotics or a low-fiber diet to mice, and trained the rodents on a motorized treadmill for several weeks. After two weeks of antibiotic treatment, the mice showed substantial reductions in exercise capacity, compared to an untreated group. Six weeks of the low fiber diet produced similar impairments. Both regimens also led to dramatic decreases in short-chain fatty acid (SCFA) levels in their plasma and feces. To figure out whether SCFAs were playing a causal role, the researchers infused acetate, an SCFA, into the antibiotic-treated mice. Sure enough, that restored their exercise capacity. And when they performed a fecal microbiome transplantation in the mice that had been fed the low-fiber diet, their running time was boosted. Taken together, this suggests that short-chain fatty acids, generated from fermentable dietary fiber, may be an important energy source for muscles, possibly sparing glycogen and even protein.
🏋🏽 SCFA-generating bacteria in elite athletes enhance exercise performance when administered to mice.
Researchers from Joslin Diabetes Center analyzed fecal samples from Boston Marathon runners that had been collected one week before the marathon and one week after the marathon, and compared them to samples from a cohort of sedentary individuals. What immediately jumped out to them is that one genus of bacteria, Veillonella, occurred in significantly higher abundance in the runners than their inactive counterparts, and was especially elevated following the race. Why this genus in particular?
Well, Veillonella is fairly unusual in that it relies upon lactate as its sole carbon source, and of course lactate is generated by muscles during hard exercise. Makes sense, right? More lactate selects for more organisms that are fueled by lactate. But here’s the cool part: When researchers supplemented mice with this strain, they showed a significant increase (+13%) in their exhaustive treadmill run time. Next, the scientists wanted to figure out how exactly Veillonella boosts exercise capacity.
They determined in the lab that Veillonella metabolizes lactate into the short-chain fatty acids acetate and propionate (kind of lines up with the above study finding related to SCFAs and endurance performance). When they introduced propionate into mice via enema, they were able to reproduce the increased running ability that had been demonstrated via supplementation with Veillonella. This appears to be an example of a symbiotic relationship: The bacteria feeds on lactate, and then converts that lactate into metabolites that enhance athletic performance to help the host produce more of the substrate.(PS: For those interested in maximizing lactate for its effects on cognition, cancer, appetite regulation, etc, the researchers found that inoculation with Veillonella did not affect levels of serum lactate).
🥣 Higher fiber oat cereal results in improved exercise performance, perhaps due to increased SCFA production.
Six recreationally active women stayed at a lab for two days (to control diet/physical activity), and then performed exercise to exhaustion on stationary bikes. Shortly before the exercise bout, they were randomized to consume either: 1) sweetened whole-grain rolled oats (75 grams of available carbs and 7 grams of fiber); 2) sweetened whole-oat flour (75 grams of available carbs and 3 grams of fiber); 3) 300 mL of water (control). Exercise time to exhaustion was 16% longer when the women consumed the whole-grain rolled oats, compared to control, and the difference between control and the oat flour was not statistically significant. Now, this is an old study (1998), so at the time the researchers speculated that the lower glycemic index of the higher-fiber cereal was responsible. But with what we know now, it seems possible that it may actually have been due to higher levels of SCFAs, and particularly propionate, since the women were given oats. A number of in vitro studies have shown that oat bran promotes production of propionate, even more so than other fiber sources, perhaps because beta glucans in oat bran boost Veillonella.
Researchers in the UK analyzed data on polyphenol intake, gut microbiome composition, and obesity in a cohort of 1810 female twins and a smaller group of 64 male volunteers. After adjusting for confounders and fiber intake, higher polyphenol intake in general was found to correlate with greater microbiome diversity. When they zeroed in on specific classes of polyphenols, they observed that flavonoid intake was associated with greater abundance of Veillonella, and Veillonella was associated with fecal abundance of lactate. As the researchers state, “The association between Veillonella and flavonoid intake then suggests one of the mechanisms whereby flavonoids may improve metabolic health…It also suggests that there may be scope for investigating the role of flavonoid supplementation or dietary interventions in improving athletic performance.”
Random Trivia & Weird News
Auto-brewery syndrome is a rare condition wherein carbohydrates are fermented into intoxicated quantities of ethanol by microorganisms in the gastrointestinal tract. This may be due to prolonged antibiotic use, genetic variations in liver enzyme activity, and certain medical conditions like diabetes or cirrhosis.
Researchers say that endogenous generation of enough alcohol to cause impairment is likely to be extremely uncommon, meaning that it is probably not something you need to worry much about (nor is it likely to be a successful defense against a DUI charge).
Podcasts We Loved This Week
- Dean & Ayesha Sherzai: Exercising for Brain Health. Via The Proof Podcast.
- Kevin Klatt and Drs. Karl & Spencer Nadolsky: Nutrition Studies and Media Headlines. Via Docs Who Lift Podcast.
Products We Are Enjoying
I am a huge fan of oat fiber. Not only does it seem to promote Veillonella and propionate production, but beta glucans in oat fiber have been shown to lower blood sugar and blood cholesterol, which is obviously a major plus in the battle against chronic disease.
It’s very easy to add to smoothies, cereals, etc without significantly altering the taste or texture (I don’t even notice it).
humanOS Catalog Feature of the Week
This week, I’d like to highlight our course on polarized training, developed by Jeff Rothschild.
In this course, Jeff examines how manipulating aspects of exercise and diet can favorably influence adaptations to endurance training. Specifically, he reviews how increasing training volume and intensity influence the number and function of our mitochondria, and takes a look at the training strategies of elite marathoners and cross-country skiiers.
At the end of the course, he puts it all together and explains how you can apply this science-based info to your own endurance training.
Thanks for reading, enjoy the weekend, and we will see y'all next week!