The microbiome: A key to better performance?

Scientists have long observed that athletes possess a more diverse and richer microbiome than sedentary individuals. But which came first—the fitness or the flora?

“It goes both ways,” Serohijos replied. Athletes often eat a healthy diet, which helps maintain a healthy microbiome, but studies suggest that some bacteria may also enhance performance.

For example, a study of marathon runners found high levels of Veillonella bacteria. When transplanted into mice, Veillonella increased their running endurance. 

“These bacteria use the lactate produced during exertion as an energy source and convert it into propionate, a short-chain fatty acid,” Santos said. “That may help improve athletic performance, although the precise mechanisms are not yet known.” 

Another small clinical trial examined Lactobacillus plantarum, which appears to enhance endurance, reduce body fat and increase muscle mass.

Microbiota may also aid recovery after exercise by controlling inflammation, and they may positively influence mood and psychological well-being through the gut-brain axis.

Other studies are investigating whether bacteria could help manage exercise-induced gastrointestinal stress, but according to Santos, the results are inconsistent.

Can we shape our microbiome by taking supplements? Prebiotics feed existing bacteria. Probiotics introduce live bacterial strains. Postbiotics deliver bacterial by-products, such as vitamins.

Probiotic foods—naturally fermented foods such as yogurt, kimchi and kombucha—are certainly beneficial to gut health. But the effectiveness of probiotic supplements is far from proven, and any effects are likely temporary. 

“Some supplements have been shown to have benefits in specific clinical contexts,” Santos said, “but there's no solid evidence to justify routine use in healthy individuals or to improve the microbiome in general. And the quantity and viability of the live bacteria in probiotic supplements can vary widely between products, which can affect their effectiveness.”

It should also be borne in mind that whole foods contain other important nutrients. “If you eat chickpeas, you'll get fibre, but that's not all. Taking prebiotics in a capsule won’t have the same effect,” she continued.

And experts are unequivocal about fecal transplants: don’t try this at home. “In a clinical setting, it can save lives, but I absolutely don't recommend it otherwise,” Santos stressed. Even in a hospital, it is a complicated procedure. For one thing, not everyone is automatically a suitable donor. “We don't know why,” she said.

Based on current knowledge, the best way for athletes or anyone else to maintain a healthy microbiome is a diet rich in fruits, vegetables, high-fibre foods and fermented foods.

We still have much to learn. “This field is moving rapidly,” said Jantchou. “Each bacterial strain is unique and must be studied individually to determine its benefits. At this stage, there’s no point having your microbiome tested at a private lab.” (One study also found that private labs use different methods and come up with conflicting results from the same sample.)

The research—mostly conducted on animal models—offers no definitive answers. “There may be bacteria that could improve athletic performance, but how do you target them precisely?” asked Serohijos. “That part is less clear. And we don't know to what extent the effects will be measurable.”

The link between physical activity and the microbiome is complex. Improving the microbiome seems to deliver the greatest benefits in people who are moderately physically active. “In people with very high activity levels, we don’t see the benefits, which is quite paradoxical, and we find an increase in intestinal permeability,” said Jantchou. 

Furthermore, each person’s microbiome is as unique as a fingerprint. “Each individual responds differently to what happens in their gut,” Santos said. A person’s microbiome also fluctuates depending on various factors: what they’ve eaten, their sleep, antibiotic use, physical activity and so on.

The marketing of supplements is outpacing the research. Science still has a long way to go before it has all the answers. “It's promising, but we'll need many more studies to get there,” Santos concluded.