How the Gut Microbiome and Mitochondria Could Boost Endurance Athletes' Performance

When mere milliseconds can separate silver from gold, endurance competitors in marathon running, cycling, rowing and swimming fine-tune every part of their physiology to gain an advantage.

Much of this work aims to improve the performance of mitochondria: the small yet powerful structures in cells that generate energy.

Precisely planned exercise doses, combined with helpful stresses such as altitude, cold and heat, as well as optimised recovery through nutrition, meditation and sleep, can improve the quantity and condition of mitochondria in muscle, heart and brain cells.

Yet athletes and coaches may have paid insufficient attention to another component of endurance training: how the gut microbiome can support mitochondrial health and fitness.

I am a physician-scientist and gastroenterologist who has spent more than 20 years examining how food influences the gut microbiome's role in health and disease.

Studies of how diet affects both the microbiome and mitochondria are improving knowledge of obesity, cancer, rheumatoid arthritis and Alzheimer's disease. They may also enable athletes to reach new levels of performance through novel nutritional strategies.

Microbiomes and mitochondria

The gut microbiome is a concealed, highly cooperative community of microorganisms in the intestines that helps keep metabolism, the immune system and the brain working properly.

Some scientists compare it with an additional organ: one that detects nutritional inputs, produces signalling molecules and readies the body to react suitably.

Studies have found that endurance athletes possess gut microbiomes that differ from those of the wider population.

Features of their microbiome's makeup and activity, including greater production of the short-chain fatty acid butyrate, are linked with higher VO₂ max. This fitness measure assesses the ability to use oxygen during strenuous exercise.

One organism in particular, Veillonella, occurs in some elite runners and may increase lactate threshold. That fitness measure is closely associated with mitochondrial function and the duration for which an athlete can maintain intense effort.

A healthy microbiome signals to mitochondria, the small cellular structures that turn calories into the basic energy needed for muscle contraction and other vital processes.

It achieves this by converting indigestible components of a healthy diet, including fibre, polyunsaturated fats and polyphenols, into molecules that improve mitochondrial number and health.

Several of these metabolites, including butyrate, conjugated linoleic acid and urolithin A, have been shown to specifically enhance muscle strength and endurance.

Exercise paired with diets rich in fibre, polyphenols - plant-derived chemical compounds - and healthy fats may therefore strengthen mitochondrial fitness and boost exercise performance.

Nutritional mistakes and shortfalls

Nutritious diets are essential to the health of both the microbiome and mitochondria. By contrast, ultra-processed diets have been associated with conditions from obesity and cancer to autoimmune disease and Alzheimer's disease.

Some argue that exercise protects athletes from the harmful health effects of ultra-processed diets. Although this may be partly correct, diet involves considerations beyond the number of calories expended.

Additives intended to enhance food flavour and appearance, such as emulsifiers, may harm the gut microbiome. They can weaken the gut barrier and trigger systemic inflammation, an unhealthy condition associated with metabolic disease, cancer, autoimmune conditions and neurodegenerative diseases.

Ultra-processed foods also lack important elements of whole foods, including fibre, polyphenols and healthy fats, which promote gut health and signal to mitochondria that calories are available for metabolism.

The drinks, shakes, bars and gels used in endurance sports are processed products designed to supply concentrated, readily available energy during hard exercise.

Though unhealthy in other settings, they can be crucial for improving performance in lengthy endurance events, when the body uses up its own readily accessible carbohydrate stores, known as glycogen.

However, these energy supplements should be accompanied by a healthy diet during the hours spent recovering after exercise.

An unhealthy underlying diet combined with high-intensity exercise may damage the gut barrier and raise inflammation. This combination has been connected with training-related problems including gastrointestinal upset, musculoskeletal injuries and respiratory illnesses.

Microbes that may enhance performance

For most people, restoring foods that benefit the microbiome during the recovery stage of training - beans, nuts, seeds, whole grains, fruit and vegetables - can help avoid the negative effects of high-intensity exercise and optimise performance.

However, antibiotic misuse and processed diets mean that some people lack the vital microbes and metabolic machinery required to turn fibres and polyphenols into useful molecules for the body. This deficiency could explain why certain healthy foods and diets may neither benefit nor be tolerated by everybody.

In such cases, healthy diets may be improved by restoring key microbes to the gastrointestinal tract.

Research indicates that particular probiotic bacterial strains can strengthen barrier function, lower systemic inflammation and potentially improve athletic performance by reducing the side effects of high-intensity exercise.

Another option is increasing intake of fermented foods, including yoghurt and pickled vegetables, which may expand microbiome diversity and reduce systemic inflammation.

In some situations, healthy foods could also be supplemented by supplying the body directly with the important metabolites made by microbes. Research suggests these metabolites, also termed postbiotics or exercise mimetics, improve muscle strength and exercise performance.

Certain postbiotics also act as prebiotics, nourishing beneficial microbes and helping to repair a damaged microbiome.

From research to the podium

Although the general-health value of nutrition aimed at the microbiome and mitochondria is becoming clearer, its use in endurance sports remains at an early exploratory stage.

For occasional exercisers and weekend warriors, comprehensive nutrition approaches that support the microbiome and mitochondria may be especially useful. Such approaches could raise performance, guard against negative training effects and prevent chronic conditions including obesity, cancer and Alzheimer's disease.

For elite athletes pursuing even the slightest improvement within an already carefully refined training programme, more research into the gut microbiome's effect on performance could prove invaluable.

In an intensely competitive arena where nothing can be left on the table - or in the cupboard - these interventions could be what determines whether an athlete finishes on the podium or outside it.

Christopher Damman, Associate Professor of Gastroenterology, School of Medicine, University of Washington

This article is republished from The Conversation under a Creative Commons licence. Read the original article.