Antibiotics kill off gut bacteria vital for athletic performance

A new study conducted on mice suggests that antibiotic use kills essential gut bacteria and decreases athletes’ motivation and endurance. 

Researchers at the University of California Riverside (UCR) have found that microbiome is a significant player that separates athletic from sedentary mice.

Previous studies have explored the effects of exercise on the gut microbiome, but this study is one of a handful that explores the reverse –– how gut bacteria also have an effect on voluntary exercise behaviours, defined as involving both motivation and athletic ability.

The research has been published in the journal Behavioural Processes.

“We believed an animal’s collection of gut bacteria, its microbiome, would affect digestive processes and muscle function, as well as motivation for various behaviours, including exercise,” says Theodore Garland, UCR evolutionary physiologist in whose lab the research was conducted. “Our study reinforces this belief.”

The study involved two groups of female mice (females were chosen for their low aggression in communal settings): ”High Runner mice [that] were selectively bred for voluntary exercise,” and control mice. 

The two groups of mice were given antibiotics in their drinking water, sweetened with Splenda. After a ten day treatment, gut bacteria was reduced in both groups, as determined by faecal samples.

The authors write that “Based on body mass, food consumption, and behavioural observations, antibiotic treatment did not appear to cause sickness behaviour”. Yet wheel running in the High Runner mice were reduced by 21 percent – a change that the researchers attributed to microbiome damage.

Moreover, “[a]fter antibiotic treatment stopped, mice remained in home cages with wheel access and regular food and drinking water for 12 days [but] the daily wheel-running distance of the HR mice did not recover to levels before antibiotics.”

The authors note the antibiotic treatment administered greatly reduced the gut microbiome in both High Runner and Control lines, based on “aerobic plating.” Yet the behaviour of the control mice was not significantly altered either during the treatment, or after it.

“A casual exerciser with a minor injury wouldn’t be affected much. But on a world-class athlete, a small setback can be much more magnified,” says Monica McNamara, UCR evolutionary biology doctoral student and the paper’s first author. “That’s why we wanted to compare the two types of mice.” 

In this experiment, upsetting the normal gut microbiome stands in for an injury. 

“One way the microbiome might affect exercise in mice or in humans is through its ability to transform carbohydrates into chemicals that travel through the body and affect muscle performance,” a news release notes.

“Metabolic end products from bacteria in the gut can be reabsorbed and used as fuel,” Garland says. “Fewer good bacteria means less available fuel.”

Following this experiment, the researchers would like to determine the exact bacteria responsible for increased athletic performance. “If we can pinpoint the right microbes, there exists the possibility of using them as a therapeutic to help average people exercise more,” Garland says. 

Exercise is recommended for physical health as well as psychological wellbeing. While exercise has many benefits, public health officials have had a hard time to promote it with much success.

“Though we are studying mice, their physiology is very similar to humans. The more we learn from them, the better our chances of improving our own health,” Garland says.  

It’s possible that some foods may increase desirable gut bacteria, such as probiotics. Garland suggests that people interested in maintaining a healthy body and mind consume a balanced diet as well as exercise regularly.

“We do know from previous studies that the Western diet, high in fat and sugar, can have a negative effect on biodiversity in your gut and likely, by extension, on athletic ability and possibly even on motivation to exercise,” Garland points out. 

HEADLINE IMAGE: Aerobic plates: 10 days of antibiotics reduced the adult gut microbiome from millions of aerobic colony-forming units to a non-detectable amount. (Monica McNamara/UCR)