New research suggests high-performing athletes could have performance-enhancing poo.

Boston Marathon runners and Olympic athletes appear to have elevated level of Veillonella bacteria in their digestive tract following races, according to a study in the journal of Nature Medicine.

When Veillonella was fed to mice, they improved their speed on treadmill runs compared to mice not given the same bacterial diet.

Each person’s gut biome consists of around 100 trillion bacteria; hundreds of different species weighing up to two kilograms collectively.

While no two people have identical microbiomes, the researchers say elite athletes’ guts appear to contain similar bacterial species that help them perform and recover.

The team from the Emory University School of Medicine in the US analysed stool samples of 2015 Boston Marathon runners throughout the week before and after the race, finding Veillonella genus bacteria increased substantially compared to other bacteria in the competitors' guts after the race.

They fed a strain of Veillonella atypica from the athletes' faeces to mice.

The animals were shown to increase their performance on a treadmill by 13 per cent compared to mice not given Veillonella.

The natural function of the bug is to break down lactic acid produced by the body during intense exercise, leading to muscle fatigue and soreness.

The researchers found that the lactate, produced when the mice exercised, was metabolised by the bacteria, creating chemical by-products that crossed into the circulatory system and resulted in a performance boost.

Previous studies had shown that Veillonella exists in higher abundance in the stools of athletes, but the new study is the first to test whether bacterial species may be enriched due to the breakdown of lactate in the gut produced by exercise.

Experts not involved in the study have told reporters that it is part of a trend of emerging papers suggesting striking effects of individual microbes, but they should be taken as preliminary reports treated with some skepticism.

Also, some of the study’s scientists work for a biotech company called FitBiomics Inc, which seeks to commercialise performance-enhancing probiotics.

The study is accessible here.