CompletedInterventional

Investigating the role of dietary probiotics on athletic performance and health

When you run hard, your body produces lactate, which can build up in your muscles and cause fatigue. Scientists believe certain friendly gut bacteria, known as probiotics, might help break down this lactate and turn it into helpful energy. This study at Nottingham Trent University aims to find out if taking daily probiotic capsules can improve running performance, stamina, and gut health in active men. The trial is looking for fit male runners aged 20 to 40 who can complete a 5 kilometre run in under 21 minutes. Over six to eight weeks, volunteers will attend laboratory visits, do treadmill running tests, and provide small blood, saliva, and stool samples. Each runner will test both the real probiotic supplement and an inactive dummy pill (placebo) at different times to see whether gut bacteria can truly boost endurance.

At a glance

Status

Completed

Sponsor

Nottingham Trent University

Enrolment target

Start

14 May 2026

Estimated completion

19 Oct 2026

Exercise performance and metabolism

What is this study about?

Intense exercise puts high demands on the human body. During hard running sessions, your muscles generate lactate. As lactate levels rise, it can lead to tired, heavy legs and slower race times. In recent years, sports scientists have started looking closely at the gut microbiome—the trillions of natural bacteria living in the digestive system—to see how gut health might influence athletic recovery.

Certain types of friendly bacteria can consume lactate and convert it into helpful substances called short-chain fatty acids. These substances can be used by the body for energy and may help support normal immune function. In theory, having more of these helpful bacteria could help athletes clear lactate more quickly, reduce tiredness, and recover better between tough workouts. However, there is still very little evidence in well-trained people to prove if taking probiotic supplements actually improves performance.

This study, run by the Sport Health and Performance Enhancement (SHAPE) Research Centre at Nottingham Trent University, aims to provide clear answers. By testing runners before and after taking a carefully designed probiotic supplement, the researchers hope to understand whether targeted gut bacteria can genuinely boost speed, stamina, and everyday wellness.

Key takeaways

Tests whether daily probiotic capsules improve running performance and stamina.
Open to healthy men aged 20 to 40 who can run a 5k in under 21 minutes.
Compares real probiotics against a dummy pill across two 14-day periods.
Involves treadmill running tests, questionnaires, and blood, saliva, and stool samples.
Takes place over 6 to 8 weeks at Nottingham Trent University.

Who may be eligible?

This study is open to healthy men aged between 20 and 40 who train at least four times a week. Because the research focuses on well-trained endurance runners, you must have recorded a 5-kilometre running time of under 21 minutes within the last three months.

You cannot take part if you have long-term digestive problems, such as irritable bowel syndrome (IBS) or Crohn's disease, or if you have a milk allergy or lactose intolerance. The study is also not suitable for people with a history of heart conditions, chest infections, or lung illnesses like asthma complications or COPD, nor for those who smoke.

In addition, you must not have taken antibiotics in the last three months, or laxatives in the last four weeks. Regular users of gut health supplements (prebiotics or probiotics), omega-3 fish oils, collagen, or daily painkiller tablets like aspirin or ibuprofen will also be excluded, as these can alter the study results.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am a man aged between 20 and 40 years old.
I train at least four times per week.
I have run 5 kilometres in under 21 minutes in the last three months.
I do not smoke and have no heart, lung, or gut conditions.
I have not taken antibiotics in the last three months.
I do not regularly take daily probiotics, fish oils, or painkillers like aspirin.

Answer every question to see your result.

What does participation involve?

Taking part lasts between six and eight weeks in total and involves visits to Nottingham Trent University. You will begin with a preliminary visit to test your baseline fitness. This includes a treadmill test where the speed increases every three minutes, alongside small blood tests, followed by a fast 5k treadmill run.

After this, you will complete two separate 14-day testing periods. During one period, you will take the probiotic supplement, and during the other, you will take an identical-looking dummy pill (placebo). You take one capsule daily for 12 days, followed by five capsules per day on days 13 and 14. There is a resting break of at least two weeks between the two periods where you take nothing. Neither you nor the research team will know which capsule you are taking first.

Across the study, you will attend four main lab sessions to repeat the running tests. You will also fill out short questionnaires about your sleep and wellness, and provide small saliva, blood, and stool samples so researchers can track your gut bacteria and energy levels.

Potential risks and benefits

By taking part, you will receive detailed feedback on your fitness levels, running performance, and gut bacteria, while helping scientists understand how nutrition supports endurance sport. However, strenuous running can cause temporary dizziness, light-headedness, or muscle soreness, and giving blood samples may cause minor stinging or bruising. While probiotics are generally well-tolerated, they can occasionally cause mild, short-term stomach bloating. Taking part is completely voluntary, and you are free to stop and leave the trial at any point without giving a reason.

Locations (1)

Nottingham Trent University
Approximate
Nottingham, England

Common questions

What is a placebo?

A placebo is a dummy pill that looks and tastes identical to the real probiotic supplement but contains no active ingredients. It helps scientists confirm that any improvements are genuinely caused by the bacteria.

Why do I need to give a stool sample?

Stool samples allow scientists to study your gut microbiome directly to see if the friendly bacteria from the supplement successfully settle in your digestive system.

Can women take part in this trial?

No. This specific study is only recruiting men to keep the metabolic and hormonal conditions consistent across the small group being tested.

Does taking part cost anything?

No, taking part is completely free, but you will need to travel to Nottingham Trent University for your fitness tests and lab appointments.

What happens if I feel unwell during a running test?

All exercise tests are supervised by trained university staff. You can stop the treadmill test immediately at any time if you feel unwell, dizzy, or uncomfortable.

How to find out more

Neil Williams

Neil.Williams@ntu.ac.uk +44 (0)115 848 5535 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.