Gut Microbiome Response to Long-Haul Travel in Elite Football Players

This study is looking for male professional football players who are actively involved in their pre-season training. You need to be generally healthy and not have any serious or ongoing illnesses that might affect the study.

It's important that you haven't taken any probiotics (like those found in some yogurts or supplements), prebiotics (certain types of fiber), or antibiotics in the four weeks before the study starts. You also need to be willing to avoid starting any new supplements during the study period.

However, you won't be able to join if you have certain gut problems like Crohn's disease or irritable bowel syndrome, or other long-term illnesses. If you've been unwell with an infection recently, have allergies to ingredients in the probiotic, or are taking medications that affect your immune system, you also can't take part. They also aren't including players who drink a lot of alcohol or use drugs, have been in another study recently, or have an injury that stops them from taking full part in training and matches.

If you decide to take part in this study, you will need to do a few things over your pre-season period. Firstly, you'll be asked to provide a stool (poo) sample multiple times – this helps researchers look at your gut bacteria. You'll also give saliva (spit) samples at various points to check your immune function.

Every day, you'll need to take a capsule. This will either be a probiotic (good bacteria) or a placebo (a dummy pill that looks the same but has no active ingredients). You won't know which one you're taking, and neither will the researchers, until the study is over. The samples will be taken at specific times: when you return from your time off, before you fly for your pre-season tour, once you arrive at your tour destination, and then within five days of getting back to the UK. The total duration of your participation will cover your pre-season training and tour.