A pilot study has explored whether daily supplementation with the multi-strain liquid probiotic Symprove could help reduce gastrointestinal symptoms in marathon runners during training.
Gastrointestinal symptoms are common among endurance athletes and can affect both training and race-day performance. Building on previous research investigating the role of Symprove in gastrointestinal health, researchers at St Mary's University, Twickenham wanted to explore whether probiotic supplementation could help reduce gastrointestinal symptoms during marathon training.
The PRIME-GUT study involved 10 recreational marathon runners who took Symprove daily for six weeks before completing a marathon. Gastrointestinal symptoms were assessed each week using the validated Gastrointestinal Symptom Rating Scale (GSRS).
Overall gastrointestinal symptom scores improved after four weeks of supplementation, with reductions of 31% after four weeks, 38% after five weeks and 43% after six weeks. Improvements were also reported in abdominal pain, bloating, flatulence, loose stools and urgent bowel movements.
The number of moderate or severe gastrointestinal symptoms also fell from week four onwards, with fewer runners reporting at least one moderate symptom during training. Although this improvement was not statistically significant on marathon day itself, the findings suggest that daily supplementation with Symprove for at least four weeks may help reduce gastrointestinal symptoms during marathon training.
Lead researcher James Fleming of St Mary’s University, Twickenham said “Findings from this research suggest that Symprove supplementation may present a promising nutritional strategy for managing gastrointestinal symptoms during marathon training and on race day, whilst also demonstrating potential to reduce systemic inflammation."
The study abstract was presented at the 2025 International Sport & Exercise Nutrition Conference and is available in the International Journal of Sport Nutrition and Exercise Metabolism (Myers E. International Sports and Exercise Nutrition Conference. 2025;36(1):5). The full paper is currently undergoing peer review with a journal.
About Symprove:
Symprove is the UK's No.1 live and active bacteria supplement*.
Founded in 1986, Symprove has spent decades investing in independent scientific research to help build a better understanding of the gut microbiome and the role it plays in overall health.
Unlike many supplements, Symprove's unique water-based formula is designed to deliver live and active bacteria to the gut, where they can have the greatest impact. It contains four strains of live and active bacteria, is suitable for everyday use and is free from dairy, gluten and artificial additives.
Today, Symprove is available on subscription from symprove.com and at leading UK retailers including Tesco, Boots, Sainsbury's, Waitrose, Superdrug, and Holland & Barrett.
For more information, visit www.symprove.com.
For samples or more information, please get in touch with press@symprove.com or call 01252 413 600.
* Source Euromonitor International Ltd; Consumer Health 2026ed., Symprove retail value sales, UK 2025 data
