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A breakthrough in gut protection for endurance athletes? That’s what scientists are calling the latest studies on CurraNZ® Original, revealing its impressive GI-protective effects in hot conditions — and offering hope for runners battling the dreaded “Runner’s Trots.”
Up to 90% of endurance athletes experience gastrointestinal (GI) issues when exercising in heat — a problem that not only disrupts performance but can be race-ending. From nausea and diarrhoea to dizziness and vomiting, GI distress during exertional heat stress is one of the most pressing challenges in sports performance.
Now, new research is showing that just seven days of supplementation with CurraNZ blackcurrant extract significantly reduces gut distress symptoms during exercise in high temperatures — an exciting development for athletes looking for a simple, effective solution.
Exertional heat stress occurs when blood is redirected away from the gut to help cool the body during exercise. This leads to reduced gut function and a condition commonly referred to as “leaky gut.”
Until now, the only prevention strategy has been complex and time-consuming heat acclimation training, often inaccessible to amateur athletes.
But this new study found that CurraNZ enhanced gut barrier function and reduced gastric distress in 73% of runners, compared to placebo. The berry’s powerful polyphenols reduced heat-induced cell damage and gut permeability by up to 40%.
“I’m impressed with blackcurrant’s ability to reduce markers of gut leak,”
says Dr. Matthew Kuennen, exercise physiologist at High Point University and study co-author.
“Blackcurrant may be a valuable option when heat acclimation isn’t feasible.”
Dr. Stefanie Flippin, a Colorado-based physician and professional ultra-runner, welcomed the study as a game-changer for runners.
“There isn’t a runner who hasn’t faced GI distress. This study highlights a meaningful, preventative strategy.
"With current strategies limited to heat training itself, any type of mitigation and protective measure is highly beneficial and New Zealand blackcurrant extract offers an exciting new supplement for runners.”
For trail and ultra runners, the ability to refuel during long events is crucial. GI distress can quickly unravel even the most prepared athletes. According to Dr. Flippin, many athletes resort to antacids, which offer little proven benefit - until now, no supplement has been shown to provide direct gut protection backed by clinical research.
Participants: Recreationally active men not acclimated to heat
Protocol: 7-day supplementation with 600mg of CurraNZ
Exercise: Moderate treadmill running in 34°C (93.2°F)
Results:
Reduced GI symptoms in 73% of participants
Improved gut barrier function
No negative impact on core temperature or thermoregulation
While some aspects of heat-induced gut stress weren’t completely prevented — such as bacterial leakage — the supplement showed real protective effects.
Elite athletes are already putting this research into action. Ruth Croft, one of New Zealand’s top ultra runners, credited her use of CurraNZ for helping her thrive in the 2023 Western States Endurance Run, where she posted the third-fastest women’s time ever, shaving 12 minutes off her previous PB.
Last year, Hayden Hawks delivered standout performances when winning CCC at UTMB and placing third at Western States - and credited the product for resolving his customary GI issues.
CurraNZ continues to build its reputation as a multi-faceted performance and recovery supplement, now with GI-protective benefits added to its already proven effects on fat oxidation, blood flow, and muscle recovery.
For runners training or racing in the heat, this study adds compelling evidence that CurraNZ may be the edge they’ve been looking for — without the need for weeks of heat training.
References
1 CurraNZ, an anthocyanin-rich New Zealand blackcurrant extract reduces treadmill running-induced gastro-intestinal symptoms in the heat: A pilot study. February 2025, Research in Sports Medicine, DOI: 10.1080/15438627.2025.2471380
2. New Zealand blackcurrant extract modulates the heat shock response in men during exercise in hot ambient conditions. European Journal of Applied Physiology https://doi.org/10.1007/s00421-024-05439-w, February 2024
3. Anthocyanin-rich blackcurrant extract preserves gastrointestinal barrier permeability and reduces enterocyte damage but has no effect on microbial translocation and inflammation after exertional heat stress, International Journal of Sports Nutrition and Exercise Metabolism, July 2022. DOI: 10.1123/ijsnem.2021-0330
