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Scientists in ‘new territory’ after study finds CurraNZ prevents gastro-intestinal distress when exercising in the heat

on February 14, 2023

Ninety percent of athletes suffer from gut issues in the heat but CurraNZ may offer them hope after exciting findings from a new study1 from the UK.

The study, performed by Dr Ben Lee, a thermal physiologist and now at Coventry University in the UK, found CurraNZ prevented gastro-intestinal (GI) damage and permeability in 50% of participants, during exercise in the heat.

Following a bout of exertional heat stress, participants on CurraNZ blackcurrant extract experienced a large reduction in small intestinal permeability and heat-induced cell damage of up to 40%.

Twelve healthy recreationally active, unacclimatised men took 600mg of New Zealand blackcurrant extract – CurraNZ - for seven days before performing 60 minutes of moderate-intensity treadmill running in hot ambient conditions (34°C, 40% humidity).

Measurements were taken of intestinal fatty acid binding protein, a marker of enterocyte damage, at rest and 20, 60 and 240 minutes post-exercise.

The findings showed the intake of blackcurrant led to:

  • 40% reduction in intestinal fatty acid binding protein (which indicates intestinal cell damage)
  • 12% reduction in lactulose and rhamnose excretion (biomarkers that indicate intestinal permeability)
  • No adverse effects on thermoregulation, with a slight reduction in deep body temperature
  • Improvements to GI function and integrity, compared to placebo, in all participants

Exercise in the heat is one of the most severe demands athletes can place on the gastro-intestinal system. Up to 90% of endurance athletes are affected by symptoms of gastrointestinal distress during exercise in the heat, which are in part caused by a redistribution in blood flow away from the gut, leading to a host of symptoms that, if left uncontrolled, can impair exercise performance and may even lead to more severe outcomes such as heat illness.

The study’s robust findings are particularly relevant to those undertaking running-based exercises known to cause GI distress in the heat.

Dr Lee says: “The caveat with this is that we didn’t prime participants with carbohydrate gels or drinks, which is what athletes typically use during training and competition and can make them ill.

“However, we did see a reduction in upper and lower GI symptoms in athletes using blackcurrant, plus a reduction in other related symptoms, such as nausea, stitch and dizziness.”

“If you were due to compete in the heat, you could consider the use of blackcurrant in the week tapering before the event if you suffer from GI distress.”

The study found the extract had no effect on reducing heat-induced downstream inflammatory responses or translocation of microbial products, which occur with heat stress.

Mark Willems, Professor of Exercise Physiology at the University of Chichester, describes these findings as “high impact”.

The experienced researcher, who has authored >30 peer-review published papers on blackcurrant for sports performance, says: “this is a very exciting finding to see an effect in exercising in the heat, which is a really stressful situation for the body. 

“We were impressed that everyone responded to blackcurrant in this project, which is very unusual in supplementation studies. Usually we either see no effect or about 80% of the subjects responding.”

Importantly, the study showed that blackcurrant had no adverse effect on the body’s core temperature or thermoregulatory processes, showing the supplement is safe to use in hot conditions.

Professor Willems adds: “We’re building a very nice picture that New Zealand blackcurrant is potent in many aspects. This study is taking us into new territory with blackcurrant and with all the data we have so far, it’s proving potent in itself, compared to other anthocyanin-rich products.

“We are realising that it maybe the specific blackcurrant anthocyanin composition that is making this berry stand out from the others.”



  1. Lee et al. Anthocyanin-rich blackcurrant extract preserves gastrointestinal barrier 1 permeability and reduces enterocyte damage but has no effect on microbial translocation and inflammation after exertional heat stress, IJSNEM (in press) doi: 10.1123/ijsnem.2021-0330.