Study finds blackcurrant supplement CurraNZ® resolves common stomach upsets in runners in the heat

A new study in Research in Sports Medicine reveals that CurraNZ®, a New Zealand blackcurrant supplement, significantly reduces the incidence and severity of gastrointestinal (GI) symptoms in runners exercising in hot conditions.

 Key Findings:

• Dramatic Reduction in GI Symptoms: After seven days of CurraNZ® supplementation, only 25% of participants reported GI symptoms during an hour of treadmill running in the heat, compared to 92% with placebo.
• Upper GI Distress Slashed: The number of runners experiencing upper GI symptoms, such as belching, bloating, and stomach pain, dropped from 75% (placebo) to 25% (CurraNZ®).
• Lower and Other GI Symptoms Reduced: Lower GI symptoms fell from 25% to 17%, and other symptoms (including nausea and dizziness) dropped from 50% to 25%.
• Severity of Symptoms Lowered: The overall severity score of GI symptoms was halved with CurraNZ® supplementation (placebo: 112, CurraNZ®: 54).

The research, led by, Mark Willems, Professor in Exercise Physiology at the University of Chichester, stated: “If you were due to compete or train in the heat, supplementing with blackcurrant in the week before would be highly beneficial if you customarily experience mild symptoms of upper and lower GI distress.

“It is impressive that the 75% participants who displayed upper GI symptoms in the study were reduced to 25% with blackcurrant. The reduction in symptoms is really meaningful for athletes and those prone to GI upsets during exercise.”

Why it Matters

GI issues are among the leading reasons athletes fail to finish endurance events in hot weather, with up to 90% affected at some point. These symptoms can impair performance, disrupt carbohydrate absorption and lead to more severe outcomes.

Currently, there are few supplemental interventions supported by research, that reduce symptoms of exertional heat stress in athletes. 

These heat-induced symptoms when exercising are caused by ‘leaky gut’ - impaired GI integrity and function, resulting from redistribution in blood flow away from the region.

Enzans™, the anthocyanin bioactives in New Zealand blackcurrant extract, have been previously shown to counteract leaky gut and prevent GI injuries in runners by reducing heat-induced cell damage and intestinal permeability up to 40%.

About The Study

In the study, researchers tested 12 healthy recreationally active, unacclimatised men during an hour of moderate-intensity running in hot ambient conditions (34°C, 40% humidity). The treadmill test followed seven days’ intake of 600mg of the standardized anthocyanin extract.

Eleven of the 12 subjects reported GI symptoms, with nine experiencing mild distress, and two severe.

• The findings showed a two capsule serving of CurraNZ®:
•           Abolished GI symptoms in 7 of the 11 participants
•           Abolished upper GI distress symptoms in 50% of the subjects (75% placebo vs 25% blackcurrant)
•           Reduced instances of lower GI distress from 25% placebo to 17%
•           Reduced the instance of nausea by 50%, from 4 to 2 participants

Professor Willems adds: “If you customarily experience mild GI symptoms from running in the heat, they are likely to be resolved by supplementing with New Zealand blackcurrant extract.

“We’re building a very nice picture that New Zealand blackcurrant is potent in many aspects. These findings are 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.”

References

1.     Willems et al. CurraNZ, an anthocyanin-rich New Zealand blackcurrant extract reduces treadmill running-induced gastrointestinal symptoms in the heat: A pilot study, Research In Sports Medicine, 2025, https://doi.org/10.1080/15438627.2025.2471380

2.     Lee et al. 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, Int J Sport Nutr Exerc Metab. 2022 Mar 14;32(4):265-274. doi: 10.1123/ijsnem.2021-0330. 

3.   Lee et al,  New Zealand blackcurrant extract modulates the heat shock response in men during exercise in hot ambient conditions, Eu J Applied Physiology April 2024, https://doi.org/10.1007/s00421-024-05439-w