Can this natural extract boost your endurance in the heat? Here’s the research

Growing up in Wales and England in the UK, I remember visiting my grandparents’ house in the Rhondda Valleys and picking blackcurrants and blackberries from the wild shrubs dotted around. Good old-fashioned British blackberry tart and a popular blackcurrant beverage were family staples. A blackcurrant extract was at the center of recent research designed as a physiological and metabolic case study during heat-acclimation training ahead of Marathon des Sables. Can a blackcurrant extract help you better handle the heat when you’re working out? What’s the impact on fat oxidation and core temperature? Here’s the research.

The study

In a small study published in the Journal of Functional Morphology and Kinesiology, one male and one female ultra-endurance runner took a New Zealand blackcurrant extract (CurraNZ) for seven days. This amounted to about 210 mg of anthocyanins per day. Anthocyanins are potent, beneficial antioxidants and water-soluble pigments that give certain plant foods their intensely vivid colors. They’ve been shown to lower inflammation and provide a range of health benefits.

Blackcurrant extract

The goal of the study was to observe the metabolic, physiological, and core temperature responses in a male and female runner during a 1-hour treadmill run in very hot conditions with blackcurrant extract. These hot conditions are similar to what runners would face in the Marathon des Sables in the Sahara Desert. The two runners regularly exercised or played sports, but they weren’t “acclimatized”, meaning they weren’t used to training in the heat. 

The researchers recorded the runners’ heart rates at 15-minute intervals. The two participants completed their runs three hours after a light breakfast and two hours after taking their final dose of New Zealand blackcurrant extract. Participants drank water during the run.

The results

The results showed the following:

• The female athlete didn’t show any clear, measurable benefits from taking the supplement. As the founder of CurraNZ, Fleur Cushman, points out, “this is actually a key result: it shows that New Zealand blackcurrant extract does not further increase fat oxidation in individuals who already exhibit intrinsically high rates of fat use and low RER, and, in such cases, responses can even diverge.” 
• The male athlete, on the other hand, did show benefits and experienced metabolic changes.
• The male athlete burned 21% more fat during the treadmill run and used 31% fewer carbohydrates.
• The male athlete had a lower core body temperature (0.4°C lower), which can help reduce the risk of overheating in severe heat. There was no change in breathing, heart rate, or oxygen use for the male athlete.

Concluding thoughts

Cushman also points out that this study “adds to the wider evidence base showing that most individuals experience higher exercise fat oxidation and lower carbohydrate use with CurraNZ, with the caveat that those starting with very low RER, who are already highly fat-adapted, may display little additional benefit or a different response profile.” It’s possible people respond differently based on their fitness level, sex, baseline fat-burning rate, and other factors. Growing studies are also highlighting the performance-enhancing effects of the CurraNZ New Zealand blackcurrant extract.