Blackcurrants and the gastro-intestinal running puzzle - new data that changes the game

    on September 20, 2023

    US-based Laurel Walker (left) is an elite mountain athlete, ultra-runner and this month's guest blogger.  With GI stress one of the main issues facing ultra-runners competing in the heat, she reflects on the CurraNZ research and her own experience of using the product for this common problem. 

    According to a 2017 presentation (1) at the Western States 100 Mile Endurance Run by CTS endurance coach, Jason Koop "gastric distress is the leading cause of DNF [did not finish] in ultra-endurance sports.”

    If you run ultramarathons, this won’t surprise you and, if you’re like me, gastro-intestinal (GI) distress is one of those pesky factors that consumes your race prep and strategy.

    You’ve tried everything from liquid calories, to heaps of mashed potatoes, and everything in between. Your crew is sick of making ramen and dealing with the aftermath of your attempted feasting at each aid station. 

    One of the reasons I love ultrarunning is that it is like a puzzle; there are many pieces that need to fit together in order to have a successful race.

    The physical act of running often takes a back seat and things such as a meticulous fueling plan, blister care and cooling strategies are front and center. 

    Of each of these puzzle pieces, the fueling plan is generally the biggest focus, because if your gas tank is empty, you won’t be getting very far.

    Add in extreme weather, targeted marketing from nutritional companies, and the myriad of dietary styles buzzing around the community right now, and fueling can become an overwhelming and seemingly impossible topic. 

    Let's take a second to dig a bit deeper into fueling, particularly in the heat.

    Many well-known ultramarathons, such as the Western States 100 Mile Endurance Run, Javelina Jundred and Badwater 135, take place in the heat of the summer. Heat adds another challenging factor on top of the already tough act of eating and running during any endurance event.

    Digesting food tends to become more difficult in the heat because the majority of our blood supply is focused away from the stomach and concentrated on muscle function and cooling our bodies (sweating). Focused training in hot weather, as well as training with the fuel and hydration you'll use on race day, can help a lot, but still does not guarantee a happy belly.

    As you can imagine, or may have experienced yourself, many ultramarathoners are still plagued by stomach issues despite attempts at specific fueling training plans. 

    Luckily, CurraNZ just might be able to help.

    CurraNZ is the award-winning all-natural blackcurrant supplement that is starting to make a splash in the trail and ultrarunning community across the globe.

    World-class ultrarunners such as Hayden Hawks and Ruth Croft are already backing the product for its recovery and performance benefits. 

    Blackcurrants are rich in anthocyanin, a chemical compound found in dark colored fruit, particularly berries. These compounds have demonstrated benefits including reduced fatigue, enhanced recovery and anti-inflammatory properties.

    However, for the purposes of this article, we are interested in how it can help reduce stomach issues, particularly in the heat.

    One particular study (2) looking at the effects of CurraNZ on GI functionality, found that a  7-day trial of 600mg/day of the anthocyanin-rich extract sufficiently reduced stomach permeability and damage to intestinal cell wall lining, commonly referred to as Leaky Gut.

    Leaky gut is the common term that you might have heard for damaged intestinal cell wall linings causing permeability.

    Our intestinal wall linings are designed to absorb water and nutrients from our food, but when they become damaged, they can let toxins into our bloodstream and make us feel sick. As you can imagine, if you are already having a difficult time eating while running, these symptoms only make it worse. 

    A second study (3), which focused specifically on the effects of CurraNZ on GI function in the heat, showed a 50% reduction in upper and lower GI distress symptoms, as well as a 25% reduction in other GI related symptoms like nausea, stitch and dizziness.

    While there is always more research to be done, these results are promising and exciting for ultrarunners!

    With my own personal experience, I've been impressed with the reduction in stomach upset symptoms I've noticed both during and after my training sessions since starting to take CurraNZ.

    If you're an ultrarunner or endurance athlete of any type, I'd encourage you to give CurraNZ a try, especially if you are training and racing in the heat. I think you'll be happy you did. 


    1. Koop, Jason (2017). Ultrarunning Training Presentation from 2017 Western States Endurance Run.

    2. Lee, B. J. , Flood, T. R. , Hiles, A. M, Walker, E.F., Wheeler, L. EV, Ashdown, K. M, Willems, M. ET, Costello, R., Greisler, L.D, Romano, P.A., Hill, G.W., Kuennen, M.R., 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 (2022). Accepted version International Journal of Sports Nutrition and Exercise Metabolism. 1-29. 

    3. Willems, M.ET., Hiles, A.M., Flood, T. R., Wheeler, L. EV. Ashdown, K. M., Kuennen, M. R., Lee, B. J. , Anthocyanin-rich New Zealand blackcurrant extract reduces running-induced gastro-intestinal symtpons in the heat. (2022). Released at ISSN, June 17, 2022.