Runners find it hard to ingest carbohydrate during running, perhaps because they are not used to it. Studies show they could benefit from higher intakes. Here I discuss the topic with Aitor Viribay.
A few years ago it was concluded that carbohydrate intake should not be more than 60g/h because we would not be able to oxidise more than this. Now we know we can use more if the right combinations of carbohydrate are used but it is still often questioned whether 90 g/h is even possible in race conditions. In the previous blog we saw that marathon mountain runners were able to ingest 90 g/h and even 120 g/h without any problems. The results also suggested that 120 g/h resulted in some benefits compared to 60 or 90 g/h.
I read the paper with great interest but wanted to find out a little more about the responses of the runners in this study. So, I contacted Aitor Viribay the first author of the paper. A year ago we discussed the theory and some experiences when we accidentally met at an altitude training camp in Sierra Nevada (Spain). Aitor, who was an elite cyclists himself, has a degree in nutrition and is highly interested in physiology and metabolism.
My first question was: is it possible to take 120g/h?
Aitor “Definitely, yes. We are seeing this everyday with professional cyclists who are winning major races and with elite runners who are setting new records. Although these intakes during running could be more challenging than in cycling, it is possible with adequate gut training. Maybe there is not enough direct evidence yet, but the field work is giving us more and more reasons to believe that this can be done. I don´t really know if SGLT-1 and GLUT5 transporters could be adapted to more glucose and fructose absorption than currently understood, or even if the basolateral GLUT2 could be translocated to the apical membrane with high glucose concentration as reported in some studies, but what it is clear is that elite athletes are tolerating these intakes really well, if trained.
“what it is clear is that elite athletes are tolerating these intakes really well, if trained.”
Why did you do the study?
The study was part of a previous project carried out by the Dr.Urdampilleta and Dr.Mielgo Ayuso. I was studying with them in the past years. Our work was focused on trail-running and, specifically, in ultra-trail. We started using extremely high carbohydrate intakes than recommended with really good results, even in 12-14h competitions. Not only good performance results, but also recovery and biochemical parameters. Moreover, my experience with professional cyclists (World Tour and ProTeam) showed me that this could be a possibility to optimize performance further. Then, we saw that major races in the world (Giro de Italia, Tour de France, Hawaii Ironman, Berlin Marathon) were won using similar methodologies. We felt it was important to carry out a study to find out if these extremely high intake could indeed be beneficial. Dr.Urdampilleta and Dr.Mielgo Ayuso designed the study and led the project and this is what started it all.
“we saw that major races in the world (Giro de Italia, Tour de France, Hawaii Ironman, Berlin Marathon) were won using similar methodologies”
What was the response of the runners?
The runners didn´t report any serious GI problems during the race that could limit their performance. The 120g/h group generally reported fullness and a little bit of stress because of the large amount of food, but no major issues. One important observations was probably that they developed some flavor fatigue as a result of the high intake and the constant sweet flavours. This is an important and practical message: we need to pay more attention to the flavor profile of the ingested carbohydrate sources.
Who were your subjects?
They were all Spanish trail runners competing in elite level (among them there were 2 world champions and international stage winners). As Dr.Urdampilleta was working with many trail runners and clubs, he knew a lot of riders that were carrying out a nutrition plan with professional colleagues and had a previous background of CHO intake in this sense.
How did the subjects respond? What did they report? What were their experiences?
The runners took the test as a real race. In fact, there was a high competitive spirit within the group. We had some casualties due to injury (3) and gastrointestinal distresses (3) (that´s the mountain), but the majority of the subjects responded really well to the test. In fact, they didn´t report any serious GI problems during the race that could limit their performance. In this sense, the 120 g/h group generally reported fullness and a little bit of stress because of the big amount of food. Moreover, the sweet flavor tolerance was the bigger nuisance as it saturated some of them from eating. This is a really practical and valuable learning to understand that flavors are more important than what we currently think.
“this doesn´t mean that only athletes who responded well could tolerate this amount of carbohydrate, but only that the working time and effort to reach this target could be longer and harder, respectively.”
Were there individual differences?
Yes. Not everyone tolerated this equally well, but the 7 finisher participants in the 120 g/h group didn´t report serious problems. I am seeing now with the cyclists I work with that there are relevant individual differences between individuals. However, this doesn´t mean that only athletes who responded well could tolerate this amount of carbohydrate, but only that the working time and effort to reach this target could be longer and harder respectively.
Viribay A, Arribalzaga S, Mielgo-Ayuso J, Castañeda-Babarro, Seco-Calvo J, Urdampilleta A. Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon on Exercise-Induced Muscle Damage in Elite Runners. Nutrients 12(5), 1367, 2020. doi: 10.3390/nu12051367.
Aitor Viribay's web site (https://glut4science.com)