Carbohydrates are the fuel for our muscles when we exercise, especially at moderate or high intensities. Drawing a comparison with a car engine, when we exercise at low intensity, it is likely that much of the energy we need can come from the “Eco” or electric mode; in our case, from fats. However, when we try to increase the intensity, we need quick energy, gasoline. And in our body, that means metabolizing carbohydrates.
Since glycogen stores are limited, just like a car's gasoline, consuming carbohydrates during exercise is an effective strategy to increase performance and reduce fatigue, as we have discussed on previous occasions (you can read more about the benefits of carbohydrates on performance and “endurance” here and here). In fact, the longer and more intense the exercise we are performing, the more it is recommended to increase carbohydrate intake, as we see in Figure 1. But, is any type of carbohydrate suitable?
Figure 1. Recommendations for carbohydrate consumption during exercise by Jeukendrup (1). Obtained from www.fissac.com.
The importance of mixing different types of carbohydrates.
Until just over a decade ago, the classic guidelines recommended consuming approximately 60 grams of carbohydrates per hour of exercise regardless of the duration, under the hypothesis that the transporters used by the intestine to absorb carbohydrates and by the muscle cell to take them in had that tolerance limit. However, later studies showed that when carbohydrates that use different transporters (such as glucose and fructose, for example) are consumed together, that amount could be increased. For example, various studies led by the prestigious nutritionist Asker Jeukendrup showed that very high doses (between 108 and 144 g/h) of a glucose and fructose mixture allowed for greater carbohydrate oxidation and induced greater performance benefits not only compared to a placebo, but also compared to the same amount of carbohydrates coming only from glucose (Figure 2) (2,3).
Figure 2. Performance during a time trial in which cyclists took a placebo (water), or the same amount of carbohydrates coming only from glucose or from a mixture of glucose and fructose (3). Obtained from www.fissac.com.
Therefore, we currently know that we can tolerate more than 60 grams per hour of carbohydrates, but it is recommended to mix different carbohydrates, usually maltodextrin and fructose or glucose and fructose. In fact, current guidelines recommend that when exercise lasts more than 2 – 3 hours, up to 90 grams per hour of carbohydrates should be consumed, and we know that in the professional peloton, even higher doses are consumed (reaching and exceeding 120 grams per hour) (you can read more about it here). But now, if different carbohydrates need to be mixed, what is the ideal mixture?
Carbohydrate ratio and performance
In the aforementioned studies that confirmed the effectiveness of mixing different types of carbohydrates on performance, glucose or maltodextrin was provided together with fructose in a ratio of 1:0,5, that is, twice as much glucose or maltodextrin as fructose (for example, 60 grams of maltodextrin and 30 of fructose per hour), compared to the classic ratio 2:1. However, later studies sought to analyze whether different carbohydrate ratios could maximize these effects. For example, a study in cyclists evaluated the effects of consuming water or 108 grams per hour of carbohydrates with different ratios: the classic 1:0,5 (or 2:1 mentioned) (half fructose and half maltodextrin), but also one of 1:0,8 (that is, 80% fructose) and another of 1:1,25 (that is, 25% more fructose than maltodextrin) (4).The results showed that the ratio of 1:0,8 not only was the one that maximized the oxidation of these carbohydrates during exercise the most, but it also was the one that improved peak power the most in an incremental test (3,6% and 3,0% more power with the ratio 1:0,8 and 1:1,25 compared to the ratio of 1:0,5). In addition, participants reported less nausea and gastrointestinal discomfort with the ratio of 1:0,8.
CONCLUSIONS
In low-intensity and short-duration exercises, carbohydrate requirements are not high, and it may be sufficient to consume small amounts (60 grams per hour or even less) of a single type of carbohydrate. However, as duration and intensity increase, especially from 2 – 3 hours, it may be advisable to aim for intakes of 90 grams per hour. To achieve this, and in order to maximize benefits and facilitate tolerance, it is important to mix different types of carbohydrates, such as maltodextrin and fructose. In this regard, it has been found that a ratio of 1:0,8 of these nutrients may be the one that most improves performance and causes the fewest gastrointestinal symptoms .
HYPER (1:0,8) LINE
AUTHOR
Pedro Valenzuela
Researcher in the Physiology Unit of the University of Alcalá and in the Performance Control Unit at the Sports Medicine Center (AEPSAD, CAR of Madrid).
Web: www.fissac.com
REFERENCES
1. Jeukendrup A. A step towards personalized sports nutrition: Carbohydrate intake during exercise. Sport Med. 2014;44(Suppl 1):25–33.
2. Jentjens RLPG, Venables MC, Jeukendrup AE. Oxidation of exogenous glucose, sucrose, and maltose during prolonged cycling exercise. J Appl Physiol [Internet]. 2004;96(4):1285–91. Available from: http://jap.physiology.org/content/96/4/1285.abstract
3. Currell K, Jeukendrup AE. Superior endurance performance with ingestion of multiple transportable carbohydrates. Med Sci Sports Exerc. 2008;40(2):275–81.
4. O’Brien WJ, Rowlands DS. Fructose-maltodextrin ratio in a carbohydrate-electrolyte solution differentially affects exogenous carbohydrate oxidation rate, gut comfort, and performance. Am J Physiol – Gastrointest Liver Physiol. 2011;300(1):181–9.
