What is the optimal glucose fructose ratio for performance?

There is so much discussion about the optimal glucose fructose ratio of carbohydrates. Companies are claiming their ratio is the best, but what does the evidence say? What is better? 2:1? 1:0.8? 1:1? These are some of the common ratios used. Here we will explore the topic in more detail, but the conclusion is that there is no optimal carbohydrate ratio, and what is optimal depends on the conditions. To understand the why and how, we need to go back to the beginning and the discovery of the benefits of carbohydrate blends such as glucose and fructose. This post is based on an earlier blog on Dr Jeukendrup's mysportscience.

The science behind carbohydrate ratios

When we started to study this topic in the late 1990s, no matter what protocols were used and what type of carbohydrate, no one seemed to be able to deliver more than 60 g/h to the muscle during exercise. We and several other researchers started to investigate this limitation and discovered it was neither gastric emptying, neither muscle glucose uptake, neither muscle metabolism that were the limiting factor. By exclusion, we concluded that it had to be absorption (1,3). The absorption of carbohydrates is facilitated by transport proteins. Glucose is transported by a sodium dependent glucose transporter 1 (SGLT1). Perhaps this transporter was becoming saturated at high glucose intakes? There were not many alternatives. GLUT5 is another transporter that transports fructose. The theory was developed that if both transporters would be used at the same time it would be possible to absorb more carbohydrate and this should then lead to greater delivery to the muscle, and greater use by the muscle (3).

Indeed, the first study to combine glucose and fructose showed exactly this. When glucose and fructose were combined oxidation rates were 50% higher compared with just glucose ingestion (4). This opened up a lot of opportunities: different combinations of carbohydrates could be tested and the amounts ingested were increased up to 3 g/min or 180 g/h in those early years (don't try this at home!!).

The highest oxidation rates were seen with intakes of 144 g/h (5), but the best results were probably obtained with 108 g/h because this resulted in the lowest residual volume (4,6). When we ingest 100 grams of carbohydrate ideally we want all of this carbohydrate to be used and we want as little of this as residual volume in the intestine. The more carbohydrate remains in the stomach, the greater the chances of intestinal problems. The highest oxidation efficiency was observed with the intake of 108 g/h as glucose and fructose in a 2:1 ratio (4,6).

What glucose:fructose ratio was recommended, and why?

We then had to summarise the findings of all these studies into practical recommendations and it seemed that 90 grams per hour was a safe amount to ingest with very few athletes displaying gastro-intestinal problems. With increasing intake above 90 g/h we saw an increased number of individuals who did not tolerate the amounts well (2,7). So we landed at the recommendation of 90 g/h purely from a practical point of view.

The ratio we suggested was 2:1 glucose:fructose or maltodextrin:fructose because of 2 reasons: first the amount of glucose needed to be just enough to saturate the glucose transporter and we had seen the highest oxidation efficiency with similar ratios and amounts (3,4). We had also shown that you can go higher with the intake and that this will result in an increase use of the carbohydrate but it came at the cost of more carbohydrate accumulating in the gut and an increased risk of gastro-intestinal problems.

Is 2:1 the optimal ratio?

There is no optimal ratio. The ratio that is optimal will change depending on amounts ingested. If 90 g/h is ingested it should be around 2:1, but if more is ingested, for example 120 g/h, 1:1 is likely better (8). There are many commercial preparations with claims of the best ratio, but the reality is that there is no best ratio. A common ratio is 1:0.8 glucose:fructose and this is the result of one study by Dave Rowlands who used this ratio and showed that in the conditions of that particular study, oxidation was slightly higher for the 1:0.8 glucose:fructose compared with 2:1 (9). But of course this doesn't mean that this ratio is the best in all conditions and it will change when different amounts are ingested.

There is no optimal ratio. The ratio that is optimal will change depending on the amount of carbohydrate ingested.

To date, we hear more and more about the higher the intake the better, and this may be the case, but evidence is currently lacking (10). We have studies to show that 2:1 is better than a single carbohydrate at intakes around 90 g/h (11). But so far, performance effects for even higher intakes (>90 g/h) have not been demonstrated (10,12). Hopefully future studies will investigate this, carefully controlling all variables, including how accustomed subjects are to ingesting large amounts of carbohydrate.

So, what can we conclude about carbohydrate ratios?

For now, we can conclude that the intake needs to be individualised based on tolerance. This tolerance might improve by training the gut (13,14), but the intake should be based on what is easily tolerated. Especially at the elite level higher intakes should be targeted. It is the target intake that will then determine what the optimal ratio is.

We should always aim for a glucose intake around 60-70 g/h but not higher and we can add fructose on top of this (3,4). Below are some examples:

• If I can tolerate 80 g/h, I would ingest 60 g/h of glucose and 20 g/h of fructose. This would be a 3:1 ratio.

• Whereas if I can tolerate 100 g/h, I would ingest 60 g/h of glucose and 40 g/h of fructose. This would be a ratio of 3:2.

Most commercial preparations are 2:1 or 1:0.8 glucose:fructose. 2:1 would be best if 90 g/h would be ingested and 1:0.8 would probably be preferred if closer to 110 g/h is ingested.

References

1. Jeukendrup AE, Jentjens R. Oxidation of carbohydrate feedings during prolonged exercise: current thoughts, guidelines and directions for future research.Sports Med 29(6) 407-424, 2000.

2. Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise.Sports Med 44(Suppl 1) S25-S33, 2014.

3. Jeukendrup AE. Carbohydrate and exercise performance: the role of multiple transportable carbohydrates.Curr Opin Clin Nutr Metab Care 13(4) 452-457, 2010.

4. Jentjens RLPG, Moseley L, Waring RH, Harding LK, Jeukendrup AE. Oxidation of combined ingestion of glucose and fructose during exercise.J Appl Physiol (1985) 96(4) 1277-1284, 2004.

5. Jentjens RLPG, Jeukendrup AE. High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise.Br J Nutr 93(4) 485-492, 2005.

6. Wallis GA, Rowlands DS, Shaw C, Jentjens RLPG, Jeukendrup AE. Oxidation of combined ingestion of maltodextrins and fructose during exercise.Med Sci Sports Exerc 37(3) 426-432, 2005.

7. Pfeiffer B, Stellingwerff T, Hodgson AB, Randell R, Pöttgen K, Res P, Jeukendrup AE. Nutritional intake and gastrointestinal problems during competitive endurance events.Med Sci Sports Exerc 44(2) 344-351, 2012.

8. Podlogar T, Bokal Š, Cirnski S, Wallis GA. Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g/h versus 90 g/h at different ratios.Eur J Appl Physiol 122(11) 2393-2401, 2022.

9. 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 300(1) G181-G189, 2011.

10. Morton JP, Fell JM, Gonzalez JT, Hearris MA, Podlogar T, Pugh JN, Wallis GA. From metabolism to medals: contemporary perspectives and revisiting carbohydrate guidelines for fueling endurance athletes during exercise.J Nutr 156(5) 101442, 2026.

11. Currell K, Jeukendrup AE. Superior endurance performance with ingestion of multiple transportable carbohydrates.Med Sci Sports Exerc 40(2) 275-281, 2008.

12. Smith JW, Pascoe DD, Passe DH, Ruby BC, Stewart LK, Baker LB, Zachwieja JJ. Curvilinear dose-response relationship of carbohydrate (0-120 g/h) and performance.Med Sci Sports Exerc 45(2) 336-341, 2013.

13. Jeukendrup AE. Training the gut for athletes.Sports Med 47(Suppl 1) 101-110, 2017.

14. Miall A, Khoo A, Rauch C, Snipe RMJ, Camões-Costa VL, Gibson PR, Costa RJS. Two weeks of repetitive gut-challenge reduce exercise-associated gastrointestinal symptoms and malabsorption.Scand J Med Sci Sports 28(2) 630-640, 2018.