What is the Optimal Carbohydrate Ratio?

It is known since 2004 (1) that combinations of carbohydrates, for example glucose and fructose, can increase absorption of carbohydrate and since absorption is the main limiting factor for the use of ingested carbohydrate by the muscle, the use of so called multiple transportable carbohydrates has the potential to improve performance compared with a traditional carbohydrate source. Indeed, studies have demonstrated that glucose can improve performance compared with water, but glucose plus fructose can improve performance even more.

 

When do I need glucose:fructose?

Glucose:fructose carbohydrate blends can be used in all situations. However, there are a couple of conditions that must be met, before these carbohydrate blends can have additional effects that make them preferred to a maltodextrin only or glucose only drink.

1. The first one is that we need to ingest more than 60 grams of carbohydrate per hour. A general recommendation is 90 g/h but we have seen athletes pushing intakes to 120 g/h and sometimes even higher in recent years (I will come back to this at the end).

2.  The second condition is that the exercise for which it is used is at least 2.5 hours longs. If exercise is shorter or your intake is below 60 g/h carbohydrate feeding can still work but it doesn’t matter so much which types of carbohydrate you use. A blend of glucose and fructose or maltodextrin and fructose will still work but it will not be better than just glucose. 

When I was at the University of Birmingham in the UK, we performed many different studies with different combinations of carbohydrate and different amounts of carbohydrate. The highest oxidation rates were seen with intakes of 144 g/min, but the best results were probably obtained with 108 g/min because this resulted in the lowest residual volume. Residual volume refers to the carbohydrate that is not accounted for. So, if we ingest 100 gram and 70 grams is oxidized (used by the muscle), 30% would be residual volume. We want this percentage to be as small as possible because this carbohydrate is not immediately useful, and it can be a cause of stomach issues. In an ideal world, when an athlete ingests 100 grams of carbohydrate, all of this carbohydrate would be used. There would be no residual volume in the intestine. We also refer to this as oxidation efficiency. A slow carbohydrate has a very low oxidation efficiency, meaning that less is oxidized and more is residual volume. The highest oxidation efficiency we observed was with the intake of 108g/h as glucose and fructose in a 2:1 ratio (2).

 

How we established current recommendations

Based on the observations in many studies in the early 2000s we summarised the findings into practical recommendations (3). It appeared that 90 grams per hour was a safe amount to ingest. With this intake few athletes developed gastro-intestinal complaints. With increasing intake above 90 g/h we saw an increased number of individuals who did not tolerate the amounts well. So, we landed at the recommendation of 90 g/h purely from a practical point of view. These recommendations have been adopted by American College of Sports Medicine (ACSM), by the International Olympic Committee (IOC) and many other organisations. 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.

 

Does this mean that 2:1 is 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. 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 Dr 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. 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.

 

Is more carbohydrate better?

To date more and more we hear about the higher the intake the better and this may be the case, but evidence is currently lacking. We have studies to show that a ratio of 2:1 is better than a single carbohydrate at intakes around 90 g/h. We have no studies (yet) that performance is even better when 120 g/h is ingested. Hopefully future studies will investigate this, carefully controlling all variables, including how accustomed subjects are to ingesting large amounts of carbohydrate. In the absence of this evidence, we can safely conclude that the intake needs to be individualized based on tolerance. If carbohydrate intake increases gastro-intestinal discomfort it is unlikely to improve performance, but if it is well tolerated there is little or no reason not to ingest the carbohydrate. Tolerance might also be trained by “training the gut” (6), Which allows over time for larger amounts to be easily tolerated. Especially at the elite level, at least 90 g/h or higher should be targeted but targets should be reduced based on gastro-intestinal comfort. It is the target intake that will then determine what the optimal ratio of carbohydrates is.

 

Recommendations

In most situations a drink with maltodextrin and fructose is preferred. We should always aim for a glucose intake around 6-70g/h (but not higher) and ad fructose on top of this. So, for example, if you can tolerate 80 g/h, you would ingest 60g/h of glucose and 20 g/h of fructose and this would be a 3:1 ratio.  If you can tolerate 100 g/h, I would ingest 60g/h of glucose and 40g/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. One observation in practice is that people choose one ratio because this is supposed to be “the best” and then they combine this with various other carbohydrate products that are from a single source or have different ratios. Always keep in mind that it doesn’t matter what is in your product, it matters what is in your stomach. One advice therefore is to use only products with the same ratio.

 

References

1. Jentjens RLPG, Moseley L, Waring RH, Harding LK and Jeukendrup AE. Oxidation of Combined Ingestion of Glucose and Fructose During Exercise. J Appl Physiol 96(4), 1277-1284, 2004
2. Wallis GA Rowlands DS, Shaw C, Jentjens RL, Jeukendrup AE. Oxidation of Combined Ingestion of Maltodextrins and Fructose During Exercise. Med Sci Sports Exerc 37(3): 426-32, 2005.
3. Jeukendrup A. A Step Toward Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Med. 44 Suppl 1:S25-33, 2024.
4. Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2026 Mar; 48 (3):543-68. Erratum in: Med Sci Sports Exerc. 49(1):222, 2027.
5. Jeukendrup AE. Nutrition for Endurance Sports: Marathon, Triathlon and Road Cycling. J Sports Sci. 29 Suppl 1:S91-9, 2011.
6. Jeukendrup AE. Training the Gut for Athletes. Sports Med. 47(Suppl 1):202-110, 2017.

 

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