Is 90 g of carbohydrate an hour still the ceiling?

A 2026 review in The Journal of Nutrition proposes that the upper limit of carbohydrate intake during endurance exercise could rise from 90 to 120 grams per hour, at least for trained athletes. The case rests on how much carbohydrate the body can burn at those intakes, not on proof of faster racing. The authors say the performance benefit above 90 g/h remains to be determined.

What do the current carbohydrate guidelines say?

The reference point is the 2016 American College of Sports Medicine guidance. The review by Morton et al., Journal of Nutrition 2026 quotes it as 30 to 60 g per hour for endurance and stop-and-start exercise lasting 1 to 2.5 hours, and up to 90 g per hour for ultraendurance exercise beyond 2.5 to 3 hours. The higher figure applies to blends of carbohydrates that use different gut transporters, such as glucose and fructose.

The proposal to raise the ceiling draws on studies that fed such blends at 120 to 144 g per hour. Average peak oxidation of the ingested carbohydrate in those studies reached 96 to 105 g per hour, above the 90 g/h figure.

Does more carbohydrate mean better performance, and what about the gut?

That is the open question. The authors write that whether intakes above 90 g/h improve performance beyond 60 to 90 g/h in exercise over 2.5 hours “remains to be determined”. The authors call for further research in both male and female athletes.

Gut comfort is part of the picture. In a marathon study described in the review, moderate gastrointestinal symptoms occurred at every intake, and nausea, stomach fullness and cramps peaked at 120 g/h. The review also reports that repeated exposure of the gut to carbohydrate in training has consistently reduced discomfort in studies at 30 to 90 g/h.

People differ. The review reports that larger athletes oxidised substantially more ingested glucose, and that body size correlated strongly with peak oxidation. Differences like these are why personal baselines can say more than group averages.

The bottom line

• A 2026 review proposes raising the carbohydrate upper limit from 90 to 120 g/h for trained athletes, based on higher oxidation rates at those intakes.
• Whether more than 90 g/h improves performance is not established, and intakes of 120 to 200 g/h are described as unsubstantiated.
• Gut symptoms and carbohydrate oxidation differ between individuals, and the review calls for research in both male and female athletes.