UK researchers have found that ingesting large amounts of two simple carbohydrates during prolonged cycling exercise allows for significantly greater conversion of carbohydrate to energy than ingesting one alone.

Eight trained cyclists performed three exercise trials in random order. Each trial consisted of 150 minutes of cycling at 55% maximum power output while ingesting a total of 2.4 litres of one of the following:

• An 11.25% maltodextrin (glucose polymer) drink;
• A drink containing maltodextrin and fructose, providing the same amount of energy as the first drink;
• Plain water.

The researchers had hypothesised that the combined maltodextrin-plus-fructose drink would elicit higher carbohydrate oxidation rates during exercise than maltodextrin alone because they use different intestinal carbohydrate transporters and so could carry more total carbohydrate ‘traffic’.

And they were not disappointed! Peak exogenous carbohydrate oxidation (conversion of ingested carbs to energy) measured during the last 30 minutes of exercise was about 40% higher with the combination drink than with maltodextrin alone – at 1.5g per minute compared with 1.06g. ‘In addition,’ they say, ‘the oxidation rates observed in the present study were higher than those previously reported for combined glucose and fructose/sucrose ingestion during exercise.

‘These data suggest that if high exogenous CHO oxidation rates are required during exercise… ingestion of a solution containing multiple transportable CHO in the form of maltodextrins and fructose is recommended.’

Med Sci Sports Exerc 2005; vol 37, no 3, 426-432