Multiple transportable carbohydrates

Multiple transportable carbohydrates are combinations of different types of carbohydrate that use separate transport proteins in the small intestine. By consuming sugars such as glucose and fructose together, athletes can increase the rate of carbohydrate absorption beyond what a single sugar can provide.

Explanation

When you ingest glucose alone, it is absorbed via the sodium‑dependent transporter SGLT1, which becomes saturated at around 60 g per hour. Fructose uses a separate transporter (GLUT5), so consuming fructose in addition to glucose allows total carbohydrate uptake to exceed the limit of SGLT1. Studies have shown that mixtures of glucose and fructose or maltodextrin and fructose can increase exogenous carbohydrate oxidation by roughly 1.5–1.75 g per minute—about 65 % higher than glucose alone—and support higher exercise intensities for longer durations. To achieve this, sports nutrition guidelines recommend ingesting up to 90 g of carbohydrate per hour from multiple sugars, typically in a 2:1 ratio of glucose to fructose. Using more than one transporter also reduces the risk of gastrointestinal distress that occurs when a single transporter is overloaded.

Optimising fueling with MTC

Many endurance drinks and gels now include blends of maltodextrin or glucose with fructose to deliver high carbohydrate doses without upset. For example, a beverage containing 60 g of maltodextrin and 30 g of fructose per litre (9 % carbohydrate) can supply 90 g per hour if consumed at one litre per hour. Athletes mixing their own drinks can combine plain glucose powder with a smaller amount of fructose or fruit concentrate to achieve the 2:1 ratio. During events lasting longer than two hours, gradually increasing carbohydrate intake up to 90 g/h from multiple sources can spare glycogen and maintain blood glucose. It is important to train the gut; sudden adoption of high intakes may still cause discomfort.

Using multiple transportable carbohydrates allows athletes to deliver more energy to working muscles, sustaining performance while minimising digestive issues.

Related Terms: Carbohydrate–electrolyte beverage, Carbohydrate concentration, Exogenous carbohydrate oxidation, Glucose, Fructose