The recommended method to achieve the greatest workout intensity is to ingest carbohydrates before and during your workout. This is a question we hear frequently. In our opinion, only small amounts, if any fructose belong in this type of performance drink. These are a number of reasons. First, there are many people with fructose intolerance and others for whom fructose causes stomach upset.
Some individuals even experience abdominal pain upon rapid ingestion of a fructose solution.
Fructose increases blood glucose levels only 20 to 30 percents, and it does that slowly. Conversely, dextrose increases blood glucose levels 60 to 80 percent providing a much greater fuel level to support a high intensity workout. Some commercially available drinks are a combination of fructose and glucose polymers. The glucose polymers are from maltodextrin which has a bland flavor. The drinks depend solely upon the fructose for sweetness and to bring out the fruit flavors, which obviously translates into significant quantities of slowly metabolized crystalline fructose in a supposedly high performance drink.