Sports Nutrition – Multiple Transportable Carbohydrates

Many manufacturers of sports supplement products are suggesting that multiple transportable carbohydrates can improve performance. Is this a fair statement or is it just marketing spin?

Multiple transportable carbohydrates refer to a carbohydrate food or liquid that provides multiple different types of the simple sugars (usually 2 or 3), when metabolised by the body. The simple sugars are fructose, glucose and galactose. The benefit lies in the fact that these different sugars are absorbed (transported) through the intestinal wall via different absorption channels, called transporters. This allows for greater availability of carbohydrate to the muscles to carry out work.

The major limiting factor in how much energy you can burn is how much energy you can absorb through the gut i.e. transporter saturation. Fructose and glucose also have an added limiting factor in that they have to be converted to glucose in the liver before they can be used for energy. It turns out that the maximum amount of glucose that someone can burn is about 60g/hr, while fructose and galactose are around 30g/hr. Therefore, by consuming say glucose and fructose together you can theoretically burn about 90g/hr of carbohydrate – 60g/hr glucose plus 30g/hr fructose. Numerous studies have reported benefits in athletes in terms of performance, gastric emptying, fatigue and gastrointestinal distress.

So why shouldn’t everyone who exercises be consuming multiple transportable carbohydrates? There’s a few points to discuss why an athlete might not benefit from multiple transportable carbohydrates:

  1. 90g/hr of carbohydrate is only beneficial where exercise duration is beyond 2.5 hrs and of a high intensity. Therefore, if you’re exercising at a medium intensity, or for less than 2.5 hrs, the research suggests that multiple transportable carbohydrates are likely not going to benefit you over a single carbohydrate.
  2. The studies have mainly been done on fasted, well trained, male cyclists in controlled conditions who exercised at a high power output. Therefore, as the author of a 2015 review concluded, more studies are required that include women and adolescents, conducted in the field, different sports, pre-exercise nutrition etc.
  3. Some people have difficulty absorbing fructose and these people are therefore more likely to suffer from gastrointestinal upset, and this has been observed during multiple transportable carbohydrate studies.

So, it appears that multiple transportable carbohydrates are not for everyone. However, if you are an endurance athlete there’s only one way to find out if it might benefit you. By trialing in training and measuring performance and gastrointestinal symptoms you can assess if you gain any benefit. Remember that you should never trial anything new during an event, only trial in training, and preferably some weeks prior to an event. A 2012 study by Rowlands et al suggests a maltodextrin:fructose ratio of 2:1 is best and this seems to be generally accepted in the sports nutrition industry.

About the Author

Rick Hallion is a nutritionist located in Coffs Harbour, NSW. Rick is passionate about providing holistic health care to athletes by combining sports nutrition with naturopathic principles. Rick believes that the physical and emotional demands on athletes can often be high resulting in a need for greater nutritional support.

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