THIS WEEK IN PRO CYCLING »

Get the VeloNews Email Newsletter FREE

  Learn More | Archive
Home » Top Stories » Training »

The feed zone - Nutrition Q&A with Monique Ryan

Published: Aug. 27, 2003

Dear Monique:
Are cyclists at risk for excess insulin production and developmentof diabetes due to ingestion of large amounts of sugar? We are using sportsdrinks, gels, and energy bars during training, and I know that I couldn’ttrain without them.
Thanks
RC
 To address the concern described above, I asked Bob Murray, PhD, anddirector of the Gatorade Sports Science Institute to answer a few questionsregarding sports drinks.Q - Many endurance athletes consume products containing sucrose,and other related sugars during exercise. How are these sugars utilizedduring exercise and why are they so important to performance?

 A - Ingesting carbohydrates in the form of "simple"sugars such as sucrose, glucose, and maltose benefits performance becauseactive muscles can use the extra glucose (the end form of all ingestedcarbs) for energy. Carbs eaten during exercise are quickly digested andabsorbed in the small intestine, enter the bloodstream, and are then transportedthroughout the body as glucose. Muscles love to use glucose for energyand doing so enables them to work at higher intensities - hence the performancebenefit.


Q - Please describe how what occurs with the insulin responseto these sugars during exercise.

A - Anytime we eat carbohydrate (in a baked potato,a plate of pasta, or a sports drink), insulin is secreted by the pancreasinto the bloodstream. This is a normal, natural, and essential responsebecause insulin enables glucose (blood sugar) to be taken up by cells throughoutthe body, particularly by muscle cells. During exercise, we actually secreteless insulin in response to eating carbs because exercise makes it easierfor the muscles to take up glucose.

Q - We have heard a lot in the past few years about the glycemicindex (GI) of foods, and now of sports drinks and other sports nutritionsupplements. What type of GI would be preferred in a sports drink and howdoes this enhance performance?

 A - A good sports drink contains a blend of carbohydratessuch as sucrose, glucose, and fructose, most of which are often referredto as having a "high" glycemic index (fructose has a low glycemic index).In short, this means that the carbs are readily digested and absorbed,resulting in a rapid increase in blood sugar and - most important - rapidentry of that sugar (glucose) into muscle cells. Once inside the muscle,the extra glucose is quickly broken down for energy, helping the musclemaintain a high-intensity output that results in improved performance.

Dear RC;
While what carbohydrate your body most easily tolerates and utilizesduring exercise is unique for training, it is important that in your dailytraining diet that your food choices emphasize whole grains as much aspossible for their higher nutrient content. Whole grains are packed withvitamins, minerals, and phytochemicals which have powerful antioxidantand disease fighting properties.  Whole grains also provide vitaminE and the mineral selenium, and regular consumption of whole grains islinked to prevention of heart disease, cancer, and diabetes. You shouldalso place a strong emphasis on fruits and vegetables for good carbohydratesources in your diet. A high intake of these foods can reduce your riskof heart disease, stroke, and certain types of cancer.The glycemic index ranks foods on how quickly the carbos they provideenter the bloodstream and elevates blood sugar. However, glycemic indexcan vary greatly for a specific food depending on how it is prepared andwhat other foods it is consumed with. The glycemic load of a food mustalso be taken into consideration (this accounts for the portion of thefood as well as the glycemic index). The insulin response of the food canalso be considered, and is an area of future research. Short-term studieson glycemic index indicate that it may be a useful tool in preventing obesityand diabetes, but larger and more long-term studies are needed. We alsowant more useful information on the clinical application and real-lifeapplication of the glycemic index. But you can emphasize lower glycemicindex foods in your daily diet as long as this is compatible with yourtraining diet requirements and training program.Monique

Monique Ryan, MS, RD, is the author of the "Complete Guide to Sports Nutrition,” and “Sports Nutrition for Endurance Athletes” from VeloPress. She is a regular columnist for Inside Triathlon and VeloNews magazines and is founder of Personal Nutrition Designs, a nutrition consulting company based in the Chicago area. Ryan regularly counsels athletes on performance and health-related nutrition concerns and offers services through her website at "www.moniqueryan.com.” She has consulted with the Saturn Cycling Team since 1994, and has also worked with Volvo-Cannondale, Trek-Volkswagen, and USA Cycling. Ryan offers answers to reader’s questions each Wednesday in this weekly column. Readers are welcome to send questions directly to Ryan. The information in The feed zone does not constitute prescriptive nutritional advice. The information provided on this web site is solely for general interest of the visitors to that site and is intended for educational purposes only.