Microsoft word - sports drinks, what works and what doesn't.doc
SPORTS DRINKS – WHAT WORKS… AND WHAT DOESN’T?
Not all sports drinks are created equal and there are many differences that exist between brands. These differences are important because they not only determine the type and quantity of nutrients provided to the body, but they also influence physiological responses related to fluid absorption, hydration and performance. For example, too little carbohydrate won't benefit performance, while too much carbohydrate slows absorption. Too few electrolytes impair hydration, but too many electrolytes ruin taste. According to research and published studies, a properly formulated sports drink should rapidly rehydrate, replenish and refuel the body. What makes an optimal sports drink?
1: An optimal level of carbohydrates.
Research indicates that 6 grams of carbohydrate per 100 ml of beverage strikes the ideal balance in taste, rapid fluid absorption, and delivery of carbohydrate energy to fuel working muscles.1,2,3 Drinks with too much carbohydrate – 8 per cent or above – delay stomach emptying and slow intestinal fluid absorption, increasing the risk of dehydration and gastrointestinal upset during exercise.1,4,5
2: The right type of carbohydrates.
A blend of carbohydrates including glucose and sucrose will take advantage of the way the body absorbs fluid and nutrients. Glucose speeds fluid absorption and provides energy that is immediately available to the body – ideal for active situations.
Low GI (glycemic index) drinks and other “sports waters” contain fructose as their primary carbohydrate. The low GI claim stems from the fact that fructose has to be converted to glucose in the liver before it can be utilised as energy. This means it is not as readily available for energy as glucose-containing beverages.6 Consumption of beverages containing only fructose or high levels of fructose during exercise have also been associated with slower fluid absorption,7 greater incidence of gastrointestinal distress, and substantially poorer exercise performance.8
3: Electrolytes – to help you replace what you lose when you sweat.
Active people lose electrolytes – sodium, potassium, chloride – every time they sweat. Water fails to replace lost electrolytes and can quench thirst before the body is properly hydrated.
Electrolytes (sodium, potassium and chloride) play a key role in hydration by stimulating thirst, enhancing fluid absorption from the small intestine, and aiding fluid retention.9,10 Gatorade recently increased the level of electrolytes by 20 per cent to enhance rehydration and help maintain the right level of electrolytes in blood.
Gatorade does not add ingredients that are unproven to aid hydration and performance to its formulation. Why? Good science doesn’t support it. Here are just a few of the things that don’t deliver what youneed in a sports drink.
HERBS& VITAMINS – Common herbal supplements, like ginseng, have very weak scientific support for use by athletes. Herbal ingredients often work like a medicine instead of a nutrient and have been linked to adverse health effects such as hypertension, insomnia and nervousness.11 While vitamins can aid in keeping athletes healthy, they have not been shown to aid hydration or to affect immediate athletic performance. MALTODEXTRIN (glucose polymers) – There are no proven performance benefits associated with maltodextrin over other carbohydrates in a sports drink.12 CARBONATION – Carbonation in a sports drink makes it very difficult to consume in large volumes, which slows down the process of rehydration.
Here is a quick summary of the contents of some of the popular sports drinks on the market…
Fluid Carbohydrate Carbohydrate per 100 mL
Source: adapted from material provided by Sports Dietitians Australia.
1 Murray R, Bartolli W, Stofan J, Horn M, Eddy D. Int J Sport Nutr: 9(3):263-74, 1999.
2 Welsh RS, JM Davis, JR Burke, and HG Williams. Med Sci Sports Exerc 34:723-731, 2002.
3 Shi, X et al. Med Sci Sports Exerc 27:1607-1615, 1995
4 Ryan AJ, GP Lambert, X Shi, RT Chang, RW Summers, and CV Gisolfi. J Appl Physiol 84:1581-1588, 1998.
5 Shi, X., M. Horn, K.L. Osterburg, J. R. Stofan, J. J. Zachwieja, C. A. Horswill, D. H. Passe and R. Murray. Inter. J. Sports Nutr. Exerc. Met. 14, 673-683, 2004
6 Massicotte, D., et al. Oxidation of a glucose polymer during exercise: comparison with glucose and fructose. Journal of Applied Physiology, 66:(1):179-183, 1989.
7 Schedl, H. P. et al Med. Sci. Sports Exerc 26, 267-280, 1994.
8 Murray, R., et al. The effects of glucose, fructose and sucrose ingestion during exercise. Medicine and Science in Sports and Exercise, 21:275-282, 1989.
9 Wilk, B. and Bar-Or, O. J Appl Physiol, 80:1112-1117, 1996.
10 Gonzalez-Alonso J, CL Heaps, EF Coyle. Inter J Sports Med. 13:399-406, 1992.
11 Maughan, R.J. and R. Murray. Sports Drinks: Basic and Practical Aspects, Chapt 9 pp. 225-255, 2001.
12 Maughan, R.J. and R. Murray. Sports Drinks: Basic and Practical Aspects, Chapt. 8 pp. 197-223, 2001.
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