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In an earlier article I discussed the ideal nutrient composition for recovery drinks. This time I will put my focus on the optimal composition for sports drinks, which are mainly required during exercise to achieve peak performance. It will clearly be shown in this article that there is a substantial difference between recovery and sports drinks!

An optimal sports drink needs to meet 5 requirements.

1) Carbohydrates:

During exercise, you want a carbohydrate source that is quickly absorbed and in sufficient amounts to feed the working muscles. Many studies have been conducted to investigate which carbohydrates are the best choice during exercise. The maximal oxidation rate for carbohydrates such as glucose, sucrose and maltodextrin is said to be around 1 g/min, while only 0.5 g/min for fructose (1, 2, 3, 4). Because fructose is oxidized more slowly, it is not advised to use fructose as the main carbohydrate source, since it will cause gastro-intestinal discomfort. From these studies you would conclude that an intake of fast oxidized carbohydrates is optimal at a dose of 60g/h.  However, the use of multiple carbohydrate sources, that use different intestinal transporters such as glucose and fructose, can increase oxidation rates up to 1.75 g/min at intakes of 144 g/h (5). Additionally, it has been shown in the same study that this approach is less likely to cause gastrointestinal discomfort because of a higher oxidation efficiency and better fluid delivery. At high intakes (1.8 g/min), a 2:1 ratio of glucose and fructose had also an additional benefit on endurance performance compared to glucose only (6).

2) Osmolarity

The osmolarity of a sports drink can influence gastric emptying and the water flux in the intestine. Therefore, it is important that a sports drink is isotonic (around 300 mOsm/l, which is also found in the body) or that the osmolarity is at least below 400 mOsm/l to prevent gastrointestinal distress (7). When a carbohydrate solution of >8 % is provided, the osmolarity of the drink increases. Disaccharides such as sucrose and polysaccharides such as maltodextrin have a lower osmolarity compared to monosaccharaides such as glucose.

3) Sodium

Sodium can be used to maintain the thirst sensation and to increase fluid absorption and water retention (8). If sodium is the only ingredient added to water, the absorption will only be slightly affected. Addition of both sodium and carbohydrates can increase water absorption drastically (9). Optimal sodium concentrations are found at 600-1100 mg/l, since sweat contains 900 mg/l (6). Very high levels of sodium can worsen the taste of the drink, that’s why most sports drinks contain lower amounts.

4) Protein:

There is no consensus regarding the benefits of protein during exercise. A study conducted in 2004 found that a sports drink containing carbohydrates and protein in a 4:1 ratio, increased time to fatigue and reduced muscle damage, but this could be attributed to the higher calorie content of the added protein (10). When iso-caloric beverages were used, no increased effect in endurance performance was found. However, markers of muscle disruption were still improved in the carbohydrate + protein group compared to the iso-caloric carbohydrate group (11). Another non-iso-caloric study conducted in a fed state during resistance-type exercise, found improvements in whole body and muscle protein synthesis rates in the carbohydrate + protein group (12).

5)Taste

Since sweat losses can be substantial, it is also necessary to consume large amounts of fluid and this is more likely to be realized when the sports drink has a good taste. Therefore, the palatability of a sports drink is of critical importance to prevent dehydration. The sports drink should not be too sweet because the taste perception can be influenced by physical activity, such as an increased sensation of sweetness (7). The taste of a sports drink is also better, when it was kept cool.

Conclusion

It can be concluded that a sports drink should contain a fast oxidized carbohydrate such as glucose, sucrose or maltodextrin as main carbohydrate source. Since most athletes have trouble drinking more than 1 L/h, a carbohydrate solution of 6-8% is optimal in most cases, since it can deliver 60 g/h at a volume of 750-1000 ml. Only during exercise lasting 2 hours or more, a higher solution (9-12 %) can be used if multiple carbohydrate sources are provided (glucose/maltodextrin: fructose in a 2:1 ratio), to achieve a delivery of 90 g/h at volumes of 750-1000 ml. If you want to use a protein containing sports drink, make sure that it contains whey protein isolate or -hydrolysate as protein source. A protein solution of 1.5-2% should be sufficient, since the intake of carbohydrates is more important during exercise. If a high carbohydrate solution is used, maltodextrin can be used instead of glucose as main carbohydrate source to reduce the sweetness of the beverage and to make sure that the osmolarity is below 400 mOsm/l. The amount of sodium is mostly lower than optimal to support the taste of the drink. So make sure you look at the label when you shop for a sports drink!!

	Carbohydrates (%)	Protein (%)	Sodium (mg/l)	Osmolarity (mOsm/l)	Taste
Optimal for < 2 hours of exercise	6-8	1.5-2	600-1100	< 400	Cool and not too sweet
Optimal for > 2 hours of exercise	9-12	1.5-2	600-1100	< 400	Cool and not too sweet

Table 1: The optimal (nutrient) composition for sports drinks

Excerpt image by sipsmart.net

Bibliography:

1. Jeukendrup, A. E. (2004). Carbohydrate intake during exercise and performance. Nutrition, 20(7-8), 669-677.
2. Achten, J., Jentjens, R. L., Brouns, F., & Jeukendrup, A. E. (2007). Exogenous oxidation of isomaltulose is lower than that of sucrose during exercise in men. Journal of Nutrition, 137(5), 1143-1148.
3. Wagenmakers, A. J. M., Brouns, F., Saris, W. H. M., & Halliday, D. (1993). Oxidation rates of orally ingested carbohydrates during prolonged exercise in men. Journal of Applied Physiology, 75(6), 2774-2780.
4. Decombaz, J., Sartori, D., & Arnaud, M. -. (1985). Oxidation and metabolic effects of fructose or glucose ingested before exercise. International Journal of Sports Medicine, 6(5), 282-286.
5. Jeukendrup, A. E. (2008). Carbohydrate feeding during exercise. European Journal of Sport Science, 8(2), 77-86
6. Currell, K., & Jeukendrup, A. E. (2008). Superior endurance performance with ingestion of multiple transportable carbohydrates. Medicine and Science in Sports and Exercise, 40(2), 275-281.
7. Brouns, F., & Kovacs, E. (1997). Functional drinks for athletes. Trends in Food Science and Technology, 8(12), 414-421.
8. Stachenfeld, N. S. (2008). Acute effects of sodium ingestion on thirst and cardiovascular function. Current Sports Medicine Reports, 7(4 Suppl), S7-13.
9. Gisolfi, C. V., Summers, R. W., Schedl, H. P., & Bleiler, T. L. (1992). Intestinal water absorption from select carbohydrate solutions in humans. Journal of Applied Physiology, 73(5), 2142-2150.
10. Saunders, M. J., Kane, M. D., & Kent Todd, M. (2004). Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage. Medicine and Science in Sports and Exercise, 36(7), 1233-1238.
11. Valentine, R. J., Saunders, M. J., Todd, M. K., & Laurent, T. G. S. (2008). Influence of carbohydrate-protein beverage on cycling endurance and indices of muscle disruption. International Journal of Sport Nutrition and Exercise Metabolism, 18(4), 363-378
12. Beelen, M., Koopman, R., Gijsen, A. P., Vandereyt, H., Kies, A. K., Kuipers, H., et al. (2008). Protein coingestion stimulates muscle protein synthesis during resistance-type exercise. American Journal of Physiology – Endocrinology and Metabolism, 295(1), E70-E77.

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