Protein Plus Mixed-Carb Drink Improves Endurance in Female Athletes

A "low-carb, mixed-carb" sports drink with added protein leads to prolonged endurance performance in trained female athletes, according to a study in The Journal of Strength and Conditioning Research.

The endurance gain likely reflects the added protein as well as a mix of carbohydrates, compared with a standard "single-carb" drink, according to the study by Erin L. McCleave, MS, and colleagues of The University of Texas at Austin.

Fourteen trained female cyclists and triathletes were studied on two occasions. After performing a long (three-hour) ride, the women performed an intense ride—averaging 75% of aerobic capacity (VO2 max)—until exhaustion. On one ride, the athletes were given a standard 6% carbohydrate supplement containing dextrose only. On the other ride, they received a three percent carbohydrate supplement containing a mix of carbohydrates plus 1.2% added protein. On each ride, the cyclists were given 275 mL of their assigned beverage every 20 minutes.

The women's time to exhaustion was significantly longer with the mixed-carb plus protein supplement: nearly 50 minutes, compared with 42 minutes with the dextrose-only drink. Thus the mixed-carb plus protein drink increased endurance performance by about 15%.

The blood glucose level was also lower with the mixed-carb plus protein supplement. Other metabolic measures—including insulin levels, lactate concentration—were similar between the two drinks.

Studies have shown that carbohydrate-containing beverages increase endurance exercise performance, compared with water and placebo drinks. Some previous studies have suggested that adding a moderate amount of protein to a low- or moderate-carbohydrate supplement can further enhance endurance.

In their effort to develop a more effective supplement, the researchers switched from a single source of carbohydrate (dextrose) to a combination of three carbohydrates: glucose, fructose, and maltodextrin. "Multiple sources of carbohydrate appear to increase exogenous carbohydrate oxidation," according to the authors.

The new formulation improves exercise endurance in female athletes, compared with a standard dextrose-only supplement. The protein plus mixed-carb (and low-carb) supplement "improved performance despite containing 50 percent lower carbohydrate content and approximately 30 percent fewer calories," McCleave and coauthors conclude. "This may be an important consideration for those individuals concerned about body weight and caloric intake."

Source: Wolters Kluwer Health: Lippincott Williams & Wilkins