Study challenges protein intake.

It's well documented that carbohydrate ingestion during endurance events lasting over one hour improves performance. Sports drinks are popular because they help runners and cyclists meet fluid requirements and obtain carbs simultaneously. Recently, there have been drinks with increased sodium as well, such as Gatorade Endurance Formula, which is now being offered at more and more marathons nationwide in place of the usual formula. The next phase of sports drink engineering involves the addition of protein into the beverages, in the hopes that protein more readily delivers carbohydrate to the muscles.

It is said that after a workout, ingesting a bit of protein along with carbohydrate improves recovery. There appears to be a window of time during which the body best uses these nutrients to repair muscle and replenish electrolytes. But whether during exercise protein improves carbohydrate delivery, does nothing, or even slows its absorption remains controversial. In recent years a few studies have suggested that protein taken with carbohydrate can improve endurance capacity in cyclists by around 30%. However, a new study has found otherwise. The present study, from the Department of Kinesiology at McMaster University in Ontario, explored the effects of adding 2% protein to a 6% carbohydrate drink on cycling performance.

Unlike previous studies, the researchers took great pains to simulate real endurance competition. The thinking was that in the two recently published studies finding favorable results with the addition of protein to an energy drink, the results may have been compromised by study design, which did not accurately simulate an actual racing environment. Specifically, cycling at a fixed workload until fatigue does not mimic the manner in which athletes usually compete. Athletes more typically face a fixed distance which they must then cover as quickly as possible. Furthermore, the rate of carbohydrate ingestion was much less than the optimal rate published in a 2004 article in Nutrition serving as a comprehensive review of the literature. This rate was found to be 60 to 70 grams per hour of carbohydrate, as compared to the 47 and 37 grams per hour used in the other two studies, respectively.

The Ontario study, which was admittedly small, had 10 male subjects ingest at the optimal rate recommended by the 2004 review, which amounted to 250 ml every 15 minutes during an approximately two-and-a-half-hour time trial simulating race conditions. Much more research is warranted, but the results were clear enough after three separate 80-km time trials separated by a week: the average time to complete the distance was identical for those ingesting the 6%-carb-plus-2%-protein beverage and those ingesting only the 6% carbohydrate drink. These times were 4.4% lower than for those drinking a placebo beverage.

(Med. Sci. Sports & Exer., 2006, Vol. 38, No. 8, pp. 1476-1483; Nutrition, 2004, Vol. 20, pp. 669-677)