Runners' nutrition has historically focused on carbohydrates. Endurance sports deplete glycogen stores, and carbohydrates are the only things that can restore them. A runner's glycogen stores can be the difference between a personal record and a so-so finish. Many runners don't realize that protein is just as important to their sport, and can help enhance recovery and improve subsequent performance. Whey protein is the best protein supplement because of its digestibility and nutrient profile.
Most runners are familiar with the relationship between carbohydrates and glycogen, as well as the "bonk" that occurs when they are not properly attended to. What they don't realize is that the part their muscles play running performance. Although you don't want big, bulky muscles that can slow you down, you need tight, springy, strong muscles to help you increase your speed and stride length so you can run more efficiently. Protein is the nutrient in charge of muscle repair, and inadequate levels can lead to the "wasted" look common among distance runners. Eating a small amount of protein at every meal helps keep your amino acids stocked, and whey protein supplements offer a way to sidestep the carbs and fat that come from whole food sources, providing a nearly pure form of protein.
Whey protein is isolated from the liquid left over after making cheese. It is the gold-standard of protein supplements because is contains all of the essential amino acids in a readily absorbable form, and your body digests it quickly to speed nutrients to your muscles when they're most needed. Whey protein isolate is at least 90 percent pure protein, containing little if any fat or carbs, and it is usually well-tolerated by the lactose-intolerant. Whey protein concentrate is between 29 and 89 percent pure and has more carbs and fat. Isolate is considered a higher-quality protein, but the nutritional profile of the concentrate may provide more value as a recovery drink.
A 2004 study in the journal "Nutrition" found that participants given an exercise recovery drink containing both carbs and protein tended toward increased lean muscle mass more than those given a drink containing only carbohydrates. According to kinesiologist Martin Gibala of the Gatorade Sports Science Institute, adding protein to your usual post-workout carbohydrate drink may help you replenish your glycogen stores faster and accelerate the muscle repair process. When you're in heavy training, this gives you the advantage of being more prepared for your next run.
According to the American Dietetic Association, endurance athletes need between 0.55 and 0.9 g of protein per pound of body weight per day. When you are training heavily, stay toward the high end of the range and don't dip below 0.7 g per pound per day. Most of your protein should come from whole foods like poultry, fish and soy, but you should use whey protein for recovery or any time you need a fast-digesting, potent, portable protein. If you're only using whey for recovery, choose a concentrate -- it's cheaper, and the carbs will assist glycogen synthesis. Isolate is better if you're lactose intolerant, but remember to add carbs like bread, cereal or crackers after your run.