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Protein has recently re-entered the spotlight.

Some sports nutrition gurus advocate getting as much as 30% of daily calories from protein, double the standard 12% to 15% recommendation. Confused? Join the club. Here are some protein questions and answers that should help.

Why is protein important for athletes? Protein is made up of chains of amino acids, some of which our bodies cannot manufacture. Protein is essential for building and maintaining muscles, as well as repairing the muscle damage that occurs during training. Protein is also needed to make red blood cells, produce hormones, boost your immune (disease-fighting) system, and help keep hair, fingernails, and skin healthy. Athletes who are protein deficient may complain about having hair that falls out easily and fingernails that grow slowly and break easily. Female athletes who eat a protein-poor diet may also stop having periods (1).

How much protein do athletes need? There isn't an exact number for athletes because protein needs vary, depending on whether an athlete is growing, rapidly building new muscle, doing endurance exercise, or dieting, in which case protein is used as a source of energy (table 1). Protein requirements for athletes are higher than the current recommended dietary allowance (RDA) of 0.4 g of protein per pound of body weight, which is based on the needs of nonexercisers. Protein recommendations for athletes are commonly expressed in a range to include a safety margin (2). If you do the math (1g of protein has 4 calories), you'll see that you don't need to have 30% of your calories come from protein.

Table 1. Recommended Grams of Protein Per Pound of Body Weight Per Day* RDA for sedentary adult 0.4 RDA for Adult recreational exerciser 0.5-0.75 RDA for Adult competitive athlete 0.6-0.9 RDA for Adult building muscle mass 0.7-0.9 RDA for Dieting athlete 0.7-1.0 RDA for Growing teenage athlete 0.9-1.0 *To find your daily protein requirement, multiply the appropriate numbers in this table by your weight in pounds.

Do bodybuilders need more protein than runners?

No. Per pound of body weight, bodybuilders actually need less protein than endurance athletes such as runners. That's because protein--or more precisely, the amino acids that are the building-blocks of protein--is actually used for fuel during intense exercise, particularly when carbohydrates are not available. Protein can provide up to 10% of energy during exercise when a person is carbohydrate depleted (3).

But here's the catch: Even though endurance athletes may need more protein per pound of body weight, they tend to need a smaller total intake of protein because they often weigh less than bodybuilders. For example, a 200-pound bodybuilder may need about 140 g of protein a day (0.7 g of protein per pound), whereas a 150-pound marathoner may need about 120 g of protein per day (0.8 g of protein per pound). Most people can get enough protein through their diet, eliminating the need for protein supplements

Thirty-five years ago, a physiologist at the University of Florida created the first sports drink.

However, in the 1990s, exercise physiologists began to experiment with adding protein to the conventional sports drink formula. They found that the addition of protein produced a stronger insulin response, resulting in faster transport of both carbs and protein into muscle cells.

The significance of this insulin boost is that faster carbohydrate delivery during exercise allows the body to conserve its stored carbohydrate, delaying fatigue.

More recent research has shown that combining protein with carbohydrate in the two-hours after exercise,

nearly doubles the insulin response, which results in more stored glycogen. The optimal carbohydrate to protein ratio for this effect is four grams of carbohydrate for every one gram of protein. Eating more protein than that, however, has a negative impact because it slows rehydration and glycogen replenishment.

Also, conservation of stored carbohydrate during exercise reduces the release of the stress hormone cortisol, which breaks down muscle tissue. And after exercise, consuming a sports drink with protein results in much faster muscle recovery than consuming a regular sports drink.

The study found that athletes who refueled with carbohydrate and protein had 100 percent greater muscle glycogen stores than those who only had carbohydrate. Insulin was also highest in those who consumed the carbohydrate and protein drink.

Protein has other important post-exercise qualities. Protein provides the amino acids necessary to rebuild muscle tissue that is damaged during intense, prolonged exercise. It can also increase the absorption of water from the intestines and improve muscle hydration. The amino acids in protein can also stimulate the immune system, making you more resistant to colds and other infections.

Researchers at the University of Texas compared the use of carbohydrate, protein, and carbohydrate-protein supplements to see whether they could speed up the replenishment of muscle glycogen after prolonged exhaustive exercise.

Nine men cycled for two hours on three occasions to deplete their muscle glycogen. Right after each 2-hour bout, they ingested a carbohydrate, protein, or carbohydrate-protein supplement. Blood and muscle tissue was sampled throughout recovery.

The replenishment rate of muscle glycogen storage during the carbohydrate-protein treatment was 38% greater than carbohydrate only, and over three times faster than the protein treatment.(4)

Ten men were studied to investigate the effects of two different supplements on endurance; one a carbohydrate drink and the other a carbohydrate-protein drink of equal calories. After a muscle-glycogen-lowering exercise, the two drinks were administered with a 60-minute interval between dosages.

The athletes went 20% longer when using the carbohydrate-protein drink than when using the carbohydrate-only drink, which correlated with elevated insulin in the carbohydrate-protein condition.

The researchers concluded that a carbohydrate-protein drink consumed after glycogen-depleting exercise might lead to a faster rate of muscle glycogen re-synthesis than a carbohydrate-only beverage.

This would hasten the recovery process and improve exercise endurance during a second bout of exercise performed on the same day.(5)

So if you are looking for the best way to refuel your body after long, strenuous endurance exercise, a 4:1 combo of carbohydrate and protein seems to be your best choice. While solid foods can work just as well as a sports drink, a drink may be easier to digest make it easier to get the right ratio and meet the 2-hour window.


1. Nelson ME, Fisher EC, Catsos P, et al: Diet and bone status in amenorrheic runners. Am J Clin Nutr 1986;43(6): 910-916
2. Lemon PW, Tarnopolsky MA, MacDougall JD, et al: Protein requirements and muscle mass/strength changes during intensive training in novice bodybuilders. J Appl Physiol 1992;73(2):767-775
3. Lemon PW, Mullin JP: Effect of initial muscle glycogen levels on protein catabolism during exercise. J Appl Physiol 1980;48(4):624-629
4. Zawadzki KM , Yaspelkis BB , Ivy JL. "Carbohydrate protein complex increases the rate of muscle glycogen storage after exercise." Journal of Applied Physiology 1992; 72:1854-9.
5. ES Niles, T Lachowetz, J Garfi, W Sullivan, JC Smith, BP Leyh, SA Headley. "Carbohydrate-protein drink improves time to exhaustion after recovery from endurance exercise." Journal of Exercise Physiology online, 2001 4:45-52.

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