Protein is used to repair cell injury (particularly muscle cells from the microscopic trauma that occurs with exercise), and is a secondary energy source. Unlike carbohydrate and fat, the body doesn’t store protein for future energy use and converts excess to fat.
Protein is made of different amino acids; these are “the building blocks of protein.” Some of these amino acids are necessary for health and cannot be made by the body— we have to obtain them from our diet. These are essential amino acids.
Complete proteins contain ample amounts of all the essential amino acids. Complete proteins are found in meat, fish, poultry, cheese, eggs, and milk. Incomplete proteins do not contain all of the essential amino acids. These proteins are found in grains, legumes, and vegetables.
Although it is important to consume the essential amino acids, it is not necessary to get them from meat, fish, poultry, and other complete-protein foods. There is a dietary strategy called mutual supplementation. Here you combine complementary partially- complete protein foods to supply adequate amounts of all the essential amino acids.
For example, although beans and brown rice are both quite rich in protein, each lacks one or more of the essential amino acids. However, when beans are combined with brown rice the result is equivalent to a complete protein that can substitute for meat. Complementary proteins need to be consumed during the course of a day; it is not necessary that they be consumed at the same meal.
Here are some combinations of complementary plant proteins that will provide you with all of the essential amino acids:
- Legumes plus grains: Black beans and rice.
- Legumes plus nuts: Lentil soup with a serving of almonds on the side.
- Legumes plus corn: Pinto beans in a corn tortilla.
- Whole-grain pasta tossed with peas.
- Whole-wheat toast with peanut butter.
- Bean soup with whole grain crackers.
- Corn tortillas with beans and rice.
Unlike most beans, soybean products (such as tofu and soymilk) are complete proteins. They contain the essential amino acids. Available in health food stores, tofu, soy oil, soy flour, soy-based meat substitutes, soy cheese, and many other soy products are healthful ways to complement a meatless diet.
While a variety of protein sources are necessary as part of the daily food choices, in my experience most athletes eat “too” much protein.
How Much Protein do Athletes Need?
Protein requirements do vary between athletes and sedentary individuals but not by much.
Based on position statements from the American College of Sports Medicine and the American Dietetic Association, an upper limit of 1.7 grams/kg/day will meet the needs of even the hardest training athletes. Using this recommendation, a 70-kilogram (154- pound) endurance athlete would need no more than 120 grams of protein per day.
The vast majority of scientific evidence suggests that consuming more than 2.2 grams/kg/day (154 grams for a 70-kilogram athlete) has little, if any benefit to endurance or strength athletes. These recommended amounts can be generally met through diet alone, without the use of expensive protein or amino acid supplements.
See Appendix A for a list of popular foods and their macronutrient distributions.
Consequences of a High Protein Diet
When an athlete eats more protein than he or she needs, the excess is generally stored as fat. Here are some reasons to consider more carbohydrate and less protein:
- A high carbohydrate diet helps restores muscle glycogen quickly.
- A high protein diet following strenuous exercise may result in incomplete replacement of muscle glycogen, which may impair future performance.
- Carbohydrate is a more efficient source of energy.
- Protein is a more expensive source of energy.
- Protein is harder to digest than carbohydrate; it may lead to feeling lethargic.
- Consuming too much protein may increase the body’s water requirement and may contribute to dehydration. This is because the kidneys require more water to eliminate excess nitrogen that is a function of protein metabolism.