What is the Connection Between Protein and Muscle?

Protein and muscle go hand in hand, because dietary protein is crucial for the maintenance and repair of muscles and other structures in the body. Protein supplies the body with amino acids necessary for this maintenance and repair during a process called protein synthesis. This is a large part of why bodybuilders and athletes often concentrate on consuming enough protein to develop and conserve muscle mass. They ensure that their diet has enough protein and muscle mass improves.

Amino acids are the smallest chemical building blocks that make up proteins. There are about 20 types of amino acids, nine of which the human body cannot make on its own. Those nine must instead be provided to the body via a protein source or sources in the diet. These so-called essential amino acids cannot be stored in the body — unlike fats and carbohydrates — and must be supplied on a daily basis. Non-essential amino acids are created by the body in the liver.

For optimal protein synthesis to occur and keep that protein and muscle bond strong, dietary protein should be of high quality, because not all types are absorbed and utilized equally. Protein digestibility depends on its source and the other foods eaten with it. The body digests from 90 percent to 99 percent of animal protein and from 70 percent to 90 percent of plant-based proteins, with the exception of soy and legumes, for which the digestion rate is more than 90 percent. Plant protein absorption can be increased by combining different but complementary foods, so vegan and vegetarian diets contain enough essential amino acids for good health. Combining beans and rice is one of the many vegan examples of a complementary, amino-rich meal.

Though the link between protein and muscle mass is emphasized, the intake of nutrients such as carbohydrates and fats is just as necessary. This is especially the case with carbohydrates, the body’s preferred source of energy. Without adequate carbohydrate intake, the protein will be burned off as fuel instead of being retained in the muscle. Those on a prolonged, very low-carbohydrate, high-protein diet, may find that not eating enough carbohydrates can make the body use its own protein stores for energy, resulting in muscle loss and undermined health. To spare protein, a minimum of 50 grams to 100 grams of carbohydrates is needed daily.

The recommended daily allowance (RDA) for protein is from 10 percent to 35 percent of total calories, or 0.08 gram per kilogram of healthy body weight per day, though this can vary slightly based on a person’s age, gender and physical activity level. Infants, children, pregnant women and active people — especially training athletes — need more protein for tissue building.