Muscle Building: Does Protein Play a Role?
Confusion regarding the role of protein in muscle building has existed for a long time, despite
conclusive evidence that shows that protein is not responsible for building muscle—muscles
grow through exercise. Lifting heavy weights and performing resistance exercises help muscles
grow and become stronger.
In the body, protein is solely responsible for the functions of growth (in childhood, adolescence,
and pregnancy) and repair (after a burn, to replace normal cell life cycles, and in hormone
production). While some protein is necessary for growing and repairing muscle fibers,
consuming adequate protein is most important in athletes, in synergy with adequate and
appropriate amounts of carbohydrate and fats for performance.
Most people—athletes and nonathletes—consume more protein than is necessary. No empirical
evidence supports the fact that excess protein benefits athletes, and no evidence proves that
protein supplementation on top of an adequate diet enhances muscle strength or size.
Consuming more protein than the body requires causes the body to burn protein as energy or
store it as fat. In defining protein needs, it is found that endurance athletes, individuals doing
intense exercise, people on calorie-restricted diets, growing teenage athletes, and untrained
people who are just starting an exercise program are the subgroups of people who may benefit
from additional protein, in excess of the recommended daily allowance.
The following table can help determine protein needs:
Current RDA for sedentary adult
Recreational exerciser, adult
Endurance athlete, adult
Growing teenage athlete
Adult building muscle mass
Athlete restricting calories
Estimated upper requirements, adult
RDA=recommended daily allowance
Grams of Protein/
Pound Body Weight
0.4
0.5-0.7
0.6-0.7
0.7-0.9
0.7-0.8
0.8-0.9
0.9
To determine protein needs, multiply weight in pounds using the chart above. For example, for a
recreational adult exerciser who weighs 150 pounds:
 1500.5=75 (minimum); 1500.7=105 (maximum)
 This person should consume an estimated 75-105 grams of protein/day
Consuming too much protein is sometimes unhealthy. Protein may replace carbohydrate-rich
foods that are needed to fuel muscles, which can result in fatigue. Because protein breaks down
to urea, a waste product, too much protein may result in increased urination and dehydration.
Most protein foods also are higher in unhealthy fats and sometimes are expensive. Choosing less
meat and fewer protein-rich foods means you will have more room for fruits, vegetables, and
complex carbohydrates.
For vegetarian athletes and individuals who are restricting calories, it is essential to incorporate
protein in the form of beans, nuts, legumes, tofu, and plant proteins into the diet. Insufficient
protein in the diet also is dangerous and may lead to iron, zinc, and calcium deficiencies.
The bottom line remains that the body cannot store amino acids or protein and uses only what it
needs. It is not beneficial to consume extra protein. Single amino acids that are taken as
supplements, such as creatine, arginine, or ornithine, do not contribute to a muscle-building
effect. Because most American diets typically contain enough or too much protein already,
health care professionals should not advise athletes to consume more protein than they need.
References and recommended readings
Christie C, ed. Florida Dietetic Association Manual of Medical Nutrition Therapy. Tallahassee,
FL: Florida Dietetic Association; 2012.
Dorfman L. Nutrition in exercise and sports. In: Mahan LK, Escott-Stump S, Raymond JL.
Krause’s Food and the Nutrition Care Process. 13th ed. St Louis, MO: Elsevier Saunders;
2012:507-530.
Review Date 3/14
G-0851