Proteins are made up of amino acids that are the basic building blocks of all proteins. Your stomach digests the proteins with hydrochloric acid that breaks them down into simpler forms that are easier to absorb in your intestines. When proteins get absorbed into the bloodstream, they are sent to various parts of your body to perform various functions, including repairing muscle tissues, support your immune system, and transport oxygen in your red blood cells.
Your skeletal muscles' job is to move your body and to provide stability for body posture. Muscles grow by increasing the muscle cells' mass and cross-section fibers that pull muscles together and separate them during contraction and stretching. According to Dr. Len Kravitz, who is a kinesiology professor at the University of New Mexico, protein helps build muscles only if there is a need to produce more contractile proteins or repair damaged tissues, such as from wounds, blunt trauma, and burns. The need also occurs during strength and anaerobic training, such as weight-lifting and sprinting, when your muscles have to adapt to the stress of exercise by recruiting more contractile proteins to do more work. Otherwise, eating proteins alone does not build muscles.
The growth size of your muscles depends on how much of a certain type of muscle fibers there are in a muscle group. Kravitz describes three primary types of muscles which are type 1, type 2a, and type 2b. Type 1 fibers are designed for sustaining contractions over a long period of time, yet they do not produce much force. However, both type 2 fibers are designed for quick, powerful contractions that produce a lot of force, but they can sustain these contractions for a very short amount of time. Type 2 fibers contain more satellite cells that determine the size of the muscles. Therefore, these types are larger than type 1.
Your body needs 20 different amino acids to form usable proteins. It can produce 12 of these amino acids, yet it could not produce the remaining eight types, which are called essential amino acids. These amino acids must be obtained from animal sources, such as meats and dairy products, contain complete proteins that your body can use. Plant-based foods do not contain all the essential amino acids. According to Matthew Kadey, who is a registered dietitian with The Ontario College of Dietitians Member of Dietitians of Canada, you can combine different plant foods to create complete proteins, such as beans and rice. This allows vegetarians to get the proteins they need to build muscles.
Eating more protein does not make your muscles bigger or grow faster. According to Kadey, your body convert excess protein into fat for storage or glucose for energy if you do not have enough carbohydrates in your diet.
Ellen Coleman, who is a registered dietitian in Riverside, California, and a former nutrition consultant for the Los Angeles Lakers, suggests that you consume a post-workout meal consisting of lean protein and carbohydrates within 30 minutes after your workout. If you wait too long, your body will use proteins in your skeletal muscles and convert them into glucose for energy.