Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily
What does protein do and what makes it so indispensable? Professor Anding discusses the function of protein.
Growth Function of Protein
Probably the most highlighted function of protein is to build and repair tissue. Not surprisingly, this function of protein is utilized after intense activity.
What you may not know, though, is that babies also require lots of protein. During periods of rapid growth and development, protein needs are going to increase.
In the first year of infancy, babies can triple their birth weight, so per pound of body weight, babies have a really high protein need. Protein needs also increase after surgery.
If you’ve ever had surgery, you’ve actually created damage to that protein structure—your skin, your muscles, and your bone—and you need extra protein to repair it. Often people believe that when they’re lying flat in the bed from surgery, they don’t need as many calories or as much protein, but physiologically, that’s not true. Your need for both goes up significantly.
Sliding Filament Theory
You also have structural proteins, like collagen, as well as mechanical proteins, such as actin and myosin, which are found in muscle. These two proteins are indispensable in terms of even simple movements like getting up out of your chair.
In muscular contraction, these two proteins slide over each other; this is called the “sliding filament theory.” The sliding movement promotes contraction, so one of the reasons why athletes always strive for more protein is to create more actin and myosin to allow protein molecules to slide over one another.
In the process of weight lifting, you’re trying to increase the mechanical strength of those proteins. When individuals do resistance training, actin and myosin fibers are sliding over one another, and your muscles tear.
Tearing your muscles is actually desirable. You’re causing some microtears, triggering the function of protein being built and repaired. This releases more amino acids to the damaged actin and myosin filaments, causing that muscle to hypertrophy or get bigger.
One of the reasons why strength training is so important is it increases the muscular work and the mechanical demand that’s created by resistance training. Thus, actin and myosin are the two proteins that predominate in muscle mass and are indispensable in terms of your mechanical function.
Protein and Immunity
Another protein function is maintaining a healthy immune system. White blood cells are protein in nature.
“In my clinical practice, where I see lots and lots of folks with anorexia nervosa, one of the key hallmarks is they have a diminished amount of white blood cells, and so they are unable to fight off as much infection,” Professor Anding said. “Now, you can have someone who eats well—who believes that they’re eating adequate amounts of protein—but in my 30 years of experience, most individuals with eating disorders don’t do that, and so most of them end up having a compromised immune function.”
Supplementing with protein, though—in particular, arginine—can help to boost your immune system, thus preventing or speeding up recovery from illnesses. Researchers have found that arginine supplementation has increased T-cells for post-surgery patients, helping those patients resist infection.
Therefore, protein is great for muscle building, but the functions of protein extend far beyond that. Protein is highly beneficial when it comes to post-surgery recovery, infant growth, and immune system support.
This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.
Professor Roberta H. Anding is a registered dietitian and Director of Sports Nutrition and a clinical dietitian at Baylor College of Medicine and Texas Children’s Hospital. She also teaches and lectures in the Baylor College of Medicine’s Department of Pediatrics, Section of Adolescent Medicine and Sports Medicine, and in the Department of Kinesiology at Rice University.