A Closer Look at Protein

Second only to water, protein is the most abundant substance in the human body. In addition to forming collagen which is the “glue” that holds the body together, proteins are involved in every function in every cell in the body. It is no surprise that protein has attracted the attention of so many people who are interested in nutrition. However, there is still much confusion about the right type and amounts of protein to consume. This confusion is often aggravated by misinformation that is spread by proponents of fad diets as well as by companies that sell protein supplements. The intent of this article is to provide a brief explanation about the nature of protein, and how it relates to getting the most utilization of it while minimizing empty calories.

All proteins are composed of amino acids which are bonded together in long chains called polypeptides. The sequences of the amino acids, along with the folds in the protein structure, determine the type and function of the protein. There are 20 amino acids that combine to form proteins, of which 9 cannot be manufactured in the human body and are therefore essential in the diet. This means that these 9 amino acids are really the essential nutrients, and that protein is nothing more than the packaging for them. Consequently, any protein source that is deficient in any of the essential amino acids is incomplete. Also, under some stressful conditions, some of the “non-essential” amino acids become essential in the diet because the body’s ability to make them becomes limited.

Essential Amino Acids	Non-Essential Amino Acids
Histidine	Alanine
Isoleucine	Arginine (Can be essential in infants)
Leucine	Asparagine
Lysine	Aspartic Acid
Methionine	Cysteine (Conditionally Essential)
Phenylalanine	Glutamic Acid
Threonine	Glutamine
Tryptophan	Glycine
Valine	Proline
	Serine
	Tyrosine (Conditionally Essential)

An amino acid has 3 major components: An amino group (NH₂), a carboxyl (COOH) or acid group, and a side chain which is often depicted in the simplified form as “R”. Each individual amino acid has a unique side chain chemical combination which makes up the R group, and which provides its distinguishing characteristic. If the body is forced to break down amino acids for energy, it must first remove the amino group. The amino group will then join with other ions to become ammonia in the system. The body is then forced to convert the ammonia into uric acid via the uric acid cycle before it is flushed out in the urine. Because uric acid is processed primarily by the kidneys, any of these conditions will force the kidneys to work harder than they normally do. This will happen if amino acids are used to make glucose or ketone bodies (due to carbohydrate deprivation), or if there is excessive protein intake or extremely rapid amino acid absorption. It can also happen from consuming poor quality protein because the body is less able to use it for structural components and enzymes and will therefore be more likely to use it for energy.

For someone who is trying to lose fat or build muscle while staying lean, it is important to maximize the percentage of protein that is being used for tissue repair, muscle building/maintenance, and other vital functions while minimizing the percentage that gets converted to empty calories. This means consuming high quality protein. It is also important to not inundate the body with excessive amounts of protein. Contrary to what is printed in muscle magazines and other literature controlled by entities that sell protein, experiments show that about .82 grams per lb of lean mass is adequate for people who are trying to gain muscle. It is equally important to make sure that protein is not absorbed more rapidly than the body can properly utilize it. Consequently, although rapidly absorbed proteins such as whey protein are good right after a workout, more slowly absorbed protein sources are better throughout the rest of the day.