The protein in your diet ensures that your body contains enough protein to carry out important functions. Protein can be used as energy, although its main functions are providing structural support to your body, helping build enzymes and hormones, maintaining the acid-base and fluid balance, and keeping your immune system healthy.
Amino Acid Sequence
Proteins are made up of single units called amino acids. The way these amino acids are linked, or their amino acid sequence, determines the type of protein that is made. There are nine amino acids that your body cannot make. You must consume these amino acids, which are called essential amino acids, through your diet to ensure that your body has access to them. Your body can synthesize the remaining 11 amino acids, which are called nonessential amino acids. Because of this, it is not necessary to consume these amino acids in your diet.
Types of Protein
The amino acid sequence determines whether a protein is considered complete or incomplete. Proteins that contain all nine of the essential amino acids, as well as some of the nonessential amino acids are classified as complete proteins. Proteins that are missing one or more of the essential amino acids are classified as incomplete proteins. Generally, complete proteins are regarded as nutritionally superior. According to "Nutrition and You" by Joan Salge Blake, proteins that come from animal sources, such as meat and eggs, tend to be complete proteins, whereas proteins that come from plant sources, such as beans and nuts, tend to be incomplete.
Digestibility
The digestibility of proteins differs as well. Generally, your body can digest animal proteins more easily than plant proteins, because plant proteins are protected by a cell wall that cannot be broken down by enzymes in your digestive tract. According to "Nutrition and You," 90 to 99 percent of animal proteins are digestible, while 70 to 90 percent of plant proteins are digestible. Complete proteins that are easily digestible are typically valued the highest nutritionally.
Fat Content
In addition to their amino acid sequence and digestibility, different types of proteins also contain different amounts and types of fat. Some proteins, such as red meat, are high in saturated fat and cholesterol, whereas other proteins, such as chicken breasts and nuts, do not offer high amounts of fat, or provide unsaturated fat rather than saturated fat. When choosing your protein sources, it is important that you consider the amount of fat and type of fat that each protein contains.
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