To reap the benefits of the protein-rich foods you eat each day, your body first has to digest and absorb the macronutrient. The processes occur primarily between your stomach and small intestine with the help of digestive juices and enzymes. The proteins that make up your body are in a state of flux; that is, they are continually degraded and replenished, and you need a steady supply of the macronutrient in your diet.
Proteins are bulky molecules consisting of a folded-up chain of amino acids. Twenty different amino acids in the foods you eat combine in a variety of ways to create the various proteins found in all the cells of your body. The purpose of protein digestion is to break down large protein molecules into its amino acids. Amino acids, once absorbed by your digestive system, become incorporated into new protein molecules, such as muscle tissue, red blood cells or hormones.
Chewing your food reduces its size so that it’s more readily digested, and digestion really gets going once protein hits your stomach. Your gastric juices include a powerful acid, which unfolds the protein and begins to clip it into smaller pieces, as well as the digestive enzyme pepsin. Pepsin also works to break down the large protein into smaller fragments. As these pieces move out of your stomach and into the less-acidic environment of your small intestine, additional enzymes secreted from your pancreas and small intestine snip off individual amino acids from the partially digested protein.
Your body absorbs single amino acids, although absorption of protein fragments containing up to four amino acids is possible. The amino acids -- once the protein is digested -- enter specific cells in your small intestine through a mechanism called active transport. These specialized cells use a transporter protein to grab hold of an amino acid, shuttle it from your gut to the inside of the cell, transport it through the interior of the cell and deposit it into your bloodstream on the other side of the cell. Your blood then carries the amino acid to wherever it is needed.
According to the Centers of Disease Control and Prevention, women over the age of 19 need about 46 grams of dietary protein each day, which amounts to 10 to 35 percent of their total calories. This amount, however, depends on your state of health and activity level. For example, if you are relatively sedentary, you may need less protein in your diet than if you are a busy mom who also lifts weights. In either case, the process of digesting and absorbing the high-quality proteins you consume will provide you with the amino acids you need for optimal health.
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