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Proteins & Peptides

By Jill Corleone, RDN, LD

You need protein for your body to function properly -- it's a building block for cells and tissues, and essential for new cell growth. Peptides are the sub-units used to make protein. During digestion, dietary proteins are broken down to their smaller peptide sub-units, which are then absorbed and used to maintain health.

What Is Protein

Proteins are complex molecules made up of strands upon strands of amino acids in very specific sequences, and are referred to as polypeptides. They're found in every cell in your body. Proteins are not only necessary for maintaining muscle mass, but are also for making hormones, enzymes and red blood cells, as well as supporting immune health.

For absorption, the body needs to break down these long, complex strands of protein into amino acids or smaller proteins, referred to as peptides. Peptides are short protein chains made up of a short sequence of amino acids.

Breaking Protein Into Peptides

Protein digestion begins in the stomach where the acid works to denature, or unravel, the protein strand. The protein enzyme pepsin begins to break apart the bonds that hold the protein together. Then, in the small intestines the smaller strands of protein are further broken down into amino acids, di-peptides and tri-peptides by proteolytic, or protein, enzymes secreted by the pancreas. Amino acids and peptides are then absorbed through the villi in the small intestines into the bloodstream.

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How Much You Need

Despite the commercial hype surrounding this essential nutrient, most people in the United States get more protein than they need, according to the Centers for Disease Control and Prevention. For general health, women need 46 grams of protein a day and men need 56 grams a day.

Sources of Protein and Peptides

Even though the body breaks down protein into peptides, certain foods also contain these small protein units. For example, the casein found in milk and gluten found in wheat, rye and barley are peptides. In addition to milk and grains, other good sources of protein and peptides include meat, poultry, seafood, beans, nuts, seeds and vegetables. High-quality proteins, such as milk, meat and poultry, contain all of the essential amino acids the body needs to make the proteins found in your body.

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