What Are Peptides? Peptides are short strings of amino acids, which are the essential components of proteins. They play a key role in many bodily functions, such as regulating hormones, supporting the immune system, and facilitating communication between cells. While our bodies create many peptides on their own, they can also be made in labs and used for medical treatments. People turn to peptides for various benefits, including muscle growth, fat loss, and anti-aging effects