Proteins are the building blocks of hair, skin, nails and muscles. They also make up antibodies, enzymes, hormones and collagen. A protein’s structure determines its function and mode of action. A protein’s atoms are linked together by chemical bonds into long chains of amino acids. These chains can twist to form 3D proteins of different shapes. Each amino acid has a unique part that sets it apart from the others; these parts are called side chains. Side chains may be positively-, negatively- or neutrally-charged. The order of the amino acids in a protein is also important; a change in their sequence can alter a protein’s function and cause disease.
Protein is not the body’s first choice for energy, that role is reserved for carbohydrates and fats. However, when the body is unable to get enough calories from other sources, it will use the protein for energy. The body stores protein for future use as fat.
Protein can be a good source of energy if it is eaten in combination with complex carbohydrates such as whole grains and legumes. The Healthy Eating Plate recommends protein foods with a low glycemic index and high soluble fiber such as lentils, beans (adzuki, black, fava, chickpea/garbanzo, kidney, lima, mung, pinto and soybeans), edamame/soybeans and peanuts. Protein should accompany fruits, vegetables and whole grains, not be the main part of a meal. Protein from animal foods has higher digestibility and quality than protein from plant-based foods. peptides