This chapter addresses macronutrients essential for human nutrition. Nutrients are present in foods that are essential for the body’s functioning, providing energy and raw materials for maintaining and repairing body tissues, as well as supporting growth. They are classified into macronutrients, such as carbohydrates, lipids, and proteins, and micronutrients, such as vitamins and minerals. Adequate nutrition requires the intake of essential nutrients that are not produced by the body in sufficient quantities and must be obtained through diet. Carbohydrates, one of the macronutrients, are specific, abundant molecules that account for up to 80% of all energy consumed by humans. They are classified as monosaccharides, disaccharides, oligosaccharides, and polysaccharides. The main function of carbohydrates is to provide energy. Carbohydrate digestion begins in the mouth with the action of salivary amylase and continues in the small intestine with pancreatic amylase. Proteins, composed of amino acids, perform a variety of functions in the body, including the formation of tissues, enzymes, hormones, antibodies, and the provision of energy. Protein digestion begins in the stomach with the action of pepsin and continues in the small intestine with pancreatic enzymes such as trypsin. Lipids, another essential macronutrient, are water-insoluble organic compounds that perform crucial functions, such as energy storage, structural components of cell membranes, and acting as hormones. Lipid digestion begins in the mouth and stomach but occurs primarily in the small intestine with the help of bile salts and pancreatic lipase.