As you use your muscles, they need to be maintained nutritionally. They must be supplied with adequate amounts of amino acids from the protein in your diet. Amino acids are also important special nutrients in their own right. For instance the amino acids tyrosine and phenylalanine are critical amino acids that are used as neurotransmitters in the brain. Fats are important constituents of your trillions of cellular membranes.
Fats are essential to make lipo-protein components of many body secretions and membranes.
Proteins and fats are relatively easy to obtain since they are widely dispersed throughout our foods. Vitamins are complex organic substances found in most foods and are essential for the regulation of metabolism and normal growth and functioning of the body. Minerals are inorganic substances that are not of animal or vegetable source. They occur naturally in the earth and have individual chemical and physical properties that are used by the body to maintain structure, like calcium, in the maintenance of healthy bones and teeth. They are important in thousands of metabolic reactions.