RDAs have not been established for all essential nutrients. RDAs for older persons have been extrapolated from studies of a younger population. Protein is essential for building and maintaining body tissues. It is a source of amino acids that function in muscles, organs, hormones, the nervous system, and the immune system. If the body is not receiving enough calories it will burn protein for its energy needs.
Protein needs increase when the body is stressed by injury, infection, surgery, or illness.
A small amount of fat is necessary for life. Fats are highly concentrated sources of energy. Fat digestion is inhibited with aging. Saturated fats are usually solid at room temperature. They are found in butter, lard, salt pork, meat fat, coconut or palm oil, and hydrogenated margarine or shortenings.