They do not cover nutritional needs that have been altered by disease, stress, chronic use of drugs, etc. RDAs are recommendations for healthy population groups. They do not take into account differences between individuals. 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.