Nutrition Health Lifestyle Other Issues Protein Proteins are large molecules made from smaller units called amino acids. There are twenty amino acids commonly found in both plant and animal proteins. There are generally considered to be eight amino acids that the body cannot make itself which need to be obtained from the food we eat. These are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Infants additionally need food sources of histidine and possibly taurine.
Proteins are necessary for maintaining tissues and for sustaining growth.
They are also used to make hormones and other physiologically active substances. Protein Requirements Experts are still not entirely sure how much protein we need and estimates have been revised often in recent years. The national and international organisations which advise on nutrient requirements suggest standards which are calculated to meet or exceed the requirements of practically everyone in the population. They take into account individual variation and so the levels have a wide inbuilt safety margin. The recommendations below are based on the complete digestibility of milk or egg protein.