Proteins are molecule made up of many building blocks, known as amino acid. Proteins are needed for the human body to function properly and play an important role by helping in the growth, and maintenance of our body structures, such as skin and hair, muscles and health development, repair and build cells and tissue such as muscle. Protein plays an important role in body processes such as blood clotting, fluid balance, and the immune response. 1,2,5
Protein common 20 amino acids are classified as either essential or non-essential.1
Essential amino acids are amino acids that cannot be produced or synthesized by the human body and must be obtained through food or dietary supplements. The 9 essential amino acids (EAA) are: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
Non-essential amino acids can be produced by the body and do not need to come from the diet. Common non-essential amino acids are: Alanine, Arginine, Asparagine, Aspartate, Cysteine, Glutamate, Glutamine, Glycine, Proline, Serine, Taurine, Tyrosine
Protein sources
Protein can be found in both plant and animal-based foods. Common high protein animal-based source are dairy based like milk (e.g. whey protein, casein) and egg, lean meat like beef, fish and chicken. The plant-based food that is high in protein (e.g. soy or pea).
Not all protein source has the same beneficial effect as protein quality is related to the capacity of dietary protein to provide dietary essential (or indispensable) amino acids (EAA) to support body composition and functions.7 Protein can be measured by protein efficiency ratio (PER), Protein digestibility-corrected amino acid score (PDCAAS) and most recently recommended by FAO/WHO Digestible essential amino acid score (DIAAS). 6
Protein Requirements
Our dietary protein requirement changes throughout life. The European Food Safety Authority (EFSA) recommends healthy adults consume at least 0.83 g of protein per kg body weight per day (e.g. 58 g/day for a 70 kg adult).1 Elderly, sarcopenia, malnutrition or hospitalised individual dietary protein requirement will vary from 1.0 to 1.5 g/day in. 3,4
Ref 1 Protein and their function
https://www.eufic.org/en/whats-in-food/article/what-are-proteins-and-what-is-their-function-in-the-body
Ref 2 US National Cancer Institute (NCI) website.
https://www.cancer.gov/publications/dictionaries/cancer-terms/def/protein
Ref 3 Protecting muscle mass and function in older adults during bed rest. Paddon-Jones et al. Curr Opin Clin Nutr Metab Care. 2010 January
Ref 4 ASPEN, American Society for Parenteral and Enteral Nutrition. https://www.nutritioncare.org/Guidelines_and_Clinical_Resources/Resources_for_Critical_Care_Clinicians/
Ref 5 High-protein foods: The best protein sources to include in a healthy diet. Harvard Health Publishing. https://www.health.harvard.edu/nutrition/high-protein-foods-the-best-protein-sources-to-include-in-a-healthy-diet
Ref 6 Protein and amino acids. Yu YM et al. Present Knowledge in Nutrition (Eleventh Edition), 2020
Ref 7 Protein: Quality and Sources. A.V. Kurpad, in Encyclopedia of Human Nutrition (Third Edition), 2013