Protein: Sources, Functions, and Daily Requirements

Sources of Protein

Protein is a vital macronutrient:

• Main sources include meats (poultry, fish, meat, offal), dairy products (cheese, milk, yoghurts), eggs, and non-meat products like nuts and pulses (beans, peas, lentils).
• The term 'protein' originates from the Greek word “protos” meaning “first”.

Functions of Protein

Essential functions of protein in the body:

• Builds new cells, maintains body tissues, and forms new proteins for basic bodily functions.
• Composed of amino acids containing nitrogen, carbon, hydrogen, oxygen, and sometimes sulphur or phosphorus.
• Broken down into amino acids for absorption by intestinal cells and distribution throughout the body.

Distribution and Importance in the Body

Protein distribution in the human body:

• Approximately 15% of body weight in a 70kg person, with 43% in muscles, 21% in skin, 19% in blood, and 5% in the liver.
• Also present in smaller amounts in other bodily tissues.
• Integral to hormones, enzymes (including digestive enzymes), and immune system components.

Daily Protein Requirements

Daily recommended intake of protein:

• Adult males aged 19-50: 55 grams per day, decreasing to 53 grams for those over 50.
• Adult females aged 19-50: 45 grams per day, increasing slightly to 46 grams for those over 50 and during pregnancy.
• General recommendation of 0.75 grams of protein per kilogram of body weight, varying based on activity level or recovery needs (up to 1.4 grams per kilogram).