Protein

Key points
• Protein is needed for growth and repair of the body.
• Protein can also provide energy; 1 gram provides 17 kJ (4 kcal).
• Different foods contain different amounts and combinations of amino acids (the building blocks of proteins). Vegans and vegetarians can get all the protein they need by combining different plant sources of protein, e.g. pulses and cereals.
• The amount of protein we need changes during a lifetime.

Protein in the diet
The average daily intake of protein in the UK is 88g for men and 64g for women and hence exceeds the reference nutrient intakes for protein of 55.5 g/day for men aged 19-50 years and 53. 3 g/day for those aged 50+ years; and 45.0 g/d for women aged 19-50 years and 46.5 g/d for those aged 50+ years. Foods vary in the amount of protein they provide but the main sources include meat, fish, eggs, milk, cheese, cereals and cereal products (e.g. bread), nuts and pulses (beans and lentils).

In Britain, on average, approximately two thirds of protein intake is obtained from animal sources, i.e. meat, fish, eggs and dairy foods. A further quarter is obtained from cereal products, and most of the remainder from nuts and pulses. Cereals, nuts and pulses are the principle sources of protein for people on a vegan diet.

Protein as a nutrient
Protein has many important functions as a nutrient:

It is necessary for the growth and repair of body tissues. The Dietary Reference Values for protein are based on estimates of need. For adults, an average requirement of 0.6g of protein per kilogram bodyweight per day is estimated. The Reference Nutrient Intake (RNI) is set at 0.75g of protein per kilogram bodyweight per day in adults. There is an extra requirement for growth in infants and children, and for pregnant and breast feeding women.

Further information

Food Standards Agency (2002) McCance and Widdowson's The Composition of Foods, Sixth summary edition. Royal Society of Chemistry: Cambridge.

Department of Health (1991) Dietary Reference Values, A Guide. HMSO: London.

Henderson L, Gregory J, Irving K et al (2003) The National Diet and Nutrition Survey: Adults Aged 19-64 years, Volume 2: Energy, Protein, Carbohydrate, Fat and Alcohol Intake. London, HMSO.

© British Nutrition Foundation