Protein
Functions
The body needs protein for a number of reasons:
- for growth, in particular during pregnancy and adolescence
- to repair body cells and tissues, including recovery after illness or injury
- to produce enzymes needed for digestion
- to produce hormones that control body functions
- protein provides a secondary source of energy
Sources
There are three types of sources we can get protein from. These are animal, plant and novel.
- Animal sources: Meat (e.g., chicken or beef), fish, dairy foods (e.g., milk or cheese) and eggs.
- Plant sources: Pulses (e.g., peas and beans), lentils, grains and nuts.
- Novel sources: Tofu, soya, TVP (Textured Vegetable Protein).
Image caption, Chicken, meat, fish, eggs and dairy products
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Biological value
Proteins are made up of amino acids.
There are two types of amino acids that you need to know about.
Indispensable (essential) amino acids: These cannot be made by the body, they must come from the diet. There are eight indispensable amino acids.
Dispensable (non-essential) amino acids: These are produced by the body. There are 12 dispensable amino acids.
LBV and HBV
The biological value relates to how many amino acids are present in a protein.
If a food is missing one or more of the indispensable amino acids, it has a low biological value (LBV). For example, baked beans have an LBV.
If a food has all the indispensable amino acids, it has a high biological value (HBV). For example, steak has an HBV.
Protein complementation
Protein complementation is when two LBV proteins are eaten together.
By eating two LBV proteins in the same meal, you can make up for the lacking amino acids in each, therefore giving yourself a meal with a high biological value (HBV).
A common example of protein complementation would be eating beans on toast.
