Food proteins are present in animal and vegetable foods.
The daily intake is 0,8 % of the body weight.
For example: 43 g of proteins for a 54 kg body weight.
In proteins there are different amino acids, some of which are essentials. This means that our body is unable to synthesise them by itself and must take them through food.
The biological value (quality) of the protein is given by the quantity of essential amino acids inside the protein.
For more information refer to this link of our Swiss Authorities (DE, FR, IT). In this link under “further information”, you can find a document (pdf) containing more information on protein in different languages (here the link of the document: DE, FR, IT).
Examples of proteins are casein (milk protein) or gluten (wheat protein), but proteins compose a huge of biochemicals (like hormones, enzyme and so on). You can find a high quantity of proteins in fish, legumes, soy (tofu), quorn and seitan.