Protein is a long-chain amino acid and basic building block of the human body. The protein requirement must be covered with food, as the body is not able to produce protein itself.

Proteins have numerous important functions in the body: they participate in the construction of tendons, bones, cartilage and muscles, also form almost all enzymes as well as some hormones, are responsible for healthy nails, skin and hair, and also enable the absorption of iron into the body. In addition, protein is essential for the immune system, it boosts the metabolism and provides a longer-lasting feeling of satiety.

For healthy adults, the recommended amount of protein is about 0.8g per kilogram of body weight per day; for people who are very active and/or do competitive sports, about 1.2 - 1.7g protein per kilogram of body weight.

To ensure an ideal protein supply for the body, attention should be paid not only to the quantity but also to the quality of the protein, which can be determined with the "biological value". This indicates how many grams of body protein can be produced from 100g of protein in the diet. The higher the biological value, the better the body can convert the protein and use it to build muscle. Whole egg (egg white plus yolk) has the highest biological value at 100; other foods with a high biological value are, for example, tuna (92), pork (85), soy (84), lean quark/lean curd (81) or lentils (60).

Foods that are generally characterised by a high protein content per 100g include soy flakes, Harz cheese, lean beef, peanuts, seitan, pumpkin seeds or tuna in its own juice. Legumes, tofu, chicken, pollock or cottage cheese are also popular sources of protein.