Kanso

Protein is the third major nutrient that we consume in our diet, along with carbohydrates and fats. The term protein was derived from the Greek word proton for "the first, the most important thing"^.1 This is because protein is the basic building block of our human cells and is essential for life. Since our body has no protein store, our body cells must be regularly supplied with protein.

Protein is a building material for all organs, for hormones and enzymes, and serves as an energy supplier alongside carbohydrates and fats. The energy content is 4 kcal per gram of protein, which is the same as carbohydrates and about half as much as fat^.2

Proteins are formed from so-called amino acids, which are linked in countless combinations to form protein molecules. Since the human organism is not able to produce proteins itself, it covers its needs through food intake. Proteins are needed for the functioning of the entire body. They perform very diverse tasks that are of great importance for the organism^.3

Structure of proteins

The individual building blocks of proteins are natural chains of amino acids. We can think of amino acids as small building blocks that can be combined very creatively.

Twenty different amino acids are needed in the human body to build proteins, these are called proteinogenic. Nine of the proteinogenic amino acids cannot be rebuilt in the human organism, they are called indispensable (formerly: essential): Isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, and for infants, histidine. Without a regular supply of these indispensable amino acids, deficiency symptoms can occur.

The remaining eleven of the proteinogenic amino acids can be built up by the metabolism itself under normal conditions and with sufficient amounts of nitrogen. They are considered "dispensable" (formerly: non-essential) amino acids: alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine and tyrosine^.4

The more indispensable amino acids a food contains, the greater its so-called "biological value. Animal foods such as dairy products, meat, fish and eggs have a high biological value. But plant foods such as cereals, potatoes and legumes are also important sources of protein. Their usually low biological value can be increased by combining them with animal or other plant protein sources, in which the protein components complement each other^.5

It is therefore important to consume foods that have as broad an amino acid spectrum as possible or to cleverly combine individual protein-rich foods. If the intake of protein-rich foods is not given, these can be supplied via suitable dietary supplements.

Tasks of protein in the organism

Protein fulfills very important functions in our body. These include the formation of cells, skin, tissues of all kinds or the formation of antibodies for our immune system. It is needed for the functionality of nerve cells and for the provision of transport proteins.

The range of tasks performed by proteins is correspondingly large:

• Energy supply
• Component of tissue (muscles, organs, tendons, cartilage, connective tissue)
• are needed for muscle movement
• Basis for enzymes and thus catalyst of our metabolic processes
• regulate metabolic processes with the help of hormones
• Co-factors in many synthesis processes
• important for DNA replication
• can turn genes on or off
• Cell signal transduction (reception and transmission of stimuli)
• Immune defense (formation of antibodies)
• important for transport and storage processes, e.g. of oxygen or ^transferrin6

How much protein does the human body need?

How much protein the body needs varies from person to person. The German Nutrition Society / DACH recommendation recommends a daily intake of 0.8 grams of protein per kilogram of body weight for people between 19 and 65 years of age at a normal activity level. The protein requirements of premature infants, babies and adolescents are significantly higher. A higher protein intake is also recommended during pregnancy and lactation (+10g/d and +15g/d, respectively)^.7

The "safe" upper limit for protein has been set at 2 grams per kilo of body weight. This is because our bodies cannot process more protein per day due to the size of the liver and kidneys. This is equivalent to about 35% of our daily caloric intake. That's why dietary recommendations don't really mess with protein intake, only fat and carbohydrate.

Good sources of protein are:

Animal sources:

• Lean meat, offal, fish and eggs
• Cheese, milk and dairy products

Plant sources:

• Legumes e.g. soy, lentils, peas
• Mushrooms
• Bread, cereals and cereal ^products8

This is how the daily recommended protein intake can be achieved (example: adult, 68 g total protein intake)

The data refer to normal weight of an adult^.9

Sources

1. Biesalski, H. K., Grimm, P., Nowitzki-Grimm, S. (2020). Pocket atlas of nutrition. Georg Thieme Verlag.
2. Landeszentrum für Ernährung - KH, fat, protein - 3 main nutrients at a glance (landeszentrum-bw.de)
3. What are proteins (ernaehrungs-lexikon.ch)
4. Selected questions and answers on protein and essential amino acids - DGE
5. The nutrients - building blocks for your health. German Nutrition Society, 6th edition, 2022
6. Nutrients | Nutrient density | Nutrition information - ernaehrung.de
7. How much protein do we need? (dge.de)
8. Fat | Protein | Carbohydrates | Food Components | Nutrition Information - ernaehrung.de
9. The nutrients - building blocks for your health. German Nutrition Society, 6th edition, 2022