Protein - also called protein - is one of the three main nutrients (alongside carbohydrates and fat) and a central building block of life. It consists of amino acids that are necessary for the formation, repair, and function of all body cells.
Approximately 15–20% of the human body consists of protein - primarily in muscles, skin, organs, enzymes, hormones, and the immune system. Without an adequate protein intake, the body cannot form new cells, maintain muscles, or carry out important metabolic processes.
Proteins consist of amino acids linked to one another by peptide bonds. There are a total of 20 proteinogenic amino acids, 9 of which are essential - meaning they must be obtained through food because the body cannot produce them itself.
Essential amino acids:
Leucine, isoleucine, valine, lysine, methionine, phenylalanine, threonine, tryptophan, histidine
Non-essential amino acids:
Can be produced by the body itself (e.g., alanine, glutamine, glycine).
High-quality proteins contain all essential amino acids in optimal proportions (e.g., from animal sources or certain plant-based combinations).
Animal-based sources:
Meat, fish, eggs
Dairy products (quark, yogurt, cheese)
Poultry
Plant-based sources:
Legumes (lentils, beans, chickpeas)
Soy and tofu
Quinoa, amaranth
Nuts, seeds, whole-grain products
Through clever combinations - e.g., grains + legumes (such as rice with beans or bread with hummus) - the biological value of plant-based proteins can be significantly increased.
1. Muscle development and maintenance:
Proteins are the basic substance of muscle tissue. They promote muscle growth, maintenance, and regeneration, especially after physical activity. The amino acid leucine plays a key role because it activates muscle protein synthesis.
2. Structure and cell formation:
Protein is a component of skin, hair, nails, bones, tendons, and connective tissue. It provides strength, elasticity, and stability to all body structures.
3. Enzymes and hormones:
Many enzymes and hormones consist of proteins. They regulate vital processes such as digestion, metabolism, cell division, and signal transmission.
4. Immune system:
Antibodies (immunoglobulins) consist of proteins and are crucial for defending against pathogens.
5. Transport and storage:
Proteins transport nutrients (e.g., hemoglobin transports oxygen, transferrin transports iron) and store important substances.
6. Energy source (in emergencies):
When energy intake from carbohydrates or fats is insufficient, protein can be used for energy production - at the expense of muscle mass, however.
Promotes muscle building and recovery
Supports the preservation of muscle mass during weight loss
Provides long-lasting satiety and stable blood sugar levels
Strengthens the immune system, skin, hair, and nails
Supports hormone and enzyme production
Contributes to healthy cell formation and wound healing
According to the German Nutrition Society (DGE):
Adults: 0.8 g of protein per kg of body weight
Physically active individuals: 1.2–2.0 g/kg
Muscle building or dieting phases: up to 2.2 g/kg
Example:
A person weighing 70 kg needs an average of about 56 g of protein per day, and with regular training up to 140 g.
Protein deficiency:
Muscle weakness and loss
Delayed wound healing
Brittle nails, hair loss
A weak immune system
Fatigue and concentration problems
Excessive intake:
Generally harmless with healthy kidneys
In the long term, very high amounts can strain the kidneys if too little fluid is consumed at the same time
A balanced diet remains crucial
Protein is the body's most important building material - indispensable for muscles, organs, skin, hormones, and the immune system. Adequate protein intake supports performance, recovery, metabolism, and satiety. What matters is not only the amount, but also the quality and variety of protein sources. A combination of animal and plant proteins ensures optimal nourishment and long-term health.
German Nutrition Society (DGE). (2020): Reference values for nutrient intake - Protein.
Phillips SM, et al. (2016): Dietary protein for athletes: from requirements to metabolic advantage. Appl Physiol Nutr Metab, 41(5), 565–572.
Paddon-Jones D, et al. (2008): Role of dietary protein in the sarcopenia of aging. Am J Clin Nutr, 87(5), 1562S–1566S.
Wu G. (2016): Dietary protein intake and human health. Food Funct, 7(3), 1251–1265.
