What is protein? Properties, function, and occurrence of protein.

Every cell in our body, from muscles to skin, requires constant renewal and regeneration. This constant process of regeneration is driven by one of the most important macronutrients in our diet – protein. A thorough understanding of its role is key to consciously maintaining health and vitality.

What is protein?

Protein is one of the most important macronutrients and a fundamental building block of all living organisms. It contains elements such as carbon, oxygen, hydrogen, nitrogen, and sulfur. Some proteins may also contain zinc, manganese, copper, iodine, and iron.

Protein structure is based on complex chains composed of smaller units—amino acids. It is the unique order and type of these amino acids that give each protein its specific properties and determine its role in the body. From muscle building to oxygen transport to defense against infections, protein is ubiquitous and irreplaceable. Maintaining health and the ability to grow and repair tissues are directly dependent on its consistent availability in the daily diet.

There are several categories of amino acids that make up proteins.

1. The most important of these are exogenous amino acids, also known as essential amino acids. The body cannot produce them, so their only source must be the food we eat.

2. In opposition to them are endogenous amino acids, which the body synthesizes on its own.

3. There is also a third group – conditionally essential amino acids. Under normal circumstances, the body produces them, but in situations of increased demand (e.g., during illness or after intense exercise), their production becomes insufficient.

A complete supply of all essential amino acids to the body is the basic assumption of a well-balanced diet.

What are the basic functions of protein in the body?

Proteins are essential for the body's growth and development, as well as for the continuous renewal and repair of cells and tissues. Without them, processes such as wound healing and recovery from exercise would not be possible. Proteins are also a key structural component of body fluids, including blood and lymph. They are also a fundamental component of milk, providing nutrients essential for newborn development. Without a constant supply of this macronutrient, the body would not be able to maintain its structural integrity.

However, the functions of proteins extend far beyond those mentioned above. As components of immune cells (antibodies), they play a key role in the immune system, protecting the body against pathogens. Furthermore, they are components of enzymes that act as catalysts, accelerating countless biochemical reactions essential for life. Proteins also participate in the regulation of physiological processes, helping to maintain normal blood pressure and acid-base balance. They act as carriers, transporting certain vitamins and minerals throughout the body. Although this is not their primary function, they can also provide a source of energy when needed.

What types of proteins are there?

The basic division of proteins is based on their nutritional value resulting from the source, which is determined by the content and proportions of exogenous amino acids:

• Complete proteins are distinguished here, providing all the essential amino acids in quantities that ensure their maximum utilization by the body. These are primarily proteins of animal origin, such as those found in meat, fish, eggs, and dairy products;

• The second group consists of incomplete proteins, which lack one or more essential amino acids, limiting their use as building blocks. This category includes most plant proteins, such as those from cereals.

Proteins can also be classified based on their chemical structure and biological functions. Based on their structure, they are divided into simple proteins, composed solely of amino acids, and complex proteins, which contain additional non-protein elements (e.g., a metal atom). Functional classification, in turn, reflects their diverse roles in the body. Among them are structural proteins ( collagen , keratin), enzymatic proteins (catalyzing reactions), transport proteins (hemoglobin), immune proteins (antibodies), and hormonal proteins (insulin).

Where does protein occur in food?

Due to their high quality and complete amino acid profile, animal protein sources are considered particularly valuable. Lean meats, including poultry (chicken, turkey) and beef tenderloin, are among the richest. Fish also play a significant role, especially oily marine fish such as salmon, mackerel, and herring, which, in addition to protein, provide omega-3 fatty acids. Chicken eggs are the benchmark in terms of amino acid composition. Dairy products are also a supplement:

• cheeses, especially cottage cheese;

• natural yogurts (including skyr);

• milk that is easy to include in a high-protein diet.

Plant-based protein alternatives are becoming increasingly popular. A significant group includes legumes: lentils, chickpeas, beans, peas, and soybeans, along with soy products such as tofu, tempeh, and edamame. Nuts (e.g., almonds, walnuts) and seeds (pumpkin, sunflower, chia, and flaxseed) also contain valuable amounts of protein. Pseudocereals, such as quinoa and amaranth, are a valuable supplement. Combining these foods appropriately can also meet the protein needs of vegetarian and vegan diets.

Convenient functional foods are also available, designed to quickly provide a balanced portion of macronutrients. Eatyx ready-to-drink, nutritionally complete liquid meals combine high-quality protein with carbohydrates, fats, vitamins, and minerals.

What are the effects of protein deficiency?

Protein deficiency in the diet can lead to a number of negative health consequences. The first, often nonspecific, symptoms include general weakness, chronic fatigue, and apathy. Without sufficient building blocks, the body begins to restrict non-essential processes. Hair may deteriorate, becoming brittle and falling out, and nails may become brittle and split. The skin may become dry, and wound healing and epidermal regeneration processes may slow down significantly. These are signals that the body is lacking essential nutrients.

Chronic and profound protein deficiency leads to more serious problems. One of the most serious consequences is sarcopenia, a progressive loss of muscle mass and strength. In search of amino acids, the body begins to break down its own muscle proteins, leading to weakness and reduced physical performance. The immune system is also significantly weakened, as antibody production is dependent on protein availability. This, in turn, increases susceptibility to all types of infections and complicates recovery.

Protein deficiency is particularly dangerous in children and adolescents. It can lead to stunted growth, delayed physical and intellectual development, and permanent impairments in bodily functions. In older adults, protein deficiency accelerates the aging process, exacerbates muscle loss, and increases the risk of falls and fractures. Therefore, ensuring an adequate supply of this macronutrient at every stage of life is crucial, and its deficiencies should never be ignored.

What are the recommended amounts of protein in the diet?

Protein requirements vary from person to person, depending on many factors, including age, weight, gender, physical activity level, and overall health. However, there are general guidelines that can serve as a guide. For the average healthy adult with low levels of physical activity, the recommended intake is approximately 0.8 grams of protein per kilogram of body weight. This means that a person weighing 70 kg should consume approximately 56 grams of protein per day to meet the body's basic needs for regeneration and maintenance.

Protein demand increases dramatically for physically active individuals. This increased intake is necessary to repair muscle micro-damage sustained during training and to build new muscle mass. Pregnant and breastfeeding women also have higher protein requirements, as protein is essential for proper fetal development and milk production.

What are the best sources of protein for different groups of people?

For those following a traditional diet, which includes animal products, the choice of protein sources is very wide. Variety is the best approach. It's recommended to include lean poultry and beef in the diet, which provide high-quality protein and iron. Fish, both lean and fatty, should be a prominent part of the diet due to their protein and omega-3 fatty acid content. Eggs are an excellent, complete source of amino acids. Dairy products should be added to the diet: low-fat cottage cheese, Greek yogurt, or skyr, which are concentrated sources of protein.

People on plant-based diets must carefully plan their meals to ensure they receive a full range of amino acids. The foundation of a vegan and vegetarian diet should be legumes—lentils, chickpeas, beans, and peas. Soybeans and soy products, such as tofu, tempeh, and soy drinks, are essential. It's also important to combine different food groups, such as grains with legumes (e.g., rice with beans), to achieve a complete amino acid profile. Nuts, seeds, and pseudocereals like quinoa are valuable supplements.

For busy people, athletes, and those who struggle to meet their needs with traditional foods, functional products are an excellent solution – especially in convenient drinking form. For example:

• A balanced, nutritious liquid meal Dubai chocolate 300 ml – lactose free ;

• Balanced, nutritious liquid meal Mango 300 ml – lactose-free ;

• A balanced, nutritious liquid meal Creamy Berry 300 ml – lactose free .

Can protein be harmful?

For healthy individuals, a diet high in protein is safe. Healthy kidneys are designed to efficiently filter and remove protein waste products, such as urea. The strain resulting from consuming even significantly higher amounts of protein than recommended does not lead to kidney damage in individuals without pre-existing conditions.

The situation is different for people with pre-existing, diagnosed kidney or liver disease. In such patients, the ability to metabolize and excrete protein waste products is impaired. In such cases, excessive protein intake can indeed overload diseased organs and exacerbate dysfunction. Therefore, people with chronic kidney failure or advanced liver disease should follow a protein-restricted diet, always under the strict supervision of a specialist.

It's also important to remember that extremely high protein intake, at the expense of other macronutrients, can also lead to problems. A diet based almost exclusively on protein can result in deficiencies in fiber, vitamins, and minerals found in fruits, vegetables, and grains. It can also increase the risk of dehydration, as the body requires more water to process nitrogen from amino acids. Therefore, the key is a balanced diet in which protein plays an important, but not the only, role, and its amount is tailored to individual needs.