Proteins As The Basic Building Blocks of Life
The scientific name protein means something like “the first” or “the most important”. Proteins perform a variety of functions in the human body. They are building blocks of tissue (for example, tendons, skin, muscles)—also, proteins from almost all enzymes and some hormones. The antibodies of the immune system also consist to a large extent of proteins. Proteins also serve as transport proteins for fats (lipoproteins) or oxygen (hemoglobin).
Amino Acids – Building Blocks of Proteins
Proteins and peptides are made up of amino acids. Most proteins are made up of a limited number of up to 20 different amino acids. Some amino acids have to be taken in with the diet (essential amino acids), while the body can synthesize some itself (non-essential amino acids).
Essential Amino Acids
The body cannot wholly synthesize the eight essential, i.e., indispensable, amino acids. These must be supplied to the body through food. The essential amino acids in humans include:
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
Non-essential Amino Acids
The body can synthesize the non-essential, therefore dispensable, amino acids itself in sufficient quantities to cover the needs. The non-essential amino acids include:
- Alanine
- Asparagine
- Aspartic acid
- Glutamic acid
- Glycine
- Proline
Semi-essential Amino Acids
A third form of the amino acids is the partially dispensable or semi-essential amino acids. The body cannot synthesize these itself under certain conditions or not to a sufficient extent (eg, during growth phases or in the event of metabolic stress). The semi-essential amino acids include:
- Arginine (newborns, serious illnesses)
- Cysteine (newborns, liver disease)
- Glutamine
- Histidine (newborns, chronic kidney disease)
- Tyrosine (newborns, phenylketonuria)
- Serine (if kidney function is impaired)
Also Read: Balanced Nutrition For Athletes
Which Foods Provide Proteins?
There are vegetable and animal protein. Animal protein is usually the higher-quality protein source; the body can use them to produce its protein more efficiently.
Typical Animal Protein Sources
- flesh
- fish
- Eie
- Dairy products
Typical Vegetable Protein Sources
- legumes
- soy
- lenses
- Beans
- Lupins
- Grain
- nuts
- Seeds
Assess The Quality of Protein
Foods differ in their amino acid composition. Since the amino acid profile of food proteins is never identical to the amino acid profile of body proteins, it is said that these are of “lower quality.” The amount of amino acids contained in dietary protein is not limiting for protein synthesis. The limiting factor is the concentration of the amino acid with the most significant deficit about the requirement. This is called the limiting amino acid.
If a limiting amino acid is used up, the body cannot produce any other endogenous proteins. Similar to a puzzle, it then lacks the right building block. We don’t have a protein requirement but an amino acid requirement.
Several methods, such as the biological value, the amino acid score, or the PDCAA score, have been developed to evaluate proteins. The “biological value” is the most common and practicable method today.
Proteins and Amino Acids are not Just Building Materials
In energy metabolism, carbohydrates and fats are preferred. Amino acids are only oxidized to an increased extent in the event of long-term stress, in starvation metabolism, or when there is a large supply of protein from food. The body uses proteins from the muscle tissue as energy reserves during hunger metabolism (in catabolic phases). He does not use excess protein to build muscle but as an energy source.
Therefore, a balanced energy balance should always be achieved. Because building “mass”, while the body is starving is virtually impossible.
Also Read: Basic Concepts Of Nutrition
Nutrient Timing
After training, the body is in an “anabolic time window” for about 3 hours. In this phase, it is particularly good at building up and regenerating new structures. Carbohydrates and proteins should be consumed at this stage. Muscle protein synthesis should be maximally stimulated through the availability of amino acids and the simultaneously stimulated release of insulin through the carbohydrates.
We recommend 45-75 g carbohydrates and around 15-25 g protein. A side effect is that the glycogen stores are then also replenished more quickly.
How Much Protein do we Need?
The DGE recommends a daily protein intake with the usual mixed diet of 0.8 grams of protein per kilogram of body weight for adults with light physical work.
However, this recommendation is increasingly being criticized. It must be taken into account that the actual protein intake in Germany is already significantly higher on average (approx. 1.2 – 1.4 g / kg body weight ). Healthy people can usually tolerate a high-protein, low-carbohydrate diet without any problems. A low-protein diet, on the other hand, often results in a high-carbohydrate diet. A diet with a high concentration of carbohydrates is believed to be partly to blame for the obesity epidemic (mainly due to refined carbohydrates such as sugar ).
The body’s protein requirement ultimately depends on various factors such as higher energy requirements or structural loads (athletes or non-athletes), exceptional circumstances (e.g., illness, injury, or pregnancy), or growth phases (children, adolescents, strength athletes). In the best-case scenario, the increased protein requirement can be covered by a balanced diet. Otherwise, there is the possibility to cover the increased protein requirement with protein supplements.
Protein Requirements of Athletes
According to the literature, there are sometimes very different intake recommendations for athletes. For endurance athletes, the protein recommendations are around 1.2 – 1.4 g / kg body weight and for strength athletes 1.6 – 1.7 g / kg body weight. Some sources recommend even higher values.