What are proteins? What are amino acids? How much protein do you need? What do we need protein for? What does biological value of proteins mean?
We will answer all these questions in this blog post!
What are proteins?
Next to fat and carbohydrates, proteins belong to macronutrients. They are the basic building blocks of life. All three together form the main suppliers of nutrients in our food. They provide energy and perform some vital functions in our body.
Structure of proteins
Proteins are macromolecules that consist of amino acid chains. Humans can even produce proteins themselves and need 21 different amino acids for this. Lined up in a different order and combination, they create amino acid chains with a total of 50 to 100 amino acids.
The 9 essential amino acids
Each protein consists of an individual sequence of amino acids and thus has its own amino acid profile.
In humans, there are 21 proteinogenic, i.e. protein-forming amino acids.
Of these 21 amino acids, humans cannot produce 9 amino acids themselves. Consequently, these 9 amino acids must be absorbed through food. They are therefore called “essential amino acids“.
The 9 essential amino acids are called:
- Thyrosine (only for children)
Functions of proteins in the human organism
There are 6 different types of protein, each of which has different functions in our body.
Structural proteins serve as components in tissues and cells. Cells thus maintain their shape, and tissues their strength and elasticity. Typical structural proteins are collagen (hair and nails), keratin (binding tissue and cartilage) and elastin (gives blood vessels the elasticity).
Without contractile proteins, we would not be able to move. They are significantly involved in the contraction of the muscles. The most important contractile proteins include myosin and actin.
Protective proteins help other proteins to maintain their shape when stressed (e.g. high temperature). Antibodies are also protective proteins. They are used to ward off invading foreign substances. Fibrinogen is an important protective protein and is partly responsible for blood clotting.
As the name suggests, storage proteins can bind other substances to themselves and thus store them. Ferritin, for example, stores iron in humans.
These proteins transport various substances, such as oxygen or fat, in the body. Typical transport proteins are albumin (binds e.g., calcium), hemoglobin (binding oxygen and carbon dioxide) and lipoprotein (transports fat).
Proteohormones and peptide hormones are special proteins that perform messenger functions in the body. Most hormones are proteohormones. Insulin, for example, is such a hormone and is responsible for regulating blood sugar levels.
The body needs enzymes to enable and accelerate (catalyze) chemical reactions in the body. For example, for our metabolism, we need digestive enzymes for the breakdown of nutrients. Amylase (digestion of carbohydrates), aldolase (splitting of fructose) and GOT (metabolism of amino acids) are such enzymes.
How much protein do humans need?
A person’s protein requirements depend on a few individual factors:
- Overall state of health
- Physical activity
For a person, it’s usually: 0.8g protein per kilogram of body weight per day (from 65 years: 1.0g).
It could also be said that the average adult should absorb about 10% of their daily energy needs through proteins. With a daily energy requirement of e.g. 2500kcal, 250kcal should come from proteins. This corresponds to 60g of protein.
Excursion to nutrients and their calories: Protein = 4.1 kcal/g Carbohydrates = 4.1 kcal/g Fat = 9.3 kcal/g Alcohol = 7.1 kcal/g
Protein and protein-rich foods are actively propagated by the food and fitness industry. That’s why most people estimate the amount of protein they need every day far too high!
Protein requirements according to WHO
Protein requirements for athletes
For competitive athletes, a slightly higher value of about 1.2-1.5g per kg of body weight applies. However, especially amateur athletes (but also competitive athletes) tend to exceed this value (by far). True to the motto: The more the better.
We have gone through this phase ourselves. Such a misjudgment of protein requirements often leads (as in our case) to a one-sided and thus deficient diet. If you eat an excessive amount of animal protein and still don’t want to gain weight, it inevitably ends in a low-carbohydrate and low-fiber diet. In the long run, this is neither healthy nor good for athletic performance.
How much protein is “too much” protein?
The food industry and especially the fitness industry love protein. The more protein, the better!
Sure, protein is essential for many bodily functions and indispensable for muscle building and muscle maintenance. BUT it is not necessary and from a health perspective also not advisable to consume large amounts above the guide value!
It is crucial to consider the protein intake not only in absolute amounts but also in relation to the total energy supply and body weight. If you want to eat a healthy diet and/or achieve sporting goals, then it is recommended not to orient your diet according to the amount of protein.
Because if protein intake leads to a one-sided diet and displaces other essential nutrients from the diet, it is too much protein.
A high-protein/low-carb diet or a high-protein/high-fat diet simply makes no sense to the average person without any illnesses in the long run and can even harm your health. Much more, you should pay attention to a varied and balanced diet!
How to recognize high-quality protein?
There are many questions regarding the quality of plant protein. Most people assume that only animal products – such as meat, fish and eggs – can provide humans with high-quality protein. But also numerous plants contain plenty of protein.
But can the human body absorb the protein from the plants? And how about the quality of plant protein compared to animal protein?
Good sources of protein
Each food contains different levels of protein. Besides, all amino acids are found in varying proportions in the individual foods – regardless of whether they are of animal or plant origin.
These differences result in foods that are more convenient to supplying us with protein and some that are less suitable.
There are some defined methods for determining whether a food is a high-quality source of protein. We want to show you a few of them.
The biological value
The biological value (BV) indicates how much of the protein eaten, can (theoretically) be converted into the body’s own proteins.
To achieve a high BV, foods must have all essential amino acids in sufficient quantities. The ultimate value is derived from the limiting amino acid. In other words, the essential amino acid that is most inadequately contained in relation to human needs.
The higher the content of the essential amino acids, the more efficient the use of the corresponding food proteins for the synthesis of the body’s own protein and the higher the BV.
The reference value for the BV is the egg (BW=100). However, this does not mean that the egg is the best possible source of protein! By combining different foods, you can even reach a BW of over 100! Here it is only important that the combined foods complement each other in their amino acid profile, i.e. the essential amino acids contained.
DIAAS and PDCAAS
Now we know what the BV is. However, it is not enough to only know the value of the theoretical intake of the food protein. Even more important is how much of the protein in the diet the body can actually absorb during digestion and use further on.
To measure this, there are two methods: the Digestible Indispensable Amino Acid Score (DIAAS) and the Protein Digestability Corrected Amino Acid Score (PDAAS).
Both scores describe the quality of proteins (food), based on human protein requirements and the ability to digest them.
The difference between biological value, DIAAS and PDCAAS
In short, the difference is that DIAAS and PDCAAS take into account the digestive process of the food proteins absorbed.
For a long time, the PDCAAS was considered a method of choice to measure protein quality. In the meantime, however, the DIAAS is considered a more accurate measure of the actual uptake of the individual amino acids.
The difference between DIAAS and PDCAA
The DIAAS assesses protein quality on the basis of the true, ileal (measured in the crumb intestine) digestibility of each essential amino acid. It gives a value for each of the nine essential amino acids. On the other hand, the PDCAAS reflects the fecal digestibility of the protein and only indicates the value of the limiting amino acid.
For all who want to know more about the ileal and fecal measurement of protein digestibility: Report of the FAO, Page 3, “Faecal versus ileal digestibility – a physiological perspective”
Proteins consist of 21 different amino acids, of which 9 are essential. We need to absorb these through our food so that our bodies can build proteins from them. Proteins perform various functions in humans. For example, some proteins are responsible for transporting oxygen or protect us against foreign bodies.
Measurement methods such as biological value, DIAAS and PDCAAS enable an independent and objective assessment of the protein quality of individual foods based on their amino acid profile. However, we should never ignore the fact that a meal consists of several ingredients. Thus, the total protein supply of all foods contained should be evaluated in combination.
Excessive consumption of protein, i.e. more than 0.8g per kilogram of body weight per day, is not recommended for the average person up to 65 years of age. Even athletes don’t have to worry about their protein intake. For top athletes, 1.2-1.5g per kilogram of body weight is usually sufficient.
Instead of focusing only on the protein value of individual foods, much more attention should be paid to a balanced and varied diet with as few processed foods and ready meals as possible. Then the protein comes by itself… 😉
We wrote another blog post on protein! In the post “Busting The Vegan Myth Of Protein Deficiency” we clarify the frequently asked question about the protein supply in a vegan diet.
Attention: We are not doctors or nutritionists! We really try to do proper research. Nevertheless, we encourage everyone to find out more themselves elsewhere. In the case of health impairments, a doctor should always be consulted.