Proteins are one of four macronutrients. They are indispensable for our health, but not all “are worth” the same. For what reason? The question is in the biological value, also in the quality of the protein, and related to its bioavailability.
Let’s see what these terms mean, what we should keep in mind when choosing food and how we can benefit from this knowledge.
Biological value, bioavailability and protein quality
When we talk about proteins they are often named associated with their “biological value”. For example, it is common to hear about the high biological value of milk proteins. What does this expression mean? It is quite illustrative, although delving deeper into its meaning, the biological value refers to the extent of absorption and synthesis of proteins in our body.
When we eat, our digestive system is responsible for “dismantling” the parts that form food. After this, all available nutrients are absorbed and pass into our system to be part of our metabolism. In the specific case of proteins, they must be isolated from the rest of the food and, hence, separated into amino acids.
These are the fundamental blocks that form the proteins themselves, therefore, they will be used to form the proteins we need. Some amino acids can only be obtained through food since we cannot synthesize ourselves. On the other hand, not all proteins have the same proportion of amino acids.
The number of proteins, the ease of digesting them and the “matrix” where they are inserted (the context of the food) are the variables that determine the biological value of the protein. Protein quality, in particular, refers to another characteristic: the proportion of available amino acids. As we said, not all proteins are the same. The proportion of these blocks can be more or less beneficial as complete.
Bioavailability is a term more associated with drugs, which speaks of the speed at which they act on their therapeutic target. In that sense, we can talk about the bioavailability of proteins to the number of useful amino acids that get absorbed and, therefore, can be used. In short, the biological value, quality, and bioavailability of proteins refer to how useful this macronutrient will be in food.
How is the biological value of proteins measured?
Indeed, the biological value of the protein is not limited to a purely abstract concept but can be measured. In short, the biological value of the protein is measured according to the amount of nitrogen from the food we can absorb.
This can be checked using special nitrogen isotopes and/or biostatistical techniques and strict dietary control. This gives us values ranging from 0 to 100, although this maximum may be even higher in some cases where the origin of the protein is combined. On the other hand, the quality of the protein can also be measured, according to, as we said, the proportions of amino acids it contains.
Thus, casein, a milk protein, has a higher quality than beef, and much higher than whole wheat. It is important to understand that the biological value depends on the metabolism of each person. In that sense, the figures are mere weighted approximations to understand the comparison between the origins of the proteins.
What do proteins serve?
Proteins are the basis of every living being since they are the most versatile biomolecules that exist. They constitute tools in themselves as they have a composition according to their function, that is, the role they will play in our body: they can be enzymes responsible for degrading, catalyzing reactions, transporting nutrients or anything that comes to mind.
There are literally billions of proteins. To be able to do them, we need the “pieces” that make them up, the amino acids. These are joined in very long chains, which fold and fold. There are millions of amino acids, but there are 20 in particular necessary to form life-related proteins. Of these, 9 (or 10) are considered essential for human beings, since we cannot manufacture them and must be obtained by eating.
Without proteins, we cannot live. As simple as that. Without the essential amino acids, we cannot form all the proteins we need. Without a quality protein and high biological value, it is much harder to get all the amino acids we need. Therefore, to ensure the best proteins is to ensure that we obtain the necessary resources for our cellular machinery.
What are the best proteins?
Protein is usually obtained from both animal and vegetable foods. It is not true that the vegetable protein is of worse quality than the animal, but it is necessary to take into account that before a vegetarian or vegan diet it is necessary to complement more since not all the necessary amino acids are available in all the foods.
On the contrary, those of animal origin, such as milk, eggs or tuna, contain high-quality protein, that is, they are practically complete proteins, so we do not need to combine so much food to complete the recommended minimum.
Some good examples of foods with high biological value, with a varied quality and that can be complemented are legumes (lentils, beans, chickpeas, beans) , some cereals such as wheat, soybeans, turkey, tuna, redfish, Nuts, eggs, milk, some vegetable drinks (especially soybeans) and also cheese.