Carbohydrates, fats and protein can all be broken down into smaller units.
Each one of those smaller units can be sub-divided. In the case of proteins, proteins are made up of amino acids. Not all proteins have the eight essential amino acids that the body needs. If you are consuming protein and you don’t get the essential ones for
long periods of time, you are putting yourself at risk of becoming malnourished. In places around the world where food isn’t so plentiful, children can become malnourished and develop diseases such as Kwashiorkor. These children have distended tummies, however the rest of their bodies are fine, this unfortunately is caused by a protein deficiency.
Scientists can measure the quality of nutrients that people are getting. The amount of protein consumed is controlled. They can measure how much is excreted, how much weight a person gains and basically they can determine how much of that protein is utilized by the body.
Some proteins are absorbed extremely well, an example would be egg albumin, which is a protein found in the white of an egg rather than the yolk. The egg white protein has an extremely high biological availability and all of the essential amino acids in
the right balance.
Gelatin has many of the essential amino acids, however, does not have an amino acid called tryptophan and because it is lacking, it isn’t considered a complete form of protein.