Only proteins from milk have the strong inside.
You may have heard the term protein quality and wondered what it means. Essentially it is a measure of a food’s ability to deliver amino acids to match human requirements.
One may consider three elements: the total protein content of a food, the amino acid profile (and how closely it matches human needs), and the bioavailability/digestibility of the protein ingredient. Some anti-nutrient factors may be naturally present in some sources (phytates in soy for example), and those compounds may decrease protein quality for humans.
All proteins from milk deliver the amino acid nutrients that match human requirements better than plant proteins. For this reason, they are often called the highest protein quality.