Proteins are like long strings of amino acids that are linked together and folded into complex shapes.
There are about 9 amino acids that we can not produce and must get from the diet.
In this regard, animal proteins are excellent… they contain all the amino acids that we need, while most plant proteins have a suboptimal amino acid profile
Not surprisingly, consumption of animal protein is associated with increased muscle mass and people who eat an omnivorous diet have more muscle than people eating a vegetarian diet (26, 27).
Another thing that protein is important for is bone health. The studies show that consumption of protein, especially animal protein, is associated with increased bone density in old age and a lower risk of fractures.
If you want to gain (or maintain) muscle, as well as prevent osteoporosis and fractures in old age, then animal protein should be a regular part of your diet.
Consumption of animal protein leads to increased muscle mass and bone density. Vegetarians have lower testosterone and less muscle mass than their meat-eating counterparts