Protein studies suggest that:

Protein aids in building muscle via muscle protein synthesis

Protein affects mTOR and Akt (anabolic pathways)

Protein seems to limit how much muscle you lose during weight loss. Several studies even show that we can gain muscle mass during a caloric deficit (even trained lifters). Read more about how to gain muscle while losing fat.

Protein might affect satiety (high protein diets might help you eat less food)

Reviews suggest that there are few negative effects of higher protein intakes for various health outcomes (assuming, for example, that your kidneys function properly). Protein might probably even improve some health markers. However, there is disagreement in the literature.

There may be sex differences in protein metabolism

Check out the previous study collection on vitamins and minerals.