A recent study evaluated if a higher protein intake above the recommended daily amounts has a positive effect on bone health in healthy people.
We can understand the scientific interest in exploring this topic; first and foremost we know by studying anatomy and physiology that  the strength of bones come from a protein matrix which provides completely resilience and elasticity, as well as many minerals deposited in the provide additional strength.   Also the modern “supplement trend” of protein powder within the last couple of years rose above and beyond consumers and manufacturers expectations and it could be an understandable and common wonder among people to find out if a higher intake of protein could benefit the bones.  Also let’s not forget the intrinsic value of protein within our whole body structure that is always of global interest the understanding of it as much as when we can.



Protein
Protein are the building block of our body and make up 25% of our body weight. They have a variety of essential functions in the human body:
-Protein are important for healthy digestion in the gut, as they serve as enzymes;
-Protein provide elasticity, fluid gel structure and allows for adhesiveness in the extra cellular fluid and in our connective tissues
-Protein allows for contraction of muscles
-Protein serves as hormones, so they play a role in our endocrine system
-Protein are necessary for the DNA and RNA
-Protein support healthy circulatory system, because they maintain correct blood pressure and transport a variety of substances
-Protein provide structural integrity and protection on a cellular level
-Protein allow for correct signaling processes: they transfer chemical messages in and out of cells
-Protein promote oxygen-based energy production inside the mitochondria
-Protein play a role in our detoxification function, as they process potential toxins to enable elimination from the body



Bones
The bone is a complex living organism that is constantly metabolically active; bones are therefore living organs that are made of different tissues. There are 206 bones in the adult human skeleton and both the bones and skeleton have key functions in the body:
•Support: The bony framework for the attachment of soft tissue and organs provide a structural support for the body
•Movement: the bones act as levers providing the transmission of muscular forces and obiously the skeleton allows and anable movement through articulation (joints)
•Storage: the bones stores essential minerals, and the release of them in response to the body’s demands: this is regulated by hormones and is imp[ortant for internal homeostasis. Fats are also stored in the yellow marrow of some bones and their storage and release depend on the body’s needs to provide energy
•Protection: Bone is a rigid structure that protects soft tissue of the body and internal organs
•Production: Some bones in the body are involved in the production of blood cells which occurs in the internal cavity of bones called red bone marrow.



The Study
In April 2019 an extensive systematic review and meta-analysis was published in the journal of “Osteoporosis International” by a team of researchers at the University of Surrey (UK). The researchers analyzed the relationship between dietary protein and bone health across the life-course; the investigation included 127 papers for inclusion from 1976 to 2016; 74 correlation studies, 23 fracture or osteoporosis risk studies and 30 supplementation trials.
The results:
•only 4% of bone density and bone mineral content in adults is dependent on protein intake
•for children a stronger relationship between protein and bones were identified with up to 14%  accounting bone mineral content
•In adults supplementation via protein shakes and tablets was not found to reduce the risk of fractures nor improve bone health
•No detrimental effect of having an increased protein intake was identified, at least within the protein intakes of the population studies (around 0.8-1.3 g/Kg/day).


More studies are needed on the association between protein intake and bone health in children and adolescent.


Conclusion
There are several factors that affect bone growth and bone health in general:
•Vitamins: A, C, D, E, K, B12
•Hormones: Human growth hormone, insulin-like growth factors, estrogens, androgens, and thyroid hormones.
•Minerals: Calcium, magnesium, phosphorus, zinc, silica, sulfur, boron, fluorine.
•Exercise: when placed under stress, bone tissue becomes stronger as remodeling occurs. Weight-bearing and body weight exercise are beneficial in this regard.


Protein does play a role in bone health due to its ability to increase calcium absorption in the gut (that is likely to mineralize the bone) and by increasing the secretion of an insulin-like growth hormone (which stimulates development).  But many more factors as we have seen are essential for maintaining the health and correct growth and functioning of our bones, with diet and exercise being key elemental factors on this regard.



Source: Osteoporosis International

https://link.springer.com/article/10.1007%2Fs00198-019-04933-8

"Dietary protein and bone health across the life-course; an updated systematic review and meta-analysis over 40 years"

Darling A.L., et al.