Does Protein Food Affect Our Bone System?

Bone is an extremely metabolically active tissue. Its role in the body far exceeds the mechanical function with which it is usually associated. It takes an active part in maintaining optimal alkaline-acid and electrolyte balance - the basis for a number of physiological processes in any other tissue. Bones are a depot for calcium and phosphorus in the body. The control over the level of these electrolytes is complex, it is influenced by many hormones, the nutritional composition and the presence of other electrolytes in the blood. What is the place of protein intake in calcium-phosphorus metabolism and bone density?

Protein is essential for proper physical development and growth. Consumption of foods rich in protein and calcium are just one of the recommendations for the accumulation of high peak bone mass and prevention of osteoporosis . On the other hand, protein-rich diets at the expense of carbohydrates, which have recently gained widespread public popularity, have raised concerns about the adverse effects of protein overload on the body in general and bones in particular.

Experts have long observed that the increased presence of calcium in the diet leads to increased loss of calcium in the urine. If this is not accompanied by increased absorption of calcium in the intestine, then it follows that its excretion through the kidneys is at the expense of resorption processes from the bones, and this in chronic terms would lead to significant bone loss. This has given rise to a number of studies in this direction with contradictory results so far.

The high protein content in the diet changes the pH of the blood to lower. This is buffered by the mechanisms available in the body, among which the kidneys themselves play an important role. At one stage or another, bones are also involved in the control of alkaline-acid balance, but this also correlates with bone resorption. Particularly unfavorable in this aspect of metabolism are proteins rich in sulfur-containing amino acids - those of animal origin. It is the excessive consumption of meat and fish that leads to a decrease in the pH of the urine to acid and to an increase in calcium loss. Of course, the effect on the alkaline-acid balance is not only due to protein, but also other factors in the diet. The opposite effect is the inclusion of more fruits and vegetables in the menu. Buffering systems reduce their capabilities with age, which makes adults more sensitive to the so-called. acidifying foods and the change in the menu is even more urgent.

The high content of protein in the diet can also play a constructive role in relation to bone tissue, when, however, the menu also contains sources of calcium and vitamin D or they are obtained additionally, especially among adolescents. It is known that bone, in addition to mineral, also has an organic component with a high protein content. In addition, a high-protein diet stimulates bone development at the hormonal level - it increases insulin-like growth factor 1.

No less dangerous can be the restriction of protein in the diet, and here we note that in some diseases this is necessary according to medical recommendations. Reducing the daily intake below 0.7-0.8 g / kg body weight suppresses the absorption of calcium in the intestine, and thus induces hormonal changes such as an increase in the level of parathyroid hormone and the active form of vitamin D - calcitriol. However, the prognostic role of these phenomena requires a larger and longer study in the control of calcium intake.

A recent meta-analysis of over 60 clinical trials did not support the negative correlation between protein intake and bone density, on the contrary, even a positive one was found, which, however, is not transferred to the frequency of fractures. Most authors today believe that the human body has sufficient mechanisms to control metabolic changes due to eating habits and that the likelihood of abnormalities in homeostasis requiring the involvement of bone tissue is very low or occurs in severe nutritional errors for one reason or another.