Excess Dietary Protein Can Adversely Affect Bone

Abstract

The average American diet, which is high in protein and low in fruits and vegetables, generates a large amount of acid, mainly as sulfates and phosphates. The kidneys respond to this dietary acid challenge with net acid excretion, as well as ammonium and titratable acid excretion. Concurrently, the skeleton supplies buffer by active resorption of bone. Indeed, calciuria is directly related to net acid excretion. Different food proteins differ greatly in their potential acid load, and therefore in their acidogenic effect. A diet high in acid-ash proteins causes excessive calcium loss because of its acidogenic content. The addition of exogenous buffers, as chemical salts or as fruits and vegetables, to a high protein diet results in a less acid urine, a reduction in net acid excretion, reduced ammonium and titratable acid excretion, and decreased calciuria. Bone resorption may be halted, and bone accretion may actually occur. Alkali buffers, whether chemical salts or dietary fruits and vegetables high in potassium, reverse acid-induced obligatory urinary calcium loss. We conclude that excessive dietary protein from foods with high potential renal acid load adversely affects bone, unless buffered by the consumption of alkali-rich foods or supplements.

The Effect of Nutrient Intake on Bone Mineral Status in Young Adults: The Northern Ireland Young Hearts Project

“…Although the in¯uence of dietary protein on bone health has been cited as being either adverse [33] or bene®cial [34], results from the present observational study found no evidence to suggest that protein intake was negatively associated with BMD in either males or females. However, in the young adult males, the calcium:protein ratio did have an independent signi®cant inverse e ect on BMD (lumbar spine).…”

Vegetarianism, bone loss, fracture and vitamin D: a longitudinal study in Asian vegans and non-vegans

“…Thus, our results when considered in relation to the existing literature suggest that higher intakes of animal proteins may have negative effect on bone health. This finding is consistent with the hypothesis that animal protein produces a large amount of endogenous acid, which leads to increase bone resorption (Barzel and Massey, 1998) and increased bone loss. Fracture is an ultimate outcome of osteoporosis.…”

Impacto dos nutrientes na saúde óssea: novas tendências

“…É sugerido que dietas hiperprotéicas (origem animal) poderiam induzir a perda óssea por indução de acidose metabólica no organismo (15) . Como as proteínas animais são ricas em aminoácidos sulfurados, íons de amônia produzidos a partir desses aminoácidos levariam à redução do pH sanguíneo, ativando a reabsorção óssea que, em decorrência, levaria à perda de carbonato e citrato de Ca ósseo, mobilizados para neutralizar esse excesso de ácidos (15)(16) . O mecanismo renal representa o principal elemento compensatório para a acidose e, no idoso, essa proteção renal pode ser incompleta, podendo o osso ser usado para neutralizar essa carga ácida (13) .…”

“…O excesso de proteína animal ou vegetal pode ser prejudicial à saúde óssea, mas esses efeitos podem ser modificados por outros nutrientes presentes na dieta, como o Ca, K e P (16) .…”