Dietary protein's and dietary acid load's influence on bone health

A variety of genetic, mechano-response-related, endocrine-metabolic, and nutritional determinants impact bone health. Among the nutritional influences, protein intake and dietary acid load are two of the factors most controversially discussed. Although in the past high protein intake was often assumed to exert a primarily detrimental impact on bone mass and skeletal health, the majority of recent studies indicates the opposite and suggests a bone-anabolic influence. Studies examining the influence of alkalizing diets or alkalizing supplement provision on skeletal outcomes are less consistent, which raises doubts about the role of acid-base status in bone health. The present review critically evaluates relevant key issues such as acid-base terminology, influencing factors of intestinal calcium absorption, calcium balance, the endocrine-metabolic milieu related to metabolic acidosis, and some methodological aspects of dietary exposure and bone outcome examinations. It becomes apparent that for an adequate identification and characterization of either dietary acid load's or protein's impact on bone, the combined assessment of both nutritional influences is necessary.