(22-04-11) Dietary protein and bone health: harmonizing conflicting theories.

Thorpe MP, Evans EM.

Division of Nutritional Science, University of Illinois at Urbana-Champaign,
Urbana, Illinois, USA. Division of Kinesiology and Community Health, University
of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
Abstract
A precise understanding of the role of dietary protein in bone health has been
evasive despite decades of research. It is known that a dietary acid load is
harmful to bone, and sulfur-containing amino acids are metabolized to provide
such an acid load. It is also known that protein elevates urine calcium loss.
However, recent clinical studies and a meta-analysis have indicated either no
effect or a modest benefit associated with higher protein intakes. These
contradictory considerations may be explained by the existence of a two-faced
relationship between protein and bone, with simultaneous positive and negative
pathways. In opposition to the negative effects of dietary acid load, protein
may exert positive effects related to improving calcium absorption, increasing
insulin-like growth factor 1, or improving lean body mass, which, in turn,
improves bone strength. Putative mechanisms behind these pathways are reviewed
here, and some limitations in the historical literature as well as suggested
measures to counter these in the future are identified. When positive and
negative pathways are considered in tandem, protein may offer modest benefits
to bone in the presence of adequate dietary calcium and acid-neutralizing
fruits and vegetables.

Source: Nutr Rev. 2011 Apr;69(4):215-30. doi: 10.1111/j.1753-4887.2011.00379.x.
2011 International Life Sciences Institute.

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