I make no secret of my leaning towards high-protein, relatively low-carb diets. I am well aware of the relatively unhealthy reputation that such diets have. However, when one looks at the research one generally finds that the criticisms of such diet are based on theoretical and ideological concerns. They are not, generally speaking, based on what the science shows.
For example, it has long been said that protein is generally not good news for the bone. One reason for this is that the metabolism of protein makes the blood more acidic, which might have detrimental effects on the bone, partly because it believed to cause calcium to be leached from the bone. I can see why this might give protein a bad name regarding bone health, but protein also promotes bone health, at least in part because amino acids (the building blocks of protein). In the end, it’s not important what effect a nutrient or foodstuff has theoretically or on some marker or other ” the important thing is the impact it has on health.
So, if it’s bone health we’re interested in, it’s bone health we need to look at.
A group of British scientists recently performed a review of the available evidence regarding dietary protein and bone health, and this was published on-line in the American Journal of Clinical Nutrition . To main types of study were used in this review; epidemiological and intervention. The epidemiological studies assessed the association between protein intake and bone mineral density (BMD) and/or bone mineral content (BMC). Some studies assessed the relationship between protein intake and risk of bone fracture.
The intervention studies involved giving individuals protein to see what effect this had on bone health. In this review, the outcome assessed was the BMD in the lumbar spine (lower back) and risk of hip fracture.
Taken as a whole, the epidemiological studies revealed that higher protein intakes were not associated with worse measures of bone health including BMD, BMC and risk of fracture. In fact, when amassed together, one type of epidemiological study (cross-sectional study) found higher protein intakes were associated with improved BMD.
The intervention studies followed suit ” protein supplementation was found to be associated with enhanced BMD. However, this did not appear to manifest itself as reduced fracture risk.
All in all, what is clear about this study is that it provides no support for the commonly-wielded criticism of high-protein diets regarding bone health. If anything, the totality of evidence shows that proteins richer in protein have benefits for bone.
1. Darling AL, et al. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr 4th November 2009 [epub ahead of print]