12 January - 20 June 2016

Higher protein intake benefits adult bone health

A narrative review published in the journal Osteoporosis International has reviewed the safety of dietary protein for bone health, reporting that a protein rich diet, provided there is adequate calcium intake, is in fact beneficial for adult bone health.

A narrative review published in the journal Osteoporosis International has reviewed the safety of dietary protein for bone health, reporting that a protein rich diet, provided there is adequate calcium intake, is in fact beneficial for adult bone health. 

Dietary protein is essential for growth and maintenance of structure and function of many organs with the recommended daily amount being 0.8g of protein per kg of body weight.  The authors of the current study note that it is proposed that the elderly have a higher protein intake to take into account acute or chronic illness, or being undernourished. Rizzoli et al. reviewed systematic reviews and meta-analyses that addressed the risk and benefits of dietary protein intakes for bone health.  The authors reviewed studies which examined dietary protein and fracture risk, dietary protein and bone mineral density, dietary protein-calcium interaction and the effect of dietary protein on acid-base status and bone.

Regarding dietary protein and fracture risk, the team examined prospective cohort studies, noting that four systematic reviews and meta-analyses have assessed this issue since 2009.  Two of the meta-analysis studies reported a decrease in high fractures between the highest vs the lowest intake of dietary protein, with one reporting a 11% decrease and the other a 16% decrease.  Whilst the other two studies, one a systematic review and the other a meta-analysis report showed either no significant difference and/or insufficient evidence.  Rizzoli et la concluded that “Based on the 4 systematic reviews with meta-analysis for 3 and a review of additional observational studies, it appears that high fracture risk is modestly decreased with higher dietary protein intakes, provided calcium intakes are adequate.”

The review examined three systematic reviews and meta-analyses that investigated the association between bone mineral density and dietary protein intake.  The team report that bone mineral density, which is an important determinant of bone strength, appears to be positively associated with dietary protein intakes. The majority of the studies examined hip fracture.

Three studies found some interaction between protein and calcium intakes for fracture risks and one did not for forearm fractures.  Two studies report that those in the lowest quartile or who consumed lower than 800 mg of calcium per day had high hip fracture risk, whilst another reported “high facture risk in relation with higher protein intake was observed in the lowest quartile of calcium intake but not in the higher calcium quartile.” In another study, calcium and vitamin D supplementation and higher protein intake was associated with better femoral neck and total body BMD outcomes.  Rizzoli et al. also discussed dairy products as sources of both protein and calcium and discuss 13 studies where bone mineral density was assessed, stating that “a blunted decrease and even an increase in BMD were observed in response to dairy products depending on the age of subjects”.  Rizzoli et al conclude by stating “protein and calcium combined in dairy produce have beneficial effect on calciotrophic hormones, bone turnover markers and BMD.  The benefit of dietary proteins on bone outcomes seems to require adequate calcium intakes.”  They also suggest, based on their review, that dietary protein supplements attenuate age-related BMD decease and reduce bone turnover marker levels.

The review discusses the effects of dietary protein on acid-base status and bones, stating that there has been much debate “on the acid-ash hypothesis which theorises that metabolism of high protein intake (particularly of animal origin with sulfur containing amino acids) leads to increased acid production and increased bone reabsorption, in turn producing hypercaliuria, bone loss and osteoporosis.”  After analysis of 4 systematic reviews and meta-analyses (one including 25 studies, another 12 studies, another 5 and another 36 studies with 19 cell studies) which investigated the acid-ash hypothesis in relation with bone outcomes, they state “there appears to be no direct evidence of osteoporosis progression, fragility fractures or altered bone strength, with the acid load from a balanced diet origin.”

The review concludes by stating that “insufficient dietary protein intake may be a more severe problem than protein excess in the elderly.”

RSSL's team of experienced product developers and food scientists can assist your with your protein food and drink development needs. To find out more please contact Customer Services telephone 0118 918 4076 or e-mail enquiries@rssl.com

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