The researchers argued that many protein intake recommendations by regulatory bodies around the world were established on non-bone health outcomes, and thus further research was needed to see how protein—which makes up 50% of bone volume and one third of its mass—can benefit bones.
“Over 53% of Americans over the age of 50 years have suboptimal bone health, greatly predisposing them to fractures,” said report co-author Dr. Taylor Wallace of the Department of Nutrition and Food Studies at George Mason University.
While systematic reviews of protein’s impact on bone health have been written (and with mixed results), Dr. Wallace argued that this present report, published in the Journal of the American College of Nutrition, “is the first systematic review of its kind that shows consuming protein above current recommended levels is beneficial for bone health.”
Selecting the studies to review
The researchers collected randomized controlled trials and prospective cohort studies where the participants are healthy adults aged 18 and over. All studies had to look at the relationship between varying doses of protein at or above the current US recommended daily allowance (0.8g/kg/d, or 10%-15% of total caloric intake).
Databases used were PubMed, Ovid Medline, and Agricola, and searching through the database lasted through April 2017. A total of 31 studies were chosen and included in the quantitative synthesis.
Multiple studies in the analysis noted statistically significant improvements in bone mineral density on different parts of the body at varying periods of intervention (from as little as 35 weeks to 104 weeks) when participants consumed more than the recommended daily allowance of protein.
However, there were also studies that saw no statistically significant change, leading the researchers to conclude, “Though many studies reported BMD outcomes, there was large variability in the site measured.”
The researchers also found that there were not many studies that looked at fracture outcome. “The most convincing data come from an analysis of the Women’s Health Initiative, where patients who consumed 20% higher calibrated protein intakes showed a significant decrease in the risk of forearm fractures,” they wrote.
But the outcomes are still promising, they added. No existing literature suggests that there is an adverse effect on consuming protein above the recommended daily allowance to the bones.
“Our systematic review supports that protein intakes above the current RDA may have some beneficial role in preventing hip fractures and bone mineral density loss,” they added.
Source: Journal of the American College of Nutrition
Published online: https://doi.org/10.1080/07315724.2017.1322924
Dietary Protein Intake above the Current RDA and Bone Health: A Systematic Review and Meta-Analysis
Authors: Taylor C. Wallace, Cara L. Frankenfeld