- Research conducted since 2000 on the association between dietary protein intake and bone disease, kidney disease, and sarcopenia risks is insufficient and inconclusive. Improving this evidence base will require more robust long-term studies.
- To assess chronic disease risk, studies used intermediate markers, including surrogate markers for bone, kidney disease, and sarcopenia diagnostic components. However, these markers may not fully represent the conditions’ complexity, presence, and progression. Sarcopenia’s absence as a study endpoint marks a significant research gap.
- Varied methods and outcome measures made it hard to compare results across studies.
- A notable research gap regarding the impact of dietary protein intake on bone health in children and adolescents highlights the urgent need for further investigation.
Objective. This review examines the association between dietary protein intake and the risk of bone disease, kidney disease, and sarcopenia, aiming to inform future Dietary Reference Intakes (DRIs) updates, including the development of a Chronic Disease Risk Reduction (CDRR) reference value for protein.
Data sources. We searched Medline, EMBASE, AGRICOLA, and Scopus from January 2000 to March 2024, and supplemented by citation searching of relevant reviews and original research.
Review methods. Following the AHRQ Methods Guide for Effectiveness and Comparative Effectiveness Reviews and registering the protocol on PROSPERO (CRD42023446621), we included randomized and non-randomized controlled trials, prospective cohort studies, and nested case-control studies that enrolled healthy participants and examined dietary protein intake without exercise. We assessed the risk of bias, performed a qualitative synthesis of studies rated as low to moderate risk of bias, and evaluated the strength of evidence.
Results. Of 10,949 studies, 82 articles detailing 81 unique studies met our inclusion criteria. Thirteen of these, rated as low to moderate risk of bias, were included in our synthesis. These included set comprised studies on bone disease (4 randomized controlled trials [RCTs] and 1 prospective cohort study), kidney disease (1 RCT), and sarcopenia (9 RCTs). The overall evidence was deemed insufficient to address the Key Questions, primarily due to a limited number of studies rated as low to moderate risk, the diversity of dietary protein interventions, and the wide range of outcomes which made synthesizing results and comparing studies challenging. Additionally, studies used intermediate markers or sarcopenia diagnostic components rather than direct outcomes to assess disease risk. Notably, we found very scant literature addressing children and adolescents. Our analysis was informed by only one study each of the impact of dietary protein intake on bone disease risk (mixed findings) in children and adolescents, and the impact of dietary protein on kidney disease risk (no significant effects) in adults. The findings related to adult bone disease were inconsistent, with some studies indicating no effect and others suggesting benefits on bone health metrics. Studies on sarcopenia risk also reported inconsistent results concerning muscle mass, physical performance, and muscle strength.
Conclusions. The evidence gathered since 2000 on associations between dietary protein intake and the risks of bone disease, kidney disease, and sarcopenia is unclear, indicating a need for more rigorous research in these areas.
