Modifiable determinants of protein consumption amongst community dwelling older adults: A systematic review

Expert groups have recommended that adults over 65 years should aim for 1.0-1.2 grams (g) of protein per kilogram of body weight per day (g/kg/d) to support health and functionality (1) . However, data from the National Diet and Nutrition Survey (2016-2019) showed 50.2% of over 65-year-olds consumed below 1.0 g/kg of adjusted body weight per day (2) . Identifying barriers and facilitators to optimising protein intake in older adults is crucial for dietary intervention. This systematic review thus aimed to evaluate modifiable determinants of protein intake amongst community dwelling adults aged over 65 years. The protocol was registered on the PROSPERO database (CRD42023399243). Eligible studies included community dwelling older adults within Organisation for Economic Co-operation and Development countries. Comprehensive searches were conducted in CINAHL, AMED, MEDLINE, PsycINFO and EMBASE, followed by backward and forward citation chasing and a search for grey literature. The latest search date was July 2024. Searches identified 2316 publications for screening once duplicates were removed. These were screened by two independent reviewers and quality assessed using the Mixed Methods Appraisal tool (version 2018). A meta-analysis was not possible due to substantial heterogeneity in the reporting of both protein consumption and the measurement of determinants. Sixty publications were included in the final analysis, reporting 54 quantitative studies. The majority of studies were cross-sectional and presented a lesser quality of evidence. Age range of participants was 65-103 years. Protein intake was reported as amount consumed per day, or a criterion applied to determine low intake which varied from 0.75 g–1.1g/kg/d. There was evidence from multiple lesser-quality cross-sectional studies that lower financial income (n=4), increased physical limitations (including an increased number of limitations in activities of daily living, reduced mobility or being housebound, n=5), dental problems (n=8) and poor appetite (n=7) are associated with suboptimal or lower protein intake. For men only, living alone appeared to determine lower protein consumption (n=2). In contrast, higher self-perceived health-status (n=3), increased physical activity (n=7), lunch club attendance (n=3) and increased dietary knowledge (n=3) were associated with a higher protein intake. Poor appetite in older adults may be expected to reduce protein intake as food consumption decreases, however evidence suggested that the diet also became less protein dense. In conclusion, determinants of protein consumption in community dwelling older adults are multifactorial, ranging across influences from socioeconomic, physical health, lifestyle and knowledge domains. These areas are likely to interact with one another, and all should be considered for future research, clinical practice and public health. There is a need for practical dietary interventions that consider affordability and accessibility for optimal uptake, additionally these need to be underpinned by increased dietary knowledge specific to older adults.