Protein Source, Dietary Fibre Intake, and Inflammation in Older Adults: A UK Biobank Study

Chronic inflammation is linked to cardiovascular disease, cancer, and other non-communicable diseases. Dietary factors like fibre and protein may affect inflammation, but limited evidence exists exploring how they interact. This study investigated associations between dietary fibre, protein sources, and the inflammatory marker C-reactive protein (CRP) in older adults.

This cross-sectional analysis included 128,612 UK Biobank participants aged 60+ years with CRP measurements and dietary data from multiple 24 h recalls. Fibre intake was reported as total fibre (g/day). Protein intake included total, animal, and vegetable protein (g/day). Robust regression analysis examined associations between quintiles of fibre, protein, and CRP, adjusted for demographics, lifestyle factors, and multimorbidity. Analyses were stratified by health status (with and without multimorbidity).

Higher fibre and vegetable protein intakes were inversely associated with CRP, while higher animal and total protein were positively associated with CRP in people with no multimorbidity. Specifically, participants in the highest quartile of dietary fibre had CRP levels that were 0.42 mg/L lower compared with the lowest quartiles. In contrast, those with the highest total protein and animal protein intakes had CRP levels that were 0.24 mg/L and 0.40 mg/L higher, respectively. In people with multimorbidity, fibre exhibited an inverted U-shaped association with the strongest association in participants in the highest quintile of intake. Vegetable protein had an inverse association with CRP. Animal and total protein had strong positive linear associations with CRP. Notably, high animal protein coupled with low dietary fibre intake resulted in CRP levels that were 0.65 mg/L higher compared with low animal protein and high dietary fibre intake.

Higher fibre and vegetable protein intakes were associated with lower inflammation in older adults. In promoting protein intake to maintain muscle mass and function, future studies should investigate replacing animal with vegetable protein to concomitantly reduce age-related inflammation.