A proinflammatory diet is associated with systemic inflammation and reduced kidney function in elderly adults

Diet can affect kidney health through its effects on inflammation. We tested whether the Adapted Dietary Inflammatory Index (ADII) is associated with kidney function and whether effects of diet on chronic low-grade inflammation explain this association. This was an observational analysis in 1942 elderly community-dwelling participants aged 70-71 y from 2 independent cohorts: the Uppsala Longitudinal Study of Adult Men (n = 1097 men) and the Prospective Investigation of Vasculature in Uppsala Seniors (n = 845 men and women). The ADII was calculated from 7-d food records, combining putatively proinflammatory and anti-inflammatory effects of nutrients, vitamins, and trace elements. The ADII was validated against serum C-reactive protein (CRP) concentrations. The estimated glomerular filtration rate (eGFR) was assessed from serum cystatin C (cys) and creatinine (crea). Associations between the ADII and eGFR were investigated, and CRP was considered to be a mediator. In adjusted analysis, a 1-SD higher ADII was associated with higher CRP (β: 6%; 95% CI: 1%, 10%; P = 0.01) and lower eGFR [Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)cys: -2.1%; 95% CI: -3.2%, -1.1%; CKD-EPIcys+crea: -1.8%; 95% CI: -2.7%, -0.9%; both P < 0.001]. CRP was also inversely associated with eGFR. Mediation analyses showed that of the total effect of the ADII on kidney function, 15% and 17% (for CKD-EPIcys+crea and CKD-EPIcys equations, respectively) were explained/mediated by serum CRP. Findings were similar when each cohort was analyzed separately. A proinflammatory diet was associated with systemic inflammation as well as with reduced kidney function in a combined analysis of 2 community-based cohorts of elderly individuals. Our results also suggest systemic inflammation to be one potential pathway through which this dietary pattern is linked to kidney function.