Diet can affect kidney health through its effects on inflammation.Objective:
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.Methods:
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.Results:
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.Conclusions:
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.