Association of dietary protein and dairy intakes and change in renal function: results from the population-based longitudinal Doetinchem cohort study

Background: Evidence has suggested that protein from dairy may be less detrimental to renal health than protein from nondairy products. However, to our knowledge, no previous studies have used cystatin C-based measures of the estimated glomerular filtration rate (eGFR). Objective: We investigated the associations of sources of protein and dairy with the change in the eGFR in persons with a normal or mildly decreased eGFR. Design: We included 3798 participants, aged 26-65 y, from the Doetinchem Cohort study who were examined >= 3 times 5 y apart. Intakes of protein and dairy and subtypes of protein and dairy were assessed at each round. With the use of the Chronic Kidney Disease Epidemiology Collaboration equation, the eGFR was estimated from cystatin C with all available samples per participant examined in one assay run. Generalized estimating equation models, which were adjusted for lifestyle, biological, and other dietary factors (mono-unsaturated fat, polyunsaturated fat, phosphorus, magnesium, calcium, and vitamin D) were performed. Results: The mean baseline eGFR in the total cohort and in subjects with a mildly decreased eGFR (>= 1 eGFR of 60-90 mL.min(-1).1.73 m(-2) during follow-up; n = 1326) was 108.6 and 95.2 mL.min(-1).1.73 m(-2), and the mean annual decline in both groups was 1.01 and 1.34 mL.min(-1).1.73 m(-2), respectively. Intakes of total, vegetable, animal, and nondairy protein, dairy protein, cheese, total dairy, high fat dairy, and fermented dairy were not associated with eGFR changes. In individuals with a mildly decreased eGFR, higher consumption of milk, milk products, and low-fat dairy was associated with less annual decline in the eGFR (P-trend = 0.003). These associations were partially explained by dietary components of dairy (mono-unsaturated fat, polyunsaturated fat, phosphorus, magnesium, calcium, and vitamin D; P-trend < 0.04). Conclusions: Higher low-fat dairy consumption, but not sources of protein, is associated with less annual decline in the eGFR, particularly in individuals with a mildly decreased eGFR. These associations are partly attributable to other major components of dairy. Confirmation of these results will improve our ability to understand the role of dairy consumption in the prevention of renal dysfunction.