Effects of Mediterranean diets on kidney function: a report from the PREDIMED trial.

BACKGROUND

Epidemiologic observations have linked healthy dietary patterns to improved kidney function.

STUDY DESIGN

We assessed the effects of the Mediterranean diet (MedDiet) on kidney function in both a cross-sectional assessment and after a 1-year intervention in a cohort of the PREDIMED (Prevención con Dieta Mediterránea) Study, a multicenter 3-arm randomized clinical trial to determine the efficacy of the MedDiet on primary cardiovascular prevention.

SETTING & PARTICIPANTS: Community-dwelling men aged 55-80 years and women aged 60-80 years at high risk of cardiovascular disease from Reus, Spain.

INTERVENTION

Participants were randomly assigned to 3 ad libitum diets: a MedDiet supplemented with virgin olive oil (MedDiet + olive oil), a MedDiet supplemented with mixed nuts (MedDiet + nuts), or a control low-fat diet.

OUTCOMES

Estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (ACR).

MEASUREMENTS

Nutrient intake, adherence to the MedDiet, lifestyle variables, cardiovascular risk factors, serum urea and creatinine concentrations, eGFR, and urinary ACR were evaluated at baseline and after intervention for 1 year.

RESULTS

Baseline kidney function markers were similar across quartiles of adherence to the MedDiet in 785 participants (55% women; mean age, 67 years). After a 1-year intervention in 665 participants, the 3 dietary approaches were associated with improved kidney function, with similar average increases in eGFR (4.7 [95% CI, 3.2-6.2], 3.5 [95% CI, 1.9-5.0], and 4.1 [95% CI, 2.8-5.5] mL/min/1.73 m(2) for the MedDiet + olive oil, MedDiet + nuts, and control groups, respectively [P < 0.001 vs baseline for each; P = 0.9 for differences among groups]), but no changes in ACRs after adjustment for various confounders.

LIMITATIONS

Generalization of results to other age groups or ethnicities. GFR was not directly measured.

CONCLUSIONS

The results do not support the notion that the MedDiet has a beneficial effect on kidney function over and above that of advice for a low-fat diet in elderly individuals at high cardiovascular risk.