Abstract P387: Effects of Reduced Dietary Sodium and the Dash Diet on Glomerular Filtration Rate: Results From the Dash-Sodium Trial

Background: While prior studies demonstrated that a low-sodium, DASH diet reduced blood pressure, the effects of sodium reduction, alone or in combination with the DASH diet, on kidney function are still unknown. Objective: We measured cystatin C in stored specimens of the DASH-Na trial, to determine the effects of sodium reduction and the DASH diet, alone or combined, on kidney function assessed by eGFR. Methods: DASH-Sodium was a controlled, feeding study in adults with pre- or stage 1 hypertension, who were randomly assigned to the DASH diet or a control diet. On their assigned diet, participants consumed each of three sodium levels for 4-weeks following a 2-week run-in period where all consumed a high sodium-control diet. The three sodium levels were low (50 mmol/d), medium (100 mmol/d), and high (150 mmol/d). Outcomes included eGFR by cystatin C (CKD-EPI 2021 equation) at baseline and at the end of each feeding period. Results: Cystatin C was measured in 409 of the original 412 participants, 207 were assigned the DASH diet, and 202 were assigned the control diet. The mean age was 48 years; 56% were women, and 56% were Black. The mean baseline BP was 135/86 mm Hg and BMI was 29.2 kg/m 2 . Compared with control, the DASH diet did not affect eGFR (β=-0.96 mL/min per 1.73 m 2 ; 95% CI: -2.74, 0.83) ( Figure ). In contrast, low versus high sodium intake decreased eGFR (β=-2.36 mL/min per 1.73 m 2 ; 95% CI: -3.64, -1.07). Together, compared to the high sodium-control diet, the low sodium-DASH diet decreased eGFR by 3.10 mL/min per 1.73 m 2 (95% CI: -5.46, -0.73). Conclusions: A combined low sodium-DASH diet reduced eGFR over a 4-week feeding period. Whether these effects are reno-protective long-term represent an important clinical inquiry for subsequent research.