Background: Elevated serum uric acid (SUA) is etiologically related to the occurrence of gout and is associated with an increased risk of cardiovascular disease. Dietary recommendations for SUA reduction are largely based on observational studies. In an ancillary study to the DASH-Sodium feeding study conducted at the Johns Hopkins clinical center (N=103), we examined the effects of the DASH diet and of sodium intake on SUA levels.
Methods: The DASH-Sodium trial was a randomized, crossover feeding trial among adults without cardiovascular disease not using antihypertensive medications. Participants were randomly assigned to either a control diet or the DASH diet; during both diets, participants were fed each of three sodium levels in random order in 4-week periods separated by 5-day breaks. Body weight was held constant. The three sodium levels were: low (50 mmol/d), medium (100 mmol/d), and high (150 mmol/d). SUA was measured at baseline and after each feeding period, allowing for comparisons by diet (DASH vs control) and sodium levels.
Results: Trial participants were 55% women and 76% black; mean age was 52 years (SD, 10) and mean SUA was 5.0 mg/dL (SD, 1.3). Mean baseline alcohol intake was low at 1.3 g/day. Compared with the control diet, the DASH diet reduced SUA by -0.35 mg/dL (95% CI: -0.65, -0.05; P = 0.02). Among participants with a baseline SUA ≥6 and <7 mg/dL (N=16), the mean effect was -0.8 mg/dL; among participants (N=8) with a baseline SUA ≥7 mg/dL the mean effect was -1.3 mg/dL (P-interaction = 0.04) (Figure). Compared to the low sodium intake, the medium sodium intake lowered SUA by -0.3 mg/dL (95% CI: -0.5, -0.2; P < 0.001) and the high sodium intake lowered SUA by -0.4 mg/dL (95% CI: -0.6, -0.3; P < 0.001). The effects of sodium intake on SUA were greater among participants with high blood pressure at baseline (P-interaction = 0.02, see Figure).
Conclusions: This study demonstrates that the DASH diet lowers SUA, that this effect differs by sodium level, and that SUA reduction is greatest in those with hyperuricemia at baseline.