Opposing effects of sodium intake on uric acid and blood pressure and their causal implication

Reducing uric acid is hypothesized to lower blood pressure, although evidence is inconsistent. In this ancillary of the DASH-Sodium trial, we examined whether sodium-induced changes in serum uric acid (SUA) were associated with changes in blood pressure. One hundred and three adults with prestage or stage 1 hypertension were randomly assigned to receive either the DASH diet or a control diet (typical of the average American diet) and were fed each of the three sodium levels (low, medium, and high) for 30 days in random order. Body weight was kept constant. SUA was measured at baseline and following each feeding period. Participants were 55% women and 75% black. Mean age was 52 (SD, 10) years, and mean SUA at baseline was 5.0 (SD, 1.3) mg/dL. Increasing sodium intake from low to high reduced SUA (-0.4 mg/dL; P < .001) but increased systolic (4.3 mm Hg; P < .001) and diastolic blood pressure (2.3 mm Hg; P < .001). Furthermore, changes in SUA were independent of changes in systolic (P = .15) and diastolic (P = .63) blood pressure, regardless of baseline blood pressure, baseline SUA, and randomized diet, as well as sodium sensitivity. Although both SUA and blood pressure were influenced by sodium, a common environmental factor, their effects were in opposite directions and were unrelated to each other. These findings do not support a consistent causal relationship between SUA and BP.