Figure 1.

Systolic blood pressure by quartiles of plasma ascorbic acid, NHLBI Growth and Health Study, Richmond, CA cohort, 1996–1997 (tests for linear trend: unadjusted p = 0.0001; adjusted for race, BMI, education, dietary fat, dietary sodium, p = 0.005). Plasma ascorbic acid concentrations by quartile: Q1, 0.59 mg/dL (SD 0.18); Q2, 1.03 mg/dL (SD 0.10); Q3, 1.36 mg/dL (SD 0.10); Q4, 1.83 mg/dL (SD 0.34). (SI units: 33.51 μmol/L, 58.50 μmol/L, 77.25 μmol/L, 103.94 μmol/L)