To determine the effect of North American ginseng on blood pressure in individuals with hypertension.

Ginseng lacks proper clinical scrutiny for its effect on blood pressure (BP), in spite of observational evidence linking its intake to hypertension. This should be addressed considering the potential overlap between the prevalence of ginseng use and hypertension.

We undertook a single centre, randomized, controlled, double-blinded, crossover trial to determine the effect of North American ginseng (NAG) on 24-hour BP and renal function. After a 4-week placebo run-in, we randomly assigned participants to NAG or placebo treatment for 12-weeks at a dose of 3g/day. This was followed by an 8-week washout, and a subsequent 12-week period in which the opposite treatment was consumed. At run-in, and at weeks 0 and 12 of each treatment period, participants were fitted with an ambulatory BP monitor to assess 24-hour BP and serum cystatin C was measured.

Inclusion Criteria:

• aged 18 to 85 years
• hypertension as defined by the use of antihypertensive drugs or a seated systolic blood pressure greater than or equal to 140 mm Hg or a diastolic BP greater than or equal to 90 mm Hg at each of 3 pre-study visits.

Exclusion Criteria:

• secondary hypertension
• diabetes
• kidney
• liver disease
• unstable angina
• ginseng use for two months prior to or during the study
• any changes in the type or dose of antihypertensive drugs one month prior to or during the study