Aged garlic extract reduces blood pressure in hypertensives: a dose-response trial

Abstract

Background/objectives: Hypertension affects about 30% of adults worldwide. Garlic has blood pressure-lowering properties and the mechanism of action is biologically plausible. Our trial assessed the effect, dose-response, tolerability and acceptability of different doses of aged garlic extract as an adjunct treatment to existing antihypertensive medication in patients with uncontrolled hypertension.

Subjects/methods: A total of 79 general practice patients with uncontrolled systolic hypertension participated in a double-blind randomised placebo-controlled dose-response trial of 12 weeks. Participants were allocated to one of three garlic groups with either of one, two or four capsules daily of aged garlic extract (240/480/960 mg containing 0.6/1.2/2.4 mg of S-allylcysteine) or placebo. Blood pressure was assessed at 4, 8 and 12 weeks and compared with baseline using a mixed-model approach. Tolerability was monitored throughout the trial and acceptability was assessed at 12 weeks by questionnaire.

Results: Mean systolic blood pressure was significantly reduced by 11.8±5.4 mm Hg in the garlic-2-capsule group over 12 weeks compared with placebo (P=0.006), and reached borderline significant reduction in the garlic-4-capsule group at 8 weeks (-7.4±4.1 mm Hg, P=0.07). Changes in systolic blood pressure in the garlic-1-capsule group and diastolic blood pressure were not significantly different to placebo. Tolerability, compliance and acceptability were high in all garlic groups (93%) and highest in the groups taking one or two capsules daily.

Conclusions: Our trial suggests aged garlic extract to be an effective and tolerable treatment in uncontrolled hypertension, and may be considered as a safe adjunct treatment to conventional antihypertensive therapy.

Figure 1

Trial flow chart. g1, garlic-1-capsule group; g2, garlic-2-capsule group; g4, garlic-4-capsule group; p, placebo group.

Figure 2

Effect of aged garlic extract on blood pressure. Mean SBP (a) and DBP (b) over 12 weeks of all participants in the planned adjusted analysis.