Reference
Ried K, Frank OR, Stocks NP. Aged garlic extract lowers blood pressure in patients with treated but uncontrolled hypertension: A randomized controlled trial. Maturitas. 2010;67(2):144-150.
Design
This study by Ried et al evaluated the effect, tolerability, and acceptability of aged garlic extract (AGE) as an adjunct treatment to existing antihypertensive medication in patients with treated, but uncontrolled, hypertension. They used a double-blind, randomized, placebo-controlled trial involving 50 patients. Patients received 960 mg (containing 2.4 mg S-allylcysteine) of AGE daily or matching placebo for 12 weeks.
Key Findings
In patients with uncontrolled hypertension (SBP≥140mm Hg), systolic blood pressure was on average 10.2±4.3 mm Hg (P=0.03) lower with garlic therapy as compared to placebo. Changes in blood pressure between the groups were not significant in patients with SBP<140 mmHg at baseline. AGE was well tolerated by 92% of participants.
Practice Implications
This study, one of several now using AGE, demonstrates the potential antihypertensive activity of this supplement. Several prior studies have used AGE to evaluate for hypertension. This current study is the best-designed and most careful evaluation of the product.
The authors demonstrated that AGE was similar to current first-line therapy medications for hypertension.
It is interesting to note that AGE lowered blood pressure quite significantly in people with baseline hypertension (>140 mm Hg), but did not lower blood pressure in those with normal or near-normal blood pressure levels. This has great implications for use of the product in people without hypertension, because although it demonstrates that AGE has the potential to lower blood pressure, the supplement did not induce hypotension in people with normal blood pressure. This is similar to medications such as ramipril, which demonstrated significant blood pressure–lowering in patients with hypertension, but little effect on blood pressure in normotensive individuals. In the Heart Outcomes Prevention Evaluation trial, despite no significant change in blood pressure in normotensive patients, ramipril lowered cardiovascular events significantly.1
Further, this reinforces the multiple effects of AGE on cardiovascular outcomes. In multiple double-blinded, randomized, controlled trials, AGE has been demonstrated to lower total cholesterol, raise high-density lipoprotein cholesterol, reduce homocysteine, improve endothelial function, and slow the progression of atherosclerosis.2,3,4 AGE was even shown to decrease adipose tissue accumulation around the heart.4 Thus, the recent study by Ried et al further validates the beneficial effects of this supplement. Given the popularity of complementary therapies and patients’ motivation and compliance with treatment,5 further research on AGE for heart disease and cardiovascular risk factors is warranted.
Limitations
The small size of the study population limits the implications somewhat. Obviously, a clinical outcome study would be more definitive, but prospective studies of antihypertensives consistently demonstrate that the magnitude of event reduction is directly related to blood pressure reduction, and larger reductions in blood pressure produce larger reductions in risk.6 Thus, this 10-point drop in blood pressure induced by AGE should be associated with an approximate 22% reduction of total major cardiovascular events.
