Aged garlic extract and blood pressure in uncontrolled hypertension
What it found
In 79 people with uncontrolled high blood pressure, taking two capsules of aged garlic extract daily lowered systolic blood pressure more than placebo over 12 weeks.
One capsule daily did not, and the effect on diastolic blood pressure was not significant.
What they found
Studies in people
Systolic blood pressure
In the planned adjusted analysis of 74 patients, the group taking two capsules daily had a significant reduction in systolic blood pressure compared with placebo over 12 weeks, averaging 11.8 mm Hg lower. The four-capsule group had a borderline significant reduction at 8 weeks, averaging 7.4 mm Hg lower. The one-capsule group did not differ significantly from placebo.
Diastolic blood pressure
Diastolic blood pressure did not show a significant difference between any garlic group and placebo. The largest drop was in the two-capsule group, averaging 5.3 mm Hg lower, but this was not statistically significant.
Tolerability and side effects
Three participants (4%) withdrew because of gastrointestinal side effects after 4 weeks, two in the four-capsule group and one in the placebo group. Minor complaints such as bloating, flatulence and reflux were reported by 32% in the four-capsule group, 15% in the one- and two-capsule groups, and 5% in the placebo group, mostly in the first week.
Acceptability and compliance
Most participants found the capsules easy to take (83% in garlic groups, 84% placebo) and acceptable (93% garlic, 90% placebo). Willingness to continue and pay for capsules was higher with fewer daily capsules.
Blinding success
About a third of participants correctly guessed whether they were taking garlic or placebo, while more than half were unsure. Differences between groups were not statistically significant.
What the authors conclude
“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.”
Also in their conclusions
- They conclude that aged garlic extract is an effective and tolerable treatment for uncontrolled hypertension.
- They suggest it may be considered as a safe adjunct treatment to conventional antihypertensive therapy.
- They note that a daily dosage of two capsules of the high potency formula is effective and more practical than four capsules, and that one capsule is not sufficient.
How it was done
High blood pressure affects many adults and is often not well controlled with standard medication. Garlic has shown blood pressure-lowering properties, and the authors wanted to test different doses of aged garlic extract as an add-on to existing medication.
They recruited 79 general practice patients with uncontrolled systolic hypertension, who were already taking blood pressure medication. Participants were randomly assigned to take one, two or four capsules daily of aged garlic extract (240, 480 or 960 mg) or placebo for 12 weeks. Blood pressure was measured at 4, 8 and 12 weeks.
What it can’t tell you
- This trial was underpowered to detect meaningful changes in diastolic blood pressure or to analyse by type of blood pressure medication.
- The results may not apply to other age groups or to people with untreated hypertension, as the participants were mainly older and already on medication.
Who paid
- Authors work at
- The University of Adelaide, Australia
The paper
- Title
- Aged garlic extract reduces blood pressure in hypertensives: a dose-response trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Ried K, Frank OR, Stocks NP (2013). Aged garlic extract reduces blood pressure in hypertensives: a dose-response trial. European journal of clinical nutrition. doi:10.1038/ejcn.2012.178Free full textPubMed 23169470DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error