Aged garlic extract and blood pressure in people with uncontrolled hypertension
What it found
Two capsules of aged garlic extract daily lowered the top blood pressure number by about 12 mm Hg over 12 weeks in people whose blood pressure was not controlled by their usual medicines.
The bottom blood pressure number did not change significantly.
What they found
Studies in people
Top blood pressure reading
People taking two capsules daily saw their top blood pressure number drop by about 12 mm Hg more than those on dummy capsules over 12 weeks. Four capsules daily also lowered it, but the difference was smaller and less certain. One capsule daily did not lower it more than dummy capsules.
Bottom blood pressure reading
The bottom blood pressure number dropped slightly more in the two-capsule group than in the dummy group. However, this difference was too small to be certain it was caused by the garlic.
Stomach side effects
Three out of 79 participants left the trial after four weeks due to stomach complaints. Two were taking four garlic capsules daily and one was taking dummy capsules. Minor issues like bloating and gas were reported mostly in the first week.
Acceptability of capsules
Most participants found the capsules easy to take, with 93% in the garlic groups calling them acceptable. People taking fewer capsules each day were more willing to keep taking them and pay for them after the trial ended.
What the authors conclude
- They suggest that aged garlic extract is an effective and well-tolerated addition to standard blood pressure medicines for people whose blood pressure remains high.
- Their results show that two capsules a day work better and are easier to take than four capsules, while one capsule is not enough.
- The authors advise that the amount of the active ingredient S-allylcysteine matters when comparing different garlic products.
How it was done
High blood pressure affects about one billion adults worldwide, and standard medicines do not always control it. The authors wanted to see if different amounts of aged garlic extract could help lower blood pressure when added to existing treatment.
The researchers studied 79 patients from two clinics in Adelaide who had high blood pressure despite taking prescription medicines. Patients took either one, two or four capsules of aged garlic extract daily, or dummy capsules, for 12 weeks. Blood pressure was measured at 4, 8 and 12 weeks.
What it can’t tell you
- This trial lasted only 12 weeks, so it cannot show whether aged garlic extract lowers the risk of heart attacks or strokes over many years.
- The study focused on older adults already taking blood pressure medicines, so the results might not apply to younger people or those not 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 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error