Protocol
Aged garlic extract (480 mg/day for blood pressure; 2.4 g/day in plaque trials)
Blood pressure: a dose-response RCT Randomized controlled trial: people are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect. of aged garlic extract specifically (Ried 2013, PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 23169470, n=79, 12 weeks) tested 240, 480 and 960 mg/day of extract (0.6, 1.2 and 2.4 mg of S-allylcysteine); systolic pressure fell 11.8 mm Hg versus placebo An inactive substitute made to look like the real treatment, so participants cannot tell which one they received. at 480 mg/day only, with no significant effect at 240 or 960 mg and no diastolic effect.
Aged garlic extract is a form of garlic sold as a supplement. In one study of 79 people with high blood pressure, 480 mg a day lowered the top number by about 12 points more than a dummy pill. The lower and higher doses did not help, and the bottom number did not change. A pooled review of garlic products found a similar drop in people with high blood pressure. One study found less soft plaque in heart arteries, but total plaque did not change, and no other team has repeated it.
Blood pressure: a dose-response RCT of aged garlic extract specifically (Ried 2013, PMID 23169470, n=79, 12 weeks) tested 240, 480 and 960 mg/day of extract (0.6, 1.2 and 2.4 mg of S-allylcysteine); systolic pressure fell 11.8 mm Hg versus placebo at 480 mg/day only, with no significant effect at 240 or 960 mg and no diastolic effect. A meta-analysis A study that pools the numbers from several trials into one combined estimate. of garlic preparations broadly (Ried 2016, PMID 26764326, 20 trials, 970 participants) found systolic pressure 8.7 mm Hg lower in hypertensive subgroups. Coronary plaque: one RCT (Matsumoto 2016, PMID 26764322, n=55, about one year, 2,400 mg/day) found low-attenuation plaque reduced on CT angiography; total plaque volume did not differ, and the finding has not been independently replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away.. Endpoints The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. throughout are biomarkers A measurable sign in the body, such as a blood test value, used to track a condition or the effect of a treatment. and imaging surrogates, not events. Ried 2016 and Matsumoto 2016 both appear in the same sponsored J Nutr supplement issue on aged garlic extract, and Ried is the author of both the 2013 trial and the 2016 meta-analysis. Allicin-free form reduces GI side effects. Bioavailability The share of a dose that reaches the bloodstream in a form the body can use. variable.
Why this gradeThe reasoning, and what the grade does not cover.
Grade B on blood pressure. A double-blind Neither the participants nor the people assessing them know who received the real treatment until the trial ends. dose-response trial of aged garlic extract in 79 people with hypertension found systolic pressure 11.8 mmHg lower than placebo at 480 mg/day, with no significant effect at 240 or 960 mg (Ried et al., 2013; PMID 23169470). A meta-analysis of 20 trials of garlic preparations found systolic pressure 8.7 mmHg lower in hypertensive subgroups (Ried, 2016; PMID 26764326).
WHY NOT Ablood pressure is a surrogate, and the dose-response trial found the effect at one dose only.
WHAT THIS GRADE DOES NOT COVERcoronary plaque. The single plaque trial at 2,400 mg/day (Matsumoto et al., 2016; PMID 26764322; 55 people) found low-attenuation plaque reduced but total plaque unchanged, and it has not been independently replicated.
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The evidence, in fullThree papers, each linked to its PubMed record.
Ried et al. (Eur J Clin Nutr, 2013; PMID 23169470) - double-blind randomized dose-response trial, n=79. Ried (J Nutr, 2016; PMID 26764326) - updated meta-analysis, 20 trials, n=970. Matsumoto et al. (J Nutr, 2016; PMID 26764322) - randomized double-blind trial, n=55, coronary CT angiography.
Blood pressure (systolic and diastolic) at baseline and 12 weeks: the consistent RCT finding is a 5-10 mmHg systolic reduction in hypertensive subjects. Also monitor LDL-C Low-density lipoprotein cholesterol, the cholesterol fraction most closely tied to plaque in the arteries. and fasting glucose at 12 weeks. The effect is specific to aged garlic extract: raw garlic and standard garlic powder have different and less consistent evidence profiles.
Evidence notes: randomized trial, meta-analysis, industry-sponsored
Endpoint graded: Blood pressure in people with hypertension (surrogate)
Last reviewed: July 2026
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment. Stopping a prescription is a decision for your physician.
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