Garlic Extract
Research reviewed: Up until 03/2026
Garlic Extract is a dietary supplement with 12 published peer-reviewed studies involving 1,062 participants, researched for Blood pressure, Diabetes/Blood Sugar, Inflammation/Oxidative Stress and 2 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Blood pressure
ModerateDiabetes/Blood Sugar
StrongInflammation/Oxidative Stress
ModerateLiver Health
ModerateCholesterol/Lipids
StrongResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Blood pressure
To investigate the blood pressure-lowering effects of an optimized aged black garlic extract given at a very low dose of S-allylcysteine (SAC) in patients with Grade I hypertension (the mildest level: systolic 140–159 mmHg and diastolic 90–99 mmHg) who were already taking prescribed antihypertensive medication.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the blood pressure-lowering effects of an optimized aged black garlic extract given at a very low dose of S-allylcysteine (SAC) in patients with Grade I hypertension (the mildest level: systolic 140–159 mmHg and diastolic 90–99 mmHg) who were already taking prescribed antihypertensive medication.
Dose
250 mg/day optimized aged black garlic extract standardized to provide 0.25 mg S-allylcysteine/day (the primary active sulfur compound in garlic), or matching placebo.
Participants
77 men and women with Grade I hypertension on prescribed antihypertensive medication
Duration
12 weeks
Results
The researchers observed that participants who received the garlic extract had reduced home blood pressure—systolic by 1.8 mmHg and diastolic by 1.5 mmHg—compared to the placebo group. In terms of secondary outcomes, the garlic extract group showed several significant improvements. Blood nitric oxide levels (a molecule that helps relax blood vessels) increased by 10.3 µM. Antioxidant capacity, measured by FRAP (ferric reducing antioxidant power), increased by +7 × 10⁻³ µM TE/min, indicating a better ability to fight harmful free radicals. Uric acid levels also decreased by 0.3 mg/dL. In addition, ACE activity (angiotensin-converting enzyme), which can narrow blood vessels, decreased by 9.3 U/L. However, there were no significant changes in endothelial function (the health of blood vessel lining) or inflammatory cytokine levels (proteins involved in inflammation).
To assess the effect of a well-characterized, optimized aged black garlic extract (standardized for S-allylcysteine content) combined with dietary recommendations, on cardiovascular disease risk factors (including blood pressure) in adults with moderate hypercholesterolemia (mildly raised blood cholesterol levels).
Study Type
Randomised, crossover, double-blind, controlled trial
Purpose
To assess the effect of a well-characterized, optimized aged black garlic extract (standardized for S-allylcysteine content) combined with dietary recommendations, on cardiovascular disease risk factors (including blood pressure) in adults with moderate hypercholesterolemia (mildly raised blood cholesterol levels).
Dose
250 mg/day of optimized aged black garlic extract (providing 1.25 mg S-allylcysteine) or placebo
Participants
67 adults (64 completing) aged 28-54 years with moderate hypercholesterolemia (LDL-cholesterol ≥115 mg/dL, raised but not yet at the threshold requiring medication).
Duration
6 weeks per treatment arm (crossover)
Results
At 6 weeks, the study found an association between aged black garlic extract and a significant reduction in diastolic blood pressure (−5.85 mmHg) compared to placebo, particularly in men with a DBP > 75 mmHg.
To investigate for the first time the effect of aged garlic extract (AGE) on both peripheral (standard cuff) blood pressure AND central hemodynamic measures, including arterial stiffness and central blood pressure, in patients with uncontrolled hypertension, a condition where blood pressure remains consistently high despite efforts to manage it through lifestyle changes or medication. Central blood pressure and arterial stiffness (how rigid the arteries are) are recognised as important independent predictors of heart attack and stroke risk, beyond standard arm-cuff BP.
Study Type
Randomised, double-blind, placebo-controlled parallel trial
Purpose
To investigate for the first time the effect of aged garlic extract (AGE) on both peripheral (standard cuff) blood pressure AND central hemodynamic measures, including arterial stiffness and central blood pressure, in patients with uncontrolled hypertension, a condition where blood pressure remains consistently high despite efforts to manage it through lifestyle changes or medication. Central blood pressure and arterial stiffness (how rigid the arteries are) are recognised as important independent predictors of heart attack and stroke risk, beyond standard arm-cuff BP.
Dose
1.2 g/day of Kyolic Reserve aged garlic extract (2 capsules), standardised to contain 1.2 mg S-allylcysteine/day, or matching placebo
Participants
88 male and female adults with uncontrolled hypertension completed the trial (average age 62 years)
Duration
12 weeks
Results
The researchers observed that daily intake of aged garlic extract (1.2 g) significantly reduced mean systolic blood pressure (SBP) by 5.0 mmHg compared to placebo over 12 weeks. For 'responders'—patients who showed a clinically meaningful reduction of more than 3% in SBP (at least 5 mmHg) or diastolic blood pressure (DBP) (at least 3 mmHg) over time—the SBP significantly dropped by an average of 11 mmHg and DBP by 6.3 mmHg compared to the placebo group. Central hemodynamic measures, which are important predictors of cardiovascular disease, also tended to improve in the garlic group, including central blood pressure, central pulse pressure, and arterial stiffness. Although not all changes reached statistical significance due to smaller subgroup sizes, beneficial trends were observed for inflammatory markers like TNFα, total cholesterol, low-density lipid cholesterol, and apolipoproteins. Importantly, the aged garlic extract was highly tolerable, acceptable to participants, and did not increase the risk of bleeding, even in patients on blood-thinning medication
To assess the effect of different doses of aged garlic extract as an add-on to existing antihypertensive medication in adults with uncontrolled high blood pressure, a condition where blood pressure remains consistently high despite efforts to manage it through lifestyle changes or medication.
Study Type
Randomised, double-blind, placebo-controlled dose-response trial
Purpose
To assess the effect of different doses of aged garlic extract as an add-on to existing antihypertensive medication in adults with uncontrolled high blood pressure, a condition where blood pressure remains consistently high despite efforts to manage it through lifestyle changes or medication.
Dose
240 mg, 480 mg, or 960 mg/day of AGE (1, 2, or 4 capsules), providing 0.6, 1.2, or 2.4 mg/day of S-allylcysteine (the primary active sulfur compound in garlic), or placebo
Participants
79 adults from two general practices in Adelaide, Australia, with uncontrolled systolic blood pressure (≥140 mmHg) on established antihypertensive medication
Duration
12 weeks
Results
The researchers observed that the systolic blood pressure was significantly reduced by an average of 11.8 Hg in the 480 mg/d garlic extract group over 12 weeks compared with placebo (P=0.006), and reached borderline significant reduction in the 960 mg/day garlic extract group at 8 weeks (−7.4±4.1 mm Hg, P=0.07). Changes in systolic blood pressure in the 240 mg/d garlic extract group and diastolic blood pressure were not significantly different to placebo. Overall, the results suggest that a daily dose of 480 mg of garlic extract (2 capsules) significantly reduced systolic blood pressure compared to placebo, while lower or higher doses did not produce statistically significant effects.
To assess the effect, tolerability, and acceptability of aged garlic extract as an add-on treatment to existing antihypertensive medication in patients whose blood pressure remained uncontrolled despite medication (uncontrolled).
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To assess the effect, tolerability, and acceptability of aged garlic extract as an add-on treatment to existing antihypertensive medication in patients whose blood pressure remained uncontrolled despite medication (uncontrolled).
Dose
960 mg/day aged garlic extract (4 x 240 mg, providing 2.4 mg S-allylcysteine/day, the primary active sulfur compound in aged garlic) or matching placebo
Participants
50 male and female adults with uncontrolled hypertension, with an average age of 66 years
Duration
12 weeks
Results
In patients with uncontrolled hypertension (SBP≥140mmHg at baseline), the researchers observed that the systolic blood pressure was on average 10.2 mmHg (p=0.03) lower in the garlic group compared with controls over the 12-week treatment period. Changes in blood pressure between the groups were not significant in patients with SBP<140mmHg at baseline.
Diabetes/Blood Sugar
To evaluate the dose-dependent effect of garlic tablets on fasting blood sugar (FBS) and HbA1c (glycated hemoglobin — a measure of average blood sugar levels over 2–3 months) in patients with type 2 diabetes mellitus.
Study Type
Single-blind, placebo-controlled dose-response trial
Purpose
To evaluate the dose-dependent effect of garlic tablets on fasting blood sugar (FBS) and HbA1c (glycated hemoglobin — a measure of average blood sugar levels over 2–3 months) in patients with type 2 diabetes mellitus.
Dose
300, 600, 900, 1200, or 1500 mg/day of garlic tablets, or metformin (standard diabetes drug), or placebo. 30 patients per group (7 groups total).
Participants
210 patients with type 2 diabetes mellitus
Duration
24 weeks
Results
Researchers observed that groups treated with garlic experienced significant reductions in both fasting blood glucose (FBS) and HbA1c in a manner that depended on the dose and treatment duration (p < 0.005), with the largest improvements seen at higher doses of 1200–1500 mg/day and over longer periods. Garlic not only outperformed placebo but also showed effects comparable to metformin, one of the most widely used diabetes medications.
To investigate garlic supplementation's effect on components of metabolic syndrome, quality of life, and sexual function in women with both polycystic ovary syndrome (PCOS) and metabolic syndrome
Study Type
Randomized, double-blind, placebo-controlled
Purpose
To investigate garlic supplementation's effect on components of metabolic syndrome, quality of life, and sexual function in women with both polycystic ovary syndrome (PCOS) and metabolic syndrome
Dose
1,000 mg/day garlic tablets (2 x 500 mg) or placebo
Participants
97 women with both PCOS and metabolic syndrome
Duration
8 weeks
Results
Researchers observed that after 8 weeks, participants taking garlic experienced significant improvements compared with a placebo group. Fasting blood sugar dropped by 10.5%, from 107.2 to 95.9 mg/dL, while triglycerides fell 17.8%, LDL (“bad”) cholesterol decreased 14.2%, and total cholesterol dropped 12.6%; all these changes were statistically significant (p < 0.01). Inflammation also went down, with C-reactive protein decreasing by 24.7%. Beyond these metabolic effects, participants reported better sexual health, with all six areas of the Female Sexual Function Index—desire, arousal, lubrication, orgasm, satisfaction, and pain—showing significant improvement). Self-reported quality of life related to polycystic ovary syndrome also significantly improved.
Inflammation/Oxidative Stress
To assess whether standardized garlic extract can reduce systemic (whole-body) inflammation in peritoneal dialysis (PD) patients — people with end-stage kidney failure who receive daily blood-filtering dialysis through their abdomen, and who typically suffer from chronic inflammation.
Study Type
Parallel-designed, double-blind, randomised controlled clinical trial
Purpose
To assess whether standardized garlic extract can reduce systemic (whole-body) inflammation in peritoneal dialysis (PD) patients — people with end-stage kidney failure who receive daily blood-filtering dialysis through their abdomen, and who typically suffer from chronic inflammation.
Dose
800 mg/d of standardized garlic extract (2 x 400 mg/day total) or placebo
Participants
42 male and female adults undergoing peritoneal dialysis
Duration
8 weeks
Results
The researchers observed that garlic extract supplementation significantly reduced chronic inflammation in a very high-risk kidney disease population, with CRP (C-reactive protein, a standard blood test for inflammation; elevated in chronic kidney disease and linked to cardiovascular death) dropping by more than 70%, compared to only 20% on placebo.
Liver Health
To evaluate the effect of garlic powder supplementation on liver fat content (hepatic steatosis) and liver enzyme levels in patients with non-alcoholic fatty liver disease
Study Type
Randomised, double-blind, placebo-controlled clinical trial
Purpose
To evaluate the effect of garlic powder supplementation on liver fat content (hepatic steatosis) and liver enzyme levels in patients with non-alcoholic fatty liver disease
Dose
800 mg/day enteric-coated garlic powder (equal to 1.5 mg allicin, taken as 2×400 mg capsules) or garlic-like placebo
Participants
98 male and female adults (out of 110 randomized) with ultrasound-diagnosed NAFLD and elevated liver enzymes, ages 20–70 years
Duration
15 weeks
Results
Significantly more patients in the garlic group achieved improvement in liver fat (steatosis) compared to the placebo group (51.1% vs. 15.7%). The garlic group also showed significant reductions in several clinical markers compared with placebo, including ALT (alanine aminotransferase) and AST (aspartate aminotransferase), which are liver enzymes elevated when liver cells are damaged; fasting blood glucose (FBS) and HbA1c, which reflect blood sugar levels and average 3-month glucose control; total cholesterol, LDL (“bad”) cholesterol, and triglycerides; as well as overall body weight.
Cholesterol/Lipids
To investigate the effect of a garlic powder supplement on lipid-lowering effects in adults, specifically examining time-released formulations that allow slow, continuous release of active compounds in the gut.
Study Type
Randomised, crossover, double-blind, controlled trial
Purpose
To investigate the effect of a garlic powder supplement on lipid-lowering effects in adults, specifically examining time-released formulations that allow slow, continuous release of active compounds in the gut.
Dose
600 mg/day time-released garlic powder (Allicor) or placebo
Participants
84 adults with mild-to-moderate hypercholesterolemia (raised blood fats)
Duration
8 weeks
Results
By the end of the study, total cholesterol in Allicor-treated patients had significantly decreased by 7.6% compared to baseline and was 11.5% lower than in the placebo group. LDL cholesterol in Allicor-treated patients also significantly decreased by 11.8% compared to baseline and by 13.8% compared to the placebo group. HDL cholesterol increased significantly after 8 and 12 weeks of treatment. Moreover, by the end of the study, HDL cholesterol in Allicor-treated patients had increased significantly by 11.5%.
To investigate the effect of high-dose garlic powder supplementation on the key components of metabolic syndrome (MetS) — a cluster of risk factors including abdominal obesity, high blood pressure, elevated blood fats, high blood sugar, and insulin resistance that together greatly raise the risk of heart disease and type 2 diabetes.
Study Type
Randomised, double-blind, placebo-controlled clinical trial
Purpose
To investigate the effect of high-dose garlic powder supplementation on the key components of metabolic syndrome (MetS) — a cluster of risk factors including abdominal obesity, high blood pressure, elevated blood fats, high blood sugar, and insulin resistance that together greatly raise the risk of heart disease and type 2 diabetes.
Dose
1,600 mg/day garlic powder or placebo
Participants
90 adults with a diagnosis of metabolic syndrome
Duration
3 months
Results
The researchers observed that garlic significantly improved several metabolic and cardiovascular markers compared with placebo. HDL-cholesterol (“good” cholesterol) significantly increased (+4.5 vs. −1.8 mg/dL), while waist circumference (a key measure of abdominal or central fat) decreased (−1.3 vs. 0.0 cm). Blood pressure also improved, with significant reductions in diastolic BP (−6.7 vs. 0.0 mmHg1) and systolic BP (−7.7 vs. 0.0 mmHg). Garlic further led to significant reductions in fasting blood glucose, triglycerides, and total cholesterol. Measures of metabolic health also improved, including a significant reduction in HOMA-IR (Homeostatic Model Assessment of Insulin Resistance, a score estimating the degree of insulin resistance) and the Fatty Liver Index (FLI, a score derived from blood tests and body measurements used to estimate the likelihood of fatty liver). Additionally, appetite scores showed significant improvement.
To evaluate garlic's effect on lipid profile and blood pressure in women with polycystic ovary syndrome (PCOS)
Study Type
Randomised, double-blind, placebo-controlled clinical trial
Purpose
To evaluate garlic's effect on lipid profile and blood pressure in women with polycystic ovary syndrome (PCOS)
Dose
800 mg/day garlic supplement or identical placebo (starch)
Participants
80 women with PCOS
Duration
8 weeks
Results
The researchers observed that garlic supplementation significantly reduced lipid levels compared with placebo, including total cholesterol (average difference −8.05 mg/dL) and LDL-C (“bad” cholesterol; average difference −7.67 mg/dL. There was also a trend on decreased triglyceride levels also decreased, but HDL-C (“good” cholesterol) did not change significantly between the groups.
Frequently Asked Questions
Common questions about Garlic Extract research
There are currently 12 peer-reviewed studies on Garlic Extract (Garlic Extract), involving 1,062 total participants. Research covers Blood pressure, Diabetes/Blood Sugar, Inflammation/Oxidative Stress and 2 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (12 human studies), and reported outcomes.
Garlic Extract has been researched for: Blood pressure, Diabetes/Blood Sugar, Inflammation/Oxidative Stress, Liver Health, Cholesterol/Lipids. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 12 out of 12 studies are human trials. Human trials carry more weight in our evidence scoring system.
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