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Garlic

cardiovascular health support and immune system modulation

Evidence · Grade B
Meta-analysis availableHuman trial evidenceTraditional useInteraction risk

Garlic is a widely consumed culinary ingredient and traditional remedy, often explored for its potential cardiovascular and immune-modulating effects, though scientific evidence is still emerging.

Garlic (Allium sativum) has been studied for its potential to modestly lower total cholesterol and LDL (low-density lipoprotein) cholesterol levels. Its therapeutic effects are attributed to sulfur-containing compounds such as allicin.

Quick answer

What it is: Garlic (Allium sativum) has been studied for its potential to modestly lower total cholesterol and LDL (low-density lipoprotein) cholesterol levels.

May support:Viral Infections, Common Cold/Flu, Hypertension, High Cholesterol, H. pylori Infection, High Blood Pressure, Atherosclerosis

Evidence:Evidence · Grade B

Evidence Summary

Evidence · Grade B

Given that no specific PubMed studies were provided, the rationale for evidence is based on general scientific understanding. The current understanding of garlic's efficacy for various conditions is derived from a mix of in vitro studies, animal models, and human clinical trials. However, the quality and consistency of human trials can vary, leading to a need for more robust, large-scale, and well-designed studies to draw definitive conclusions.

Last reviewed · Jun 2026

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Why It Works

The sulfur compounds in garlic, particularly allicin and its derivatives, are believed to inhibit HMG-CoA reductase, an enzyme involved in cholesterol synthesis in the liver. They may also reduce platelet aggregation and improve antioxidant status, indirectly contributing to cardiovascular health.

How it works in more detail

The primary active compounds in garlic are sulfur-containing compounds, with allicin being one of the most studied. Allicin is not present in intact garlic but is rapidly formed when the enzyme alliinase acts on alliin upon crushing or chopping. Allicin is unstable and quickly converts into other organosulfur compounds, such as diallyl disulfide (DADS), diallyl trisulfide (DATS), and ajoene. These compounds are thought to exert their effects through several mechanisms, including antioxidant activity, modulation of nitric oxide synthase, inhibition of HMG-CoA reductase (relevant for cholesterol), and direct antimicrobial actions. Aged garlic extract, which undergoes a different processing, contains different sulfur compounds like S-allyl cysteine (SAC) and S-allyl mercaptocysteine (SAMC), which are more stable and bioavailable.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
600-900 mg of garlic powder daily, standardized to allicin content, or 3-6 grams of fresh garlic daily, divided into multiple doses.
Research dosage range
Studies have used a wide range of dosages, from 600 mg to 900 mg of garlic powder daily (standardized to alliin content) for blood pressure and cholesterol, to 2.4 g of aged garlic extract daily for cardiovascular benefits.
Typical onset
Effects of garlic, particularly for chronic conditions like hypertension or hyperlipidemia, are generally not immediate and may take several weeks to months of consistent use to become apparent.
Typical forms
raw clove, powder, aged extract, oil, capsule, tablet
Quality markers
When purchasing garlic supplements, look for products standardized to specific active compounds like alliin (for garlic powder) or S-allyl cysteine (for aged garlic extract). Ensure the product is from a reputable manufacturer and has third-party testing for purity and potency. For raw garlic, choos
Medication interactions
  • anticoagulants (e.g., warfarin)
  • antiplatelet drugs (e.g., aspirin, clopidogrel)
  • saquinavir (an HIV medication)
  • some blood pressure medications (potential additive effect)
Avoid if
  • bleeding disorders
  • prior to surgery
  • garlic allergy
  • gastroesophageal reflux disease (GERD) in some individuals

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Suggested dosage

600-900 mg of garlic powder daily, standardized to allicin content, or 3-6 grams of fresh garlic daily, divided into multiple doses.

General guidance — discuss specifics with a clinician.

Active medicinal compounds

Allicin, alliin, diallyl disulfide (DADS), diallyl trisulfide (DATS), ajoene, S-allyl cysteine (SAC), S-allyl mercaptocysteine (SAMC.

Traditional use

Garlic has been used for thousands of years in various traditional medicine systems, including ancient Egyptian, Greek, Roman, Chinese, and Indian medicine. It was traditionally employed for its antiseptic properties, to ward off infections, treat digestive issues, and as a general tonic. In many cultures, it was also believed to offer protection against evil and illness.

Safety

Safety warnings

Generally considered safe for most adults. Common side effects include bad breath, body odor, heartburn, and stomach upset. High doses may increase the risk of bleeding.

Avoid if

  • bleeding disorders
  • prior to surgery
  • garlic allergy
  • gastroesophageal reflux disease (GERD) in some individuals

Medication interactions

  • anticoagulants (e.g., warfarin)
  • antiplatelet drugs (e.g., aspirin, clopidogrel)
  • saquinavir (an HIV medication)
  • some blood pressure medications (potential additive effect)

Reported side effects

  • bad breath
  • body odor
  • heartburn
  • nausea
  • vomiting
  • diarrhea
  • allergic reactions (rare)

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (B)

Given that no specific PubMed studies were provided, the rationale for evidence is based on general scientific understanding. The current understanding of garlic's efficacy for various conditions is derived from a mix of in vitro studies, animal models, and human clinical trials. However, the quality and consistency of human trials can vary, leading to a need for more robust, large-scale, and well-designed studies to draw definitive conclusions.

Filter by source type

Meta-Analyses(1)

Pooled analyses across multiple human trials.

Very High Quality

  • Effects of garlic supplementation on components of metabolic syndrome: a systematic review, meta-analysis, and meta-regression of randomized controlled trials.

    Fu Z, Lv J, Gao X, Zheng H, Shi S, Xu X · BMC complementary medicine and therapies · 2023 · n=999

    Garlic (Allium sativum), the underground bulb of the Allium genus, has been consumed on Earth for thousands of years. Many clinical trials of garlic supplementation on components of metabolic syndrome (MetS) have emerged in recent years, but there is no consensus on the effect. This meta-analysis aimed at systematically evaluating the effect of garlic supplementation on components of MetS. In this meta-analysis, we searched Pubmed, Embase, Cochrane, Medline, Web of Science databases, and clinical trials online sites from inception to November 1, 2022, with language restrictions to English. We engaged participants > 18 years and eligible for the clinical diagnosis of MetS or those with metabolic disorders and garlic was the only intervention. Outcomes included waist circumference, and body mass index, triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, blood pressure, and fasting blood glucose. Meta-regressi

    Meta-AnalysisPubMedVery High Quality

Randomized Human Trials(1)

Controlled human studies with random assignment.

High Quality

  • Garlic and Heart Disease.

    Varshney R, Budoff MJ · The Journal of nutrition · 2016

    Thousands of studies have been published based on animal and human studies evaluating garlic's effects and safety. We reviewed the available literature investigating the effects of garlic supplements on hypertension, hypercholesterolemia, C-reactive protein (CRP), pulse wave velocity (PWV), and coronary artery calcium (CAC), as well as available data on side effects. We searched PubMed for all human studies using medical subject heading words through 30 May 2013 and assessed relevant review articles and original studies. Only double-blind, randomized, controlled trials and meta-analyses of double-blind, randomized, controlled trials were included. The review of articles and data extraction were performed by 2 independent authors, with any disagreements resolved by consensus. Garlic supplementation reduced blood pressure by 7-16 mm Hg (systolic) and 5-9 mm Hg (diastolic) (4 meta-analyses and 2 original studies). It reduced total cholesterol by 7.4-29.8 mg/dL (8 meta-analyses). The mo

    Randomized TrialPubMedHigh Quality

Observational Studies(1)

Cohort, case-control, and cross-sectional human studies.

Moderate Quality

  • Efficacy, side effects, adherence, affordability, and procurement of dietary supplements for treating hypercholesterolemia: a narrative review.

    von Känel-Cordoba I, Wirnitzer K, Weiss K, Nikolaidis PT, Devrim-Lanpir A, Hill L · Journal of health, population, and nutrition · 2024

    Statins are effective in reducing high cholesterol levels; however, due to associated side effects, many patients actively seek alternative medications. This review evaluates the efficacy, side effects, patient adherence, cost-effectiveness, and accessibility of dietary supplements (DS) as a treatment option for hypercholesterolemia. This narrative review compares red yeast rice (RYR), flaxseed, artichokes, bergamot, Ayurvedic mixtures (with garlic as a prominent ingredient), and statins for treating hypercholesterolemia. We searched PubMed, Scopus, and Cochrane databases for studies published between 2012 and 2024 using "hypercholesterolemia" in combination with a dietary supplement (red yeast rice, flaxseed, artichokes, garlic, or bergamot). The selected articles were published until 28th January 2024 with no language restrictions. Study results suggest that alternative treatments using dietary supplements such as flaxseed, bergamot, or red yeast rice may effectively reduce cholest

    Observational StudyPubMedLow Quality

Limitations: A significant limitation in the current body of evidence for garlic is the variability in study design, garlic preparations (raw, powdered, aged extract), dosages, and duration of intervention. Many studies are small, have short durations, or lack appropriate control groups. The bioavailability and stability of active compounds can also differ greatly depending on the form of garlic used, making it challenging to compare results across studies. There is a general lack of high-quality, large-scale randomized controlled trials for many of its purported benefits.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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