Garlic
In short
Summary of findings for quick reference
Garlic (Allium sativum) is one of the oldest and most widely travelled medicinal plants in the world. It appears among the herbal preparations of the Egyptian Ebers Papyrus around 1550 BCE and was a ration for the workers who built the pyramids. The Greeks recorded it as skorodon, Pliny gave it a Roman chapter of sixty-one remedies, Ayurveda kept it as rasona and Chinese medicine as da suan, and the Greco-Arabic physicians carried it forward. In Austria and across the German-speaking world it sits firmly in the kitchen and the household cabinet, where Knoblauch im Honig has been taken at the first signs of a cold for generations.
The modern monographs are more measured than garlic's reputation. The European Medicines Agency (EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC)) lists garlic bulb under traditional use only, both as an adjuvant for the prevention of atherosclerosis and for the relief of cold symptoms, on the basis of long-standing use rather than well-established clinical proof. The German Commission E gives a separate positive assessment for elevated blood lipids and age-related vascular changes, and ESCOP supports the cardiovascular and respiratory uses. Two forms dominate the research and they are not interchangeable: freshly crushed garlic, which delivers the unstable but active allicin, and aged garlic extract, which is allicin-free but rich in stable S-allyl-cysteine, so the dose on the package is the right reference for the extract.
Modern clinical work concentrates on the heart and circulation. Ried and colleagues reported a modest reduction in total and LDL cholesterol across thirty-nine trials in 2013, and the Stabler and colleagues Cochrane review in 2012 found a modest reduction in blood pressure. The effects are real but moderate, the trials use very different preparations, and the dose-response picture is uneven, so the evidence is supportive rather than definitive. The antiplatelet effect matters most as a safety point: people on blood thinners should speak to their doctor before taking concentrated garlic supplements, and these should be stopped at least a week before any planned surgery. Garlic is best read as a deep traditional and culinary herb with a moderate modern evidence base for cardiovascular support, not as a clinical treatment.
Clinical evidence ↔ Historical significanceWe display two separate evidence categories: clinical evidence from modern trials and historical significance from documented healing tradition. Both are valuable, but they answer different questions.Read more
In every encyclopedia entry we evaluate two distinct categories of evidence. Clinical evidence as used in trials meets a narrower but scientifically essential bar. At the same time, the hundreds of thousands of plant species worldwide have only partially been captured and tested in modern studies.
Alongside the trial picture our researchers compile a comprehensive overview of where and since when a plant has been used across different traditions of natural medicine. When a plant has been used as a medicinal plant in many cultures across many generations, that historical significance deserves to be visible too.
Our position: a truly informative overview emerges only when both categories sit side by side. We communicate transparently what counts as what.
Overview
Garlic (Allium sativum) is a pungent bulb in the Amaryllidaceae family with a culinary and medicinal history stretching back at least five thousand years. The papery-skinned bulb is made up of separate cloves, each containing alliin, a sulphur-amino-acid precursor that converts to the active compound allicin when the clove is crushed or chopped. The European Medicines Agency Committee on Herbal Medicinal Products (EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC)) lists Allium sativum bulb as a traditional herbal medicinal product on two counts: as an adjuvant for the prevention of atherosclerosis, and for the relief of symptoms of the common cold. Both indications rest on long-standing use rather than well-established use. The German Commission E is the body that gives the cardiovascular use a positive assessment, supporting it for dietary measures in elevated blood lipids and for the prevention of age-related vascular changes.
In Austria and across the German-speaking world, garlic is a kitchen staple and a household herb. The traditional Hausmittel Knoblauch im Honig (garlic in honey) has been used in autumn and winter for generations. The two main forms in modern research are crushed fresh garlic (which delivers the unstable but active allicin) and aged garlic extract or AGE (which is allicin-free but rich in stable S-allyl-cysteine). Ried et al. published a 2013 meta-analysis on garlic and cholesterol; Stabler et al. published a 2012 Cochrane review on garlic and hypertension. Garlic is best described as a long-established traditional and culinary herb with a moderate evidence base for cardiovascular support, not as a clinical treatment.
History
Garlic is one of the oldest cultivated plants. Cloves were found in the tomb of Tutankhamun, Hippocrates and Dioscorides recommended it for a wide range of complaints, and Roman soldiers and labourers carried it on long marches. Across European folk tradition garlic appears as a household herb against winter illness and as a flavouring of last resort in the lean months when little else stood in the cellar.
In Austria and across the German-speaking world, garlic sits firmly in both the kitchen and the Hausmittelschrank. The traditional preparation Knoblauch im Honig (a fresh clove steeped in honey) has been taken at the first signs of a cold for generations. The European Medicines Agency Committee on Herbal Medicinal Products (EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC)) lists Allium sativum bulb under traditional use for both of its indications: as an adjuvant for the prevention of atherosclerosis, and for the relief of symptoms of the common cold. Both rest on long-standing use rather than well-established use. The German Commission E is the body that gives the cardiovascular use a positive assessment, recognising garlic for supportive treatment of dietary measures in elevated blood lipids and for the prevention of age-related vascular changes.
Mechanism
The signature chemistry of garlic starts with alliin, a sulphur-amino-acid precursor stored in the intact clove. When the clove is crushed, chopped, or chewed, the enzyme alliinase comes into contact with alliin and converts it to allicin within seconds. Allicin is highly reactive and short-lived: it breaks down within minutes at room temperature and rapidly during cooking. Letting crushed garlic stand for about ten minutes before heating is the traditional cook trick to give the alliinase reaction time to run.
Aged garlic extract (AGE) is a separate category. The bulbs are macerated in dilute ethanol for many months, which destroys allicin but produces stable, water-soluble sulphur compounds, most notably S-allyl-cysteine (SAC). AGE is therefore odourless and stable, and most of the modern clinical work on cardiovascular endpoints uses standardised AGE products. The two forms work through related but distinct chemistry, and the dose-response curves do not transfer cleanly from one to the other.
Modern clinical work on garlic has focused mainly on cardiovascular endpoints. Ried and colleagues published a 2013 meta-analysis on garlic preparations and blood lipids, reporting a modest reduction in total cholesterol and LDL cholesterol across thirty-nine trials, with a larger signal in adults with elevated baseline cholesterol. Stabler and colleagues published a 2012 Cochrane systematic review of garlic for hypertension, finding a modest reduction in blood pressure compared with placebo across the included trials. Antiplatelet effects of fresh garlic have been described in a smaller body of mechanistic and clinical work, including ex-vivo platelet-aggregation studies on aged garlic extract.
Across this body of work the picture is one of a traditional culinary herb with a moderate but not definitive evidence base for cardiovascular support. The effects on blood lipids and blood pressure are real but modest, the trials use very different preparations (aged garlic extract, garlic powder, garlic oil, fresh garlic), and the dose-response picture is uneven. The cold-and-cough indication is traditional rather than clinical: the EMA HMPCEuropean Medicines Agency, Committee on Herbal Medicinal Products (HMPC) monograph lists it under traditional use, and modern trial evidence on this endpoint is limited. Garlic is best read as a well-loved kitchen staple with a moderate evidence base for cardiovascular support, not as a substitute for medical treatment.
Evidence
| Outcome | Class | Grade | Effect | Studies |
|---|---|---|---|---|
| Blood lipids (total cholesterol, LDL)Ried et al. 2013 meta-analysis of thirty-nine trials reported a modest reduction in total cholesterol and LDL across garlic preparations, with a larger signal in adults with elevated baseline lipids. The EMA HMPC lists the cardiovascular indication under traditional use; the German Commission E is the body that gives it a positive assessment. Framed here as supportive rather than as a CNP claim.Adults with mildly elevated cholesterol | EmergingEmerging research. Early small trials suggest an effect but await replication. | CEvidence quality grade C. Mixed or limited evidence. Small trials, signals, or traditional use under an EMA HMPC traditional-use monograph. This is an evidence rating, not a product endorsement. | Modest Improvement | |
| Blood pressureStabler et al. 2012 Cochrane systematic review reported a modest reduction in blood pressure across the included trials. Effect is real but moderate; preparations and doses vary.Adults including those with hypertension | EmergingEmerging research. Early small trials suggest an effect but await replication. | CEvidence quality grade C. Mixed or limited evidence. Small trials, signals, or traditional use under an EMA HMPC traditional-use monograph. This is an evidence rating, not a product endorsement. | Modest Improvement | |
| Antiplatelet activitySmaller body of mechanistic and ex-vivo platelet-aggregation studies on fresh garlic and aged garlic extract. Practical relevance shows up most clearly as a safety caveat for blood-thinner interactions and pre-surgery use rather than as a stand-alone benefit claim.Healthy adults and adults with cardiovascular risk | EmergingEmerging research. Early small trials suggest an effect but await replication. | CEvidence quality grade C. Mixed or limited evidence. Small trials, signals, or traditional use under an EMA HMPC traditional-use monograph. This is an evidence rating, not a product endorsement. | Modest Effect | |
| Common cold symptomsEMA HMPC traditional-use indication for relief of symptoms of the common cold. Modern trial evidence on this endpoint is limited; the indication rests primarily on long-standing traditional use across European households.Adults with seasonal upper respiratory complaints | TraditionalTraditional use. Long-standing folk practice or EMA HMPC traditional-use monograph. | DEvidence quality grade D. Preliminary signal. A single small trial, pilot result, or laboratory or animal model. Clinical relevance unclear. This is an evidence rating, not a product endorsement. | Traditional Use |
Usage
Forms and preparation
For culinary and traditional use, crush or finely chop a fresh clove and let it stand at room temperature for about ten minutes before cooking. This pause gives the alliinase enzyme time to convert alliin into allicin and is the simple kitchen step that distinguishes a clove dropped into hot oil from a clove that delivers the full sulphur chemistry. Add to food at the end of cooking where possible; high heat shortens the life of the active compounds. For Knoblauch im Honig, peel one to three fresh cloves, slice or lightly crush them, and submerge them in a clean jar of raw honey. Keep at room temperature for at least three days before use, longer if you can. Take a teaspoon at the first signs of a cold. For aged garlic extract take the capsule or liquid dose on the package; the AGE form is odourless and stable and follows package directions rather than the kitchen-clove method.
Dosage
In food, one to two fresh cloves per day is the everyday culinary range and is broadly aligned with the lower end of the doses studied in clinical work. The EMA HMPC traditional-use monograph for the atherosclerosis-prevention indication cites a typical daily dose equivalent to four grams of fresh garlic, taken as a standardised preparation. The German Commission E is the body that gives this cardiovascular use a positive assessment. Aged garlic extract is typically taken at six hundred to twelve hundred milligrams per day; garlic powder products at six hundred to nine hundred milligrams per day. Read the dose on the package; the right reference number depends entirely on the preparation. Build slowly. Start with the lower end of the package dose for the form you choose, take it with food, and see how you feel for a week before adjusting. The kitchen-clove route is the gentlest entry point and a traditional one. For concentrated extracts the package dose is the right reference, and the antiplatelet caveat in the safety section below is the most important practical note.
Safety
Look-alikes
Toxic look-alikes
Allium ursinum (Bärlauch, wild garlic / ramsons)
Wild garlic (Allium ursinum, Baerlauch in German) is a harmless relative from the same genus and is not a danger to a garlic garden. It grows in damp riverside forests in spring with broad, lance-shaped leaves and a clear garlic smell when crushed between the fingers. The actual risk runs the other way: when foraging for wild garlic in the woods, the leaves can be confused with lily-of-the-valley or autumn crocus, which are highly toxic. The simplest field test is to smell a crushed leaf. If it smells of garlic, it is Baerlauch.
FAQs
What is the difference between fresh garlic and aged garlic extract?
Fresh garlic delivers allicin, the reactive sulphur compound that forms when alliin meets the enzyme alliinase as the clove is crushed. Allicin is the source of the strong garlic smell and is responsible for much of the short-term biological activity, but it breaks down within minutes at room temperature and rapidly during cooking. Aged garlic extract (AGE) is made by macerating bulbs in dilute ethanol for many months. The allicin is gone, but the process produces stable, water-soluble sulphur compounds, most notably S-allyl-cysteine. AGE is therefore odourless and shelf-stable, and most modern cardiovascular trials use standardised AGE products. Each has its place; the package dose is the right reference for AGE, and the kitchen-clove method for fresh garlic.
I take aspirin. Can I still take garlic supplements?
Garlic has a documented antiplatelet effect that can add to the effect of aspirin, warfarin, clopidogrel, and other blood-thinning medication. The risk is higher with concentrated standardised garlic supplements taken daily than with normal culinary garlic. Talk to your doctor before adding a daily garlic capsule or aged garlic extract on top of prescribed blood thinners, and stop concentrated garlic preparations at least one week before any planned surgery, including dental work. Garlic in normal cooking amounts is generally not the issue here; the caution is for supplement-strength dosing.
How do I deal with garlic breath?
The garlic smell comes from sulphur compounds that are released both in the mouth and through the lungs after digestion, which is why brushing alone never quite gets rid of it. Traditional kitchen tricks include chewing fresh parsley, mint, or coriander leaves; eating an apple; drinking milk during the meal; and brushing your tongue after. If you want the cardiovascular benefits without the social cost, aged garlic extract is odourless by design and a reasonable choice; the trade-off is that the chemistry is different from fresh garlic and the package dose is the right reference.
How do I make Knoblauch im Honig?
Knoblauch im Honig is a traditional Austrian and German Hausmittel for the first signs of a cold. Peel one to three fresh cloves, slice or lightly crush them so the cut surfaces are open, and submerge them in a clean glass jar of raw, unpasteurised honey so they are completely covered. Keep at room temperature for at least three days before use, longer if you can. The honey draws moisture out of the cloves and turns slightly thinner over time. Take a teaspoon at the first scratchy throat or first chilly evening. A finished jar keeps for several months in a cool, dark cupboard. As with any honey preparation, this is not for children under one year of age.
Legal notice: The depiction of historical significance and traditional use is context within our encyclopedia and not a health claim for any product, not a treatment promise, and not a substitute for medical advice. What may be stated on product labels, product pages, or in advertising is governed by the applicable legal requirements.