Garlic
In short
Summary of findings for quick reference
Garlic (Allium sativum) has a long history as food and medicine. Herodotus reports its consumption by Egyptian pyramid workers. Dioscorides describes it as skorodon, and Pliny devotes a chapter of sixty-one remedies to it. Garlic is also known in Ayurveda as rasona or lashuna and in Chinese medicine as da suan. In Austria it is an everyday culinary ingredient and a traditional household remedy.
Modern monographs assess garlic cautiously. The EMA lists only traditional indications for specific preparations: as an adjunct in the prevention of atherosclerosis and for common cold symptoms. The German Commission E assessed uses for elevated blood lipids and age-related vascular changes positively; ESCOP discusses cardiovascular and respiratory uses. Fresh garlic, garlic powder and aged garlic extract differ in composition, so extracts should be dosed according to the specific product.
Research focuses mainly on blood lipids and blood pressure. Ried and colleagues’ 2013 meta-analysis included 39 trials and found evidence of small cholesterol reductions, especially with elevated baseline levels. However, some well-designed trials found no benefit. Stabler and colleagues’ 2012 Cochrane review considered blood-pressure evidence from two small trials uncertain. Garlic supplements can also affect bleeding risk. Discuss their use with your doctor if you take blood thinners or have surgery planned. Such supplements should be stopped at least seven days before the procedure.
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 bulbous plant in the Amaryllidaceae family, used as food and medicine for thousands of years. Its bulb consists of individual cloves wrapped in papery skin. Crushing allows alliinase to convert the sulphur compound alliin into reactive allicin. The European Medicines Agency (EMA) lists specific garlic preparations as traditional herbal medicines: as an adjunct in the prevention of atherosclerosis and for relief of common cold symptoms. This rests on long-standing use, not well-established clinical efficacy. The German Commission E assessed garlic positively as an adjunct to dietary measures for elevated blood lipids and for prevention of age-related vascular changes.
In Austria and the German-speaking world, garlic is a familiar culinary ingredient and household remedy. Studies examine fresh garlic, garlic powder and aged garlic extract (AGE), among other preparations. Their sulphur compounds differ, and their doses are not interchangeable. A 2013 meta-analysis by Ried and colleagues found evidence of small reductions in cholesterol. In contrast, the 2012 Cochrane review by Stabler and colleagues could not establish a reliable blood-pressure effect. Garlic supplements do not replace recommended medical treatment.
History
Garlic has long been cultivated as a culinary and medicinal plant. In his Histories, Herodotus reports garlic as food for Egyptian pyramid workers; this is a later account, not a contemporary construction record. Dioscorides describes medicinal uses including coughs and intestinal worms. Pliny devotes a Natural History chapter to it, headed “Garlic: Sixty-one remedies”. Such texts document historical beliefs and uses, not present-day efficacy.
Garlic remained a household remedy for respiratory complaints in European herbal medicine. The EMA now lists two traditional indications for specific garlic bulb preparations: as an adjunct in the prevention of atherosclerosis and for relief of common cold symptoms. Both rest on long-standing use. The German Commission E assessed garlic positively as an adjunct to dietary measures for elevated blood lipids and for prevention of age-related vascular changes. These assessments do not establish that garlic prevents heart attacks or strokes.
Mechanism
Garlic’s characteristic chemistry starts with alliin, a sulphur-containing compound in the intact clove. Crushing, chopping or chewing brings alliinase into contact with alliin, allowing allicin to form. Its subsequent breakdown depends on factors including temperature and preparation; it does not universally disappear within minutes at room temperature. Heating changes the sulphur compounds and can inactivate alliinase.
Aged garlic extract (AGE) is made by extracting garlic in dilute ethanol over many months. This changes its composition: the finished extract contains little or no allicin but includes stable, water-soluble sulphur compounds such as S-allyl-cysteine (SAC). These extracts are generally low in odour. Clinical trials examine garlic powder and fresh garlic as well as AGE. Results and doses cannot simply be transferred between preparations.
Clinical garlic research mainly examines blood lipids and blood pressure. Ried and colleagues reviewed 39 lipid trials in 2013. Evidence of small reductions in total and LDL cholesterol was strongest with elevated baseline levels and use for more than two months. Results remain inconsistent: in a six-month trial of 192 adults, Gardner and colleagues found no significant LDL reduction versus placebo with raw garlic, garlic powder or aged extract in 2007. Stabler and colleagues’ 2012 Cochrane review included two small trials involving 87 people with hypertension. It could not establish a reliable blood-pressure effect or prevention of cardiovascular disease.
Small studies also describe changes in platelet function. In a trial of 34 healthy adults, aged garlic extract affected some measures of platelet aggregation and adhesion at doses of 2.4 to 7.2 g daily. This does not establish protection against heart attacks or strokes. Potential interactions with blood thinners are the more relevant practical concern. Clinical evidence for colds is also insufficient: the EMA indication rests on tradition, and a Cochrane review found insufficient evidence for prevention or treatment. Overall, results depend on the preparation and outcome studied. Garlic does not replace medical treatment.
Evidence
| Outcome | Class | Grade | Effect | Studies | Refs |
|---|---|---|---|---|---|
| Blood lipids (total cholesterol, LDL)Ried and colleagues’ 2013 meta-analysis included 39 lipid trials and found evidence of small reductions in total and LDL cholesterol, particularly with elevated baseline levels and use for more than two months. Preparations and results varied; a six-month trial of 192 adults found no significant LDL effect versus placebo with raw garlic, powder or aged extract. This does not establish protection against heart attacks or strokes.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 | [1][3] | |
| Blood pressureStabler and colleagues’ 2012 Cochrane review included two trials involving 87 people with hypertension. There were signals of lower blood pressure, but small samples and imprecise results prevented a reliable conclusion. Cardiovascular morbidity and mortality outcomes were not reported. The study count refers to this 2012 review.Adults with hypertension in the included trials | 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. | Uncertain effect | [2] | |
| Antiplatelet activityA randomized trial in 34 healthy adults examined 2.4 to 7.2 g of aged garlic extract daily. Some measures of platelet aggregation and adhesion changed according to dose and assay. This does not establish protection against cardiovascular events. Potential interactions with anticoagulant or antiplatelet medicines and precautions before surgery are the practical concerns.Healthy adults; platelet function as a surrogate outcome | 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. | Changes in laboratory measures | [4][9] | |
| Common cold symptomsThe EMA lists specific garlic preparations for relief of common cold symptoms as traditional medicines. A 2014 Cochrane review found only one eligible trial and judged evidence for prevention or treatment insufficient. Traditional use therefore does not establish that colds will be shorter or milder.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 | [7][9] |
Usage
Forms and preparation
For cooking, crush or finely chop a fresh clove. This starts allicin formation; strong heating changes its composition. Briefly resting chopped garlic before cooking gives the enzyme reaction time but does not guarantee a health benefit. Adding it early or near the end also depends on the flavour you want. Steeping raw garlic in honey at room temperature is not an adequately validated method of safe preservation. Do not prepare such mixtures for prolonged storage; a clean jar does not make the process safe. For aged garlic extract, follow the preparation and dose instructions for the specific product. Its composition cannot be converted into a particular number of fresh cloves.
Dosage
There is no generally recommended therapeutic daily dose for garlic as food. Medicinal dosing depends on the exact preparation. For adults, the EMA monograph gives 900 to 1,380 mg of garlic powder daily in three to five divided doses for traditional adjunctive use in the prevention of atherosclerosis. This is not a dose for arbitrary extracts or fresh cloves. Follow the specific product instructions for other preparations, including aged garlic extract. For traditional common cold use, the EMA specifies a particular dry extract (drug-extract ratio 5:1; extraction solvent ethanol 34% V/V), at 100 to 400 mg daily from age twelve. This use is not recommended below twelve; the atherosclerosis indication is for adults only. Seek medical advice if cold symptoms last more than a week or worsen. Also observe the medication and surgery precautions in the Safety section.
Safety
Look-alikes
Similar plants and look-alikes
Wild garlic / ramsons (Allium ursinum)
Wild garlic (Allium ursinum) is an edible relative with broad, lance-shaped leaves that grows in damp deciduous woodland in spring. When foraging, its leaves can be confused with highly poisonous lily-of-the-valley or autumn crocus. Garlic smell alone is not a safe identification test, as it can transfer to fingers and other leaves. Gather only plants you can confidently identify using several features, checking each leaf individually. Leave unfamiliar plants untouched.
FAQs
What is the difference between fresh garlic and aged garlic extract?
Crushing a fresh clove allows alliinase to convert alliin into the sulphur compound allicin. Its stability depends on temperature and preparation; it does not invariably break down within minutes. Aged garlic extract (AGE) is produced by extraction in dilute ethanol over many months. It contains little or no allicin but stable compounds such as S-allyl-cysteine and is usually low in odour. Trials examine AGE, garlic powder and fresh garlic. Their results and doses are not interchangeable.
I take aspirin. Can I still take garlic supplements?
Garlic supplements can add to effects on blood clotting and increase bleeding risk. Talk to your doctor before taking them alongside aspirin, including products sold without prescription. Garlic supplements should be stopped at least seven days before planned surgery; inform your dental care team too. Usual culinary amounts and concentrated preparations require different assessment, but discuss overall use before procedures. Do not independently stop prescribed medicines.
How do I deal with garlic breath?
The smell comes from volatile sulphur compounds, some of which are released in breath after digestion, so brushing does not remove it completely. Raw apple and fresh mint reduced some garlic breath compounds in an experimental study, but this is not a guaranteed instant remedy. Aged garlic extract is often lower in odour but differs in composition from fresh garlic. There is no need to replace culinary garlic with a supplement simply because of the smell.
Is garlic in honey safe?
There is no adequately validated safe-preservation method for raw garlic steeped in honey at room temperature for several days. A botulism risk cannot reliably be ruled out. We therefore do not recommend making such mixtures for storage or keeping them in a cupboard for months. A teaspoon of this mixture also has no established efficacy for a cold. Honey in any preparation is unsuitable for infants under one year.
9 sources.
- Karin Ried; Catherine Toben; Peter Fakler. Effect of garlic on serum lipids: an updated meta-analysis. 2013. doi:10.1111/nure.12012
- Sarah N Stabler; Aaron M Tejani; Fong Huynh; Claire Fowkes. Garlic for the prevention of cardiovascular morbidity and mortality in hypertensive patients. 2012. doi:10.1002/14651858.CD007653.pub2
- Christopher D Gardner; Larry D Lawson; Eric Block; Lorraine M Chatterjee; Alexandre Kiazand; Raymond R Balise; Helena C Kraemer. Effect of raw garlic vs commercial garlic supplements on plasma lipid concentrations in adults with moderate hypercholesterolemia: a randomized clinical trial. 2007. PMID:17325296
- M Steiner; W Li. Aged garlic extract, a modulator of cardiovascular risk factors: a dose-finding study on the effects of AGE on platelet functions. 2001. doi:10.1093/jn/131.3.980S
- Hiroyuki Fujisawa; Kaoru Suma; Kana Origuchi; Hitomi Kumagai; Taiichiro Seki; Toyohiko Ariga. Biological and chemical stability of garlic-derived allicin. 2008. doi:10.1021/jf8000907
- Stephen C Piscitelli; Aaron H Burstein; Nada Welden; Keith D Gallicano; Judith Falloon. The effect of garlic supplements on the pharmacokinetics of saquinavir. 2002. doi:10.1086/324351
- Elizabeth Lissiman; Alice L Bhasale; Marc Cohen. Garlic for the common cold. 2014. doi:10.1002/14651858.CD006206.pub4
- Rita Mirondo; Sheryl Barringer. Deodorization of Garlic Breath by Foods, and the Role of Polyphenol Oxidase and Phenolic Compounds. 2016. doi:10.1111/1750-3841.13439
- European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). European Union herbal monograph on Allium sativum L., bulbus. 2017. Source
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.