Amaryllidaceae

Allium sativum

Garlic

Mixed Caution

Part used: bulb
Native range: Central Asia; a cultigen, sterile in most varieties and propagated by cloves
Morphology: A perennial grown as an annual, with flat strap leaves and a compound bulb of cloves in a papery sheath. Most cultivated garlic does not set viable seed and every plant of a variety is a clone.

What is in it

sulphur compounds alliin, allicin, ajoene

saponins

Evidence

Small and inconsistent effects on blood pressure and lipids, with meta-analyses generally finding a modest blood pressure reduction. Cochrane finds insufficient evidence for preventing the common cold. Antimicrobial activity is real in the laboratory and does not translate to systemic infection in people.

Safety

Culinary use is benign. Higher doses carry real antiplatelet activity, and bleeding complications are reported, particularly around surgery. Topical raw garlic causes chemical burns, which is a recurring presentation in emergency departments after home remedy use. Gastrointestinal irritation is common at supplement doses.

Interactions: Additive bleeding risk with anticoagulants and antiplatelets; Reduces levels of some antiretrovirals, notably saquinavir

Regulatory: Permitted as a food and as a listed medicine ingredient.

How the traditions classify it

Galenic Classed as hot and dry in the fourth degree — the most extreme heating classification available, applied to very few plants.

Chinese Da suan — pungent and warm, for cold conditions and for parasites.

Ayurvedic Pungent and heating, and traditionally avoided by those following a sattvic diet because it is held to be stimulating.

Three systems, rating the same plant. Where they disagree, none of them is correcting the others — they are separate frameworks that arrived at their categories independently.

Historical use

Fed to the builders of the Egyptian pyramids, prescribed by Hippocrates, carried by Roman soldiers, and used against infection in both world wars when antibiotics were unavailable or exhausted. One of the most consistently used medicinal plants in human history.

Recorded as history and attributed where possible. Long use establishes that a plant was widely used, not that it worked, and not that it was safe.

Worth knowing

Garlic's chemistry is a defence mechanism, and it only exists once the plant is damaged.

Intact cloves contain alliin, which is inert, kept separate from the enzyme alliinase. Crushing the clove breaks the compartments, the enzyme meets the substrate, and allicin is produced within seconds — the compound responsible for both the smell and most of the activity. It is also unstable and degrades quickly with heat and time.

That single fact explains why garlic preparations disagree so wildly. Raw crushed, aged extract, oil-macerated and dried powder are chemically different products, and a trial of one says very little about the others. It also explains why Galen graded it hot in the fourth degree: a plant that produces a burning agent on being cut is doing something a humoral framework could genuinely detect.

Nomenclature verified against GBIF backbone taxonomy.