Materia Medica

Allium sativum (Liliaceae). The common name is garlic and the chinese name is hsiao-suan.

Garlic has been grown and used by humans for so long that no one knows for certain where it originated, but probably in central Asia. It has been cultivated for at least 5,000 years, and the name sativum means cultivated. It was used by the Greeks and Romans, and was mentioned by Aristotle, Dioscorides, Virgil, and Galen. They used it for such things as infection, intestinal disorders, wounds and coughs. It has always had mystery and magic involved with it also.  These stories range from warding off vampires to using it to win horse races.

The Chinese have also long used garlic. They consider it acrid with a warm property and to be useful for many conditions. It is thought to have particular influence upon the spleen, stomach and kidney, acting as a sedative and removing poisons.

The allium family includes onions, shallots, chives, leeks and other edible and ornamental members. It is an easy to grow bulb that is cultivated in temperate climates. It is readily available in grocery stores because of its popularity in cooking.

The underground bulb, which is divided into cloves is the part of the plant that is used. Garlic is readily available in its fresh state in any grocery store, but the active constituents can vary widely between garlic varieties.  There are many preparations available in the marketplace with a wide variability in their efficiency. There is suggestive evidence that the best forms of garlic supplements are enteric coated tablets, or capsules of dried garlic or garlic powder. There are products that are standardized for alliin content, and the dosage of the commercial product should provide a daily dose of 8 mg of alliin.

Garlic walks the fine line between food and medicine, and is known for its role in the therapy of malnutrition due to its high mineral and vitamin content.  There is a good deal of free-radical scavenger action due, at least in part, to its germanium, glutathione, selenium and zinc content. It has also been shown to be effective in the treatment of lead, mercury, cadmium and arsenic poisoning.

Garlic has been shown to have hypolipemic activity that lowers serum cholesterol and triglycerides and increases the amount of high-density lipoproteins.¹ The effectiveness of garlic in this roll is controversial, although the bulk of data currently points to this benefit.  The most recent study debunking this use by the JAMA, has been brought under question because of the study’s small sample size and the use of an inferior garlic oil supplement.² 

Studies have also shown that garlic has great potential in inhibiting platelet aggregation and enhancing fibrinolytic activity. The blood flow increase may help prevent thrombosis. This is believed to be due primarily to alliin and its conversion to allicin by the enzyme alliinase.

Garlic has the long time reputation for lowering blood pressure and is one of the most popular self-medications for this effect. Some early clinical studies support a mild hypotensive effect and there are some animal studies that also support this. The lack of research leaves the effectiveness of garlic as a hypotensive remedy in the realm of anecdotal evidence.³

Garlic is particularly useful in its antimicrobal effects.  It has been shown to have antiviral, antifungal, antiprotozoan, antiparasitic and antibacterial activity. These effects are due to allicin and other sulfur compounds and again to ajoene. It is effective against a number of gram-negative, gram-positive and acid-fast bacteria, including Staphylococcus, Salmonella, Vibrio, Mycobacterium, and Proteus species. Fungi that are killed by garlic include Coccidioides, Aspergillus, Histoplasma, Trichophyton, Candida and Cryptoccocci. It has also been used for amebic dysentary⁴

 The anticancer effects of garlic are under intense study at this time.  The diallyl sulfide (DAS) inhibits colon cancer and reduces radiation damage.  Garlic and onions both inhibit an enzyme that is thought to promote tumors.  The most well known study was done by the National Cancer Institute and documented that the more garlic, onions and other alliums people ate, the less stomach cancer.⁵

Garlic is a common folk remedy for coughs, colds, infections, intestinal parasites, high blood pressure and other circulatory disorders. It increases the flow of urine and so is used with urinary related conditions. Garlic stimulates the production of bile and is thus used for digestion difficulties.

Fresh, whole garlic is pharmacologically inactive, but it contains a sulfur-containing amino acid, alliin. When the garlic is crushed or cut the alliin comes in contact with the enzyme alliinase and the compound allicin is formed. Alliin has almost no odor, but the compound allicin has the strong garlicky smell. Allicin is considered the strongest cause of the antimicrobal action. Allicin decays spontaneously or in cooking, to stronger smelling diallyl sulfide, disulfide and trisulfide.

The compound ajoene is also formed and is considered to be an important inhibitor of PAF and platelet aggregation.

There does not seem to be agreement about the correct dosage. The parameters generally prescribed are 6 to 12 gms of the dried bulb or about three cloves of fresh garlic daily.

The biggest problem with garlic is the smell that causes social problems for so many people. The smell is essential to the effectiveness of garlic, but enteric coated or hard capsules that dissolve in the intestine may help this.  The common advice is to also eat parsley or other chlorophyll rich greens, or aromatic seeds such anise seeds, with the garlic.

Garlic must have the smell present to be effective as a medicinal agent. Odorless garlic products, and garlic oil products are probably not clinically active and should be considered more of a nutritional product. Some odorless products are simply odor controlled. One method of testing the products is to bite into it and if the taste and smell is characteristic of garlic, the active components are present.

Caution should be used in pregnancy as it has an emmenogogue and uterine stimulant action in large amounts. Garlic should not be used in acute or chronic stomach inflammations, as the disulfide components can cause gastroenteritis. It is also contraindicated with low thyroid function, as high levels on a regular basis can cause a reduced iodine uptake by the thyroid. Fresh garlic can occasionally cause nausea or a burning sensation in the mouth and gastrointestinal tract and nausea. In large quantities it could cause gastroenteritis. Garlic may potentially interact with anticoagulants such as warfarin and even aspirin, close monitoring is in order.