Natural Products

Garlic

Scientific names: Allium sativum

Common names: Garlic also is known as allium, stinking rose, rustic treacle, nectar of the gods, camphor of the poor, and poor man's treacle.

Efficacy-safety rating:

ÒÒ...Ethno or other evidence of efficacy.

Safety rating:

●...Little exposure or very minor concerns.

What is Garlic?

A perennial bulb with a tall, erect flowering stem that grows to 2 to 3 feet. The plant produces pink to purple flowers that bloom from July to September. The bulb is odiferous.

What is Garlic used for?

Overview

Garlic bulbs contain an odorless, colorless, sulfur-containing amino acid called alliin, which has no pharmacologic activity. When the bulb is ground, the enzyme allinase is released, resulting in the conversion of alliin into allicin. Allicin gives the pungent characteristic odor to crushed garlic and is believed to be responsible for some of the pharmacologic activity of the plant.

Traditional/Ethnobotanical uses

The name Allium comes from the Celtic word all, meaning burning or smarting. Garlic was valued as an exchange medium in ancient Egypt. Its virtues were described in inscriptions on the Great Pyramid of Cheops. The folk uses of garlic have ranged from the treatment of leprosy in humans to managing clotting disorders in horses. Physicians prescribed the herb during the Middle Ages to cure deafness and the American Indians used garlic as a remedy for earaches, flatulence, and scurvy.

Cholesterol/Cardiovascular effects

Evidence suggests that garlic may beneficially affect cholesterol and lipids. The evidence for lowering LDL and total cholesterol still is questionable and may not be clinically meaningful. The antithrombotic effects of garlic have been studied with inconsistent results. Strong evidence for the effect of garlic on blood pressure is lacking. No firm conclusions about the benefits of garlic in lowering blood pressure can be drawn at this time.

Antiseptic/Antibacterial

Among its traditional uses, it has been employed for its antiseptic and antibacterial properties. While garlic does exhibit antimicrobial properties, its effectiveness in humans may be insignificant.

Cancer/Immune system effects

Garlic contains the trace elements germanium and selenium, which have been thought to play a role in improving host immunity. To date, research reveals no clinical data regarding the use of garlic in immunology. Scant data from clinical studies suggest that dietary garlic consumption is associated with decreased odds of certain cancers. It was concluded that high intake of garlic may offer protection. More clinical studies are needed to determine the exact benefits of garlic in cancer prevention.

Other uses

The effect of garlic on the GI system has been a topic of some debate. There is no clinical data regarding the use of garlic for hypermotile intestinal disorders or any other GI effects. Garlic also has been suggested to reduce blood glucose levels and increase serum insulin. Conflicting results in clinical studies have shown that garlic should not be recommended for this because of lack of good clinical studies.

What is the dosage of Garlic?

Garlic dosage is complicated by the volatility and instability of important constituents and by such products as “deodorized garlic,” “aged” extracts, and distilled oils. Doses of fresh bulbs studied in clinical trials for hyperlipidemia or atherosclerosis range from 2 to 4 g/day and a daily intake of 2 to 12 mg allicin has been proposed. Because garlic is a widely consumed foodstuff, dosage will remain a matter of personal tolerance.

Is Garlic safe?

Contraindications

Contraindications have not yet been identified.

Pregnancy/nursing

Documented emmenagogue effects. Avoid use.

Interactions

Garlic may reduce saquinavir plasma concentrations. Patients taking saquinavir should be cautioned to limit their ingestion of garlic and to avoid garlic supplements without consulting their health care provider. Based on available reports, no special precautions are necessary in patients eating garlic and taking warfarin. However, since warfarin has a narrow therapeutic index, patients should be cautioned against use of herbal products without consulting their health care provider and to report any signs of bleeding. Based on an initial study, garlic does not appear to interact with alprazolam, dextromethorphan, or ritonavir.

Side Effects

Ingestion of a single 25 mL dose of fresh garlic extract has caused burning of the mouth, esophagus, and stomach, nausea, sweating, and lightheadedness; safety of repeated doses of this amount has not been defined. Rarely, ingestion also may cause anaphylaxis. Topical exposure to crushed, uncooked garlic cloves for 3 to 5 minutes has resulted in toxic contact dermatitis. Repeated exposure to garlic dust can induce asthmatic reactions. Garlic may also cause allergic reactions.

Toxicities

Research reveals little or no information regarding the toxicology of this product.

References