Garlic

Prepared by Susan A. Latta

What are the folklore uses of garlic?

Garlic traditionally has been used as a natural antibiotic thought to protect against infection, to lower blood pressure, and to treat atherosclerosis, asthma, arthritis, cancer, and circulatory problems.

What is garlic?

Garlic grows in the form of a bulb. It is used in cooking to enhance the flavor, and it may also have some medicinal value.

How does garlic work?

Allicin, SAC (S-Allyl-Cystine) and ajoene are the three active compounds found, in varying amounts, in fresh garlic, many commercially produced garlic pills, and in garlic powder. Allicin, a chemical formed when garlic is crushed, appears to have antibacterial properties. SAC has been shown to be effective against the initiation of tumors in animals. Ajoene appears to be an anti- blood clotting agent.

Garlic supplements contain alliin, an odor-less precursor of the garlic smell in the active compounds of allicin and ajoene. The enzyme alliinase is needed to convert alliin to allicin and ajoene.

How effective is garlic?

Research on medicinal uses of allicin in fresh garlic indicate it can lower blood pressure and cholesterol. Ajoene may be useful in slowing blood clotting. In this way, garlic protects against heart disease and stroke. These results do not apply to garlic supplements, however. Studies also show that fresh garlic, in large quantities, can lower cholesterol levels. Because garlic thins the blood, it may lower blood pressure.

Other findings suggest that high levels of garlic may prevent development of cancer by stimulating the immune system and hindering growth of cancer cells. Laboratory studies show that garlic can inhibit bacteria growth and may fight infection. However, those results are unproven in humans.

How does cooking affect garlic?

Cooking preserves allicin, since heat inactivates the enzyme that weakens its antibacterial effect. Cooking garlic also decreases the likelihood it will cause gastrointestinal disturbances.

What are the recommended forms and dosages of garlic?

Research has shown that relatively large amounts must be consumed for garlic to be medicinally beneficial: one to five or more cloves a day.

A third of a teaspoon of garlic powder equals one dose of the most potent commercial supplement. If you take garlic supplements regularly, read the labels to identify the active compounds and their amounts.

Dried garlic does not contain the active compounds of allicin or ajoene, but does contain alliin. The enzyme alliinase may be present in garlic that has been dried at low temperatures, but it is unstable in the presence of acid. When dried garlic is consumed and reaches the stomach, the alliinase is destroyed by stomach acid; therefore, not much alliin is converted to allicin.

Sources:

Tyler, V. 1993. The Honest Herbal. The Haworth Press, Binghamton, N.Y. 3rd Edition. pp. 139-143.

Golub, C., Pungent, Powerful Garlic May Help Fight Infection, Heart Disease, Environmental Nutrition, December 1995. (18) 12. pp. 5-6.

Ward, E.M., Respect Grows for Botanical, But Can You Trust the Herbs You Buy? Environmental Nutrition, May 1995. (18) 5. pp. 5-6.