Garlic: Stinking Rose or Magic Bullet?

Garlic (Allium sativum), a member of the lily family, is possibly the most popular herb in world cuisines. While it originated in central Asia, garlic has been cultivated worldwide for millennia. Garlic has been used throughout the centuries for both food and medicine. Garlic owes much of its popularity in Europe to the Benedictine monks who grew garlic in their monastery gardens.

The Greek historian Herodotus reported that large amounts of garlic, radishes, and onions were consumed by construction workers of the Egyptian pyramids. He claimed that the large amounts of garlic were necessary to protect the builders from illnesses. In the ancient Codex Ebers, an Egyptian medical papyrus, no less than 22 of the medicinal formulations contained garlic.

Garlic belongs to the genus Allium along with leeks, onions, shallots, and chives. Allium plants are perennials and usually form underground bulbs. The garlic bulb contains a cluster of five or more secondary bulbs called cloves. The bulbs are harvested and the cloves used either fresh, dried, or powdered. Cut cloves have a pungent odor and strong flavor, because of the presence of many sulfur compounds.

Much of the garlic eaten in the United States is grown in Gilroy, California. About 80 percent of the garlic crop is used for various dehydrated: garlic products, while the rest is sold as fresh garlic. Garlic can be used in an endless variety of soups, dips, salad dressings, sauces, entrees, and vegetable dishes.

Antimicrobial Action

Garlic has been the subject of hundreds of scientific studies. It has a broad spectrum antibiotic activity inhibiting the growth of a variety of microorganisms, including such bacteria as Staphylococcus, Streptococcus, Salmonella, Escherichia coli; such molds and yeasts as Candida albicans; influenza and herpes viruses; and parasites. Garlic can also kill Helicobacter pylori, the bacteria associated with peptic ulcers. Garlic was used in Africa by Albert Schweitzer for the treatment of amebic dysentery.

Protection Against Heart Disease

Regular use of garlic can lower blood cholesterol levels and possibly raise HDL cholesterol levels. An analysis of 40 clinical studies revealed that, on average, one half to one clove of garlic per day can reduce elevated blood cholesterol levels by about 10 percent and blood triglyceride levels by about 13 percent of the initial value. Garlic also lowers blood pressure levels because of its vasodilator properties and may be useful for patients with mild hypertension. In addition, garlic inhibits the formation of blood clots. In a well-controlled clinical study of the elderly, high-dose garlic powder significantly reduced the growth of atherosclerotic plaque by almost 20 percent and even achieved a slight regression over a four-year period. Garlic also has some ability to lower blood glucose levels, especially in patients with diabetes.

Each clove of garlic contains about 1 percent of alliin, which converts to allicin when the clove is crushed, cut, or chewed. Garlic contains a large number of health-promoting substances, but it is allicin that is essential for garlic's antimicrobial, lipid-lowering, and anti-clotting properties. Allicin is transformed into a variety of sulfur compounds dependent upon the method of food preparation.

Different garlic preparations have various effects. The most important factor is the content of alliin. Various formulations may differ in terms of standardized alliin content by as much as twentyfold. Enteric-coated pills, which dissolve in the intestinal tract, cut down on odor problems and improve the absorption of allicin (the key ingredient). Garlic powders best represent the composition of fresh garlic cloves than any other processed garlic.

Aged garlic extract (Kyolic), which is prepared by storing sliced garlic in 1520 percent alcohol for 20 months, has lower amounts of sulfur and lacks the active sulfur compound alliin. Clinical studies using aged garlic extract have been less conclusive than those with fresh garlic or garlic powder products. In some studies with aged garlic extract it took about six months to lower blood lipids, while garlic cloves and standardized garlic powder showed significant decreases after one or two months.

Protection Against Cancer

Various studies show that garlic can reduce the development of a number of cancers, including stomach, prostate, and colon cancer. Risk of prostate cancer was found to be 44 percent lower in those using garlic two or more times per week. In China, persons with the highest intake of garlic, onions, and other allium vegetables had a 40 percent lower risk of stomach cancer than those with the lowest intake. In the Iowa Woman's Health Study, the highest consumption of garlic was associated with a 32 percent reduced risk of colon cancer.

Garlic is also reported to stimulate the immune system--even in AIDS patients. It can enhance the activity of the lymphocytes and macrophages that destroy cancer cells, and disrupt the metabolism of tumor cells. Garlic inhibits the formation of nitrosamines in the stomach and thereby reduces the risk of gastrointestinal cancer. More research is needed to actually determine the quantity of garlic needed to minimize cancer risk. Garlic contains other health-promoting compounds such as fructans, flavonoids, phenolic acids, phytosterols, and saponins, which protect against chronic diseases.

Conclusion

Garlic has a strong antimicrobial action. It can lower lipid levels, inhibit blood clots, and enhance the immune system. To maintain good health a person should consume about one clove (four grams of fresh garlic) a day. Some people are allergic to garlic and suffer gastrointestinal distress. Large amounts should be avoided, since they may cause heartburn and stomach complaints.

Remember:

Herbal products and dietary supplements can have pharmacological effects, may produce adverse reactions in some people, and could interact with over-the-counter and prescription medications you may take. Discuss with your physician your decision to use any herbal product. Anything mentioned in this article is not intended to diagnose, prescribe, or treat any ailment.

Winston J. Craig, Ph.D., R.D., is a professor of nutrition at Andrews University, Berrien Springs, Michigan.