Herbs for Health: Medicinal Benefits of Garlic

Garlic has become the herb of choice in the 1990s not only for flavoring meals, but also for enhancing health. In the United States, garlic is one of the top-selling herbal dietary supplements on the mass market and the second-best selling supplement (next to echinacea) on the health-food market. In 1995, this country imported more than 5.3 million kg of dehydrated garlic valued at about $2.9 million and exported nearly 3.6 million kg of dehydrated garlic worth about $8.5 million. Fresh garlic sales in the United States top $80 million a year, according to the most recent figures available.

Garlic (Allium sativum) is not known in the wild. In fact, garlic is intertwined with human experience. Humans have cultivated it for at least 5000 years, beginning perhaps in the Asian steppes; it was later grown in China, India, the Middle East, and Europe. The Greek histor­ian Herodotus (484-425 b.c.) noted that the quantity of garlic consumed by laborers was inscribed on an Egyptian pyramid. The Roman physician and naturalist Pliny the Elder (a.d. 23-79) wrote that garlic has “powerful properties, and is of great benefit against changes of water and of residence.” He recommended it to treat asthma, suppress coughs, and expel intestinal parasites.

For centuries, the Chinese have used garlic as a folk medicine to treat fevers and dysentery, as well as to kill intestinal parasites. In 1858, Louis Pasteur was the first to recognize garlic’s antibacterial effects. As much as any other plant, garlic fits Webster’s definition of an herb: a plant valued for its savory, aromatic, or medicinal qualities.

Complex Chemistry

Whether for its flavor or its health benefits, garlic’s appeal boils down to its explosive array of sulfur compounds, chiefly allicin. Allicin is not present in the whole, uncrushed or uncut bulb; however, slicing or crushing a clove releases the compound alliin and an enzyme, allinase. Together, they react to form allicin–the main sulfur compound associated with garlic’s health benefits–and hundreds of other compounds.

Cancer Prevention

Garlic’s well-documented health benefits are nearly as numerous as its chemical compounds. It has been shown to lower cholesterol and triglycerides in the blood, lower blood pressure, thin the blood (much like aspirin), inhibit the growth of microorganisms, stimulate the immune system, and protect against free radicals. At least nine studies of populations that consume a good deal of garlic have shown that cancers, especially those of the gastrointestinal tract, are significantly reduced when garlic is consumed regularly. The old adage about the apple could be recast to “a clove of garlic a day keeps the doctor away.”

Indeed, a clove a day may be just what the doctor ordered. According to the 1988 German therapeutic monograph on garlic, the daily recommended dose is equivalent to 4 g of fresh garlic cloves, or about one medium-sized clove. Recent clinical studies indicate that a daily dose of 600 to 900 mg of garlic powder containing 3.6 to 5.4 mg of allicin can significantly lower cholesterol and other blood lipid levels.

H. D. Reuter, a medicinal plant researcher from Cologne, Germany, recently analyzed twenty-eight clinical studies of garlic. He evaluated them based on their design and purpose, number of patients treated, length of treatment, types of garlic consumed, and dosages. Treatment lasted from several weeks to several months. Studies included healthy patients as well as those with high cholesterol, high blood pressure, coronary heart disease, and other conditions. Researchers measured decreases in total cholesterol, increases in high-density lipoproteins (HDL or “good” cholesterol), inhibition of low-density lipoproteins (LDL or “bad” cholesterol), and decreases in triglycerides. Participants treated with garlic averaged a 10.3 percent decrease in cholesterol levels and a 14.3 percent decrease in triglycerides.

Whether for its flavor or its health benefits, garlic’s appeal boils down to its explosive array of sulfur compounds, chiefly allicin.

Garlic can also help reduce the accumulation of blood fat on the cell walls of arteries and the resulting buildup of plaque. As the blood flow is slowed through the narrowed vessel, the platelets tend to congregate, which may result in clotting and a health emergency. Garlic helps correct this by thinning the blood and reducing the stickiness of the platelets, allowing them to move more freely.

Garlic apparently lowers blood pressure by dilating blood vessels. In one study, the blood pressure of healthy volunteers dropped six hours after they took garlic, but that of those who took a placebo did not drop. In eight studies, those individuals with normal blood pressure experienced little benefit from garlic after one to six months, while patients in the initial stages of high blood pressure showed the greatest response.

Garlic’s Potential

Although garlic use produces occasional side effects such as heartburn, flatulence, and, rarely, allergic reactions, its benefits are worth exploring. In Germany, therapeutic use of garlic is allowed in the treatment of high blood-lipid levels and as a preventative for age-related changes to the vascular system.

So eat garlic, or take it as a dietary supplement. The health benefits of garlic are better understood than they were ten years ago and are backed by more than 2500 creditable scientific studies. If your food should be your medicine, then garlic should be part of your diet.


• Foster, S. Garlic. Botanical Series, No. 311. Austin, Texas: American Botanical Council, 1991.
• Koch, H. P., and L. D. Lawson (eds.). Garlic–The Science and Therapeutic Application of Allium sativum L. and Related Species. 2nd ed. Baltimore: Williams & Wilkins, 1995.
• Reuter, H. D. Phytomedicine 1995, 2(1): 73-91.

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