The story of garlic's role in human history could fill a book, as indeed it has, many times. Its species name, sativum , means cultivated, indicating that garlic does not grow in the wild. So fond have humans been of this herb that garlic can be found almost everywhere in the world, from Polynesia to Siberia.
From Roman antiquity through World War I, garlic poultices were used to prevent wound infections. The famous microbiologist Louis Pasteur performed some of the original work showing that garlic could kill bacteria. In 1916, the British government issued a general plea for the public to supply it with garlic in order to meet wartime needs. Garlic was called Russian penicillin during World War II because, after running out of antibiotics, the Russian government turned to this ancient treatment for its soldiers.
After World War II, Sandoz Pharmaceuticals manufactured a garlic compound for intestinal spasms, and the Van Patten Company produced another for lowering blood pressure.
What Is Garlic Used for Today?
Garlic is widely used as an all-around treatment for preventing or slowing the progression of atherosclerosis
Garlic has a long folkloric history as a treatment for colds and is commonly stated to strengthen the immune system. However, up until 2001, there was no supporting evidence for this use. Since then, however, evidence including a well-designed
When applied topically, garlic can kill fungi,
Traditionally, garlic was often combined with the herb mullein in oil products designed to reduce the pain of middle ear infections (
Based on extremely weak evidence, garlic has been proposed as a treatment for problems related to the yeast
, such as
What Is the Scientific Evidence for Garlic?
Garlic preparations have been found to slow hardening of the arteries in animal studies.
In a double-blind,
Heart Attack Prevention
In one study, 432 people who had suffered a
A number of studies published in the 1980s and early 1990s found evidence that garlic preparations can reduce
Hypertension (High Blood Pressure)
Numerous studies have found weak evidence that garlic lowers blood pressure slightly, perhaps in the neighborhood of 5% to 10% more than placebo.
One study followed 47 subjects with an average starting blood pressure of 171/101.
The herb garlic has a long history of use for treating or preventing
The results showed that participants receiving garlic were almost two-thirds less likely to catch cold than those receiving placebo. Furthermore, participants who did catch cold recovered about one day faster in the garlic group as compared to the placebo group.
A study performed in Russia also reported benefits.
Thus, regular use of garlic might help prevent colds. However, there is no evidence as yet that if you take garlic at the onset of a cold you will recover more quickly.
A 20-week, double-blind, placebo-controlled crossover trial followed 80 Swedish soldiers and measured the number of
However, another study failed to find one-time use of garlic helpful for repelling mosquitoes.
Evidence from observational studies suggests that garlic may help
The interpretations of studies like this one are always a bit controversial. For example, it's possible that the women who ate a lot of garlic also made other healthful lifestyle choices. While researchers looked at this possibility very carefully and concluded that garlic was a common factor, it is not clear that they are right. What is really needed to settle the question is an intervention trial, where some people are given garlic and others are given a placebo. However, none has yet been performed that evaluated garlic for cancer prevention.
There is no question that raw garlic can kill a wide variety of microorganisms by direct contact, including fungi, bacteria, viruses, and protozoa.
Oral garlic could theoretically offer benefits against organisms in the stomach or intestines because it can come into direct contact with them. However, there is only the scantiest evidence as yet that it works for any specific infection of this type.
A typical dosage of garlic is 900 mg daily of a garlic powder extract standardized to contain 1.3% alliin, providing about 12,000 mcg of alliin daily, or 4-5 mg of “allicin potential.” Alliin-free aged garlic is taken at a dose of 1 to 7.2 g daily.
Alliin is a relatively odorless substance found in garlic. When garlic is crushed or cut, an enzyme called allinase is brought in contact with alliin, turning it into allicin. Allicin is responsible for much of the typical odor of garlic. It is very active chemically and probably helps the garlic bulb defend itself from attack by insects and other threats. However, allicin is unstable, and soon breaks down into a variety of other substances. When garlic is ground up and encapsulated, the effect is similar to cutting the bulb: Alliin contacts allinase, yielding allicin, which then breaks down. Unless something is done to prevent this process, garlic powder won't have any alliin or allicin left by the time it is purchased.
Some garlic producers believe that alliin and allicin are not essential for garlic's effectiveness and do not worry about this. Aged garlic, for example, has very little of either compound. But other manufacturers believe that allicin is the primary active ingredient in garlic. Because allicin is an unstable chemical, these manufacturers are faced with a challenge.
One solution might be to chemically stabilize allicin so that it doesn’t break down. However, allicin has a strong garlic smell, and a relatively odorless product is preferable. Many manufacturers of garlic powder products seek to stabilize the alliin in the product, and to do so in such a way that the alliin converts to allicin after it is consumed. How well their methods work remain a matter of controversy.
Note : Do not confuse essential oil of garlic with garlic oils. The term "garlic oil" refers to garlic extracted by means of oil. Garlic essential oil is the pure oily component of the herb, and, like other essential oils
As a commonly used food, garlic is on the FDA's GRAS (generally recognized as safe) list. Rats have been fed gigantic doses of aged garlic (2,000 mg per kilogram body weight) for 6 months without any signs of negative effects. 87
The only common side effect of garlic is unpleasant breath odor. Even "odorless garlic" produces an offensive smell in up to 50% of those who use it.
Other side effects occur only rarely. For example, a study that followed 1,997 people who were given a normal dose of deodorized garlic daily over a 16-week period showed a 6% incidence of nausea, a 1.3% incidence of dizziness on standing (perhaps a sign of low blood pressure), and a 1.1% incidence of allergic reactions.
When raw garlic is taken in excessive doses, it can cause numerous symptoms, such as stomach upset, heartburn, nausea, vomiting, diarrhea, flatulence, facial flushing, rapid pulse, and insomnia.
Topical garlic can cause skin irritation, blistering, and even third-degree burns, so be very careful about applying garlic directly to the skin.
Since garlic might "thin" the blood, it is probably imprudent to take garlic pills immediately prior to or after surgery or labor and delivery, because of the risk of excessive bleeding.
Garlic may also combine poorly with certain HIV medications. Two people with
Garlic is presumed to be safe for pregnant women (except just before and immediately after delivery) and nursing mothers, although this has not been proven.
Interactions You Should Know About
If you are taking:
- Blood-thinning drugs such as warfarin
9. Superko HR, Krauss RM. Garlic powder, effect on plasma lipids, postprandial lipemia, low-density lipoprotein particle size, high-density lipoprotein subclass distribution and lipoprotein (a). J Am Coll Cardiol. 2000;35:321-326.
22. Mader FH. Treatment of hyperlipidaemia with garlic-powder tablets. Evidence from the German Association of General Practitioners' multicentric placebo-controlled double-blind study. Arzneimittelforschung. 1990;40:1111-1116.
23. Steiner M, Khan AH, Holbert D, et al. A double-blind crossover study in moderately hypercholesterolemic men that compared the effect of aged garlic extract and placebo administration on blood lipids. Am J Clin Nutr. 1996;64:866-870.
28. Bordia A. Garlic and coronary heart disease. The effects of garlic extract therapy over three years on the reinfarction and mortality rate [translated from German]. Dtsch Apoth Ztg . 1989;129(suppl 15):16-17.
41. Hughes BG, Lawson LD. Antimicrobial effects of Allium sativum L. (garlic), Alliumampeloprasum L. (elephant garlic), and Allium cepa L. (onion), garlic compounds and commercial garlic supplement products. Phytother Res . 1991;5:154-158.
52. Bordia A. Garlic and coronary heart disease. The effects of garlic extract therapy over three years on the reinfarction and mortality rate [translated from German]. Dtsch Apoth Ztg . 1989;129(suppl 15):16-17.
55. Mader FH. Treatment of hyperlipidaemia with garlic-powder tablets. Evidence from the German Association of General Practitioners' multicentric placebo-controlled double-blind study. Arzneimittelforschung . 1990;40:1111-1116.
56. Steiner M, Khan AH, Holbert D, et al. A double-blind crossover study in moderately hypercholesterolemic men that compared the effect of aged garlic extract and placebo administration on blood lipids. Am J Clin Nutr . 1996;64:866-870.
60. Superko HR, Krauss RM. Garlic powder, effect on plasma lipids, postprandial lipemia, low-density lipoprotein particle size, high-density lipoprotein subclass distribution and lipoprotein (a). J Am Coll Cardiol. 2000;35:321-326.
80. Hughes BG, Lawson LD. Antimicrobial effects of Allium sativum L. (garlic), Allium ampeloprasum L. (elephant garlic), and Allium cepa L. (onion), garlic compounds and commercial garlic supplement products. Phytother Res. 1991;5:154-158.
81. Ledezma E, Lopez, JC, Marin P, et al. Ajoene in the topical short-term treatment of tinea cruris and tinea corporis in humans. Randomized comparative study with terbinafine. Arzneimittelforschung. 1999;49:544-547.
99. Turner B, Molgaard C, Marckmann P, et al. Effect of garlic ( Allium sativum ) powder tablets on serum lipids, blood pressure and arterial stiffness in normo-lipidaemic volunteers: a randomised, double-blind, placebo-controlled trial. Br J Nutr . 2004;92:701-706.
104. Turner B, Molgaard C, Marckmann P, et al. Effect of garlic ( Allium sativum ) powder tablets on serum lipids, blood pressure and arterial stiffness in normo-lipidaemic volunteers: a randomised, double-blind, placebo-controlled trial. Br J Nutr . 2004;92:701-706.
111. Gardner CD, Lawson LD, Block E, et al. Effect of raw garlic vs commercial garlic supplements on plasma lipid concentrations in adults with moderate hypercholesterolemia: a randomized clinical trial. Arch Intern Med . 2007;167:346-53.
113. Sobenin IA, Nedosugova LV, Filatova LV, et al. Metabolic effects of time-released garlic powder tablets in type 2 diabetes mellitus: the results of double-blinded placebo-controlled study. Acta Diabetol. 2007 Sep 6. [Epub ahead of print]
Last reviewed September 2009 by EBSCO CAM Review Board
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