Garlic

Botanical names:

Allium sativum

Parts Used & Where Grown

Garlic has been used since time immemorial as a culinary spice and medicinal herb. Garlic has been cultivated in the Middle East for more than 5,000 years and has been an important part of Traditional Chinese Medicine. The region with the largest commercial garlic production is central California. China is also a supplier of commercial garlic. The bulb is used medicinally.

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a7_2star Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

a7_1star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

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This supplement has been used in connection with the following health conditions:

Used for	Amount	Why
Atherosclerosis	900 mg daily of a powder standardized for 0.6% allicin	Garlic has been shown to slow down the process of the arteries hardening. Aged garlic extract has been shown to prevent oxidation of LDL ("bad") cholesterol, a significant factor in atherosclerosis development.
Atherosclerosis 900 mg daily of a powder standardized for 0.6% allicin Garlic has been shown to prevent atherosclerosis in a four-year double-blind trial.¹ The preparation used, standardized for 0.6% allicin content, provided 900 mg of garlic powder per day. The people in this trial were 50 to 80 years old, and the benefits were most notable in women. This trial points to the long-term benefits of garlic to both prevent and possibly slow the progression of atherosclerosis in people at risk. Garlic has also lowered cholesterol levels in double-blind research,² though more recently, some double-blind trials have not found garlic to be effective.³ ^{, 4} ^{, 5} Some of the negative trials have flaws in their design.⁶ Nonetheless, the relationship between garlic and cholesterol-lowering is somewhat unclear.⁷ Garlic has also been shown to prevent excessive platelet adhesion (stickiness) in humans.⁸ Allicin, often considered the main active component of garlic, is not alone in this action. The constituent known as ajoene has also shown beneficial effects on platelets.⁹ Aged garlic extract, but not raw garlic, has been shown, to prevent oxidation of LDL cholesterol in humans,¹⁰ an event believed to be a significant factor in the development of atherosclerosis. Garlic and ginkgo also decrease excessive blood coagulation. Both have been shown in double-blind¹¹ and other controlled¹² trials to decrease the overactive coagulation of blood that may contribute to atherosclerosis. Numerous medicinal plants and plant compounds have demonstrated an ability to protect LDL cholesterol from being damaged by free radicals. Garlic,¹³ ginkgo,¹⁴ and guggul¹⁵ are of particular note in this regard. Garlic and ginkgo have been most convincingly shown to protect LDL cholesterol in humans. Learn More

Used for	Amount	Why
Warts	Rub cut clove onto area nightly and cover until morning, or apply oil-soluble extract twice per day	Studies have shown topically applied garlic to be effective at clearing common warts.
Warts Rub cut clove onto area nightly and cover until morning, or apply oil-soluble extract twice per day In a preliminary trial, topical application of garlic cloves was used successfully to treat warts in a group of children. A clove was cut in half each night and the flat edge of the clove was rubbed onto each of the warts, carefully cleaning the surrounding areas, so as not to spread any garlic juice. The areas were covered overnight with Band-Aids or waterproof tape and were washed in the morning. In all cases, the warts cleared completely after an average of nine weeks.¹⁶ In another study, 23 people with warts applied an oil-soluble garlic extract twice a day to the warts. Complete recovery was seen in every case after one to two weeks. A water-soluble garlic extract was less effective.¹⁷ Side effects after application of the oil-soluble extract included blistering, redness, burning, and increased pigmentation of the skin around the application area, which usually disappeared completely in one to two weeks. Zinc oxide ointment was applied to the surrounding normal skin in all cases in an attempt to prevent these side effects. Learn More

Used for	Amount	Why
Benign Prostatic Hyperplasia	1 ml aged extract per 2.2 lbs (1 kg) of body weight daily	A special garlic extract (Kastamonu Garlic) reduced prostate size and significantly improved urinary symptoms in one study.
Benign Prostatic Hyperplasia 1 ml aged extract per 2.2 lbs (1 kg) of body weight daily In many parts of Europe, herbal supplements are considered standard medical treatment for BPH. Although herbs for BPH are available without prescription, men wishing to take them should be monitored by a physician. In a preliminary study, supplementation with a special aged garlic extract (Kastamonu Garlic) in the amount of 1 ml per 2.2 pounds of body weight per day for one month resulted in a 32% reduction in the size of the prostate gland and a significant improvement in urinary symptoms.¹⁸ It is not known whether other forms of garlic would have the same effect. Learn More

Used for	Amount	Why
Breast-Feeding Support and Increased Duration of Infant Breast-Feedings	Follow label instructions	Infants have been shown in some studies to nurse longer when their mothers ate garlic. However, some infants may develop colic from garlic in breast milk.
Breast-Feeding Support and Increased Duration of Infant Breast-Feedings Follow label instructions Numerous herbs are used traditionally around the world to promote production of breast milk.¹⁹ Herbs that promote milk production and flow are known as galactagogues. Stinging nettle (Urtica dioica) enriches and increases the flow of breast milk and restores the mother’s energy following childbirth.²⁰ Vitex (Vitex agnus castus) is one of the best-recognized herbs in Europe for promoting lactation. An older German clinical trial found that 15 drops of a vitex tincture three times per day could increase the amount of milk produced by mothers with or without pregnancy complications compared with mothers given vitamin B1 or nothing. Vitex should not be taken during pregnancy.²¹ Goat’s rue (Galega officinalis) also has a history of use in Europe for supporting breast-feeding. Taking 1 teaspoon of goat’s rue tincture three times per day is considered by European practitioners to be helpful in increasing milk volume.²² Studies are as yet lacking to support the use of goat’s rue as a galactagogue. In two preliminary trials, infants have been shown to nurse longer when their mothers ate garlic than when their mothers took placebos.²³ ^{, 24} However, some infants may develop colic if they consume garlic in breast milk.

Used for	Amount	Why
Common Cold and Sore Throat	Follow label instructions to take a product containing stabilized allicin	In one study, taking garlic during the winter months reduced the occurrence and duration of colds.
Common Cold and Sore Throat Follow label instructions to take a product containing stabilized allicin In a double-blind trial, participants took one capsule per day of a placebo or a garlic supplement that contained stabilized allicin (the amount of garlic per capsule was not specified) for 12 weeks between November and February. During that time, the garlic group had 63% fewer colds and 70% fewer days ill than did the placebo group.²⁵ Learn More

Used for	Amount	Why
High Cholesterol	600 to 900 mg a day of a standardized herbal extract	Taking garlic may help lower cholesterol and prevent hardening of the arteries.
High Cholesterol 600 to 900 mg a day of a standardized herbal extract Reports on many double-blind garlic trials performed through 1998 suggested that cholesterol was lowered by an average of 9 to 12% and triglycerides by 8 to 27% over a one-to-four month period.²⁶ ^{, 27} ^{, 28} Most of these trials used 600 to 900 mg per day of garlic supplements. More recently, however, several double-blind trials have found garlic to have minimal success in lowering cholesterol and triglycerides.²⁹ ^{, 30} ^{, 31} ^{, 32} ^{, 33} One negative trial has been criticized for using a steam-distilled garlic “oil” that has no track record for this purpose,³⁴ while the others used the same standardized garlic products as the previous positive trials. Based on these findings, the use of garlic should not be considered a primary approach to lowering high cholesterol and triglycerides.³⁵Part of the confusion may result from differing effects from dissimilar garlic products. In most but not all trials, aged garlic extracts and garlic oil (both containing no allicin) have not lowered cholesterol levels in humans.³⁶ ^{, 37} Therefore, neither of these supplements can be recommended at this time for cholesterol lowering. Odor-controlled, enteric-coated tablets standardized for allicin content are available and, in some trials, appear more promising.³⁸ Doctors typically recommend 900 mg per day (providing 5,000 to 6,000 mcg of allicin), divided into two or three admininstrations. Learn More

Used for	Amount	Why
High Triglycerides	600 to 900 mg daily of a concentrate standardized for 5,000 to 6,000 mcg of allicin	Supplementing with garlic may help keep triglyceride levels in check.
High Triglycerides 600 to 900 mg daily of a concentrate standardized for 5,000 to 6,000 mcg of allicin Reports on many clinical trials of garlic performed until 1998 suggested that triglycerides were lowered by an average of 8–27% and cholesterol by 9–12% over a one- to four-month period.³⁹ ^{, 40} ^{, 41} Most of these trials used 600–900 mg per day of a garlic supplement standardized to alliin content and allicin potential. More recently, however, three double-blind clinical trials have found garlic to have minimal success in lowering triglycerides and cholesterol.⁴² ^{, 43} ^{, 44} One negative trial has been criticized for using a steam distilled garlic “oil” that has no track record for this purpose,⁴⁵ while the others used the same standardized garlic products as the previous positive clinical trials. Based on these findings, the use of garlic should not be considered a primary approach to lowering high triglycerides and cholesterol.⁴⁶ Odor-controlled, enteric-coated garlic tablets standardized for allicin content can be taken in the amount of 900 mg daily (providing 5,000–6,000 mcg of allicin), divided into two or three daily portions. Learn More

Used for	Amount	Why
Hypertension	600 to 900 mg of a daily herbal extract	Taking garlic may improve heart and blood vessel health and may help lower blood pressure.
Hypertension 600 to 900 mg of a daily herbal extract Garlic has a mild blood pressure-lowering effect, according to an analysis of ten double-blind trials.⁴⁷ All of these trials administered garlic for at least four weeks, typically using 600–900 mg of garlic extract per day. Onion—closely related to garlic—may also have a mild blood pressure-lowering effect, according to preliminary research.⁴⁸ Learn More

Used for	Amount	Why
Intermittent Claudication	400 mg of a standardized extract twice per day	In one study, people given a garlic powder extract could walk a significantly greater distance than those given a placebo.
Intermittent Claudication 400 mg of a standardized extract twice per day A standardized extract of garlic has been tested as a treatment for intermittent claudication. In a double-blind trial, the increase in walking distance was significantly greater in people receiving garlic powder extract (400 mg twice per day for 12 weeks) than in those given a placebo.⁴⁹ Learn More

Used for	Amount	Why
Athlete’s Foot	Refer to label instructions	The compound ajoene, found in garlic, is an antifungal agent that has been shown to be effective against athlete’s foot. Crushed, raw garlic applied topically may also be effective.
Athlete’s Foot The compound known as ajoene, found in garlic, is an antifungal agent. In a group of 34 people using a 0.4% ajoene cream applied once per day, 79% of them saw complete clearing of athlete’s foot after one week; the rest saw complete clearing within two weeks.⁵⁰ All participants remained cured three months later. One trial found a 1% ajoene cream to be more effective than the standard topical drug terbinafine for treating athlete’s foot.⁵¹ Ajoene cream is not yet available commercially, but topical application of crushed, raw garlic may be a potential alternative application. Learn More

Used for	Amount	Why
Chronic Candidiasis	Refer to label instructions	Garlic has been shown to have significant anti-Candida activity.
Chronic Candidiasis Garlic has demonstrated significant antifungal activity against C. albicans in both animal and test tube studies.⁵²^{, 53}^{, 54} Greater anti-Candida activity has resulted from exposing Candida to garlic, than to nystatin—the most common prescription drug used to fight Candida.⁵⁵ No clinical studies of garlic in the treatment of candidiasis have yet been conducted. However, some doctors suggest an intake equal to approximately one clove (4 grams) of fresh garlic per day; this would equal consumption of a garlic tablet that provides a total allicin potential of 4,000 to 5,000 mcg. Learn More

Used for	Amount	Why
Ear Infections	Refer to label instructions	Ear drops with mullein, St. John’s wort, and garlic in an oil or glycerin base are traditional remedies used to alleviate symptoms, particularly pain, during acute ear infections.
Ear Infections Ear drops with mullein, St. John’s wort, and garlic in an oil or glycerin base are traditional remedies used to alleviate symptoms, particularly pain, during acute ear infections. No clinical trials have investigated the effects of these herbs in people with ear infections. Moreover, oil preparations may obscure a physician’s view of the ear drum and should only be used with a healthcare professional’s directions. Learn More

Used for	Amount	Why
HIV and AIDS Support	Refer to label instructions	Garlic may help combat opportunistic infections. In one trial, an aged garlic extract reduced the number of infections and relieved diarrhea in a group of patients with AIDS.
HIV and AIDS Support Garlic may assist in combating opportunistic infections. In one trial, administration of an aged garlic extract reduced the number of infections and relieved diarrhea in a group of patients with AIDS.⁵⁶ Garlic’s active constituents have also been shown to kill HIV in the test tube, though these results have not been confirmed in human trials.⁵⁷ Learn More

Used for	Amount	Why
Infection	Refer to label instructions	Garlic is an herb that directly attack microbes.
Infection Herbs that directly attack microbes include the following: chaparral, eucalyptus, garlic, green tea, lemon balm (antiviral), lomatium, myrrh, olive leaf, onion, oregano, pau d’arco (antifungal), rosemary, sage, sandalwood, St. John’s wort, tea tree oil, thyme, and usnea. Learn More

Used for	Amount	Why
Parasites	Refer to label instructions	Garlic has been shown to kill parasites, including amoeba and hookworm, in test tubes and in animals. Other studies support the use of garlic to treat roundworm, pinworm, and hookworm.
Parasites Garlic has been demonstrated to kill parasites, including amoeba⁵⁸ and hookworm,⁵⁹ in test tubes and in animals. Older studies in humans support the use of garlic to treat roundworm, pinworm, and hookworm.⁶⁰ However, due to a lack of clinical trials, the amount of garlic needed to treat intestinal parasites in humans is not known. Learn More

Used for	Amount	Why
Peptic Ulcer	Refer to label instructions	Garlic has been reported to have anti-Helicobacter activity in test-tube studies and may be helpful for peptic ulcers.
Peptic Ulcer Garlic has been reported to have anti-Helicobacter activity in test-tube studies.⁶¹^{, 62} In a preliminary trial, garlic supplementation (300 mg in tablets three times daily for eight weeks) failed to eradicate H. pylori in participants with active infections.⁶³ In another preliminary trial, participants with active H. pylori infections added 10 sliced cloves of garlic to a meal.⁶⁴ The addition of garlic failed to inhibit the growth of the organism. Further trials using garlic extracts are needed to validate the anti-Helicobacter activity of garlic observed in test tubes. Until then, evidence to support the use of garlic for H. pylori-related peptic ulcers remains weak. Learn More

Used for	Amount	Why
Sickle Cell Anemia	Refer to label instructions	In one trial, patients with sickle cell anemia who were given folic acid plus aged garlic extract, vitamin C, and vitamin E saw significant improvement and less painful crises.
Sickle Cell Anemia In a preliminary trial, 20 patients with sickle cell anemia were given either 1 mg of folic acid per day or folic acid plus 6 grams of aged garlic extract, 6 grams of vitamin C, and 1,200 mg of vitamin E per day for six months.⁶⁵ Patients taking the combination had a significant improvement in their hematocrit (an index of anemia) and less painful crises than those taking just folic acid. Learn More

Traditional Use (May Not Be Supported by Scientific Studies)

Garlic is mentioned in the Bible and the Talmud. Hippocrates, Galen, Pliny the Elder, and Dioscorides all mention the use of garlic for many conditions, including parasites, respiratory problems, poor digestion, and low energy. Its use in China was first mentioned in A.D. 510. Louis Pasteur studied the antibacterial action of garlic in 1858.

Also indexed as:

Allium sativum,
botanicals,
garlic,
herbal dietary supplements,
herbal medicine,
herbal remedies,
herbal therapy,
herbalism,
plant Medicine

About this treatment

Botanical names:

Allium sativum

How It Works

The sulfur compound allicin, produced by crushing or chewing fresh garlic or by taking powdered garlic products with allicin potential, in turn produces other sulfur compounds: ajoene, allyl sulfides, and vinyldithiins. Aged garlic products lack allicin, but may have activity due to the presence of S-allylcysteine.

Many publications have shown that garlic supports the cardiovascular system. While earlier trials suggest it may mildly lower cholesterol and triglyceride levels in the blood, more recent trials found garlic to have minimal success in lowering cholesterol and triglycerides. Garlic also inhibits platelet stickiness (aggregation) and increases fibrinolysis, which results in a slowing of blood coagulation. It is mildly antihypertensive and has antioxidant activity.

Garlic’s cardiovascular protective effects were illustrated in a four-year clinical trial on people 50–80 years old with atherosclerosis. It was found that consumption of 900 mg of a standardized garlic supplement reduced arterial plaque formation by 5–18%. The benefits were most notable in women.

In test tube studies garlic has been found to have antibacterial, antiviral, and antifungal activity. However, these actions are less clear in humans and do not suggest that garlic is a substitute for antibiotics or antifungal medications.

Human population studies suggest that eating garlic regularly reduces the risk of esophageal, stomach, and colon cancer. This may be partly due to garlic’s ability to reduce the formation of carcinogenic compounds.

How to Use It

People who wish to consume garlic and have no aversion to its odor can chew from one to two whole cloves of raw garlic daily. For those who prefer it with less odor, enteric-coated tablets or capsules with approximately 1.3% allin are available. Clinical trials have used 600–900 mg (delivering approximately 5,000–6,000 mcg of allicin potential) per day in two or three divided amounts. Aged-garlic extracts have been studied in amounts ranging from 2.4–7.2 grams per day.

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Last Review: 05-11-2011

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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2011.

© 1995-2011 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated. This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.

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