(Last edited: Thursday, 24 September 2015, 11:02 AM)
Also Known As:
Aged Garlic Extract, Ail, Ajo, Allii Sativi Bulbus, Allium.
Family: Alliaceae or Liliaceae.
Garlic is used for hypertension, hyperlipidemia, coronary heart disease, age-related vascular changes and atherosclerosis, myocardial infarction, earaches, chronic fatigue syndrome, and menstrual disorders. Garlic is also used to treat Helicobacter pylori infection. Other uses include treatment of allergic rhinitis, traveller's diarrhoea, colds, and flu. It is also used for immune system stimulation, and prevention and treatment of bacterial and fungal infections. Other uses include treatment of fever, coughs, headache, stomachache,sinus congestion, athlete's foot, gout, rheumatism, bronchitis, low blood pressure. It is also used as an aphrodisiac, for enhancing circulation, fighting stress and fatigue.
Topically, garlic oil is used for fungal infections.
Intravaginally, garlic is used alone or in combination with yogurt for vaginitis.
In foods and beverages, fresh garlic, garlic powder, and garlic oil are used as flavour components.
No concerns regarding safety when used orally and appropriately. Garlic has been used safely in clinical studies lasting up to 7 years without reports of significant toxicity.63,64,65,66,67,68,69,70,71,72,73,74,75,76
Children: Likely to be safe when used orally and appropriately, short-term. In one study, garlic extract 300 mg three times daily had side effects comparable to placebo when used in children ages 8-18 years for eight weeks.77 There are no case reports available of significant adverse events or mortality in children associated with ingestion of garlic.
Pregnancy and Lactation: No concerns regarding safety when used orally in amounts commonly found in foods.78
Atherosclerosis. Taking low doses of garlic powder orally, 300 mg per day, seems to lessen age-related decreases in aortic elasticity.
Higher doses of 900 mg per day seem to slow development of atherosclerosis in both aortic and
femoral arteries when used over a four-year period.79,72,73
Colorectal cancer. Several population studies suggest that increased dietary garlic consumption can decrease risk of developing colorectal cancer.84,80,81,82 However, garlic supplements do not seem to offer this benefit.83
Gastric cancer. Some evidence from population studies suggests that increasing dietary garlic consumption is associated with a decreased risk of developing stomach cancer.84,85,86
High Blood Pressure. Some clinical research shows that taking garlic orally can modestly reduce blood pressure in patients with hypertension and in people with normal blood pressure.87,88,89,63,75,90
In one analysis, garlic reduced systolic blood pressure by about 8% and diastolic blood pressure by about 7%, compared to placebo in patients with hypertension.90
Ringworm. Applying a garlic gel containing 0.6% ajoene seems to be as effective as terbinafine 1% cream.91
Tinea pedis (athlete's foot). Applying a garlic gel containing 1% ajoene seems to be more effective than 0.6% ajoene gel, and seems to beas effective as 1% terbinafine (Lamisil) for tinea pedis infections. Sixty days after completing one week of treatment 1% ajoene produces 100% mycologic cure, 0.6 % produces 72% mycologic cure, and 1% terbinafine produces 94% mycologic cure.92,93
INSUFFICIENT SCIENTIFIC EVIDENCE to RATE
Common cold. Preliminary clinical research suggests garlic might reduce the frequency and number of colds when taken prophylactically.94
Mechanism of Action:
The applicable part of garlic is the bulb. Garlic is mostly used for its antihyperlipidemic, antihypertensive, and antifungal effects. However, it is also reported to have antibacterial, antiparasite (worms), antiviral, antispasmodic, promotes sweating, expectorant, immunostimulant, and antithrombotic effects.95,96,97,98,99 Many of the pharmacological effects of garlic are attributed to the allicin, ajoene, and other organosulfur constituents such as S-allyl-L-cysteine.98
It's thought that the effectiveness of garlic products might to be determined by their ability to yield allicin, which in turn triggers production of other active constituents.100
Intact garlic cells in fresh garlic contain the odorless amino acid, alliin. When intact cells are broken, alliin comes intocontact with the enzyme alliinase in garlic, producing allicin, an unstable, odiferous compound.100,97 Fresh garlic contains approximately 1% alliin. One milligram of alliin is converted to 0.458mg allicin.101 Further conversion yields ajoene. The amount of allicin in garlic preparations is dependent upon the method of preparation. Processes that involve maceration of the garlic clove increase the activity of allicinase. Freeze-dried garlic may contain little or no allicin. To improve effectiveness, garlic preparations may be coated to protect the active constituents from degeneration
by stomach acid.102 Heat and steam distillation used to produce garlic oil from crushed garlic converts allicin to allyl sulfides which are also thought to have biological activity.100
Garlic is aged to reduce the content of other sulfur compounds and the odor commonly associated with garlic. The process to produce odorless aged garlic extract reduces the alliin content to only 3% of what is typically contained in fresh garlic.101
Aged garlic extract is usually standardized to S-allyl-L-cysteine, another major organosulfur constituent in garlic.95
In patients with hyperlipidemia, garlic might lower cholesterol levels by acting as a HMG-CoA reductase inhibitor (statin).103,104 There is some evidence the constituent S-allyl-L-cysteine may be a potent inhibitor of hepatic cholesterol synthesis.105
For age-related vascular changes and atherosclerosis, garlic is thought to be beneficial and protect vascular endothelial cells from injury by reducing oxidative stress, inhibiting low-density lipoprotein (LDL) oxidation, and through antithrombotic effects.106,107,98,108 There is evidence that LDL oxidation may be inhibited by the constituents S-allyl cysteine, S-allyl mercaptocysteine, alliin, allixin, and by N-acetyl-S-allyl cysteine, a metabolite of S-allyl cysteine.108 Garlic appears to prevent endothelial cell depletion of glutathione, which may be responsible for its antioxidant effects.106
Garlic powder and aged garlic preparations have been shown to have antiplatelet properties in both patients with cardiovascular disease and in healthy volunteers.109,95,96,110,111
Garlic has been found to have antithrombotic properties and can increase fibrinolytic activity,decrease platelet aggregation and adhesion, increase the prothrombin time (PT), and inhibit metabolic enzymes in platelets responsible for the conversion of arachidonic acid into prostaglandins and other products.95,96,98,112 Raw garlic seems to have more potent antiplatelet properties
than cooked garlic.113,114,115 Crushing garlic before cooking might prevent some of the loss of antiplatelet activity.115 Garlic oil does not appear to affect platelet aggregation.116
Garlic is thought to reduce blood pressure by causing smooth muscle relaxation and vasodilation by activating production of endothelium-derived relaxation factor (EDRF, nitric oxide).117
Garlic also seems to have humoral and cellular immunostimulant activity.
The constituents allicin and ajoene are thought to beresponsible for garlic's antifungal activity against ringworm infections.98,93 Fresh garlic, but not aged garlic, has shown activity against Escherichia coli, methicillin-resistant Staph aureus, salmonella enteritidis, and Candida albicans in the laboratory; it has been suggested as a food additive to prevent food poisoning.
118 Preliminary evidence suggests that garlic compounds might have activity against viruses
Orally, garlic has dose-relatedadverse effects, which most commonly include breath and body odour, mouth and gastrointestinal burning or irritation, heartburn, flatulence, nausea, vomiting, and diarrhoea. These effects can be more pronounced with consumption of raw garlic or in patients unaccustomed to eating garlic.78,65,101 Oral use of garlic can also cause changes to the intestinalflora,78 ,101 which might result in gastrointestinal upset. Garlic's effect on platelet function is well known, and can possibly increase the risk of bleeding.
Interactions with Herbs & Supplements:
Anticoagulatn/Antiplatelet Herbs and Supplements: Concomitant use of herbs that have constituents that might affect platelet aggregation could theoretically increase the risk of bleeding in some people. These herbs include angelica, clove, danshen, ginger, ginkgo, red clover, turmeric, vitamin E, willow, and others.109,95,96,110,111
Interactions with Drugs:
Anticoagulatn/Antiplatelet Drugs including Warfarin.
Cyclosporine: (transplant patients).
Isoniazid (TB treatment).
Saquinavir (HIV treatment).
Interactions with Foods:
Interactions with Lab Tests:
Blood Pressure: Garlic can lower blood pressure and blood pressure readings.87,88,89
Cholesterol: Garlic can lower serum cholesterol concentrations and test results.87,88,89
Interactions with Diseases or Conditions:
Bleeding Disorders:95,96,98 Contraindicated.
Gastrointestinal (GI) Irritation: Garlic can irritate the GI tract; dose related, resolves on stopping garlic.
Surgery: discontinue one to two weeks prior to scheduled surgery.121,101,122
Dr Clare’s Blends: 1gm/day
Specific References: GARLIC
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87. Silagy CA, Neil HA. A meta-analysis of the effect of garlic on blood pressure. J Hypertension 1994;12:463-8.
88. McMahon FG, Vargas R. Can garlic lower blood pressure? A pilot study. Pharmacotherapy 1993;13:406-7.
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