Garlic

Garlic, botanically known as Allium Sativum, is used for reducing high blood pressure, preventing age-related vascular changes, reducing reinfarction and mortality post-MI, decreasing LDL (bad) and VLDL cholesterol, and increasing HDL (good) cholesterol for coronary heart disease. Garlic is also used in Chinese medicine for diarrhea, amoebic and bacterial dysentery, tuberculosis, bloody urine, diphtheria, whooping cough, scalp ringworm, hypersensitive teeth and vaginal trichomoniasis.

Traditionally, garlic has had many other uses as well, including the treatment of colds and flu, fever, cough, headache, stomach ache, sinus congestion, athlete’s foot, gout, rheumatism, hemorrhoids, asthma, bronchitis, shortness of breath, arteriosclerosis, low blood pressure, hypoglycemia, hyperglycemia, cancer, old ulcers, snakebites and as an aphrodisiac. In foods and beverages, garlic and its components are used for flavoring.

Effectiveness

The bulb and clove are the applicable parts of garlic. Garlic has proven effects that include antibacterial, antihelmintic (worms), antimycotic (fungal), antiviral, antispasmodic, diaphoretic, expectorant, fibrinolytic, hypotensive, promoting leukocytosis, lipid-lowering (total serum cholesterol, LDL cholesterol and triglycerides) and inhibiting platelet aggregation.

Possible Mechanism of Action and Active Ingredients

An odorless amino acid, alliin, is contained in intact garlic cells. When the intact cells are broken, alliin comes into contact with an enzyme called allinase and produces an unstable and odiferous compound called allicin (antibacterial). Further conversion of allicin yields the components E-ajoene and Z-ajoene (antithrombotic). Another constituent, allylpropyl disulfide, can reduce blood sugar while increasing insulin.

Safety

Typically, garlic is taken orally as a component of food or as a dietary supplement. This would be the equivalent of 1 clove fresh garlic taken 1-2 times daily. Garlic is safe in adults when ingested in amounts commonly found in foods and when used orally and appropriately in medicinal amounts. In larger amounts and topically, it is possibly unsafe. In children, large amounts taken orally can be dangerous or even fatal. There is insufficient reliable information available regarding topical use in children or in pregnancy and lactation. During pregnancy, when used in amounts typically found in foods, it is likely safe. However, larger amounts might predispose the onset of menstruation or uterine contractions. In lactation, it is contraindicated in amounts greater than is typically found in foods.

Adverse Reactions

Garlic has dose-related effects when taken orally that include breath odor, mouth and gastrointestinal burning or irritation, heartburn, flatulence, nausea, vomiting and diarrhea. It can produce changes in intestinal flora. There is one report of spinal epidural hematoma and platelet dysfunction with ingestion of fresh garlic and one report of post-operative bleeding and prolonged bleeding with high dietary garlic consumption. Topically, exposure can result in contact dermatitis and blistering.

Possible Interactions with Herbs and Other Dietary Supplements

EPA (Eicosapentanoic acid) in fish oil, when taken concomitantly with garlic, can enhance antithrombotic effects. The concomitant use of herbs that affect platelet aggregation and could theoretically increase the risk of bleeding in some people include angelica, anise, arnica, asafetida, bog bean, boldo, capsicum, celery, chamomile, clove, danshen, fenugreek, feverfew, garlic, ginger, ginkgo, ginseng (Panax), horse chestnut, horseradish, licorice, meadowsweet, prickly ash, onion, papain, passionflower, poplar, quassia, red clover, turmeric, wild carrot, wild lettuce, willow and others.

Possible Interactions with Drugs

ANTICOAGULANT DRUGS – can enhance the effects of Coumadin (warfarin)
ANTIPLATELET DRUGS – concomitant use may increase risk of bleeding with these drugs
HYPOGLYCEMIC DRUGS – concomitant use may increase the effects and adverse effects of these drugs
INSULIN – insulin dosage adjustments may be necessary

Possible Interactions with Lab Tests
BLOOD GLUCOSE – can lower blood glucose levels resulting in lower test results
BLOOD INSULIN – can increase blood insulin levels resulting in higher test results
INTERNATIONAL NORMALIZATION RATIO (INR) – there are two cases of increased INR associated with concomitant use of garlic and warfarin

Use garlic with caution in bleeding disorders, diabetes and infectious or inflammatory gastrointestinal conditions.

Note: The effectiveness of garlic dietary supplements is determined by their ability to yield allicin (which leads to the production of other active principles). To be effective, dried garlic preparations should be enterically coated to protect the constituents from stomach acid. Some products do not generate the amount of allicin equivalent to one clove of fresh garlic or contain no active compounds at all.

Resources

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