- Indications with possible efficacy:
- Indications with possible, but poorly documented efficacy:
Athlete's foot (topically)
Age-related vascular changes and artherosclerosis
Colorectal or stomach cancer
- Indications with no proof of efficacy:
Antibacterial and antifungal
Benign prostatic hyperplasia
Cold and flu (symptoms)
To improve immune system
To prevent the formation of blood clots
To reduce hyperglycemia
- Risk of Drug Interactions: Moderate
- Adverse Effects: Not Frequent
Part of the plant used: bulb
For millennia, man has used garlic extensively in cooking. Across the ages, garlic has been used, rightly or wrongly, to treat a multitude of diseases. Allicin is a sulfur compound produced when a garlic bulb is chewed or crushed; it is responsible for garlic's characteristic odor and appears to be the plant's active principle, which means that "odorless" garlic would be ineffective.
Direction of use
There is no evidence that garlic is effective in any indication. However it is used to treat certain medical conditions in which it may be of some benefit:
- Hyperlipidemia, hypertension and age-related vascular changes and atherosclerosis:
Fresh garlic: one to two cloves (2 to 8 grams) per day (contains 1% alliine)
Dried garlic powder: 0.4 to 1.2 grams per day
Garlic extract: 300 to 1000 mg divided in 3 doses (contains approximately 1.3% of alliine)
Other preparations: must contain 4 to 12 mg of alliine or 2 to 5 mg of allicine
- Side effects
Garlic is not associated with any severe toxicity. In some cases, people may report gastro-intestinal upset: heartburn, nausea, flatulence, diarrhea. Taking it while eating must help to prevent those side effects. Those who eat raw garlic or are unaccustomed to eating garlic appear more at risk for these malaises. The breath and skin can get the typical garlic odor which comes from respiration itself and sweat. The odor can be masked but not completely eliminated.
Bleeding risks may be increased. Due to this, important garlic consumption should be avoid if bleeding or coagulation disorders.
Garlic apparently interacts with oral anticoagulants, such as Coumadin, and increase the effects of antiplatelet agents. Bleeding risks may be increased. Garlic is also thought to increase the effect of hypoglycemic agents, including insulin. Garlic can also interact with some drugs used for HIV treatment. Before taking garlic, check with your pharmacist to make sure that there are no interactions with your regular medication.
- Pregnancy and lactation
Garlic appears safe during pregnancy in amounts typically found in foods. However, pregnant women should not take garlic supplements, since they may enable the onset of menstruation or cause uterine contractions.
- According to a German study, only about 25% of the garlic products commercially available contain enough allicin to meet the levels found in fresh garlic.
- In addition, some "odorless" garlic products contain no trace of allicin.
In 2004, Canada adopted new regulations that control the manufacturing, packaging, labeling and importing of natural health products. The new regulations also include an adverse reaction reporting system. Products that conform to the regulation's criteria are identified with a natural product number (NPN) and can be legally sold in Canada. This number indicates that the product meets specific criteria for safety and purity, not that it is effective for any indication.
Medicinal plant contents vary naturally from plant to plant - just as fruits from the same package may vary in taste and texture. There is no standard to measure the active content of each plant. Thus, efficacy of natural products should be expected to vary from brand to brand as well as from bottle to bottle of the same brand.
For more information about the Natural Health Products Regulations, or to check if a product has been assessed, visit the Health Canada website at www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.
- Blumethal M et al. The Complete German Commission E monographs, 1998
- Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2010
- Lininger S. et Al. The Natural Pharmacy, Prima Health, 1998
- Pierce Andrea, Practical Guide to Natural Medicines, 1999
- Passeportsanté.net. Ail. www.passeportsante.net
- Barnes J. et Al. Herbal Medicines, 2nd edition, Pharmaceutical Press, 2002
- Herbal Companion to AHFS DI, American Society of Health-System Pharmacists, 2001
- Taylor J. CE: Phytomedicinals: Uses, precautions, and drug interactions. Drug Topics 2003;1:79
- Barnes J. et Al. Herbal Interactions, The Pharmaceutical Journal 2003; volume 270
- Natural Therapeutics Pocket Guide, 2000-2001
- The Review of Natural Products, 6th Edition, 2010
- Health Canada, Natural Products Database
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.