Natural Products

Garlic

Allium sativum

Efficacy

• Indications with proven efficacy:
  None
• Indications with possible, but poorly documented efficacy - the use of this product cannot be recommended:
  Athlete's foot (topically)
  Age-related vascular changes and artherosclerosis
  Hyperlipidemia (adjunct)
  Hypertension
• Also used for these other indications, but with no proof of efficacy:
  Antibacterial and antifungal
  Cold and flu (symptoms)
  Fever
  Intestinal worms
  To prevent some cancers (colon, stomach, prostate)
  To prevent the formation of blood clots
  To reduce hyperglycemia

Security

• Risk of Drug Interactions: Moderate
• Adverse Effects: Not Frequent

What is it?

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. The bulb is the most interesting part of the plant. Allicin is a sulphur 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.

Warning

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) or homeopathic medicine number (DIN-HM) 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 plants content varies 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 http://www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.

Does it work?

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:
  Tablets, extracts, oil and fresh garlic are used. Someone would need to ingest about one to two cloves (4 to 8 grams) of fresh garlic daily, 200 to 400 mg standardized extract (allicine 1.3%) 3 times daily or aged garlic 600 to 7200 mg daily, to observe a significant effect.
  
• Tinea Pedis (athlete's foot):
  Cream or gel with ajoene (0,4 to 1%).

There is insufficient reliable information to conclude that garlic is effective in any other indication. For example, as an antibacterial agent, garlic's activity against certain bacteria is about 1% of penicillin's activity. Its antibacterial activity is thus very weak.

Is it safe?

• Garlic is not associated with any severe toxicity. In some cases, people may report gastro-intestinal upset: heartburn, nausea, flatulence, diarrhea. 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.
• 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.
• Topical application should be avoided since some individuals develop contact dermatitis.
• Garlic apparently interacts with oral anticoagulants, such as CoumadinTM, and increase the effects of antiplatelet agents. Bleeding risks may be increased. Due to an increased bleeding risk, important garlic consumption should be avoid before and after surgery. Garlic is also thought to increase the effect of hypoglycemic agents, including insulin. Before taking garlic, check with your pharmacist to make sure that there are no interactions with your regular medication.

Clinical Notes

• 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.

References

1. Blumethal M et al. The Complete German Commission E monographs, 1998
2. Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2007
3. Lininger S. et Al. The Natural Pharmacy, Prima Health, 1998
4. Pierce Andrea, Practical Guide to Natural Medicines, 1999
5. Passeportsanté.net. Ail. http://www.passeportsante.net
6. Barnes J. et Al. Herbal Medicines, 2nd edition, Pharmaceutical Press, 2002
7. Herbal Companion to AHFS DI, American Society of Health-System Pharmacists, 2001
8. Taylor J. CE: Phytomedicinals: Uses, precautions, and drug interactions. Drug Topics 2003;1:79
9. Barnes J. et Al. Herbal Interactions, The Pharmaceutical Journal 2003; volume 270