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Important garlic facts

Garlic is a plant food that has been valued for its therapeutic effects for thousands of years. It has been used for its antibacterial and wound healing properties.

A fresh garlic clove (that has not been crushed or cut) contains an odourless sulphur compound called. When garlic is cut or crushed, another sulphur compound, allicin is released. Allicin is then broken down very quickly into other sulphur compounds that are responsible for all the health benefits of garlic.

Garlic is part of the Allium family and is closely related to the onion, chives, shallots and the leek.

  • The active component in garlic is called allicin which is activated when garlic is crushed
  • While the whole plant is beneficial, the bulb contains the most flavour and healing effects
  • Cooking garlic can break down and destroy some of the allicin therefore reducing some of garlic's therapeutic effects
  • Garlic powder may be the most effective form of supplementation due to the way it has been processed - leaving much more of the allicin available when ingested
  • Garlic has excellent (and proven) anti-bacterial, anti-viral and anti-fungal properties
  • In ancient times, people who ate garlic seemed to have more resistance to disease
  • The botanical name of garlic is allium sativum

Garlic and health

  • Heart disease - garlic prevents the blood cells required to clot blood (platelets) from sticking to each other and from sticking to artery walls, thus preventing artery blockages. Another effect of clotting prevention is protection against strokes and coronary thrombosis (blood clots within coronary artery)
  • Cholesterol - there is evidence, in numerous studies, that garlic lowers blood levels of harmful fats - triglycerides and "bad" (LDL) cholesterol, as well as raising the levels of "good" (HDL) cholesterol. Other studies have shown that garlic prevents LDL cholesterol from being oxidised, thereby preventing LDL from sticking to artery walls and causing heart problems
  • High blood pressure - garlic acts as a vasodilator, by widening the blood vessels and lowering blood pressure
  • Cancer - a study by the National Cancer Institute has shown that people that have a diet high in garlic, onions and other plants from the allium family have lower rates of stomach cancer than those that do not consume as much of these foods. Other studies have shown garlic is effective on other types of cancers
  • The immune system - garlic contains sulphur compounds which act against bacteria and prevent infection by enhancing the actions of the immune system. In various studies, garlic has been shown to be effective against the following microbes: Candida albicans, Cryptococca meningitis, Streptococcus and Staphyloccocus. The allicin in garlic blocks the enzymes that allow organisms to invade and damage body tissues

People who wish to take an acidophilus supplement should talk to a medical professional BEFORE taking it.

Garlic recommended intake

Dosage of garlic depends on the condition that is being treated. A medical doctor and/or alternative health care provider can advise on individual cases - this information is provided as a guide only:

Lifestage Age Amount (per day)
INFANTS 0-12mths Not recommended
CHILDREN 1-8yrs Not recommended
CHILDREN 9-18yrs
Seek medical advice before taking it
ADULTS 19-50yrs
1-3 tablets, 3 times a day or
fresh cloves
SENIORS 51+yrs 1-3 tablets, 3 times a day or
fresh cloves
PREGNANT   Not recommended
LACTATING   Seek medical advice before taking it


Types of garlic supplements

Garlic is only available in the one food - garlic! Garlic supplementation is available in the following ways:

  • Tablet - freeze-dried garlic powder is compressed and formed into a tablet
  • Capsule - are filled with garlic oil liquid extracts
  • Soft gel - soft gelatin capsules are filled with liquid garlic oil
  • Dried - fresh garlic is freeze-dried
  • Powder - freeze-dried garlic is crushed and made into a powder
  • Fresh bulbs - the whole bulb can be eaten raw for best effect or cooked with food

All forms of garlic supplements have an odourless variety, as garlic has a pungent aroma that remains long after it has been eaten or ingested as a supplement, especially the oil.

Some garlic supplements contain parsley oil, renowned to mask the odour of garlic.

Garlic supplementation checklist

  • For a no-odour garlic supplement, choose the odourless variety
  • Check the dosage of allicin: there should be at least 4000mcg (4g) of allicin in the supplement, which is about the same as the amount of allicin found in one clove of garlic
  • For better masking of the pungent odour of garlic, choose an odourless supplement and/or one which contains parsley oil

Garlic works best with

Overdosage, toxicity and cautions for garlic

The following gastrointestinal problems can occur for some people taking high doses of garlic supplements or even eating large amounts of fresh garlic:

  • heartburn
  • intestinal gas
  • nausea
  • diarrhoea
  • skin rashes (rare)

Enteric coated tablets may reduce the above side effects in some people.

People experiencing any types of side effects or problems with garlic supplements or even with fresh garlic are advised to reduce the dose or stop supplementation.


  • People having surgery - garlic supplements should be avoided two weeks prior to and one week after any surgery due to possible complications with bleeding. The anti-clotting properties of garlic can prolong bleeding
  • People taking warfarin - garlic may increase the risk of bleeding in people taking Warfarin
  • People taking saquinavir - garlic supplements have been shown to impede HIV/AIDS medication. Studies have shown the garlic supplements can reduce the blood levels of the medication Saquinavir, thus making the medication ineffective
  • People on certain medications - garlic may inhibit or nullify some medications, seek medical advice prior to taking garlic supplements
  • People with medical conditions - garlic's anti-clotting properties may be a problem for some people, seek medical advice prior to taking garlic supplements
  • People with stomach conditions - people with ulcers or other stomach conditions such as gastritis, should be cautious when taking garlic supplements as the garlic could cause further irritation



  • Groff J L, Gropper SS, Hunt SM, Advanced Nutrition and Human Metabolism. West Publishing, USA, 1995
  • Piscitelli S C, Burstein A H, Welden N, Gallicano K D, Falloon J. The Effect of Garlic Supplements on the Pharmacokinetics of Saquinavir, University of Chicago Press Journal of Clinical Infectious Diseases, Dec 2001
  • Bianchini F and Vainio H. Allium Vegetables and Organosulfur Compounds: Do They Help Prevent Cancer? Environmental Health Perspectives Volume 109, Number 9, September 2001
  • Garlic: Effects on Cardiovascular Risks and Disease, Protective Effects Against Cancer, and Clinical Adverse Effects. Summary, Evidence Report/Technology Assessment: Number 20. Agency for Healthcare Research and Quality (AHRQ) Publication No. 01-E022, October 2000

Last reviewed 21 April 2019