Garlic (Allium sativum)

Description Garlic is the fresh bulb of Allium sativum, which is related to the lily family (Liliaceae). Known for its pungent odour, garlic has been used as both a food and a medicine in many cultures for thousands of years.

Construction workers who built the Egyptian pyramids were supposedly given huge rations of garlic to sustain their resistance against fevers2.

Function/ Used for Garlic is thought to have antibacterial properties. Modern research has focused on exploiting its potential to reduce the risk of heart disease which may be as a result of its antiplatelet effect and anti-oxidant properties. Garlic also has antimicrobial properties.

To get the full benefits of fresh garlic, it should be eaten raw. Alliin, a substance present in fresh garlic, is converted into allicin, an important active ingredient, when the garlic bulb is crushed.

Intake N/A
As a supplement Garlic supplements come in many forms, including capsules, tablets, softgels and those made from garlic powder. Some are deodorised, and others have an enteric coating to prevent ‘garlic breath’.

Dosage range2 is: 2-5g fresh garlic daily (or 1-2 cloves); 0.4-1.2g dried powder daily; 2-5mg garlic oil daily.

Some supplements may be standardised for allicin potential. One clove of garlic is roughly equivalent to 4000mcg allicin potential. However, allicin is now known not to be the only important active ingredient in garlic3.

Found in (dietary sources) N/A
Deficiency N/A
Precautions and contraindications Individuals with hypersensitivity to garlic should avoid it.

Individuals with bleeding abnormalities should avoid doses greater than usual dietary intake.1,2

Use in pregnancy and breastfeeding Garlic is not recommended in doses greater than usual dietary intake, during pregnancy and breastfeeding.2
Interactions e.g. with other medications People who are taking drugs to prevent blood clots (anticoagulants, antiplatelets or aspirin) or to reduce high blood pressure (anti- hypertensives) should consult their doctor before taking as garlic may intensify the effects of these drugs.1, 2
Adverse effects Some people develop indigestion when taking high doses of garlic.

Hypersensitivity reactions such as contact dermatitis and asthma have also been reported occasionally3.

References 1.   Mills, S. & Bone, K. Principles and practice of phytotherapy. Churchill Livingstone, 2000.

2.   Braun & Cohen. Herbs and Natural Supplements: An evidence-based guide. Churchill Livingstone, 2005.

3. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001.