Garlic products are made from whole fresh garlic, fresh or dried garlic cloves, garlic powder made from the dried cloves, freeze-dried garlic, or oil garlic extracts.
Not all garlic contains the same amount of active ingredients. In fact, there is a fairly wide variation in the amount of allicin and other important ingredients in both fresh garlic and commercial products. The amount present depends on where the garlic is grown as well as how the product is prepared. Some experts believe that the wide variation in the quantity of active ingredients in garlic preparations explains why there is some variability in how well the substances lower cholesterol, improve blood pressure, and fight infection in different people.
Aged garlic products are made by fermenting garlic. Fermentation may reduce the amount of active ingredients in garlic. In addition, cooking garlic at very high temperatures may destroy its active components.
It is important to carefully read the label on all garlic products. It is best to use standardized garlic products to ensure that you are getting a specified concentration of allicin and other active substances. Also, follow the directions of a qualified healthcare practitioner with knowledge and experience in herbal medicine.
How to Take It
An appropriate medicinal dose for children has not been established. For this reason, use of garlic for health-related reasons in children should be directed by a qualified healthcare practitioner who has experience treating children with herbal remedies.
Whole garlic clove: 2 to 4 grams per day of fresh, minced garlic clove (each clove is approximately 1 gram)
Capsules or tablets of freeze-dried garlic standardized to 1.3% alliin or 0.6% allicin: 600 to 900 mg daily
Infusion: 4 grams in 150 mL of water/day
Fluid extract of 1:1 (g/mL) solution: 4 mL/day
Tincture of 1:5 (g/mL) solution: 20 mL/day
Oil: 0.03 to 0.12 mL three times a day
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain active substances that can trigger side effects and that can interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine.
Garlic is considered to have very low toxicity and is listed as Generally Recognized as Safe (GRAS) by the Food and Drug Administration (FDA) of the United States.
Side effects from garlic include upset stomach, bloating, bad breath, body odor, and a stinging sensation on the skin from handling too much fresh or dried garlic. Handling garlic may also cause the appearance of skin lesions. Other side effects that have been reported by those taking garlic supplements include headache, fatigue, loss of appetite, muscle aches, dizziness described as vertigo (namely, the room spinning), and allergies such as an asthmatic reaction or contact dermatitis (skin rash).
Garlic has blood-thinning properties so people with bleeding disorders, such as hemophilia or platelet disorders, should not use garlic supplements or medicinal doses of garlic. This is also important to know if you are going to have surgery or deliver a baby. Too much garlic can increase your risk for bleeding during or after those procedures.
Some experts recommend that pregnant and breastfeeding women avoid garlic. This may be due to the fact that a safe dose of medicinal garlic has not been established for infants and children.
If you are currently being treated with any of the following medications, you should not use garlic supplements without first talking to your healthcare provider.
Garlic may exaggerate the activity of medications that inhibit the action of platelets in the body. Examples of such medications include indomethacin, dipyridamole, and aspirin.
There have been reports of a possible interaction between garlic and warfarin that could increase the risk of bleeding in people taking this blood thinning medication. Therefore, when taking medications that may thin the blood, such as aspirin and warfarin, you should refrain from consuming large quantities of garlic, either fresh or commercially prepared.
When used with a class of medications for diabetes called sulfonylureas, garlic may lower blood sugar considerably. Medications from this class include chlorpropamide, glimepiride, and glyburide. When using garlic with these medications, blood sugars must be followed closely.
Garlic may reduce blood levels of protease inhibitors, a medication used to treat people with the human immunodeficiency virus (HIV), including indinavir, ritinavir, and saquinavir.
It is thought that garlic may behave similarly to a class of cholesterol lowering medications called statins (such as atorvastatin, pravastatin, and lovastatin) and to a class of blood pressure lowering medications called ACE inhibitors (including enalapril, captopril, and lisinopril). It is not known, therefore, whether it is safe to take this supplement in large quantities with these medications or not. This possible interaction has never been tested in scientific studies.