|| Allium sativum
Garlic has been used as both food and medicine in many cultures for thousands
of years, dating as far back as the time that the Egyptian pyramids were built.
Later, gravediggers in early eighteenth-century France drank a concoction of
crushed garlic in wine which they believed would protect them from getting the
plague that killed many people in Europe. More recently, during both World Wars
I and II, soldiers were given garlic to prevent gangrene and today people use
garlic to help prevent atherosclerosis (plaque build up in the arteries causing
blockage and possibly leading to heart attack or stroke), improve high blood
pressure, and reduce colds, coughs, and bronchitis.
Medical research has been underway to assess whether these traditional uses
of garlic have scientific validity. While the science is not definitive at this
point, much of the research is showing real promise and many clinicians continue
to report improvements in the areas of infection and heart-related risk factors
for their individual patients. For example, test tube and animal studies suggest
that garlic can kill many types of bacteria, some viruses and fungal infections,
and even intestinal parasites. The belief is that properties of garlic may prove
to help support immune function and prevent infection in people. Some experts
believe that science may prove that garlic is particularly useful when taken
together with medications (like antibiotics) prescribed for these infections.
Garlic also has antioxidant properties. Antioxidants help scavenge free
radicals -- particles that can damage cell membranes, interact with genetic
material, and possibly contribute to the aging process as well as the
development of a number of conditions including heart disease and cancer. Free
radicals occur naturally in the body, but environmental toxins (including
ultraviolet light, radiation, cigarette smoking, and air pollution) can also
increase the number of these damaging particles. Antioxidants can neutralize
free radicals and may reduce or even help prevent some of the damage they cause
The conditions for which garlic is showing the most promise include:
Studies suggest that fresh garlic and garlic
supplements may prevent blood clots and destroy plaque. Blood clots and plaque
block blood flow and contribute to the development of atherosclerosis. Blockage
of blood flow to the heart, brain, and legs, can lead to heart attack, stroke,
or peripheral vascular disease (PVD). People with PVD experience pain in the
legs when they walk and move. If garlic does reduce the build up of plaque, then
stroke, heart attacks, and PVD may be less likely to occur in people who eat
garlic or take garlic supplements.
Garlic may also be beneficial for risk factors for heart disease, including
high blood pressure, high cholesterol, and diabetes. An animal study suggests
that garlic may help lower homocysteine levels as well. Homocysteine, similar to
cholesterol, may contribute to increasing amounts of blood clots and plaque in
Long hailed for its beneficial effects, a
number of studies have found that garlic reduces elevated total cholesterol
levels more effectively than placebo. However, the extent to which garlic lowers
cholesterol in these studies has been small, and study limitations make it
somewhat difficult to draw any firm conclusions. More research with
better-designed studies is needed in order to fully assess the safety and
effectiveness of garlic and to determine the most appropriate dose and form (see
In the meantime, work with a qualified healthcare practitioner, knowledgeable
in herbal medicine, to determine if garlic is safe and appropriate for you to
try. The specialist will assess what other medications you are taking to make
sure that there are no potentially dangerous interactions, and will follow your
cholesterol levels closely.
High Blood Pressure
Studies suggest that raw garlic may lower
blood pressure. Similar to cholesterol, however, the drop in blood pressure
caused by garlic is fairly small. For this reason, further research is necessary
before it can be routinely recommended for people with high blood pressure.
Since garlic is considered relatively safe and has a number of other
potentially healthful benefits for the heart, a professional herbalist may
recommend the use of this herb. Again, work closely with a knowledgeable herbal
specialist to determine if garlic is safe and appropriate for you. A healthcare
provider will also monitor your blood pressure closely while you are taking this
Garlic has been used as a traditional dietary
supplement for diabetes in Asia, Europe, and the Middle East. Preliminary
studies in rabbits, rats, and limited numbers of people have demonstrated that
garlic has some ability to lower blood sugars. One well-designed study conducted
in Thailand, however, found that garlic was no better than placebo in lowering
blood sugar levels in people with type 2 diabetes. More research in this area is
Possible Interactions regarding some
concern about using garlic with certain medications for diabetes.)
A well-designed study of nearly 150 people
supports the value of garlic for preventing and treating the common cold. In
this study, people received either garlic supplements or placebo for 12 weeks
during "cold season" (between the months of November and February). Those who
received the garlic had significantly fewer colds than those who received
placebo. Plus, when faced with a cold, the symptoms lasted a much shorter time
in those receiving garlic compared to those receiving placebo.
Test tube and animal studies suggest that garlic may
have some anti-cancer activity. Observational, population-based studies (which
follow groups of people over time) suggest that people who have more raw or
cooked garlic in their diet are less likely to have certain types of cancer,
particularly colon and stomach cancers. Dietary garlic may also offer some
protection against the development of breast, prostate, and laryngeal (throat)
cancers. However, these types of cancer have not been as extensively studied as
colon and stomach cancer.
While these results are intriguing, more research is needed to best
understand whether dietary intake of garlic and other substances in the same
family (such as onions, leeks, scallions, chives, and shallots) truly help to
prevent cancer. In addition, studies looking at garlic supplements (as opposed
to dietary garlic) and cancer have been limited. Thus far, however, use of
garlic supplements does not appear to reduce the risk of developing prostate,
colon, stomach, lung, or breast cancer.
Numerous test tube studies have demonstrated that
garlic extract inhibits the growth of different species of bacteria, including
Mycobacterium tuberculosis, the organism responsible for tuberculosis.
However, very high concentrations of garlic extract were needed to slow down the
growth of M. tuberculosis in these studies, so some experts are concerned
that these levels may be toxic to people. While further research in people is
needed, one animal study found that garlic oil (which is a higher concentration
than the extract) also inhibited M. tuberculosis and reduced the
tuberculosis lesions in the lungs of these animals. Some scientists speculate
that a combination of garlic extract or garlic oil with anti-tuberculosis drugs
may eventually prove effective against the disease. Research to test this theory
Laboratory studies suggest that large
quantities of fresh, raw garlic may have antiparasitic properties against the
roundworm, Ascaris lumbricoides, which is the most common type of intestinal
parasite. Garlic for this purpose, however, has not yet been tested in
Ear Pain from Otitis Media
Most children with an ear infection
known as otitis media experience pain. Often, ear drops with pain killers are
prescribed to relieve this discomfort. A recent study compared this standard
treatment to a combination herbal extract (also used as ear drops) containing
garlic as well as calendula, St. John's wort, and mullein flower. The herbal
combination worked as well as the prescription ear drops. The number of children
included in the study, however, was small. More research in this area would be
Garlic originally came from central Asia, and is now cultivated throughout
the world. Garlic is a perennial that can grow two feet high or more. The most
important part of this plant for medicinal purposes is the compound bulb. Each
bulb is made up of 4 to 20 cloves, and each clove weighs about 1 gram. The parts
of the plant used medicinally include fresh bulbs, dried bulbs, and oil
extracted from the garlic.
|What's It Made Of?|
There are several important components of garlic that have been identified,
and many more that have not. Alliin is an odorless sulfur-containing chemical
derived from the amino acid cysteine. When garlic bulbs are crushed, alliin is
converted into another compound called allicin. Allicin appears to be at least
one of the primary active compounds that gives garlic its characteristic odor
and many of its healing benefits.
Allicin appears to have infection-fighting action as well as potential
cardiovascular effects including, possibly, the ability to lower blood pressure
and cholesterol. In addition, test tubes have shown that allicin has anti-cancer
Allicin is further broken down to a compound called ajoene, which may be the
substance that inhibits blockage in blood vessels from clots and
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
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
- 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
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
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
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
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.
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|Review Date: April 2002|
|Reviewed By: Participants in the review process include: Jacqueline A. Hart, MD,
Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University
and Senior Medical Editor Integrative Medicine, Boston, MA; Gary Kracoff, RPh
(Pediatric Dosing section February 2001), Johnson Drugs, Natick, MA; Steven
Ottariono, RPh, Veteran's Administrative Hospital, Londonderry, NH; David
Winston, Herbalist (April 1999), Herbalist and Alchemist, Inc., Washington, NJ;
Leonard Wisneski, MD, FACP (April 1999), George Washington University,
Rockville, MD; Tom Wolfe, P.AHG (April 1999), Smile Herb Shop, College Park, MD.
All interaction sections have also been reviewed by a team of experts including
Joseph Lamb, MD (July 2000), The Integrative Medicine Works, Alexandria,
VA;Enrico Liva, ND, RPh (August 2000), Vital Nutrients, Middletown, CT; Brian T
Sanderoff, PD, BS in Pharmacy (March 2000), Clinical Assistant Professor,
University of Maryland School of Pharmacy; President, Your Prescription for
Health, Owings Mills, MD; R. Lynn Shumake, PD (March 2000), Director,
Alternative Medicine Apothecary, Blue Mountain Apothecary & Healing Arts,
University of Maryland Medical Center, Glenwood, MD; Ira Zunin, MD, MPH, MBA
(July 2000), President and Chairman, Hawaii State Consortium for Integrative
Medicine, Honolulu, HI.|
Copyright © 2004 A.D.A.M., Inc
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regarding dosage, precautions, warnings, interactions, and contraindications
before administering any drug, herb, or supplement discussed