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Garlic is taken orally to reduce high
blood pressure, prevent heart disease and artherosclerosis, treat
earaches, stimulate both the immune and circulatory systems and prevent
cancer. Other applications include treating diabetes, arthritis, colds
and flu, fighting stress and fatigue and maintaining healthy liver
function (3).
Various official monographs list garlic as being both antibacterial and
antimycotic (suppresses the growth of certain fungi) (1) (4) (5).
Consequently garlic is administered to treat Helicobacter pylori
infections (3) (7), and to inhibit the growth of Candida albicans,
particularly in cases of recurrent yeast infections (6).
Parasitic worms are also apparently susceptible to garlic. The World
Health Organization “Monographs on Selected Medicinal Plants” reports
garlic has having been used to treat roundworm (Ascaris strongyloides)
and hookworm (Ancylostoma caninum and Necator americanus) infestations,
listing allicin as the active anthelmintic constituent (5).
The United States Department of Agriculture lists garlic as being a
viricide on its Medicinal Plant Database (8).
What accounts for the antibacterial action of garlic? The garlic bulb
contains an amino acid derivative called alliin, which is in fact
odorless and contains no antibacterial properties. However when the
garlic bulb is crushed or ground, alliin comes into contact with an
enzyme (alliinase) that converts the alliin into allicin. Allicin is the
reason for garlic’s distinctive odor, and is a potent antibacterial
agent (2).
TRADITIONAL USE
The use of garlic in history goes back thousands of years, with
Hippocrates, Galen, Pliny the Elder, and Dioscorides all reporting its
use for various conditions, including parasites, low energy, and
respiratory and digestive disorders. Garlic’s reputation in Western
medicine was established in 1858 when Louis Pasteur confirmed its
antibacterial properties (6).
Traditional Chinese medicine has used garlic since at least A.D. 510
(6), and is still using it for amoebic and bacterial dysentery,
tuberculosis, scalp ringworm and vaginal trichomoniasis.
Other folk medicine cultures have traditionally used garlic for treating
colds and flu, fever, coughs, headache, hemorrhoids asthma,
arteriosclerosis, low blood pressure, both hypoglycemia and
hyperglycemia, cancer and as an aphrodisiac (amongst other things) (3)
(4). Garlic has also been used to treat pinworms (4).
The anti-parasitic nature of garlic is demonstrated in the uses to which
it has been applied in folk medicines around the world. For example, it
has been traditionally used to treat parasitic worms in such diverse
cultures as East Asia, India, Italy, North America, Peru, Saudi Arabia,
Tunisia and the West Indies. Traditional practitioners in Greece have
long used garlic extracts to protect against amoebic infections (10).
Laboratory tests (both in test tubes and in animals) have demonstrated
that fresh garlic has antimicrobial activities (including antibacterial,
antiviral, antifungal, anti-protozoal, and anti-parasitic) (3) (7) (10).
Particular activity against B. subtilis, E. coli, P. mirabilis,
Salmonella typhi, methicillin-resistant Staph aureus, Staph faecalis,
salmonella enteritidis, and V. cholerae have been noted (3) (7).
Bacteria shown to be susceptible to garlic in the test tube include
species from Staphylococcus, Escherichia, Proteus, Salmonella,
Providencia, Citrobacter, Klebsiella, Hafnia, Aeromonas, Vibrio and
Bacillus genera (7). Human trials as well as in vitro studies have shown
that garlic consumption is active against Mycobacterium tuberculosis
(10).
An epidemiological study in China among 214 people from the Shandong
province suggested that garlic consumption might have a protective
effect against H. pylori infection and the development and progression
of precancerous gastric lesions (9).
Fungi demonstrated to be susceptible to garlic in lab tests include the
genera Microsporum, Epidermophyton, Trichophyton, Rhodotorula,
Torulopsis, Trichosporon, Cryptococcus neoformans, and Candida,
including Candida albicans. It is reported that garlic is more effective
against pathogenic yeasts than nystatin, especially Candida albicans (3)
(7) (10) (11).
Essential garlic oils were active on Entamoeba histolytica in clinical
trials, confirming its potential for anti-amoebic activity (10).
Anti-protozoan activity has also been demonstrated in lab tests against
Paramecium caudatum (14).
Garlic has also shown itself in lab tests to have several
immune-enhancing effects (12).
Fresh garlic, garlic extracts, oil and oleoresin have been generally
recognized as safe when consumed in amounts commonly found in food.
Garlic has been used for medicinal purposes in clinical studies lasting
up to 4 years without reports of significant toxicity. It is possibly
unsafe when consumed in large amounts, with the American Herbal Products
Association Botanical Safety Handbook claiming that high doses could be
dangerous or even fatal for children. There are, however, no reported
cases of significant adverse reactions or mortality in children
associated with the ingestion of garlic (3).
There are no published reports of garlic adversely affecting pregnancy,
although it would be wise to avoid consuming large amounts during these
times. (Theoretically large amounts of garlic might act as an
abortifacient causing uterine contractions.) There is a lack of reliable
information dealing with the use of garlic while breastfeeding, but it
has been generally accepted that consuming it in amounts commonly found
in food would be safe (3). |
