Garlic (Allium sativum), a herb used widely as a
flavoring in cooking, has also been used as a medicine throughout ancient and
modern history to prevent and treat a wide range of conditions and diseases.
Garlic belongs to the onion genus Allium, and is
closely related to the onion, rakkyo, chive, leek, and shallot. It has been
used by humans for thousands of years and was used in Ancient Egypt for both
culinary purposes and its health and therapeutic benefits.
Garlic for food and medicine - a brief history
Garlic
has been used all over the world for thousands of years. Records indicate that
garlic was in use when the Giza pyramids were built, about five thousand years
ago.
Richard S. Rivlin wrote in the Journal of Nutrition1 that the ancient Greek physician Hippocrates (circa. 460-370
BC), known today as "the father of Western medicine", prescribed
garlic for a wide range of conditions and illnesses. Hippocrates promoted the
use of garlic for treating respiratory problems, parasites, poor digestion and fatigue.
The original Olympic athletes in Ancient Greece were given
garlic - possibly the earliest example of "performance enhancing"
agents used in sports.
From
Ancient Egypt garlic spread to the advanced ancient civilizations of the Indus
Valley (Pakistan and western India today). From there it made its way to China.
According to experts at Kew Gardens2, England's royal
botanical center of excellence, the people of ancient India valued the
therapeutic properties of garlic and also thought it to be an aphrodisiac. The
upper classes avoided garlic because they despised its strong odor, while
monks, "...widows, adolescents and those who had taken up a vow or were
fasting could not eat garlic because of its stimulant quality".
Throughout history in the Middle East, East Asia and Nepal,
garlic has been used to treat bronchitis,
hypertension (high blood pressure), TB (tuberculosis),
liver disorders, dysentery, flatulence, colic,
intestinal worms, rheumatism, diabetes, and fevers.
The
French, Spanish and Portuguese introduced garlic to the New World.
Rivlin
found it interesting that several cultures in history that were never in
contact with one another had similar conclusions regarding the therapeutic
benefits of garlic.
Garlic is used widely today for its therapeutic
properties
According to the National Library of Medicine3, part of the NIH
(National Institutes of Health), USA, garlic is widely used for several
conditions linked to the blood system and heart, including atherosclerosis (hardening of the arteries), highcholesterol, heart attack, coronary heart disease and hypertension.
Garlic is also used today by some people for the prevention of lung cancer, prostate cancer, breast cancer, stomach cancer, rectal cancer, and colon
cancer.
The
NIH adds "Some of these uses are supported by science."
A study published in the journal Food and Chemical Toxicology4 warned that short-term heating reduces the anti-inflammatory
effects of fresh raw garlic extracts. This may be a problem for some people who
do not like or cannot tolerate the taste and/or odor of fresh garlic. Ask your
pharmacist for garlic supplements or oil which have not been exposed to too
much heat.
Health
benefits of garlic - scientific studies
What
is the difference between scientific and anecdotal evidence? Anecdotal evidence
refers to a person's personal experience - like the evidence from a witness.
This type of evidence is crucial in a court of law when somebody (a witness)
saw something happen with their own eyes. In medicine, however, anecdotal
evidence, when compared to scientific evidence, is not compelling enough.
If
I cross the road with my eyes closed and so does a friend of mine, and we do
not get run over, it would be irresponsible to tell everybody around us,
including our children that crossing the street with your eyes closed is safe.
A scientific study using thousands of participants, comparing crossers with
their eyes closed against others with their eyes open, would soon show that
crossing the street with your eyes closed is extremely dangerous.
Below
are examples of some scientific studies published in peer-reviewed academic
journals about the therapeutic benefits (or not) of garlic.
Lung cancer risk
People who ate raw garlic at least twice a week had a 44% lower
risk of developing lung cancer, according to a study carried out
at the Jiangsu Provincial Center for Disease Control and Prevention in China.
The researchers, who published their study in the journal Cancer Prevention Research,
had carried out face-to-face interviews with 1,424 lung cancer patients as well
as 4,543 healthy individuals. They were asked about their diet and lifestyle
habits, which included questions on their smoking habits and how often they ate
garlic.
The study
authors wrote "Protective association between intake of raw garlic and
lung cancer has been observed with a dose-response pattern, suggesting that
garlic may potentially serve as a chemo-preventive agent for lung cancer."
Brain cancer
Organo-sulfur compounds found in garlic have been identified as
effective in destroying the cells in glioblastomas, a type of
deadly brain tumor.
Scientists at the Medical University of South Carolina reported
in the journal Cancer that three pure organo-sulfur
compounds from garlic - DAS, DADS and DATS - "demonstrated efficacy in
eradicating brain cancer cells, but DATS proved to be the most effective".
Co-author, Ray Swapan,
Ph.D., said "This research highlights the great promise of plant-originated
compounds as natural medicine for controlling the malignant growth of human
brain tumor cells," Ray said. "More studies are needed in animal
models of brain tumors before application of this therapeutic strategy to brain
tumor patients."
Hip osteoarthritis
Women whose diets were rich in allium vegetables had lower levels
of osteoarthritis, a team at King's College London and the
University of East Anglia, both in England, reported in the journal BMC Musculoskeletal Disorders.
Examples of allium vegetables include garlic, leeks, shallots, onions and
rakkyo.
The
study authors said their findings not only highlighted the possible impact of
diet on osteoarthritis outcomes, but also demonstrated the potential for using
compounds that exist in garlic to develop treatments for the condition.
The long-term study, involving more than 1,000 healthy female
twins, found that those whose dietary habits included plenty of fruit and
vegetables, "particularly
alliums such as garlic", had fewer signs of early
osteoarthritis in the hip joint.
Potentially a powerful antibiotic
Diallyl sulfide, a compound in garlic, was 100 times more
effective than two popular antibiotics in fighting theCampylobacter bacterium, according to a study
published in the Journal
of Antimicrobial Chemotherapy.
The Campylobacter bacterium is one of the most common
causes of intestinal infections.
Senior author, Dr. Xiaonan
Lu, from Washington State University, said "This work is very exciting to
me because it shows that this compound has the potential to reduce
disease-causing bacteria in the environment and in our food supply."
Heart protection
Diallyl trisulfide, a component of garlic oil, helps protect the heart during cardiac
surgery and after a heart attack, researchers at Emory
University School of Medicine found. They also believe diallyl trisulfide could
be used as a treatment for heart failure.
Hydrogen
sulfide gas has been shown to protect the heart from damage. However, it is a
volatile compound and difficult to deliver as therapy. Hence, the scientists
decided to focus on diallyl trisulfide, a garlic oil component, as a safer way
to deliver the benefits of hydrogen sulfide to the heart.
In
animal experiments using laboratory mice, the team found that after a heart
attack the mice that had received diallyl sulfide had 61% less heart damage in
an area of risk, compared to the untreated mice.
The
team presented their findings at the American Heart Association (AHA)
Scientific Sessions conference in Orlando, Florida in November, 2011.
In another study, published in the Journal of Agricultural and
Food Chemistry, scientists found that garlic oil may help protect diabetes patients from cardiomyopathy.
Cardiomyopathy
is the leading cause of death among diabetes patients. It is a chronic disease
of the myocardium (heart muscle), which is abnormally thickened, enlarged
and/or stiffened.
The
team fed diabetic laboratory rats either garlic oil or corn oil. Those fed the
garlic oil experienced significantly more changes associated with protection
against heart damage, compared to the corn oil fed animals.
The study
authors wrote "In conclusion, garlic oil possesses significant potential
for protecting hearts from diabetes-induced cardiomyopathy."
Human
studies will need to be performed to determine whether they confirm the results
of this study.
High cholesterol and high blood pressure
Researchers at Ankara university set out to determine what the
effects of garlic extract supplementation might be on the blood lipid (fat)
profile of patients with high blood cholesterol. Their study was published in
the Journal of Nutritional
Biochemistry5.
The
study involved 23 volunteers, all with high cholesterol; 13 of them also had
high blood pressure. They were divided into two groups:
§ The
high-cholesterol normotensive group (normal blood pressure)
§ The
high-cholesterol hypertensive group (high blood pressure)
They
took garlic extract supplements for four months and were regularly checked for
blood lipid parameters, as well as kidney and liver function.
At the end of the four months the researchers concluded
"...garlic extract supplementation improves blood lipid profile,
strengthens blood antioxidant potential,
and causes significant reductions in systolic and diastolic blood pressures. It
also leads to a decrease in the level of oxidation product (MDA) in the blood
samples, which demonstrates reduced oxidation reactions in the body."
In
other words, the garlic extract supplements reduced high cholesterol levels,
and also blood pressure in the patients with hypertension. The scientists added
that theirs was a small study - a larger one needs to be carried out.
Prostate cancer
Doctors
at the Department of Urology, China-Japan Friendship Hospital, Beijing, China,
carried out a study evaluating the relationship between Allium vegetable
consumption and prostate cancer risk.
They gathered and analyzed published studies up to May 2013 and
reported their findings in the Asian Pacific Journal of Cancer
Prevention6.
The study authors wrote "Allium vegetables, especially garlic intake,
are related to a decreased risk of prostate cancer".
The
team also commented that as there were not that many studies, they recommend
further well-designed prospective studies be carried out to confirm their
findings.
Alcohol-induced liver injury
Alcohol-induced
liver injury (ethanol-induced liver injury) is caused by the long-term
over-consumption of alcoholic beverages.
Scientists at the Institute of Toxicology, School of Public
Health, Shandong University, China, wanted to determine whether diallyl disulfide
(DADS), a garlic-derived organosulfur compound, might have protective effects
against ethanol-induced oxidative stress.
The
researchers concluded that DADS may help protect against ethanol-induced liver
injury.
Preterm (premature) delivery
Microbial
infections during pregnancy raise a woman's risk of preterm delivery, several
studies have demonstrated. Scientists at the Division of Epidemiology,
Norwegian Institute of Public Health, wanted to find out what impact foods
might have on antimicrobial infections and preterm delivery risk.
Ronny
Myhre and colleagues concentrated on the effects of Alliums and dried fruits,
because a literature search had identified these two foods as showing the
greatest promise for reducing preterm delivery risk.
The
team investigated the intake of dried fruit and Alliums among 18,888 women in
the Norwegian Mother and Child Cohort, of whom 5% (950) underwent spontaneous
PTD (preterm delivery).
The study authors concluded "Intake of food with
antimicrobial and prebiotic compounds may be of importance to reduce the risk
of spontaneous PTD. In particular, garlic
was associated with overall lower risk of spontaneous PTD."
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