Garlic and Cancer Prevention
 Garlic is the edible bulb from a plant in the lily family.
Garlic, onions, leeks, scallions, shallots and chives are
classified as members of the Allium genus. Thus, they are
commonly described as Allium vegetables.
1. Does garlic
prevent cancer?
A host of studies provide compelling evidence that garlic
and its organic allyl sulfur components are effective
inhibitors of the cancer process. These studies reveal that
the benefits of garlic are not limited to a specific
species, to a particular tissue, or to a specific
carcinogen. Of 37 observational studies in humans using
garlic and related allyl sulfur components, 28 studies
showed some cancer preventive effect. The evidence is
particularly strong for a link between garlic and prevention
of prostate and stomach cancers. However, all of the
available information comes from observational studies
comparing cancer incidence in populations who consume or do
not consume garlic (epidemiologic studies), animal models,
or observations with cells in culture. These findings have
not yet been verified by clinical trials in humans.
Although health benefits of garlic are frequently reported,
excessive intake can have harmful effects. Studies have
reported symptoms including garlic odor on breath and skin,
occasional allergic reactions, stomach disorders and
diarrhea, decrease in serum protein and calcium levels,
association with bronchial asthma, and contact dermatitis,
and possible associations with production of sperm in males.
Garlic preparations vary in concentration and in the number
of active compounds they contain. Thus, quality control is
an important consideration when foods such as garlic are
considered for use as a cancer-fighting agent.
2. How might
garlic prevent cancer?
Several compounds are involved in garlic's possible
anticancer effects. Garlic contains allyl sulfur and other
compounds that slow or prevent the growth of tumor cells.
Allyl sulfur compounds, which occur naturally in garlic and
onions, make cells vulnerable to the stress created by
products of cell division. Because cancer cells divide very
quickly, they generate more stressors than most normal
cells. Thus, cancer cells are damaged by the presence of
allyl sufur compounds to a much greater extent than normal
cells.
The chemistry of garlic is complicated. As a result, the
quality of garlic products depends on the manufacturing
process. Peeling garlic and processing garlic into oil or
powder can increase the number and variety of active
compounds. Peeling garlic releases an enzyme called allinase
and starts a series of chemical reactions that produce
diallyl disulfide (DADS). DADS is also formed when raw
garlic is cut or crushed. However, if garlic is cooked
immediately after peeling, the allinase is inactivated and
the cancer-fighting benefit of DADS is lost. Scientists
recommend waiting 15 minutes between peeling and cooking
garlic to allow the allinase reaction to occur.
Processing garlic into powder or garlic oil releases other
cancer-fighting agents. The inconsistent results of garlic
research may be due, at least in part, to problems
standardizing all of the active compounds within garlic
preparations. Some of the garlic compounds currently under
investigation are: allin (responsible for the typical garlic
odor), alline (odorless compound), ajoene (naturally
occurring disulfide), diallyl sulfide (DAS), diallyl
disulfide (DADS), diallyl trisulfide (DAT), S-allylcysteine
(SAC), organosulfur compounds and allyl sulfur compounds.
- Source: National Cancer Institute |
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