Several studies from around
the world have found that people
who eat more garlic seem to
have a lower risk of certain
types of cancer. In particular,
large human studies that looked
at diet and cancer have suggested
that people who eat more garlic
have a lower risk of stomach,
prostate, mouth and throat,
kidney, and colorectal cancer.
The effect on risk of breast,
bladder, ovarian, and lung cancers
is less clear. As always in
population-based studies, it
is possible that other factors
may account for the differences
in cancer risk. The few human
studies that have looked at
garlic supplements have not
found them to be helpful against
cancer.
Many laboratory studies done
in cell cultures and animals
suggest garlic may help reduce
tumor growth. Cell culture studies
have shown garlic can help cancer
cells die off normally, a process
called apoptosis. Other studies
in cell cultures have found
that substances in garlic seem
to be able to act as antioxidants.
Some studies have also suggested
that garlic can act against
Helicobacter pylori, a bacterium
thought to be a major cause
of stomach cancer. Studies in
laboratory animals have found
garlic may help protect against
cancer of the colon, skin, liver,
and breast, among others.
Although results of some observational
studies are encouraging, randomized
clinical trials in which people
assigned by researchers to receive
either garlic or an inactive
control substance provide more
reliable information. Very few
studies of this type have studied
garlic and cancer risk. In one
recent study conducted in China,
where stomach cancer is quite
common, aged garlic extract
and steam-distilled garlic oil
did not prevent this disease.
While some research on garlic
is promising, it is very hard
to determine the exact role
a particular food may have against
cancer. It is even more difficult
when the food in question is
often used in small amounts,
as is garlic. A balanced diet
that includes 5 or more servings
a day of fruits and vegetables
along with foods from a variety
of other plant sources such
as nuts, seeds, whole grain
cereals, and beans is likely
to be more effective than eating
one particular food in large
amounts.
Some studies suggest that garlic
can lower blood cholesterol
levels, although a recent clinical
study funded by the National
Center of Complementary and
Alternative Medicine did not
confirm any effect. This California
study compared raw garlic with
aged garlic extract, powdered
garlic, and a placebo in nearly
200 randomly assigned volunteers.
The garlic was given in doses
of 4 grams per day over 6 months.
At the end of the study, there
was no significant difference
in LDL ("bad") cholesterol
among the 4 groups. Other studies
suggest that garlic makes blood
less likely to form clots, which
might help prevent heart disease
and stroke. However, there is
no reliable direct clinical
evidence that garlic can actually
prevent heart attacks or strokes.
Evidence on garlic and blood
pressure is mixed.
While some research on garlic
is promising, it is very hard
to determine the exact role
a particular food may have against
cancer. It is even more difficult
when the food in question is
often used in small amounts,
as is garlic. A balanced diet
that includes five or more servings
a day of fruits and vegetables
along with foods from a variety
of other plant sources such
as nuts, seeds, whole grain
cereals, and beans is likely
to be more healthful than eating
one particular food in large
amounts.
