Vegetables, Sulforaphane Glucosinolate (SGS™)
and the Reduction of Cancer Risk - An Overview
A staggering 10.3 million new cancer cases are
diagnosed each year worldwide, making cancer prevention a top
public health priority. Fortunately, the right diet can be a
powerful weapon against development of this devastating disease.
According to a recent international expert report changes in
diet may prevent 30 to 40 percent of cancer cases, or three
to four million cases annually.
Reducing the Risk of Some Cancers with Diet
Cancer can be controlled through two complementary routes:
- Prevention - Reducing exposure to cancer-causing chemicals
such as tobacco, environmental carcinogens, and harmful dietary
components.
- Chemoprotection - Increasing the body's defense system
against carcinogens. Cells in the body contain a family of detoxification
enzymes (Phase 2 enzymes) that neutralize cancer-causing chemicals
as well as free radicals before they damage DNA and initiate
cancer. A diet rich in antioxidants helps the cells in fighting
the harmful effects of free radicals.
Health experts agree there is compelling scientific evidence
that consumption of vegetables and fruits helps to reduce the
risk of some cancers. Dietary Guidelines for Americans, as well
as National Research Council and American Institute of Cancer
Research recommendations all reflect this growing knowledge. This
consensus was also the basis for the National Cancer Institute's
"5-A-Day" program to encourage increased consumption
of vegetables and fruits. The chemoprotective effect of vegetables
from the Brassica family, such as broccoli, cauliflower and kale,
are particularly well documented.
The Power of Protective Phytochemicals
Through pioneering research, medical investigators worldwide
are beginning to unravel the mysteries of how diets rich in vegetables
and fruits reduce the risk of cancer.
One explanation is that plants are rich sources of naturally
protective substances called phytochemicals. Plant phytochemicals
number in the thousands. Only a small number of them have been
identified and their mechanisms of action studied. Some familiar
protective phytochemicals are:
- Allicin in garlic;
- Isoflavones in soybeans;
- Lycopene in tomatoes;
- Flavanoids in green and black teas;
- Sulforaphane glucosinolate (SGS) in broccoli and broccoli
sprouts;
- Carotenoids in carrots;
- Lignans in flax seed.
The Science of Sulforaphane
Sulforaphane is a naturally occurring phytochemical that enhances
the cancer-protective capacity of animal cells. According to studies
by Dr. Paul Talalay and his colleagues at Johns Hopkins University
School of Medicine, sulforaphane induces Phase 2 (detoxification)
enzymes. These are the enzymes which deactivate carcinogens and
free radicals, thus enhancing the body's own defense system against
cancer-causing chemicals.
In animal studies, administration of sulforaphane blocked tumor
development, reducing incidence, multiplicity, and size of carcinogen-induced
mammary tumors. (see Broccoli sprouts: An exceptionally rich source
of inducers of enzymes that protect against chemical carcinogens)
In general, Brassica family plants such as broccoli are rich
in sulforaphane in its glucosinolate precursor form. However,
the evidence suggests that broccoli must be eaten in large quantities
to substantially reduce the risk of cancer. In addition, supermarket
broccoli varies considerably in sulforaphane content, whereas
certain varieties of young broccoli sprouts, grown under standardized
conditions, contain large and highly uniform quantities of the
compound.
Talalay and his colleagues identified the specific varieties
of three-day-old broccoli sprouts containing 20 times the concentration
of sulforaphane glucosinolate found in mature broccoli.
More importantly, small quantities of broccoli sprout extracts
reduced the incidence and size of mammary tumors in animals. (see
the paper) Clinical studies are underway to further explore the
effects of broccoli sprouts on protective biomarkers against human
cancer.
The Bottom Line
Chemoprotection has great promise as a way to use the diet to
reduce the risk of some cancers. Chemoprotection can be accomplished
by activating the body's Phase 2 "defense" enzymes.
Cruciferous plants, such as broccoli, contain a natural precursor,
sulforaphane glucosinolate (SGS), which is readily converted to
sulforaphane. Sulforaphane acts by raising the activity of these
enzymes. Research into the chemoprotective powers of sulforaphane
is promising and exciting. While more research is needed, supplementing
a healthy diet rich in fruits and vegetables may help maintain
the body's natural defenses.