Soy Protein:
Can It Really Prevent Cancer?
Suzanne Clark 
Some Fast
Facts About Cancer
Society possesses a natural fear of the disease
cancer. Even though this term is common, uncertainty surrounds its
meaning. What exactly is cancer? A simple definition for a
complicated disease is this: abnormal cell growth. Cancer can
develop in just about any part of the body, and as abnormal cells grow,
they crowd and destroy healthy tissue. This disease is not
infectious, for if it were, a vaccination would have probably been
developed by now. However, extensive research is continuously being
conducted to find a cure or more effective treatments for this mysterious
disease.
Considering Foods
"Evidence shows that lifestyles
and diet are mostly responsible for the different cancer rates around
the world." The following information discusses possible cancer prevention
by the consumption of soy products.
What Is
Soy?
Again,
a familiarity with the studied term is necessary. What is soy?
"Soy"
comes from soybean, a legume which is native to Northern China. It
is often called a complete
protein. This is because it is the most complete protein source
from vegetables and is as good as animal protein in meat products.
Why Consider
Soy?
Soy protein, which has been stated to be of "highest caliber," contains
many essential nutrients. It has been stated that populations who
regularly include soy protein in their diets and reduce meat intake are
generally healthier in that their risks for certain diseases are reduced.
These include cancer, especially breast
cancer in women and prostate cancer in men. The basic assumption
that has been made about soy is that its consumption as a dietary staple
reduces the risk of a variety of cancers, such as breast cancer, prostate
cancer, and colon cancer. A relationship between soy and lung cancer
has even been assumed.
Components
Of Soy
The assumed effectiveness of soy has been contributed to its natural constituents,
namely chemicals called phytochemicals. This term simply refers to
chemicals involved in plants, plant processes, and plant products.
One chemical in soybeans is phytate. Phytate
is an organic acid present in the hulls of plant seeds. It is the
storage form of the mineral phosphorous. This chemical binds iron
and calcium in the intestines. Chemicals called saponins
protect DNA from damage and thus from cancer. Protease
inhibitors are also found in soy, which is important because the chemical
protease inhibits the digestion of protein. Other chemicals are phytosterols,
which are derived from plants and inhibit colon cancer growth by shielding
against liver-secreted bile acids. Claims have linked phytosterols
to both colon and skin cancer. The final group of chemicals to be
discussed are collectively called isoflavones. These natural chemicals
are unique to soybeans, and one in particular has been extensively studied:
genistein. Genistein
is believed to be a dietary source that enacts direct
tumor cell differentiation, or it simply slows cancer cell and tumor
growth. Perhaps this chemical will emerge as an anticancer
drug.
Other
Benefits Of Soy
A "Top 10"
list of benefits of soy has been published. Five of the ten benefits
are a direct correlation to cancer and are summarized as follows:
1. Antioxidant: protects against cell damage that may
be linked
to various forms of cancer
2. Breast Cancer: women eating soy products are at a
lower
risk; Asian women have lower levels of breast cancer
3. Colon Cancer: lowered rates by eating soy
4. Lung Cancer: a relationship has been observed
5. Prostate Cancer: inhibited growth of cells in laboratory
experiments
Scientific
Research
Studies have been conducted to investigate the actual effects of genistein.
One study used F344 rats that had been treated with genistein. The
genistein was administered in the diet one week before a carcinogen was
introduced to four weeks after the carcinogen was introduced. The
goal of this study was to test genistein for its ability to inhibit colon
tumors in the rats. The study was conducted over a period of
five weeks. At doses of 75 and 150mg/kg, the average number of cancerous
cells was reduced significantly.
Several studies were conducted in animal models of cancer to investigate
the effects of genistein in soy products. In two-thirds of the studies,
the risk of cancer (incidence) was reduced. Purified genistein also
reduced the appearance of mammary tumors in rats when injected neonatally.
Twenty-six studies conducted on animals sought to experiment chemopreventive
effects in which diets containing soy were employed. Seventeen of
the studies reported protective effects. This was 65% of the studies.
No study showed that soy enhances tumor development.
One study was conducted using humans consuming soy and rats with catheters.
Genistein was found to be absorbed well and inhibit the growth of breast
cancer cells. The study stated that genistein regulates the proliferation
of epithelial cells in the breast.
A final study proved that genistein aided in the flattening of prostate
carcinoma cells and also breast cancer cells. Cell adhesion was also
discovered in those introduced to genistein.
The Safety
Of Soy
Few contradicting articles exist that question the safety of soy products
as a dietary staple. An increase
in liver and pancreatic cancer occurred in Africa possibly when soy
products were consumed in large quantities.
What Does
All Of This Mean?
Soy consumption is probably beneficial when consumed in a balanced diet.
However, its impact on cancer prevention is not significant enough to worry
about eating soy daily. No need to panic if soy is not eaten!
You probably won't end up in a doctor's office for inadequate soy consumption!
Works Cited
Barnes, S.,
et al. "Soy Isoflavonoids and Cancer Prevention."
Advances in Experimental Medicine & Biology 401.
(1996): 87-100.
Barnes,
Stephen. "Anticancer Effects of Genistein." The Journal
of Nutrition
125 (1995): 777S-783S.
Bergan,
R., et al. "Genistein-stimulated Adherence of Prostate Cancer Cells
Is Associated with the Binding of Focal Adhesion Kinase to
Beta-1-integrin." Clinical & Experimental Mestastasis
14(4)
(1996 Sept.): 389-398.
Messina,
M. J., et al. "Soy Intake and Cancer Risk: A Review of the
In Vitro
and in Vivo
Data." Nutrition & Cancer 21(2) (1994): 113-131.
Steele,
Vernon E., et al. "Nonisoflavone Soybean Anticarcinogens."
The Journal of Nutrition 125 (1995) 713S-716S.
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