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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