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Cancer, Chemotherapy, and Diet

What are the role of dietary changes, antioxidants, and herbal supplements?

Thomas Blom, MD
Medical Oncologist and Hematologist
Princeton Medical Group

Carcinogenesis, the formation of a cancer cell from a normal cell, involves a complex process through which the genetics of a cell are altered in a manner that causes uncontrolled cell growth.  This ultimately leads to tumor formation when the cell growth forms a mass of cells.  There are many known carcinogens, the most easily recognized is tobacco smoke, however very few direct links exist between dietary choices and cancer.  It is known that diets high in fat increase the incidence of colon cancer and increase recurrence rates of breast cancer after treatment.  It is unknown, though, if the high fat diet generates cancer causing free radicals effectively causing cancer or if the high fat diet only changes the body’s natural defenses.  For example, by providing less antioxidants, substances thought to combat cancer causing free radicals. 

There is an extensive collection of books, web sites, support groups, and medical practicioners who speak to diet and cancer.  All would agree, a healthy lifestyle is a tremendous asset in the fight against cancer, but what should patients be doing?  Most physicians do not recommend a dramatic departure from one’s diet after a diagnosis of cancer is made.  Most Oncologists also do not recommend large doses of antioxidant supplements.  Much of the potential benefit of foods rich in antioxidants such as broccoli, sweet potatoes, tomatoes, kale, and squash is thought to be in the prevention of cancer and not necessarily in it’s treatment.  Initially there were studies which showed a potential benefit to antioxidant supplements such as beta carotene.  However, in a recent concerning development, there have been a number of studies which have shown increased death rate from cancer when high doses of antioxidants such as selenium or beta carotene were used.  One theory is that the antioxidants are actually working against treatment, protecting the very cells chemotherapy or biotherapy is trying to kill.  Very reputable institutions such as the NIH cite the lack of consistent evidence as pause for concern. 

A similar lack of evidence exists for herbal supplements.  There are many reports of successful additions of complementary or integrative herbal remedies to standard allopathic chemotherapy treatments.  Wheat germ has been reported to boost immune function while on chemotherapy in small studies.  Possibly decreasing infection.   Some early studies show glutamine may decrease neuropathy.  What is not known because of a lack of large studies, is which patients are these remedies appropriate for, and does their positive effect also negate the cancer treatment effect.  Larger studies are needed. 

With the lack of clear evidence showing benefit and the potential to do harm, patients should be careful not to add herbal supplements, antioxidants, or make dramatic dietary changes without discussing it with their doctor.  For most patients the time to change is not when beginning a treatment that can cause changes in appetite, nausea, or weight loss, but after treatment is complete.  At that time a diet low in fat, high in naturally occurring antioxidants, and combined with exercise may lead to the most meaningful change in survival.