The Role of Complementary and Alternative Therapies in Cancer

Dietary Modification and Supplementation

Evidence from epidemiological studies strongly supports a relationship between dietary factors and the risk for developing certain types of cancers. In general, a diet that is rich in certain food constituents (e.g., fruits, vegetable, fiber) appears to be protective against the development of cancer. In contrast, excessive consumption of other dietary substances (e.g., animal fats, alcohol) appears to increase the risk of certain types of cancers. Some vitamins that possess antioxidant properties (e.g., vitamins A, C, and E) may protect against certain types of cancers by protecting the body's cells from damage by certain compounds known as free radicals.

The role of dietary modification and antioxidant vitamin supplementation in slowing the progression of cancer continues to be an area of ongoing research. Currently, there are no conclusive studies which prove that any type of dietary modification or antioxidant vitamin supplementation can alter the progression of the disease in cancer patients.

Cancer patients who are considering dietary modification and/or antioxidant vitamin supplementation need to be aware of certain risks that may be associated with these regimens:

• Unintentional weight loss is a relatively common side-effect of cancer treatment, particularly among patients who are undergoing chemotherapy and/or radiation therapy. Excessive reduction of certain dietary components, such as dietary fat intake, may increase the risk of malnutrition in cancer patients. It is, therefore, important for patients to discuss the potential risks and benefits of any dietary modification with their oncologist before making a decision to modify their dietary intake.

• Some radical dietary regimens, such as macrobiotic diets (that are primarily vegetarian) may potentially promote the progression of disease in women with estrogen-receptor positive breast cancer or endometrial cancer due to their high content of isoflavonoid phytoestrogens. The same concern applies to diets that promote soy supplementation as a means of slowing the progression of cancer. Soy products contain high amounts of isoflavonoid phytoestrogens and should be avoided by women with estrogen-receptor positive tumors.

• High doses of certain antioxidant vitamin supplements (vitamins C and E) may increase the risk of bleeding complications in patients who have low levels of platelets in the bloodstream (thrombocytopenia) or patients who are taking anticoagulant medications. High doses of vitamin A can cause a condition called Hypervitaminosis A (Vitamin A toxicity) that can cause symptoms such as nausea, vomiting, headaches, blurry vision, and impaired consciousness.