Much interest has been expressed in the therapeutic role of vitamins in cancer patients. This has led a number of alternative and complementary practitioners to advocate the use of high-dose vitamins for cancer patients. It has been know for some time that some vitamin-deficiency states may predispose some individuals to develop cancer. In a study of 29 000 vegetarian Chinese with a high frequency of oesophageal cancer, subjects were given supplements of ^-carotene and vitamin E. Raising their daily intake above the minimum requirement reduced the incidence of deficiencies and reduced the number of oesophageal cancers. This type of study on vitamins and the etiology of cancer has led many practitioners and laypeople to extrapolate he role of vitamins into cancer treatment.
Although vitamins in food, especially vegetables and fruits, have been shown to be beneficial in reducing the incidence of particular types of cancer when included in the diet, the beneficial effects have not always been shown with vitamin and mineral supplements. Some supplements may promote tumor growth, as was seen in a study using ^-car-otene supplementation in patients with lung cancer. Supplementation increased the rate of tumor recurrence in such patients.
The potential therapeutic role of vitamins, such as vitamins D, K, B6, B12, and folate, has been investigated. However, additional studies are required to determine the role, if any, of such vitamins. It may be that some vitamins help protect against the side effects of tumor therapy, whereas some may modify tumor growth. Excessive dietary supplementation in cancer patients should be avoided until further evidence is available on the effects of vitamins on tumor growth.
See also: Cancer: Epidemiology and Associations Between Diet and Cancer; Epidemiology of Gastrointestinal Cancers Other Than Colorectal Cancers; Epidemiology of Lung Cancer; Effects on Nutritional Status. Cobalamins. Colon: Nutritional Management of Disorders. Diarrheal Diseases. Eating Disorders: Anorexia Nervosa. Folic Acid. Nutritional Support: Adults, Enteral; Adults, Parenteral; Infants and Children, Parenteral. Supplementation: Dietary Supplements. Vitamin B6. Vitamin D: Physiology, Dietary Sources and Requirements. Vitamin E:
Metabolism and Requirements; Physiology and Health Effects. Vitamin K.
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