The role of your cancer health professional is to create an environment of openness and trust, and to help in making informed decisions about alternative/ complementary therapies. Collaboration will improve the safe integration of all therapies during your experience with cancer. The "Summary" and "Professional Evaluation/ Critique" sections of this Unconventional Therapies manual are cited directly from the medical literature, and are intended to help in the objective evaluation of alternative/ complementary therapies.
Summary
The evidence for vitamin E as a preventive agent against cancer is inconclusive. There is no evidence that vitamin E has efficacy as a treatment for cancer. Further studies on the effects of vitamin E on cancer are needed.
Description/ Source/ Components
"Vitamin E is a fat-soluble vitamin that exists in a variety of forms in many foods." (Kaegi)
"Absorption of vitamin E is dependent on an individual's ability to digest and absorb fat." (Loescher)
"Vitamin E is found in natural sources such as vegetable oils, wheat germ, margarine, whole grains, liver, almonds, hazelnuts, peanut butter and sunflower seeds." (Ontario)
"Its most common form in a Western diet is alpha-tocopherol." (Kaegi)
The recommended adult daily intake for vitamin E is 5-10mg [milligrams]. (Health and Welfare Canada)
History
"Initial studies of the relationship of vitamin E and cancer occurred in 1946 when Jaffe compared rats injected with methylcholanthrene (a carcinogen) alone or supplemented with wheat germ oil." (Loescher)
Proponent/ Advocate Claims - Use in Preventing Cancer
Proponents believe that "vitamin E acts as an immune enhancer, defending the body against free radicals, which are believed to lead to cancer." (Ontario)
"Vitamin E also has the potential to decrease DNA damage and inhibit malignant transformation through its antioxidant function. Additionally, this fat-soluble vitamin affects the immune system: decreased vitamin E is associated with decreased immune response while high levels of the substance have a stimulatory effect on immune function. (Meydani)" (Olson)
"A diet high in vitamin E is linked to a reduced risk for developing cancers of the liver, lung, oral cavity, esophagus, and colon, whereas low blood levels of vitamin E increase the risk for developing cancer." (Somer)
A 32% decrease in the incidence of prostate cancer was observed among the subjects receiving alpha-tocopherol (vitamin E) compared to those not receiving it... Mortality from prostate cancer was 41% lower among men receiving alpha-tocopherol." (Heinonen)
"A clinical study revealed a positive response to vitamin E therapy in patients with oral leukoplakia. (Benner)" (Kaegi)
"High dietary vitamin E intake possibly decreases the risk of cervical cancer." (World Cancer Research Fund)
"The results of the trial conducted by the Alpha-Tocopherol, Beta Carotene (ATBC) Cancer Prevention Study Group should not be seen as proving the vitamins to be ineffective or even hazardous, since the trial was of limited duration and the daily dose of vitamin E was rather small." (Hennekens) [See (Alpha), under Professional Evaluation/ Critique - Use in Preventing Cancer.]
It was concluded that alpha-tocopherol had no effect on the risk of lung cancer in smokers. However, further analysis of the ATBC Prevention Study also yielded the conclusion that "long term supplementation with alpha-tocopherol substantially reduced prostate cancer incidence and mortality in male smokers." "Other controlled trials are required to confirm the findings. (Heinonen)
In the Linxian, China trials, small but significant reductions in cancer mortality were observed in subjects taking beta-carotene, alpha-tocopherol and selenium. (Blot)
"Vitamin E administration can counteract vitamin A toxicity." (Ontario) (Loescher)
Professional Evaluation/ Critique - Use in Preventing Cancer
In a randomized, double-blind, placebo-controlled primary-prevention trial performed by the Alpha-Tocopherol, Beta Carotene (ATBC) Cancer Prevention Study Group in Finland, there is "no evidence of a beneficial effect of supplemental vitamin E in terms of the prevention of lung cancer." (Alpha)
Regarding the results from the ATBC study (see proponent claims and above), "Silvia Franceschi (Aviano Cancer Centre, Aviano, Italy) warns that the results of studies of vitamin supplementation can be difficult to interpret, especially when there are multiple endpoints and no strong a priori hypothesis. 'If the effect of a vitamin supplement is examined at, say, 20 cancer sites', says Franceschi, 'it is likely to appear protective at one site purely by chance.'" (Bonn)
Greenberg, et al conducted a "randomized, controlled clinical trial to test the efficacy of beta carotene and vitamins C and E in preventing colorectal adenoma, a precursor of invasive cancer." They concluded; "the lack of efficacy of these vitamins argues against the use of supplemental beta carotene and vitamins C and E to prevent colorectal cancer. Although our data do not prove definitively that these antioxidants have no anticancer effect, other dietary factors may make more important contributions to the reduction of the risk of cancer." (Greenberg)
Vitamin E did not confer any protection against prostate cancer induction in rats. (McCormick)
"Data from a study of 1,993 cases and 2,410 controls were used to evaluate the associations between the four most common forms of dietary vitamin E and supplemental vitamin E and colon cancer. After adjusting for other health and life-style factors, we did no observe a statistically significant association between dietary tocopherols and colon cancer." (Slattery)
"Supplementation with alpha-tocopherol or beta-carotene for 5 years has no major impact on the occurrence of neoplastic changes of the stomach in older male smokers with atrophic gastritis." (Varis)
"High dietary vitamin E intake possibly has no relationship with the risk of stomach cancer." (World Cancer Research Fund)
"A study involving patients with benign breast disease showed that vitamin E supplements were not beneficial. (Meyer)" (Kaegi)
"The evidence that vitamin E intake may prevent breast cancer is fairly strong from theoretical considerations and animal experiments but much weaker from epidemiologic studies in humans... Overall, however, it appears that further investigation into whether vitamin E plays a role in breast cancer prevention is justified." (Kimmick)
Proponent/ Advocate Claims - Use in Treating Cancer
"Vitamin E inhibits the growth of pre-existing cancer cells possibly by blocking the synthesis of DNA and protein in the abnormal cells." (Somer)
"It is suggested that inhibition of tumour angiogenesis by vitamin E may be an additional mechanism for the anticancer action of vitamin E." (Shklar)
Professional Evaluation/ Critique - Use in Treating Cancer
"Although there has been some research into vitamin E's role in cancer prevention, very little research was found that addressed its potential role in cancer treatment." (Kaegi)
"Fifteen eligible [breast cancer] patients with measurable/evaluable disease refractory to standard hormonal therapy were treated [with tocotrienols, a form of vitamin E] between February 1994 and December 1996... There were no partial or complete responders." (Vandenberg)
Toxicity/ Risks
"The toxicity of vitamin E in adults appears to be low. Clinical trials have shown that large doses (e.g., 200-800 mg/d) do not result in serious side effects in most adults, with the possible exception of individuals taking oral anticoagulant therapy and those with vitamin K-related clotting disorders. High levels of vitamin E can adversely affect the absorption of vitamins A and K, and long-term use of high doses may cause nausea, diarrhea and blurred vision. High-dose therapy in infants may be associated with more serious side effects." (Kaegi)
"Megadose of vitamin E may depress blood coagulation. Platelet aggregation is inhibited and the prothrombin time may be prolonged." (Loescher) (Ontario)
According to one study, alpha-tocopherol increased the risk of coronary heart disease. "Based on these findings, we recommend that patients with a previous myocardial infarction who smoke should not use this agent." (Rapola)
Reduced sexual function is a sign of vitamin E overdose, although it is rare. (Cassileth)
According to Roberts, the most common complaints attributable to megadose vitamin E supplementation were hypertension, thrombophlebitis [inflammation of a vein due to obstruction by an aggregation of blood factors], pulmonary embolism [the closure to the pulmonary artery by a blood clot], painful or enlarged breasts, and severe fatigue. "Other reactions included the apparent precipitation or aggravation of angina pectoris [spasmodic, choking, or suffocating thoracic pain], infection, urticaria [hives], headache, and hypoglycemia [abnormal decrease in sugar in the blood]." (Roberts)
"Animal studies showed that vitamin E is not mutagenic, carcinogenic, or teratogenic. The toxicity of vitamin E is very low." (Helzlsouer)
References
Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. New England Journal of Medicine 1994 Apr 14;330(15):1029-1035.
Benner SE, et al. Regression of oral leukoplakia with alpha-tocopherol: a community clinical oncology program chemoprevention study. J Natl Cancer Inst 1993;85:44-7.
Blot WJ, et al. The Linxian trials: mortality rates by vitamin-mineral intervention group. American Journal of Clinical Nutrition 1995;62 (suppl.):1424S-1426S.
Bonn D. Vitamin E may reduce prostate cancer incidence. Lancet 1998;351:961.
Cassileth BR. Alternative medicine handbook: the complete reference guide to alternative and complementary therapies. New York: W.W.Norton & Co., 1998:71.
Greenberg ER, et al. A clinical trial of antioxidant vitamins to prevent colorectal adenoma. N Engl J Med 1994;331:141-7.
Health and Welfare Canada. Nutrition recommendations. The Report of the Scientific Review Committee 1990.
Heinonen OP, et al. Prostate cancer and supplementation with alpha-tocopherol and beta-carotene: incidence and mortality in a controlled trial. J Natl Cancer Inst 1998;90:440-6.
Helzlsouer KJ. Summary of the round table discussion on strategies for cancer prevention: diet, food, additives, supplements, and drugs. Cancer Research 1994 Apr 1;54(Suppl):2044s-2051s.
Hennekens CH, Buring JE. Antioxidant vitamins - benefits not yet proved. New England Journal of Medicine 1994 Apr 14;330(15):1080-1081.
Kaegi E, on behalf of the Task Force on Alternative Therapies of the Canadian Breast Cancer Research Initiative. Unconventional therapies to cancer: 5. Vitamins A, C, and E. Canadian Medical Association 1998; 158:1483-88.
Kimmick GG, et al. Vitamin E and breast cancer: a review. Nutrition and Cancer 1997;27:109-117.
Loescher LJ, Sauer KA. Vitamin therapy for advanced cancer. Oncology Nursing Forum 1984 Nov/Dec;11(6):38-45.
McCormick D, et al. Differential activity of 9-cis-retinoic acid, alpha-tocopherol, and selenomethionine as chemopreventive agents in the rat prostate (Meeting Abstract). Proc Annu Meet Am Assoc Cancer Res 1997;38:A1754.
Meyer EC, et al. Vitamin E and benign breast disease. Surgery 1990;47:253-7.
Meydani M. Vitamin E. Lancet 1995;345:170-5.
Olson BK, Pienta KJ. Vitamins A and E: further clues for prostate cancer. J Natl Cancer Inst 1998;90:414-5.
Ontario Breast Cancer Information Exchange Project. Guide to unconventional cancer therapies. 1st ed. Toronto: Ontario Breast Cancer Information Exchange Project, 1994:134-135.
Rapola JM, et al. Randomized trial of alpha-tocopherol and beta-carotene supplements on incidence of major coronary events in men with previous myocardial infarction. Lancet 1997;349;1715-20.
Roberts HJ. Vitamin E [letter]. Lancet 1995 Mar 18;345:737.
Shklar G, Schwartz JL. Vitamin E inhibits experimental carcinogenesis and tumour angiogenesis. Eur J Cancer B Oral Oncol 1996;32B:114-9.
Slattery ML, et al. Vitamin E and colon cancer: is there an association? Nutr Cancer 1998;30:201-6.
Somer E and Health Media of America. Essential guide to vitamins and minerals. USA: Harper Perennial, 1995:32-3,188.
Vandenberg TA, et al. A phase I study of the tocotrienol rich fraction (TRF) of palm oil in metastatic breast cancer. Proc Annu Meet Am Soc Clin Oncol 1997;16:A685.
Varis K, et al. Gastric cancer and premalignant lesions in atrophic gastritis: a controlled trial on the effect of supplementation with alpha-tocopherol and beta-carotene. The Helsinki Gastritis Study Group. Scandanavian Journal of Gastroenterology 1998;33:294-300.
World Cancer Research Fund in Association with American Institute for Cancer Research. Food, nutrition and the prevention of cancer: a global perspective. World Cancer Research Fund/American Institute for Cancer Research, 1997;157,235-6,307.
Revised February 2000