Antioxidant Vitamins Associated with Reduced Risk of Ovarian Cancer

Women taking vitamins C and E may have a lower risk of developing ovarian cancer, according to a recent study published in the journal Nutrition and Cancer.¹

In this new study, the authors surveyed the dietary habits and nutritional supplement use of 168 women with a new diagnosis of ovarian cancer. The results of the survey were then compared with a similar survey of 250 women of similar age with no history of ovarian cancer.

Women taking the most supplemental vitamin C (over 90 mg per day) had a 60% lower risk of ovarian cancer, compared with women not taking vitamin C. The protective effect of vitamin C was more pronounced in nonsmokers (68% reduction in risk) than in smokers (19% reduction). Similarly, women taking amounts of vitamin E above 30 mg per day (this would be approximately 30 IU of synthetic or 45 IU of natural vitamin E per day) had a 67% reduction in ovarian cancer risk, compared with women not taking vitamin E. The researchers controlled for other potential risk factors, such as smoking, use of birth control pills, and age at menopause.

Contrary to earlier research,^{2 3 4} antioxidants from the diet were not found to offer significant protection against ovarian cancer. Frequent consumption of green, leafy vegetables appeared particularly beneficial in earlier studies; however, these foods may contain protective factors other than the ones assessed in the new study. Supplementation with either selenium or vitamin E has been shown to reduce risk of certain cancers in large clinical trials.^{5 6}

There were an estimated 23,000 new cases of ovarian cancer in the United States in 2001.⁷ It is the fifth most common cause of cancer death in women.

This new study, known as a case-control study, is considered weak evidence in scientific circles due to the potential for identifying a false association. For example, in this study there is a possibility that women who take nutritional supplements also engage in other health-promoting activities (exercise, for example) that could have been responsible for the benefits seen by the authors. To confirm these preliminary results, a double-blind clinical trial of vitamin C and E supplementation will need to follow.

In the meantime, women concerned about ovarian cancer risk may in fact derive some protection from supplementation with vitamins C and E, which are safe and relatively inexpensive. These vitamins, together with a diet high in vegetables and low in saturated fat, might be a reasonable ovarian cancer-prevention strategy until more evidence becomes available.

References:

1. Fleischauer AT, Olson SH, Mignone L, et al. Dietary antioxidants, supplements, and risk of epithelial ovarian cancer. Nutr Cancer 2002;40:92–8.
2. Parazzini F, Chatenoud L, Chiantera V, et al. Population attributable risk for ovarian cancer. Eur J Cancer 2000;36:520–4.
3. Kushi LH, Mink PJ, Folsom AR, et al. Prospective study of diet and ovarian cancer. Am J Epidemiol 1999;149:21–31.
4. La Vecchia C, Decarli A, Negri E, et al. Dietary factors and the risk of epithelial ovarian cancer. J Natl Cancer Inst 1987;79:663–9.
5. Clark LC, Combs GF Jr, Turnbull BW, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA 1996;276:1957–63.
6. Heinonen OP, Albanes D, Virtamo J, 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.
7. Greenlee RT, Hill-Harmon MB, Murray T, Thun M. Cancer statistics, 2001. CA Cancer J Clin 2001;51:15–36.

Matt Brignall, ND, is in practice at the Seattle Cancer Treatment and Wellness Center and at the Evergreen Integrative Medicine Clinic in Kirkland, WA. He specializes in integrative treatment of cancer. He is a contributor to Healthnotes and Healthnotes Newswire.

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