Antioxidant use may or may not be beneficial to breast cancer patients

A new US study speculates that the frequent use of vitamin C and vitamin E in the period after breast cancer diagnosis may be associated with a decreased likelihood of recurrence, whereas frequent use of a combination of carotenoids may be associated with increased mortality. Experts warn against jumping to conclusions.

In the observational study, the potential associations between antioxidant use in a 2-year period after diagnosis of early stage breast cancer and death from breast cancer as well as recurrence were examined in 2264 women (1). The study results showed that the use of one or more antioxidant -containing supplements after diagnosis was reported by 81% of women. Among antioxidant users, daily use of vitamin C and vitamin E seemed to be associated with a decreased risk of breast cancer recurrence. In addition, vitamin E use was associated with a decreased risk of death from any cause. Conversely, frequent use of combination carotenoids, such as beta-carotene and lycopene, seemed to be associated with an increased risk of death from breast cancer and all-cause mortality.

The scientists concluded that frequent users of vitamin C and vitamin E supplements after breast cancer diagnosis may benefit from decreased risk of breast cancer recurrence and mortality compared to women not using supplements. Although the mechanism by which carotenoid supplementation may increase mortality could not be distinguished, the results would suggest that there may be cause for concern with carotenoid supplementation in the period after a breast cancer diagnosis and during treatment.

Experts criticized that the observational study did not prove a causal relationship between antioxidants and breast cancer recurrence or mortality. Thus, as the authors of the study restrictively admitted, the findings should be considered hypothesis-generating. Another critique was that the study lacked information on specific doses, formulations, and duration of use of the single antioxidants in the supplements used. The experts reminded with their critique that dietary supplements should not be evaluated in the same way drugs are. Antioxidants may have a supportive role in preventing diseases but should not be seen or measured as treatment for complex diseases such as cancer. Moreover, the study results could not be applied to normal, healthy woman using antioxidant supplements.

1. Greenlee H. et al. Antioxidant Supplement Use After Breast Cancer Diagnosis and Mortality in the Life After Cancer Epidemiology (LACE) Cohort. Cancer. October 2011.