Antioxidants may reduce breast cancer risk

Increased intakes of beta-carotene, vitamin C, vitamin E and zinc may protect against breast cancer in postmenopausal women, suggests a new Canadian study.

In the population-based case-control study, intakes of antioxidants from diet and from supplementation as well as other potential risk factors for breast cancer were collected by a self-reported questionnaire from 2,362 individuals with pathologically confirmed incident breast cancer and 2,462 controls (1). The study results showed that supplementation of zinc in premenopausal women, and supplementation of multivitamins, beta-carotene, vitamin C, vitamin E and zinc in postmenopausal women for 10 or more years significantly reduced breast cancer incidence. No significant effect of antioxidant intakes from dietary sources or from supplementation less than 10 years was observed.

The researchers concluded that long-term intake of antioxidants from diet or supplements may protect women from developing breast cancer. As they could not assess the exact dose of antioxidants from dietary supplements (different producers, years and batches), they were unable to determine the overall effect of total dose or intake from both diet and supplements. Antioxidants may exert their preventive effect over a long period of time which may be the reason why the effect for supplementation of 10 years or longer only was observed.

Antioxidants such as vitamin A and its precursor beta-carotene, vitamins C and E, as well as selenium have drawn a lot of attention as they have been shown in experimental studies to neutralize or trap reactive oxygen species thereby preventing cellular (DNA) damage potentially causing diseases such as cancer. Although there is considerable evidence of anticancer effect of antioxidants from cell culture and animal studies, the results from observational studies and intervention trials are inconsistent (2). However, since antioxidant enhancement, either through increased dietary intake or by supplementation, is a preventive measure that can be easily implemented, further studies to look at this association are warranted.

1. Pan S. Y. et al. Antioxidants and breast cancer risk – a population-based case-control study in Canada. BMC Cancer. 2011; 11(1):372.
2. Michels K. B. et al. Diet and breast cancer: a review of the prospective observational studies. Cancer. 2007; 109:2712–2749.