By David Liu, PHD

Thursday April 4, 2013 (foodconsumer.org) -- It has been well known for many years that estrogen, endogenous or exogenous, promotes breast cancer.  A new study in Carcinogenesis suggests that taking antioxidant supplements like vitamin C or eating high amounts of vitamin C rich vegetables can help offset this "side effect" of estrogen, which is a female hormone.

The study led by Bhupendra Singh and Hari K. Bhat from University of Missouri-Kansas City shows that vitamin C, naturally occurring in green vegetables and butylated hydroxyanisole - an artificial antioxidant that is commonly used in processed foods can induce the production of superoxide dismutase 3, which was found to reduce a biomarker that is associated with breast cancer among other things.

Epidemiological evidence shows estrogen plays a role in the development of breast cancer and estrogen induces DNA damaging oxidative stress, according to the study report.

Earlier the researchers have demonstrated that antioxidants vitamin C and butylated hydroxyanisole effectively inhibit 17β-estradiol (E2)-induced breast tumor development in female ACI rats.  The current study was intended to examine how antioxidants like vitamin C prevent breast cancer development in animals exposed to estrogen.

In the study, female rats was exposed to 17β-estradiol, vitamin C, vitamin C plus 17β-estradiol, BHT, and BHT plus 17β-estradiol for up to weight months.

Superoxide dismutase 3 (SOD3), an antioxidant enzyme, was found suppressed in 17β-estradiol-exposed mammary tissues and in mammary tumors of rats treated with 17β-estradiol. However, the suppression was reduced in rats treated with 17β-estradiol along with vitamin C or BHT indicating that antioxidants can overcome the suppression.

Also, 8-Hydroxydeoxyguanosine (8-OHdG) a marker of oxidative DNA damage was found lower in mammary tissue and mammary tumors of rats treated with both estrogen and an antioxidant - vitamin C or BHT compared with rats treated with estrogen only.

The researchers said "Increased DNA damage, colony and mammosphere formation, and migration in SOD3 knocked down MCF-10A cells, and nuclear translocation of SOD3 in vitamin C-treated mammary tissues and in MCF-10A cells suggest protective role of SOD3 against DNA damage and mammary carcinogenesis." 

They concluded "Our studies further demonstrate that SOD3, but not SOD2 and SOD1, is induced by antioxidants and is regulated through NRF2. SOD3 may thus be an important gene in defense against oxidative stress and in the prevention of estrogen-mediated breast cancer."

Estrogen is commonly used in contraceptives and hormone replacement therapy.   An authoritative organization says that two biggest risk factors for breast cancer are hormone replacement therapy and medical radiation used in diagnostics and cancer screening and treatment.

Breast cancer is expected in one out of eight women in their lifetime in the U.S.  Each year, more than 230,000 American women are diagnosed with the disease and 37,000 die from the disease.