Researchers Believe Common Antioxidant May Decrease Risk of Breast Cancer

Washington, D.C. – Researchers believe that higher total cysteine levels may be associated with a lower risk of breast cancer, according to a study presented recently at the 94th Annual Meeting of the American Association for Cancer Research (AACR). Cysteine, an amino acid, is the precursor to glutathione (a powerful antioxidant and important detoxifying agent). Glutathione is used to cleanse the body of harmful toxins. N-acetylcysteine, a synthetic precursor of cysteine, is commonly used as a mucolytic agent and as an antidote against acetaminophen-induced hepatotoxicity.

Women in the highest level of plasma cysteine group had a significant 56 percent reduction in risk of developing breast cancer as compared with those in the lowest level group. The association was not significantly altered by any other major risk factors related to breast cancer, except that a stronger association was observed among leaner women.

“The findings suggest that higher levels of total cysteine may predict a reduced risk for breast cancer,” said Dr. Shumin Zhang, of Brigham and Women’s Hospital, Harvard Medical School, and Harvard School of Public Health, and lead investigator on the study. “Based on these results, we are hopeful that cysteine or its precursors may have potential chemopreventive benefits against breast cancer.”

The prospective, case-controlled study was conducted among 32,826 women in the Nurses’ Health Study. A total of 712 incidents of breast cancer were matched to 712 controls by year of birth, time of day that the blood was drawn, fasting status, month of blood sampling, recent use of postmenopausal hormones at the time of blood collection, and menopausal status. Scientists used conditional logistic regression with adjustment for other breast cancer risk factors to estimate the relative risks for breast cancer by levels of plasma total cysteine.

The Nurses’ Health Study was initiated in 1976 at Brigham and Women’s Hospital. The NHS is the longest running major women’s health study ever undertaken and has resulted in hundreds of journal articles, many containing groundbreaking findings on how to prevent some of the major causes of disease and death in women.

More than 212,600 new cases of breast cancer will be diagnosed and nearly 40,000 women will die in 2003, according to the American Cancer Society. Breast cancer is the second leading cause of cancer-related death in women.


Founded in 1907, the American Association for Cancer Research (AACR) is a professional society of more than 20,000 laboratory and clinical scientists engaged in cancer research in the United States and more than 60 other countries. AACR’s mission is to accelerate the prevention and cure of cancer through research, education, communication and advocacy. Its principal activities include the publication of five major peer-reviewed scientific journals (Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention). AACR’s annual meeting attracts more than 12,000 participants who share new and significant discoveries in the cancer field, and the AACR’s specialty meetings throughout the year focus on all the important areas of basic, translational and clinical cancer research.

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