A prospective study of plasma cysteine and risk of breast cancer Shumin M. Zhang, Walter C. Willett, Jacob Selhub, JoAnn E. Manson, Graham A. Colditz, Susan E. Hankinson, Division of Preventive Medicine and Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, and Departments of Epidemiology and Nutrition, Harvard School of Public Health, Boston MA 02215; the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA Background: Cysteine is the precursor of glutathione, a powerful intracellular antioxidant and an important detoxifying agent of carcinogens. However, data relating plasma cysteine to breast cancer risk are sparse. Methods: We conducted a prospective nested case-control study among 32,826 women in the Nurses' Health Study who provided blood specimens during 1989-1990. Through 1996, a total of 712 incident breast cancer cases were identified and individually matched to 712 controls by year of birth, time of day that blood was drawn, fasting status, month of blood sampling, recent use of postmenopausal hormones at the time of blood collection, and menopausal status. Conditional logistic regression with adjustment for other risk factors for breast cancer was used to estimate the relative risks of breast cancer by levels of plasma cysteine. All statistical tests were two-sided. Results: Higher plasma cysteine concentrations were significantly associated with a lower risk of breast cancer. For women in the highest quintile of plasma cysteine, compared with those in the lowest quintile, the multivariate relative risk was 0.44 (95% confidence interval = 0.26-0.74). This association was dose-dependent (P value for trend = 0.002) and independent of plasma measures of folate, vitamin B6, vitamin B12, and homocysteine. The inverse association between plasma cysteine concentrations and risk of breast cancer was not significantly modified by other risk factors for breast cancer, except that a stronger association was observed among women who were leaner. Conclusions: The findings from this prospective study suggest that higher plasma concentrations of cysteine predict a reduced risk of breast cancer. N-acetylcysteine, a synthetic precursor of cysteine, might have the potential to be chemopreventive against breast cancer. AACR Abstract Number: LB-3, 2003 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.