Increasing levels of the amino acid cysteine may be able to reduce the risk of breast cancer, according to a study presented on Saturday at the 94th Annual Meeting of the American Association for Cancer Research (AACR).
Cysteine is the precursor to glutathione, a powerful antioxidant and also used to cleanse the body of toxins. N-acetylcysteine, a synthetic precursor of cysteine, is commonly used as an antidote to paracetamol-induced liver damage.
Women in the group with highest levels of plasma cysteine had a significant 56 per cent 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, said the researchers.
"The findings suggest that higher levels of total cysteine may predict a reduced risk for breast cancer," said lead investigator Dr Shumin Zhang of Brigham and Women's Hospital, Harvard Medical School, and Harvard School of Public Health. "Based on these results, we are hopeful that cysteine or its precursors may have potential chemopreventive benefits against breast cancer."
Breast cancer is the second leading cause of cancer-related death in women. More than 212,600 new cases of breast cancer will be diagnosed in the US in 2003, according to the American Cancer Society.
The prospective, case-controlled study was conducted among 32,826 women in the Nurses' Health Study, started in 1976 at Brigham and Women's Hospital. 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.
Cysteine is found in high protein foods such as poultry, wheat, broccoli, eggs as well as garlic, onions and red peppers.
For proceedings of last weekend's meeting, see the AACR website.