Asian Pacific Journal of Cancer Prevention, Vol 9, 2008 343 Antioxidants, Oxidative Stress and Breast Cancer Risk in Malaysia Asian Pacific J Cancer Prev, 9, 343-350 Introduction Breast cancer is the commonest cancer among women in Malaysia (MAKNA, 2003) and developing countries (WHO, 1997). A total of 4,337 breast cancer cases were reported in the year 2002 by the National Cancer Registry Report (2002). Almost 30% of the cancer disease suffered by Malaysian women is breast cancer. Every woman in Malaysia has a 1 in 19 chance of getting breast cancer in their lifetime. Chinese women have the highest risk of getting breast cancer with the ratio of 1:14, followed by Indian women 1:15 and Malays 1:24 (National Cancer Registry, 2002). Among the risk factors contributing to breast cancer are menarche at early age, having first pregnancy at late age, low number of children and late menopause, related 1 Dept. of Nutrition and Dietetics, Faculty of Allied Health Sciences, National University of Malaysia, 2 Dept. of Dietetics, International Medical University Malaysia, 3 Dept. of Biomedical Sciences, Faculty of Allied Health Sciences, National University of Malaysia, Jalan Raja Muda Abd Aziz 50300, Kuala Lumpur, 4 Dept. of Nutrition and Dietetics, Faculty of Medical and Health Sciences. Universiti Putra Malaysia, Selangor, 5 Toxicology and Pharmacology Unit, Herbal Medicine Research Centre, Institute for medical Research, Jalan Pahang, 50588 Kuala Lumpur, MALAYSIA. *For correspondence: Email: suzanas@medic.ukm.my Abstract A case control study was carried out to investigate associations between breast cancer risk, antioxidant status and oxidative stress among women in Klang Valley and Selangor. A total of 57 newly diagnosed cases aged 30 to 66 years old participated and were matched for age and ethnicity with 139 controls with no diagnosis of cancer or other chronic diseases. An interview based questionnaire designed to collect information on demographic and socioeconomic status, as well as reproductive, medical and dietary history was used. Anthropometric measurements including weight, height, waist and hip circumference were made and a 10 ml fasting venous blood sample was taken for glucose testing and analysis of plasma vitamin antioxidants and malondialdehyde. Hair and toenail samples were taken for selenium analysis. Results showed that the mean intake of vitamin A, vitamin E and selenium among cases (606.8± 334.8μg/d, 6.1± 2.4 g/d, 56.9 ± 16.2 μg/d) was lower than controls (724.7 ± 414 μg/day, 6.9 ± 3.0 g/d, 60.8 ± 17.5 μg/d, respectively) (p<0.05 for all parameters). A similar trend was noted for plasma vitamin A and E and also selenium in hair and toenails. Poor antioxidant status as indicated by low plasma vitamin A (<284.3 μg/l or <366.3 μg/l) increased risk of breast cancer by approximately two fold, whilst low plasma vitamin E (<2.5 mg/dl, <2.8 mg/dl and <3.1 mg/dl) increased the risk by two to three fold [Adjusted OR 2.97 (95% CI 1.38-3.48), 2.32 (95% CI 1.07-2.41) and 2.12 (95% CI 1.00- 4.21)]. Cases had a greater level of malondialdehyde 4.4 ± 1.1 mmol/g protein), an indicator of oxidative stress, as compared to controls (3.2 ± 1.7 mmol/g protein)(p<0.05). A high level of MDA (≥ 4.8 mmol/g protein) was associated with breast cancer [Adjusted OR 6.82 (95% CI 1.95-23.9)]. It is concluded that a poor antioxidant status and high oxidative stress are associated with breast cancer risk. Thus, it is essential for Malaysian women to obtain a good antioxidant status by consuming a diet rich in vitamins A and E as well as selenium and adopt healthy behaviour to reduce oxidative stress in order to prevent breast cancer. Key Words: Breast cancer risk - antioxidant status - oxidative stress - selenium - malondialdehyde to endogenous hormones (Hulka & Stark, 1995; World Cancer Research Fund, 1997) and the use of hormone replacement therapy (Rodriguez et al., 2001). Higher levels of hormone, especially estrogen, could play the role in enhancing the first phase of carcinogenesis in breast (Del Giudice et al., 1998; Hankinson et al., 1998). The most prominent modifiable risk factor of breast cancer is diet. High intake of animal fat and meat more than once a week may increase the risk (Lee et al., 2004) as it increases insulin resistance and IGF-1 (Stoll, 1996). In contrast, the intake of vegetables rich in antioxidant may prevent up to 33% incidence of breast cancer (World Cancer Research Fund, 1997). Thus, a reduction in antioxidant level due to the presence of free radicals may increase risk of breast cancer, particularly in alcohol drinkers (Terry et al., 2001) and smokers (Egan et al., RESEARCH COMMUNICATION Antioxidants Intake And Status, And Oxidative Stress In Relation To Breast Cancer Risks: A Case-Control Study Shahar Suzana 1 *, H Normah 1 , A Fatimah 2 , R Nor Fadilah 3 , G Ahmad Rohi 3 , I Amin 4 , BG Cham 1 , R Mohd Rizal 2 , MN Fairulnizal 5