Prospective study of smoking, antioxidant intake, and lung cancer in middle-aged women (USA) F.E. Speizer 1, *, G.A. Colditz 1 , D.J. Hunter 1 , B. Rosner 1 & C. Hennekens 1 1 Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, and the Departments of Nutrition and Epidemiology, Harvard School of Public Health, Boston, MA, USA Received 11 August 1998; accepted in revised form 25 May 1999 Key words: cigarette smoking, dietary antioxidants, lung cancer. Abstract Background: Although substantial evidence suggests that higher intake of fruits and vegetables can reduce the adverse impact of smoking on lung cancer risk, great uncertainty exists regarding the speci®c foods and their constituents that are protective. We therefore examine prospectively the relation between cigarette smoking and lung cancer incidence among women, and quantify the associations between dietary antioxidants, other nutrients, and lung cancer risk. Methods: In a 16-year prospective cohort study (the Nurses' Health Study), 593 cases of lung cancer were con®rmed during 1,793,327 person-years of follow-up. Dietary data, including vitamin supplement use and food intake, were collected in 1980 using a validated semiquantitative food frequency questionnaire. Results: The risk of lung cancer increased with the number of cigarettes smoked and with early onset of cigarette smoking. The risk decreased rapidly with the discontinuation of smoking but took 15 years to fall to about the level of risk for women who had never smoked. Dietary intake of fat was not related to the risk of lung cancer. Although b-carotene intake was not related to risk, intake of carrots showed a strong inverse relation: women who reported consuming ®ve or more carrots per week had a relative risk of 0.4 (95% CI = 0.2±0.8) compared with the risk for women who never ate carrots. Conclusions: Smoking is the most important risk factor for lung cancer in women, as it is in men. Higher vegetable consumption, particularly of carrots, may signi®cantly reduce the risk of lung cancer, but dietary modi®cation cannot be considered a substitute for smoking prevention and cessation. Introduction Although the overwhelming positive association of cigarette smoking with lung cancer has been recognized for over 40 years, lung cancer remains the most common fatal cancer in the United States. Since 1990, lung cancer killed more women each year than breast cancer. While prospective data among women are limited, the follow-up of the American Cancer Society CPS-I and II and the cohort of Kaiser Permanente participants show strong relations between smoking and lung cancer [1, 2]. There is no question that cigarette smoking is the major cause of lung cancer in both men and women. National statistics indicate that the gender- related dierence in rates of lung cancer in the United States is explained, in large part, by the dierent times at which men and women took up smoking [3]. Generally, smoking became prevalent among women in the United States in the mid-20th century; men began smoking cigarettes in large numbers some 25 years earlier. Contemporary data from large prospective studies are important in tracking the epidemic as it evolves. More recently, risk factors for lung cancer other than active smoking have been considered. These risk factors include occupational exposures, family history of lung * Correspondence to: Frank E. Speizer, MD, Co-Director, Chan- ning Laboratory, 181 Longwood Avenue, Boston, MA 02115, USA, representing the Nurses' Health Study Research Group. e-mail to frank.speizer@channing.harvard.edu. Cancer Causes and Control 10: 475±482, 1999. 475 Ó 1999 Kluwer Academic Publishers. Printed in the Netherlands.