Chronic Obstructive Pulmonary Disease (COPD) is a major cause of morbidity and mortality in the United States and is a growing cause of chronic disease internationally. Presently, there are limited treatment options for this disease to modify the progression of airflow obstruction and decrease periodic exacerbations. Recent evidence has emphasized the central role of oxidative stress as a mechanism of COPD pathobiology. Evidence from investigators' group has shown that COPD patients and animals exposed to cigarette smoke have impairment of antioxidant defenses which are caused by a defect in activity of nuclear factor erythroid 2 like 2 (Nrf2), a prolific regulator of anti-oxidant enzymes, glutathione homeostasis, and cytoprotective proteins. Activation of Nrf2 protects mice with chronic smoke exposure from developing emphysema, decreases oxidative stress, increases proteasomal anti-apoptotic cytoprotective responses, improves bacterial phagocytosis and killing, and reverses tobacco-smoke induced corticosteroid resistance. Similarly, in vitro Nrf2 activation in human COPD lung cells has shown improved cytoprotection, improved bacterial clearance, and restoration of steroid sensitivity. This trial focuses on sulforaphane, a derivative of cruciferous vegetables, which is a potent in vitro and in vivo stimulator of Nrf2 activity. The investigators want to investigate whether ingestion of sulforaphane by chronic obstructive pulmonary disease (COPD) patients will increase Nrf2 activity and expression of downstream antioxidants in alveolar macrophages and bronchial epithelial cells. Accordingly, the investigators are conducting a placebo-controlled randomized proof of principle trial of two oral doses of sulforaphane, 25 and 150 micromoles, for 4 weeks in 90 COPD patients. Collections of alveolar macrophages by Bronchoalveolar lavage (BAL), bronchial epithelial cells by endobronchial brushings will be performed at baseline and 4 weeks. Other bio-specimens will include nasal epithelial cells, Peripheral Blood Monocyte Collection (PBMCs), and expired breath condensate (EBC). The investigators' goal is to establish a safe and tolerable dose of sulforaphane that effects in vivo antioxidants via Nrf2, then the investigators will have a novel candidate treatment for longer-term efficacy trials. Ancillary studies are proposed to explore the efficacy and mechanisms of sulforaphane to increase bacterial clearance and to restore steroid sensitivity in COPD lung cells.