For this randomized, placebo-controlled, crossover study we recruited 16 non-atopic, non-smoking healthy volunteers between the ages of 18–50 years. The O
3 study protocol was approved by the University of North Carolina’s Institutional Review Board, and written informed consent was obtained from all study subjects. All subjects underwent a standardized screening protocol including allergy skin testing and methacholine challenge as previously described [
7,
8]. Volunteers were randomized in a 1:1 ratio to consume either 200 g of BSH (equivalent to 111 g of commercially available Broccosprouts® (Brassica Protection Products LLC)), or 200 g of alfalfa sprout homogenate (ASH), which lacks SFN. The dose of BSH and ASH were chosen based on results of a prior study that found maximal induction of NRF2-dependent gene expression by BSH with a 3 day 200-g dosing regimen [
4]. Subjects received supplements once daily for 3 days during the initial study period, and the alternate treatment during the crossover period. On the third day of supplementation, each subject was exposed to O
3 (0.4 ppm) for 2 h while performing four 15 min sessions of intermittent moderate exercise (defined as minute ventilation or VE
min = 30–40 L/min) on a treadmill, separated by 15 min of seated rest. Induced sputum was obtained at screening and at 4 h post-O
3 exposure and processed for measurement of cytokines and cell counts as previously described [
7,
8]. Blood was collected at screening and post-O
3 for determination of SFN and SFN-conjugate levels by mass spectroscopy. Additionally, blood and nasal epithelial cells (NECs) were collected 4 h post-O3 to measure NRF2-regulated gene expression (HO-1, NQO-1, GSTM-1). There was a minimum washout period of 14 days between treatment periods.