Cruciferous vegetables (CVs) have been widely studied for their anticarcinogenic properties. The aim of the present study was to evaluate the protective effect of broccoli intake in smokers and nonsmokers. Twenty young healthy males (10 smokers and 10 nonsmokers) were randomized in a cross-over design and received a portion of broccoli (200 g) or maintained a controlled diet for 10 days each. The two periods were separated by a wash-out period (20 days). Blood samples were collected at 0, 10, 30, and 40 days and used for the evaluation of DNA damage, insulin-like growth factor-I (IGF-I) and histone deacetylase (HDAC). Ex vivo protection from H(2)O(2)-induced DNA damage and endogenous DNA damage were evaluated in lymphocytes by means of the comet assay. Strand breaks decreased significantly after the broccoli diet in smokers as well as in nonsmokers (-22.2%; P < 0.0001), whereas oxidized purines decreased significantly only in smokers (-51.0%; P < 0.0001). Broccoli intake did not modify HDAC activity and IGF-I serum levels. Our results strengthen the importance of consuming CVs to increase cell protection against DNA damage. Future investigation, with different amount of broccoli and/or different time of exposure, is needed to understand the lack of effect on HDAC activity and IGF-I levels.