Effects of dietary broccoli on human in vivo caffeine metabolism: A pilot study on a group of Jordanian volunteers

Objectives: Induction or inhibition of cytochrome P450 (CYP) enzyme activities, enzymes that activate or detoxify xenobiotics, is one mechanism by which vegetables may alter cancer risk. As the effect of food on CYP enzyme activities have not been studied in the Jordanian population, we examined the effect of supplementing the diet with broccoli on CYP1A2 and CYP2A6 activities. Methods: Five men and five women, non-smokers, consumed a standard diet of broccoli (500 g) for 6 days. Enzyme activities were determined by measuring urinary metabolite ratios after a 100 mg caffeine tablet on the seventh day. Results: The mean CYP1A2 activity for men (21.1 +/- 3.2) was significantly lower than that for women (27.6 +/- 1.6) before the consumption of broccoli (P < 0.05). These activities were significantly induced in both men (52.5 +/- 6.6) and women (36.6 +/- 8.4) after a standard diet of broccoli (P < 0.005). Similarly, the mean value of CYP2A6 activity for men was 0.061 +/- 0.040 and for women, 0.144 +/- 0.039 before consumption of broccoli, which were significantly different (P < 0.05). The activity of CYP2A6 was induced in both groups significantly after broccoli consumption (P < 0.05). The mean value for men was 0.193 +/- 0.02 and for women, 0.214 +/- 0.064. Conclusion: Our study on a group of Jordanians confirmed the well-established observation that broccoli induces CYP1A2 activity. This study also demonstrates the effect of gender and broccoli consumption on CYP2A6 activity in Jordanians.