Khat (Catha edulis) consumption causes genotoxic effects in humans

We used the micronucleus (MN) test to determine the genetic damage caused b y khat, a widely consumed psychostimulant plant, in exfoliated cells of vol unteers who chewed the drug on a regular basis. In the first study in which we compared the frequency of MN in buccal and bladder mucosa cells in 20 k hat consumers (10-160 g/day) and 10 controls, a pronounced (8-fold) increas e in micronucleated buccal mucosa cells was seen among khat consumers; khat consumption did not lead to a detectable elevation of micronucleated bladd er mucosa cells. Among heavy khat chewers, 81 % of the MN had a centromere signal indicating that khat is aneuploidogenic. To investigate the effect o f simultaneous consumption of tobacco and alcoholic beverages, we compared the MN frequency in buccal cells of 25 khat consumers (20-85 g/day) who smo ked cigarettes (15-60/day) and drank alcoholic beverages (15-80 g of pure e thanol/day) with a control group (control group I) of 25 individuals matche d for age, body weight, tobacco and alcohol consumption and with another co ntrol group of 25 individuals (control group II) not consuming any of the d rugs. The frequency of buccal mucosa cells with MN was higher in control gr oup I than in group II and the effect of khat, tobacco and alcohol was foun d to be additive. A time-kinetics study on khat-induced MN showed that the highest frequency of MN was observed during the fourth week after consumpti on. In light of the large body of evidence on the close association between genetic damage and cancer, these results suggest that khat consumption, es pecially when accompanied by alcohol and tobacco consumption, might be a po tential cause of oral malignancy. (C) 2001 Wiley-Liss, Inc.