ANALYSIS OF THE POTENTIAL CARCINOGENICITY OF COFFEE AND ITS RELATED-COMPOUNDS IN A MEDIUM-TERM LIVER BIOASSAY OF RATS

The potential carcinogenicity of coffee and related compounds was exam ined using a medium-term liver bioassay based on the induction of glut athione S-transferase placental form (GST-P)-positive foci in F344 rat s. A total of 230 males were initially injected with diethylnitrosamin e (200 mg/kg body weight, ip) or saline as controls and 2 wk later wer e fed on diet or drinking water supplemented as follows for 6 wk: 5% r egular instant coffee; 5% decaffeinated instant coffee; freshly brewed coffee, 8 g in 140 mi water; 0.1% caffeine, 0.2% methylglyoxal, 0.2% glyoxal; or 0.3% theophylline in the drinking water (w/v); and 0.4% th eobromine in the diet (w/w). AH rats were subjected to two-thirds part ial hepatectomy at wk 3 and killed at wk 8. The resultant values for G ST-P-positive hepatic focus induction were slightly increased with met hylglyoxal and decreased with glyoxal and theobromine compared with th e corresponding controls. Although the increase in number of foci for methylglyoxal was statistically significant at P < 0.05, the value was within the historical control levels. Regular and decaffeinated insta nt coffee as well as fresh-brewed coffee, caffeine and theophylline ex erted no effects on focus development. Thus, the coffee-related compou nds examined demonstrated no obvious enhancing potential, and it is th erefore concluded that coffee and its main constituents are not carcin ogenic for the rat liver.