Sister chromatid exchange induced by several types of coffees in Chinese hamster ovary cells.

Different brands of commercial caffeinated and decaffeinated coffees (roasted, high roast, blend ground, and instant coffees) were studied. These coffees were tested for their ability to induce sister chromatid exchanges (SCE) in CHO-K1 cells. Tests were performed in the presence and in the absence of a metabolic activation system (S-9 mix). Results were compared to the roasting procedure because genotoxic products could be formed from these processes. Our results indicate that caffeinated instant coffees showed higher genotoxic activity than decaffeinated coffees. Non-significant genotoxic activity was detected with the green coffee (unroasted). The highest increase of the frequency of SCE occurred when the caffeinated instant coffee was tested in the absence of metabolic activation system. The repeatability of the test was checked through three assays with the same sample.