Why do some people become jittery after one cup of coffee whereas others are able to drink it continuously without the slightest negative effect? The answer it seems may lie in your genes. A certain enzyme CYPIA2 may be responsible for how quickly our bodies break down caffeine. One variant of this gene causes the liver to metabolize caffeine at a faster rate. If this particular gene is inherited from both parents it can in turn increase the metabolism of caffeine by as much as four times. A study was funded by The National Institute of Health in which there were 4,000 participants. Those that were fast metabolizes were able to clear caffeine from their systems rapidly allowing the antioxidants and polyphenols to kick in without any negative effects of caffeine. There may be multiple genes that are responsible but more research is now underway on how caffeine and the CYPIA2 gene can affect an athlete”s performance.