CYP2E1 and liver disorder: On the other hand, the hypothesis that response to fasting might have a role in discriminating breath composition depending on liver disease severity is also consistent with data reported by Van der Velde and co-workers [1] who analyzed breath of subjects 30 minutes from food intake (a time that might be too short to modify concentration of ketones from previous fasting) and with the observation by Mathews and co-workers [27] that a reduced of CYP2E1 enzyme activity (as in liver disease) increased breath ketones in rats.