Background: Cognitive disturbances are relatively common in patients with liver disease. High protein load precipitates hepatic encephalopathy in cirrhotic patients. Minimal hepatic encephalopathy (MHE) is a prevalent neurocognitive complication of cirrhosis. Objective: Because the influence of nutritional factors on the progression of cognitive impairment has not been explored in depth, this study aimed to investigate the effect on cognition of acute metabolic changes induced by breakfast consumption. Design: Twenty-one subjects (10 women) with Child A cirrhosis and 21 age- and sex-matched healthy controls were enrolled. Patients and controls were divided into 2 groups: those receiving a breakfast of 500 kcal and 21 g protein and those receiving no breakfast. Serum ammonia concentrations and cognitive functions were studied (Mindstreams; NeuroTrax, Fresh Meadows, NY) before and 2 h after breakfast. A mixed model was used to analyze the data. Results: At baseline, cirrhotic patients had significantly lower total scores and significantly lower subscores (P< 0.015 global cognitive score) in 4 of 7 cognitive categories, which is indicative of MHE. Patients with hyperammonemia (>85 μg/dL) scored significantly lower for attention than did patients with normal serum ammonia concentrations (P < 0.003). After 2 h, MHE patients and controls responded differently to breakfast consumption with regard to attention and executive functions (P< 0.003 and P< 0.04, respectively). Although patients' scores improved after breakfast consumption, despite an increase in serum ammonia, healthy controls who continued to fast performed better. Conclusions: Chronic hyperammonemia may negatively affect attention. Eating breakfast improves attention and executive functions of patients with MHE. Prolonged periods of starvation may be partly responsible for these changes. This trial was registered at clinicaltrials. gov as NCT01083446.