Transferrin modulates tumor necrosis factor-α secretion by cultured human mononuclear cells: influence of iron status

Abstract

examined by studying night workers who had slept during the day and were having “breakfast” in the afternoon. The results of this study confirmed that caffeine improves encoding of new stimuli. There were no indications of effects of cereal consumption on memory, although aspects of mood were more positive after eating the cereal. These results suggest that sleep inertia is not the major factor determining whether memory changes after consumption of breakfast cereal. The next study examined whether prolonged fasting was the crucial factor. In addition, the experiment investigated whether caffeine withdrawal was associated with mood and performance changes and whether withdrawn and non-withdrawn volunteers responded differently to a caffeine challenge. In this experiment, volunteers were tested in the early morning and then required to a) follow their normal pattern of eating and consumption of caffeinated beverages, b) fast, c) abstain from caffeine, or d) fast and abstain from caffeine. Volunteers were retested in the late afternoon and were then assigned to cereal/no cereal and caffeinated/ decaffeinated coffee groups. The results from the session before eating and having coffee showed that those who had been fasting had a more negative mood and recalled fewer words. No effects of caffeine withdrawal were apparent. The postdrink data showed that caffeine improves encoding of new stimuli. However, no interactions between caffeine and withdrawal conditions were observed. The mood data showed significant interactions between fasting conditions and cereal conditions. These interactions were due to cereal having little effect in the non-fasted volunteers but producing large increases in positive mood in the fasted participants. There were no similar effects in the data on memory. Recent research on the behavioral effects of breakfast cereal and caffeine has shown that breakfast improves aspects of memory and mood. The effects of breakfast on mood probably reflect predigestive factors and are observed whenever the cereal is eaten. In contrast to this finding, the effects of cereal on memory are only observed in the early morning and cannot be attributed solely to fasting or sleep inertia. Caffeine produces a different profile of effects, having little effect on memory but improving the encoding of new information and increasing alertness when the person is fatigued. These effects appear to be context independent, being observed at most times of day and when both caffeine has been withdrawn and the person continues with normal patterns of consumption. Overall, new reviews of the literature, studies performed in parallel projects, and the new empirical work reported here have greatly increased our knowledge of the mechanisms underlying the behavioral changes produced by breakfast and caffeinated coffee.