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The post-lunch dip in cognition is a well-established phenomenon of decreased alertness, memory and vigilance after lunch consumption. Lunch composition reportedly influences the post-lunch dip. Moreover, dieting is associated with cognitive function impairments. The negative effects of dieting have been reversed with nut-supplemented diets. The aims of this study were to (1) evaluate the acute effect of an almond-enriched high-fat lunch or high-carbohydrate lunch on the post-lunch decline in cognitive function, and (2) evaluate the effects of chronic almond consumption as part of an energy-restricted diet on the memory and attention domains of cognitive function. In total, eighty-six overweight and obese adults were randomised to consume either an almond-enriched diet (AED) or a nut-free control diet (NFD) over a 12-week weight loss intervention. Participants were also randomised to receive either an almond-enriched high-fat lunch (A-HFL) (>55 % energy from fat, almonds contributing 70–75 % energy) or a high-carbohydrate lunch (HCL) (>85 % energy from carbohydrates) at the beginning and end of the weight loss intervention. Memory and attention performance indices decreased after lunch consumption (P<0·001). The A-HFL group ameliorated the decline in memory scores by 57·7 % compared with the HCL group (P=0·004). Both lunch groups had similar declines in attention. Moreover, memory and attention performance indices increased after the 12-week intervention period (P<0·05) with no difference between the AED and NFD groups. In conclusion, almond consumption at a midday meal can reduce the post-lunch dip in memory. However, long-term almond consumption may not further improve cognitive function outcomes in a weight loss intervention. [ABSTRACT FROM AUTHOR]

The ‘post-lunch dip’ is a commonly experienced period of drowsiness in the afternoon hours. If this inevitable period can be disrupted by an environmental cue, the result will be enhanced workplace performance. Because blue light is known to be a critical cue for entraining biological rhythms, we investigated whether blue light illumination can be a practical strategy for coping with the post-lunch dip. Twenty healthy participants underwent a continuous performance test, during which the electroencephalogram (EEG) was recorded under four different illumination conditions: dark ( < 0.3 lx), 33% blue-enriched light, 66% blue-enriched light and white polychromatic light. As a result, exposure to blue-enriched light during the post-lunch dip period significantly reduced the EEG alpha activity, and increased task performance. Since desynchronisation of alpha activity reflects enhancement of vigilance, our findings imply that blue light might disrupt the post-lunch dip. Subsequent exploration of illumination parameters will be beneficial for possible chronobiological and ergonomic applications. Practitioner Summary:As blue light is a crucial cue to entrain human circadian rhythms, we investigated whether blue light can cope with the post-lunch dip. As a result, blue light significantly improved cognitive performance, and reduced the EEG alpha activity, reflecting enhancement of vigilance. Therefore, blue light helps in avoiding the post-lunch dip. [ABSTRACT FROM AUTHOR]

Electrooculography (EOG) was used to explore performance differences in a sustained attention task during rested wakefulness (RW) and after 7 days of partial sleep deprivation (SD). The RW condition was based on obtaining regular sleep, and the SD condition involved sleep restriction of 3 h/night for a week resulting in a total sleep debt of 21 h. The study used a counterbalanced design with a 2-wk gap between the conditions. Participants performed a sustained attention task for 45 min on four occasions: 10:00–11:00, 14:00–15:00, 18:00–19:00, and 22:00–23:00 h. The task required moving gaze and attention as fast as possible from a fixation point to a target. In each session, 120 congruent and 34 incongruent stimuli were presented, totaling 1232 observations/participant. Correct responses plus errors of omission (lapses) and commission (false responses) were recorded, and the effect of time-of-day on sustained attention following SD was investigated. The analysis of variance (ANOVA) model showed that SD affected performance on a sustained attention task and manifested itself in a higher number of omission errors: congruent stimuli ( F(1,64) = 13.3, p < .001) and incongruent stimuli ( F(1,64) = 14.0, p < .001). Reaction times for saccadic eye movements did not differ significantly between experimental conditions or by time-of-day. Commission errors, however, exhibited a decreasing trend during the day. The visible prevalence of omissions in SD versus RW was observed during the mid-afternoon hours (the so-called post-lunch dip) for both congruent and incongruent stimuli ( F(1,16) = 5.3, p = .04 and F(1,16) = 5.6, p = .03, respectively), and at 18:00 h for incongruent stimuli ( F(1,13) = 5.7, p = .03). (Author correspondence: ) [ABSTRACT FROM AUTHOR]

There is a rapidly growing interest in the scientific study of the effects of foods on psychological processes involved in the control of behaviour (performance) and cognitive functions such as memory, perception, attention and vigilance. This study forms part of innovative research on functional foods, which provides an active arena for collaboration between researchers in universities, institutes and industry. Research outputs will inform legislation currently being drawn up in Europe. This article describes some basic issues of functional food research exemplified by evidence on the effects of carbohydrate foods. These effects implicate glucose metabolism in some aspects of human memory and performance. One specific issue concerns the problem of daytime lethargy and the "post-lunch dip". An exciting prospect for this type of work is the potential to develop foods to maintain or improve performance in the working environment and to enhance quality of life. [ABSTRACT FROM AUTHOR]

Twelve male students who normally ate a large lunch and 12 who normally ate only a light lunch performed a sustained attention task before and after eating a light lunch and before and after eating a heavy lunch. The speed and accuracy of performance were measured; so also were temperature, pulse rate and subjective estimates of tension, alertness and hunger. The changes brought about by the meals were examined. Speed alone showed no change over the lunch interval. Of the remaining seven measures, only temperature, which seems to reflect endogenous processes, was unaffected by the size of the lunch that was eaten. Accuracy, pulse rate and hunger were influenced by the size of the habitual lunch as well as by the size of the experimental lunch. Tension and alertness were responsive only to the size of the experimental lunch. The results are discussed in relation to diurnal rhythms, with a particular emphasis on the acquisition of endogenous component processes, as exemplified by habits of eating. [ABSTRACT FROM AUTHOR]

Forty students performed on a perceptual discrimination task both before and after a mid-day lunch interval. Half of the students consumed a three-course lunch during the interval, the remaining half abstained from lunch. It was found that the actual ability to discriminate between events was significantly impaired following the consumption of lunch, but did not alter when no food was ingested. The magnitude of the post-lunch dip in discrimination efficiency was significantly greater in the less 'neurotic' and the more 'extraverted' individuals, according to scores on the Eysenck Personality Inventory, and was also significantly though negatively related to the extent of the drop in sublingual temperature that occurred over the lunch interval. It is concluded that operational efficiency and safety may be at risk following lunch. [ABSTRACT FROM AUTHOR]