Influences of dietary and intraduodenal lipid on alertness, mood, and sustained concentration

Abstract

The effects of intraduodenal and dietary lipid on alertness, mood and performance in a task requiring sustained attention were investigated in two studies. The first experiment compared the effect of duodenal infusion of either 100 g/l Intralipid (836 kJ/min) or isotonic saline (9 g NaCl/l) in paired studies carried out on two non-consecutive days on five male volunteers. Two consecutive 3 h infusions, one of lipid, the other saline, were given blind on each day using a crossover design. Analysis of variance indicated that lipid significantly reduced alertness (P < 0.05) and affected the speed and accuracy of performance in a sustained attention task (P < 0.05). A second experiment compared the effects on eight male volunteers of two isoenergetic lunches of similar appearance, taste and protein content but Wering fat and carbohydrate (CHO) contents (fat energy:CHO, 64:18 v. 7:76). Alertness was lower (P < 0.05) and responses to stimuli in a sustained attention task were slower after the high-fat meal than after the lowfat meal (P < 0.05). In conclusion, infusion of lipid into the small intestine, and the substitution of fat for carbohydrate while keeping energy and protein constant in a lunch, both cause an enhanced postprandial decline in alertness and concentration. This may be related to the presence of lipid in the small intestine.

Nutritional influences on cognitive function: mechanisms of susceptibility

“…Half an hour after low-or high-fat meals, alertness increased and sleepiness declined, whereas 2·5-3 h later fatigue increased while arousal declined to the greatest extent after a high-fat meal (Wells et al 1995, 1997; Wells & Read, 1996). By comparison, when lipid was infused directly into the duodenum, a decline in alertness was apparent much earlier, by 30-90 min after the meal (Wells et al 1995). Wells & Read (1996) found an increase in fatigue and reduction in vigour after a high-fat meal when eaten mid-morning but not at lunchtime (when mood changes were similar but independent of fat level).…”

“…45 %) and high-fat (e.g. 56-74 %) breakfasts, mid-morning and midday meals (Lloyd et al , 1996Wells & Read, 1996;Wells et al 1997) as well as intraduodenal infusions of lipid or saline (Wells et al 1995). Again these studies have recently been reviewed (Bellisle et al 1998;Dye et al 2000), so we concentrate on discussing patterns in findings, and their possible mechanisms.…”

“…Moreover, the meals were designed to disguise variation in fat level from the subjects. It is therefore possible that effects on mood may have resulted from discrepancies between subjects' expectations of certain post-ingestive effects, and the actual effects that resulted from neurohormonal responses to detection of specific nutrients in the duodenum and liver (Wells et al 1995(Wells et al , 1998. A case in point may be the increase in tension, 90 min post-lunch, with increasing fat intake, reported by the predominately female subjects of Lloyd et al (1994); we suggest that this finding might reflect an aversive reaction to (unexpected) fat-related post-ingestive sensations.…”

Post-prandial changes in measures of fatigue: Effect of a mixed or a pure carbohydrate or pure fat meal

“…In terms of functional performance, studies to date have not provided clear answers as to the role of nutrients. The acute effects of meals high in fat on increasing fatigue (Wells et al, 1995) in psychological and mood tests suggest that fat may induce fatigue while another study found that adaptation to a 70% fat diet led to signi®cant increases in endurance during cycle exercise (Lambert et al, 1994). In addition, although carbohydrate loading can lead to increased exercise endurance (Rauch et al, 1995) the more acute intake of carbohydrate has been implicated in the genesis of post-prandial fatigue (Spring et al, 1989).…”

Potential benefits of satiety to the consumer: scientific considerations

“…In contrast, Wells & Read (102) observed little change in cognitive performance and no change in hunger/satiation following lower-energy high-fat/lowcarbohydrate and higher-energy low-fat/high-carbohydrate meals consumed either mid-morning or at lunchtime in eighteen healthy males. Wells et al (101) adopted a different approach and found that intraduodenal infusions of dietary lipid (Intralipid; Kabi Pharmacia) significantly reduced speed and accuracy of performance on a sustained attention task in five male volunteers compared with an isotonic saline control. This postprandial decline in performance occurred with concomitant decreases in hunger over the early part of the morning.…”