Food and mood

We had been investigating the effects of intestinal infusions of lipid on small bowel transit times in rats when we observed that animals that received the lipid tended to fall asleep. We wondered whether this might explain why people tend to feel drowsy after a rich meal and irritable after changing to a low fat diet. This led to a series of experiments in human volunteers by Anita Wells showing that dietary or intestinal infusion of fat reduces alertness, enhances mood and impairs concentration, while carbohydrate does the reverse. Fat also reduced heart rate, altered EEG activity and suppressed pain. These effects are probably either related to release of gut hormones particularly CCK or enhancement of activity in the sensory (afferent) component of the vagus nerve.

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  2. Wells, A.S., Read, N.W. Influences of fat, energy and time of day on mood and performance. Physiology & Behaviour 1996; 59: 1069-1076.
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  6. Wells AS, Read NW, MacDonald I. (l997) The effect of carbohydrate and lipid on resting energy expenditure, heart rate, sleepiness and mood. Physiology and Behaviour 1998; 63 (4): 621-628.
  7. Zmarzty SA, Wells AS, Read NW. The influence of food on pain perception in healthy human volunteers. Physiology and Behaviour 1997; 62 (l):185-191.
  8. Zmarzty SA, Read NW. (1999) An examination of isoenergetic intragastric infusions of pure macronutrients on cold pain perception in healthy human volunteers. Physiology and Behaviour. 1999; 65(4):643-648.