Adaptive drive

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Food intake
Hunger is associated with wakefulness. This has a survival advantage in that wakefulness is retained until sufficient food has been eaten. After eating, humans tend to relax and readily fall asleep. This is due to complex reflex and humoral factors.

Carbohydrates and milky drinks which contain tryptophan, a precursor of 5HT, and melatonin, have a greater sleep-promoting effect than other foods.

Tryptophan is also present in bananas, peanuts and figs. Lettuce contains lactucarium, an opioid which may promote sleep. Dietary unsaturated fatty acids such as oleamide bind to GABA receptors and can promote sleep and reduce motor activity. Conversely a low serum cholesterol level has been associated with violence.

High protein foods which are rich in tyrosine may promote noradrenaline synthesis and lead to wakefulness.

Large meals taken before sleep can cause gastrooesophageal reflux leading to heartburn and awakenings. Large volumes of liquid should be avoided before sleep since they may lead to nocturia, especially if there is renal impairment or prostatic hypertrophy.

Very severe Malnutrition can induce excessive daytime sleepiness and inactivity, but, in general, weight loss, whether it is due to Anorexia Nervosa, mania or thyrotoxicosis, leads to insomnia and hyperactivity.

Weight loss in depression is associated with insomnia, but if weight is gained, as in seasonal affective disorder, sleepiness is common. There may be a link in otherwise normal subjects between weight loss, hyperactivity and insomnia, and between weight gain, inactivity and excessive daytime sleepiness. The chemical basis of these associations is uncertain, but weight gain may also lead to excessive daytime sleepiness through causing obstructive sleep apnoeas.

Sexual activity
Sexual intercourse usually promotes the onset of sleep, in contrast to other types of physical activity.

RELATED STORIES:
Neurophysiology of sleep and wakefulness   Neuroanatomy of sleep and wakefulness   Output from SCN - Circadian rhythms   Pineal gland - Circadian rhythms   Sleep rhythms   Melatonin - Circadian rhythms   Coordination of circadian rhythms   Circadian rhythms   SCN clock genetics - Circadian rhythms   Input to SCN - Circadian rhythms   Control of sleep and wakefulness   REM sleep ultradian rhythm

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