This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
The custom of spending half an hour in making a leisurely toilet for dinner is beneficial in giving the rest to mind and body which puts the latter into the most favourable conditions. Dyspeptics and persons subject to an irritable or feeble digestive system can often derive much benefit by observing the rule of not eating when suffering from bodily or mental fatigue. They should lie down from half an hour to one hour and quietly rest before each meal, which may then be digested in comfort. Muscular fatigue and overexertion demand food for the replenishment of waste material, but the immediate digestive process is much facilitated by an intervening period of rest. It is often advisable for them to rest (but not sleep) for a similar time after meals. The practice of sipping hot coffee after dinner and of smoking a cigar is conducive to the rest which should be taken, whenever possible, after the ingestion of a heavy meal.
During profound sleep the different functions of the body are all more or less reduced in activity, and the motility of the stomach is lessened. The rate of circulation and respiration becomes slower, and gland secretion and digestive processes are retarded. For this reason, after eating a heavy meal at night, it is unwise to retire for two or three hours until the stage of gastric digestion is in part completed. It is true that many of the lower animals, particularly the carnivorous, who eat very frequently, are accustomed to lie down and sleep immediately after taking their food, but their functions in so many ways differ from those of man that but little is to be gained by a comparison with them, and their sleep is usually light until digestion is accomplished. On the other hand, in man, if profound sleep follows the eating of a heavy meal, digestion is very apt to be disturbed. A large volume of blood is kept in the abdominal vessels during digestion, and the cerebral circulation must be modified in consequence. It is possible also that the various products of nutrition which are being absorbed into the blood may act in stimulating the central nervous system in peculiar ways.
Such sleep is restless, and is disturbed by dreams and nightmares, and even feverishness.
On the other hand, a light doze, in cases of exhaustion and for the aged, taken for half an hour after dinner, does certainly no harm, and may promote digestion by allowing more blood to be diverted to the digestive organs, none being required for other activities.
Persons whose health is below the average on account of disorders of digestion and assimilation not infrequently find that they become very sleepy after eating, more particularly after eating a heavy meal at noon; this condition is sometimes very annoying, and always indicates a lack of balance between the income and output of energy, which must be regulated by proper attention to diet and exercise. Usually in such cases the difficulty consists in habitually 24 eating more food than the system can appropriate, and cleansing the body through the emunctories, with a temporary reduction in the quantity of food eaten, will remove it. In other cases the trouble arises from the exhaustion of the nervous system, which is unable to properly conduct two functions at once - that is, to regulate digestion and at the same time exercise the mind. Obviously, in such cases, rest and tonic treatment are indicated. The food should be given more often, but in small amount.
In England the custom is very prevalent among some classes of people outside of the larger cities of taking four meals a day. A breakfast at about eight o'clock and dinner from one to two, and a heavy tea - that is, a lunch with tea and some solid food - between five and six, which is followed by supper from eight to nine. This practice is well adapted for some persons, especially young, growing children at school (see Diet in Schools), but older children are apt to overeat if they follow such a custom. An interval of from one and a half to two hours should elapse between eating supper and retiring, and from two to three hours between dinner and bedtime if the alimentary canal is too empty; sleep will be retarded on this account, and the earlier stages of hunger before great exhaustion has occurred may be accompanied by restlessness and insomnia. A very little food taken into the stomach under these conditions will often produce sleep promptly. The aged, whose systems are susceptible to slight changes in their condition or environment, are liable to become sleepy after their meals, and they find it to their advantage to take a brief nap after dinner; but this sleep is not usually profound, and if it is too prolonged it indicates exhaustion, which should be met by more careful attention to the diet and stimulation.
Hunger produces wakefulness and restlessness, and starvation may cause persistent insomnia. Going to bed late without dinner or supper results in restlessness and insomnia, which may often be cured by taking a glass of hot milk, or a cup of chocolate and some light farinaceous article, or a light sandwich and a bottle of beer. In all ordinary cases of insomnia it is well to see what help can be got from diet and regular habits before resorting to hypnotics. (See Insomnia).
In some diseases, notably diphtheria, it becomes a grave question between nourishment and sleep as to which is the more important. Vigorous local measures may be needed to control the spread of the membrane in the throat, necessitating half-hourly applications day and night, which of course interrupt sleep; and yet the patient may need to be wakened for such applications, and the giving of nourishment and stimulants as well. Sleep is often more needful than food, and it is the duty of the physician to see that there is a proper balance between them. In general, in exhausting disease, protracted typhoid or other fevers, etc., nourishment must be given once in two hours day and night; but if the patient does not fall asleep readily at night after being aroused for food, the intervals may be made three-hourly, and as strength returns, four-hourly. In such cases it is sometimes well to relax the rule, and give the patient one good night's rest of five hours without awakening him for food; but the degree of exhaustion and need of cardiac stimulants must be the guide in each separate case.