The Factor Of Idiosyncrasy is an important one. Individuals differ greatly, quite irrespective of age, in their digestive and metabolic capacities. We meet with children who are unable to tolerate foods which old people can digest quite easily, and, again, with others who are made ill by even a slight excess, while their grandparents can perhaps consume a large excess with comparative impunity. Some old people have, in fact, prodigious powers of digestion and metabolism, and we may look upon them as corresponding, in the physiological sphere, to the Shakespeares and the Newtons in the realms of mind : they are physiological geniuses. Most of these remarkable old people would doubtless enjoy better health, be more amiable and have greater consideration for others, on a more abstemious diet; nevertheless, in regulating their food we must make due allowance for their prodigious powers.
It may be observed in passing that the capacity to cope with an excess of food differs in different races. The Jews appear to be pre-eminent in this respect, possibly because for longer than any other people they have been able, by reason of their prosperity, to obtain an habitual excess of food, and have in this way become racially adapted to it.
Those who even in early life are feebly endowed in respect of digestion and metabolism, are, continuing our former comparison, physiological imbeciles. The wiser among them soon find this out for themselves; others only learn the lesson late, and even if they learn it, may be deficient in prudence and unwilling to forego the immediate pleasure of indulging in what are for them at least indiscretions. This class of patient offers the physician fruitful scope in the matter of dietetic treatment.
Making due allowance, however, for the personal element, our rule obtains, that while all should endeavour to conform as far as possible to the ideal dietary, allowing themselves no more than an occasional excess, it becomes with advancing years increasingly necessary for the majority of people to eat moderately of simple foods, and not to swallow starchy foods without having first insalivated them thoroughly. If we add to these rules the further ones that old people should take full advantage of dental surgery, that in the case of the toothless, certain of the tougher varieties of food should be broken up mechanically before being taken, and finally that due regard should be had to the influence of idiosyncrasy and habit, we have said all that is worth saying concerning the diet of the aged.
Only in the case of the very feeble is it needful to predigest the food, though material help may often be got from the administration of amylolytic and peptic ferments.