Although the average healthy adult uses a great variety of food stuffs, combined in the kitchen in many different ways and differing widely in bulk and weight, and although he eats these in quantities differing widely at different meals, there is a general tendency to vicarious use of approximately similar food stuffs so that about the same average quantity of a similar group is taken in a day. So, too, while different individuals habitually make one or other meal light or heavy, there is a tendency towards equilibrium on any average day. Many food stuffs, also, such as cheese and relishes are taken in negligible quantities, and many others, such as the bulky vegetables, contain comparatively small proportions of nutriment and so imbedded in cellulose that little is assimilated. For these reasons, the standard diet may be outlined in comparatively simple form.

The units are the 100 calories according to Prof. Irving Fisher's table. The total consumption of calories is, then, about 2850, a full allowance for a business or professional man. The protein content of such a dietary is 60 - 75 grams. The cream and sugar taken as such are largely used for beverages. The milk used at breakfast is allowed for the cereal; that at dinner for cooking vegetables, soup, etc.

Obviously, if one eats two shredded wheat biscuits or two ordinary servings of cereal at breakfast, or uses both cereal in the limited sense and bread or toast, or if one follows the standard breakfast with meat and potato, the breakfast equals or even exceeds the standard luncheon. So, too, the luncheon may be magnified into a dinner and the dinner into a banquet, and the equivalent of a breakfast or luncheon may be added late in the evening. Thus, without conspicuous gluttony, the daily intake may be as follows:

But any such intake is attended with a very decided compensatory digestive failure, even a moderate delay in digestion allowing the destruction by bacteria of considerable quantities of protein and still greater quantities of carbohydrate and fat, and to direct elimination of practically unchanged fat through the bowel, beyond the usual loss which is not considered in the standard table. Thus, if on a dietary sufficient in other respects much over 100 grams of fat is ingested, there is a direct loss of 20 or 30 grams of fat corresponding to about 2 100-calorie units. Counting all sources of loss, the ingestion of food representing 5000 calories probably does not involve the assimilation and metabolism of more than 4000 calories, perhaps much less.

Owing to the vast number of individual food stuffs, their varying percentages of protein, fat and carbohydrate, the relative lack of natural food stuffs containing only one of these dietetic elements, the lack of availability of artificial food stuffs for continued use, and the absolute lack of any single natural food stuff which may be considered as in any practical sense a complete aliment - even in the limited sense of organic foods - it is impossible to make out a dietary by algebra.

Generally speaking, for persons in health and those not acutely sick, the most practical plan is to have prepared a table stating that the patient has actually eaten such and such food stuffs, in given amounts, for each of the three meals. If considerable accuracy is required, the food stuffs should be weighed and foods which are elaborately blended in the kitchen should be avoided, unless the proportion of each single food stuff in the blended preparation is accurately known from the recipe followed. If only approximate results are desired, Fisher's table of "portions" may be followed, with due precautions as to certain ingredients which are obviously not easily measured by guess.

A balance is better than a spring scale and new five-cent pieces may be used as 5-gram weights. A cheap and quite delicate balance may be improvised from a metal rod, shallow aluminum cups, tin can covers, etc., suspended by silk threads or fine wires. Small smooth holes should be drilled through the rod, at the middle and two points equidistant from the respective ends. Such a balance should be tested empty and can be adjusted by filing away the ends of the rod or by placing weights in the lighter pan. With a little care it should easily be made to weigh within an error of half a gram.

Knowing from the table that the patient is taking so many grams of meat, bread, butter, potato, etc., in the day (translating from amounts stated in ounces, if necessary), recourse is had to analytic food tables to determine the amount of protein, fat, carbohydrate in each ingredient, for the day. The number of calories may be added in a fourth column if desired. The labor is much simplified by asking the patient to confine himself to articles listed in the analytic tables.

If the diet actually taken contains 50 - 100 grams of protein, 10 - 100 grams of fat and 250 - 400 grains of carbohydrate, and the total calories are about 2500, the diet may be considered satisfactory, unless, for any reason, it is desired to decrease or increase any ingredient or to exceed or reduce the standard amount of nutriment; and unless, also, any particular food stuff is indigestible, liable to cause alimentary saprophytosis or otherwise undesirable.

If the protein intake is correct but the total number of calories high, a diminution must be made in butter, oils, sugar, syrup, corn starch, etc. If, as may happen, none of these nearly pure non-protein food stuffs are used in excess, and the protein is not too high or even rather low, bread stuffs, cereals and vegetables must be reduced and more meats or whites of eggs must be taken to make good the ration of protein.