By roughly arranging foods according to such a table we can arrive approximately at a suitable balance of its various constituents.
PERCENTAGE OF TOTAL HEAT VALUE OF FOOD FURNISHED BY ITS | |||||
PROTEIN | FAT | CARBOHYDRATE | |||
Per cent. | Per cent. | Per cent. | |||
| Lean beef (boiled) | 90 | Butter | 99 | Tapioca (cooked) | 98 |
| Chicken | 79 | Bacon | 94 | Prunes (dried) | 97 |
| Mackerel | 50 | Cream | 87 | Figs (dried) | 95 |
| Skim Milk | 37 | Brazil Nuts | 86 | Rice (boiled) | 89 |
| Eggs | 32 | Fat Ham | 81 | Oysters | 89 |
| Beef with fat | 25 | Fat Beef | 75 | Potatoes (boiled) | 88 |
| Cheese | 25 | Cheese | 73 | Bread | 81 |
| Fat Ham | 19 | Eggs | 68 | Peas | 72 |
| Milk | 19 | Boiled Mutton | 65 | Milk | 29 |
| Bread | 13 | Milk | 52 | Cream | 8 |
| Potatoes | 11 | Mackerel | 50 | Brazil Nuts | 4 |
| Boiled Rice | 10 | Chicken | 21 | Cheese | 2 |
| Brazil Nuts | 10 | Boiled lean Beef | 10 | ||
| Bacon | 6 | Bread | 6 | ||
| Cream | 5 | Bananas | 5 | ||
| Bananas | 5 | Potatoes | 1 | ||
| Butter | 5 | ||||
But the chemical side of the problem is not the only one to study. Idiosyncrasy, appetite for certain foods, distaste for others, and personal experience must all receive due consideration. The appetite for certain foods varies much at different periods of life. Fat is abhorrent to many children, and their lives and digestions are much troubled by the parental, but unscientific order to “clear up their plates.” In later years the same persons will welcome fat and need it. Sugar again is loved by children, scorned in middle age, when its place is often supplied by wine or beer, and is again welcomed and of great value in old age, for it helps much to maintain the failing heat of the body, to keep the home fires burning. Good cane-sugar at all stages of life seems to act as a special food, or at any rate stimulant, to the heart muscle; given in large quantities it often gives a failing heart a new lease of life. The digestibility of food is not governed entirely by its chemical composition. Twice cooked meat must contain nearly as much potential nourishment as once cooked, but experience tells most of us that we digest it with difficulty; and if the digestion of a food is not perfect, there is more unwholesome waste product to be cleared away; there is impure blood circulating in all our organs, but we feel it perhaps more in our brains; the lethargy, the depression, the irritability that we all recognize as the accompaniments of indigestion, all stand as cause and effect. Again hot fat and cold fat must contain the same constituents, but many can do well with cold fat, while they get bilious with the other. The same thing applies to butter. All these things we must honestly observe, each man for himself, and we must not let our likes and our appetites, nor our prejudices, sway the conclusions of personal experience and scientific knowledge. Dr. Haig has shown us how many of our ailments are connected with excess of uric acid in the blood, and how much this excess is due to certain foods such as meat, which contains what Fischer named purine bodies. The following extract from Halliburton’s Handbook of Physiology will partially explain this subject:
Origin of Uric Acid.—Uric acid is not made by the kidneys; when these organs are removed, uric acid continues to be formed, and accumulates in the organs, especially in the liver and spleen. After extirpation of the liver in birds (in which animals uric acid is such an important katabolite) the formation of uric acid practically ceases, and its place is taken by ammonia and lactic acid, and the conclusion is therefore drawn that in these animals ammonia and lactic acid are normally synthesized in the liver to form uric acid. But in mammals this is not the history of uric acid formation; in these animals, including man, uric acid is the end-product of the metabolism of nuclein, from the bases of which it arises by oxidization. Nuclein, the main constituent of the nuclei of cells, yields on decomposition certain products called purine substances, and their close relationship to uric acid is shown by their formulæ:
Purine Bases.
| Purine | C5H4N4 |
| Hypoxanthine (monoxypurine) | C5H4N4O |
| Xanthine (dioxypurine) | C5H4N4O2 |
| Adenine (amino-purine) | C5H3N4NH2 |
| Guanine (amino-oxypurine) | C5H3N4ONH2 |
| Uric acid (trioxypurine) | C5H4N4O3 |
“Just as the ordinary protein metabolism is both exogenous and endogenous, so is it the case with nuclein metabolism. There are certain kinds of food (such as liver and sweetbread) which are rich in nuclei, and others, such as meat, which are rich in purine bases (especially hypoxanthine). The increase in uric acid excretion after partaking of such food is exogenous, and those liable to uric acid disorders should avoid such articles of diet. Other forms of diet lead to an increase of uric acid formation by increasing the number of leucocytes in the blood, and there is a consequent increase in the metabolism of their nuclei. Increase in leucocytes may, however, be present independently of diet, and in the disease known as leucocythæmia this occurs to a marked degree; in such cases uric acid formation increases. Although special attention has been directed to the nuclei of leucocytes, because these can be readily examined during life, it must be remembered that the nuclein metabolism of all cells may contribute to uric acid formation. Uric acid, which originates by metabolism, is spoken of as endogenous.”
These purine bodies taken in excess, it is almost certain, tend to raise blood-pressure and to favour the production of gout and arterio-sclerosis. Much can be done, when these threaten, by reducing the amount of these in our food. There is, except in very extreme cases, no need for an absolute purine-free diet, but the diet should be in that direction and so towards a sensible, liberal vegetarianism. The following table of ordinary foods, showing the purine contents in grains per pound, pint or teacup, is from the Lancet, 1906, vol. ii, p. 933, Potts:
| Sweetbread | 70.43 | Halibut | 7.14 | |
| Liver | 19.26 | Plaice | 5.56 | |
| Beef Steak | 14.45 | Cod | 4.07 | |
| Salmon | 9.13 | Beans | 4.16 | |
| Chicken | 9.06 | Lentils | 4.16 | |
| Loin of Pork | 8.48 | Oatmeal | 3.45 | |
| Veal | 8.13 | Coffee | 1.70 | |
| Ham | 8.08 | Ceylon Tea | 1.21 | |
| Mutton | 6.75 | China Tea | 0.75 |
In sclerosis perhaps the chief thing is to avoid the flesh extracts, such as beef-tea, strong meat soups, and rich gravies; for this reason boiled or stewed meats are better than fried or roast. This applies to fish and chicken also; a plain grill is good, but the frying-pan is a danger. Vegetable soups made with bone stock may be taken. Cheese, eggs and milk should supply the greater part of the nitrogenous or protein food. The better sorts of vegetable foods, such as oatmeal, lentils, peas and nuts, will all help to take the place of albuminous animal foods. A certain amount of fat should be taken. A fish and chicken diet contains too little fat and should be perfected by bacon, hot or cold. All the farinaceous foods are good, but the more starchy ones, such as sago, rice and cornflour, are with some people more liable to cause fermentative dyspepsia.