The following table by Dr. Stevenson Macadam gives an idea of the relative amount of flesh-formers and heat-producers in certain articles of food, showing the amount of heat-producing elements they contain for every 10 parts of flesh-formers.
| Flesh-forming. | Heat-producing. | |
| Rice | 10 | 123 |
| Potatoes | 10 | 115 |
| Barley | 10 | 57 |
| Oatmeal | 10 | 50 |
| Wheaten Flour | 10 | 44 |
| Milk | 10 | 40 |
| Fat Pork | 10 | 30 |
| Fat Mutton | 10 | 27 |
| Beans | 10 | 22 |
| Beef | 10 | 17 |
| Hare | 10 | 2 |
| Veal | 10 | 1 |
In the tropics, where little exercise can be taken, the waste of tissues is small, so that little nitrogenous food is required, and only a moderate amount of fat is taken; the need of heat-producers is comparatively small, so that starchy products, as millet and rice, are the principal articles of food. But gradually as we come north there is a marked increase both in the fatty and nitrogenous articles of food, until in the Arctic zone oily substances and animal food are the staple articles of existence, the amount of them that an Esquimaux will eat being something almost incredible, yet necessary to resist the severe cold.
The vegetable kingdom alone can supply all that is necessary for the human body both of flesh-forming and heat-producing substances, and we must not for a moment imagine that animal food is the only source of flesh-formers, as the world’s population is supported to a large extent on vegetable products, especially in tropical regions, while in colder climates, where vegetable products are hardly to be obtained, flesh and fat are indispensable. Thus man is clearly omnivorous; while men may be advantageously almost vegetarians in one climate, mixed eaters in another (as with us), and almost exclusively flesh eaters in a third, as in the Arctic regions. But there are some people who live exclusively on a vegetable diet (vegetarians) in our country, believing that such a diet is right in principle. Only those are true vegetarians who exclude milk, butter, eggs and cheese, as these are the very essence of animal food.
Man is capable of deriving all that is required for living and working from the animal or vegetable articles of food, either separately or combined. The question, therefore, is whether a purely vegetable diet or a mixed diet of vegetable and animal food is the better suited for our existence. To judge the question we have some facts to go upon. (1) We are so physically constructed as to be able to derive our nourishment from both animal and vegetable food. (2) In the Arctic regions hardly any vegetables are to be obtained. (3) Man alone has the intelligence to obtain food from all sources, and, by cooking, to render it fit for nourishment. It apparently follows, therefore, that while we are suited for either diet, or rather a combination of both, we may also select to some extent our diet according to our individual taste, habit of body, and other circumstances, as work and climate, experience having taught us that for the enjoyment of good health our diet must be regulated by the circumstances we have mentioned.
Nutritive values of Foods.—The following tables, based on those published by Letheby,[2] show the nutritive values (per lb.) of various food-stuffs, with their composition.
(a) Animal Food-stuffs.
| Value per lb. | Carbon. | Nitrogen. | |
| d. | Grains per lb. | Grains per lb. | |
| Butter, fresh | 16 | 6456 | — |
| Butter, salt | 12 | 4585 | — |
| Lard | 9 | 4819 | — |
| Bacon, dry | 9 | 5987 | 95 |
| Cheese, cheddar | 8 | 3344 | 306 |
| Beef | 8 | 1854 | 184 |
| Bacon, green | 8 | 5426 | 76 |
| Suet | 7 | 4710 | — |
| Pork, fat | 7 | 4113 | 106 |
| Dripping | 6 | 5456 | — |
| Mutton | 5 | 1900 | 189 |
| Herrings, red | 4 | 1435 | 217 |
| Cheese, skim | 3 | 1947 | 483 |
| Liver, bullocks’ | 3 | 934 | 204 |
| White fish | 2 | 871 | 195 |
| Milk, new | 2 | 599 | 44 |
| Milk, skimmed | 1 | 438 | 43 |
| Buttermilk | ½ | 387 | 44 |
| Whey | ½ | 154 | 13 |
(b) Vegetable Food-stuffs.