Part 1 (1/2)
The Chemistry of Food and Nutrition.
by A. W. Duncan.
PREFACE.
The first edition of 1884 contained but 5 pages of type; the second of 1898, 14 pages. Only by conciseness has it been possible to give even a summary of the principles of dietetics within the limit or this pamphlet.
Should there appear in places an abruptness or incompleteness of treatment, these limitations must be my excuse.
Those who wish to thoroughly study the science of food are referred to the standard work, ”Food and Dietetics,” by Dr. R. Hutchison (E. Arnold, 16s.). The effects of purin bodies in producing illness has been patiently and thoroughly worked out by Dr. Alexander Haig. Students are referred to his ”Uric Acid, an epitome of the subject” (J. & A. Churchhill, 1904, 2s.6d.), or to his larger work on ”Uric Acid.” An able scientific summary of investigations on purins, their chemical and pathological properties, and the quant.i.ties in foods will be found in ”The Purin Bodies of Food Stuffs,” by Dr. I. Walker Hall (Sherratt & Hughes, Manchester, 1903, 4s.6d.). The U.S. Department of Agriculture has made a large number of elaborate researches on food and nutrition. My thanks are due to Mr.
Albert Broadbent, the Secretary of the Vegetarian Society, for placing some of their bulletins in my hands, and for suggestions and help. He has also written several useful popular booklets on food of a very practical character, at from a penny to threepence each.
Popular literature abounds in unsound statements on food. It is unfortunate that many ardent workers in the cause of health are lacking in scientific knowledge, especially of physiology and chemistry. By their immature and sweeping statements from the platform and press, they often bring discredit on a good cause. Matters of health must be primarily based on experience and we must bear in mind that each person can at the most have full knowledge of himself alone, and to a less degree of his family and intimates. The general rules of health are applicable to all alike, but not in their details. Owing to individual imperfections of const.i.tution, difference of temperament and environment, there is danger when one man attempts to measure others by his own standard.
For the opinions here expressed I only must be held responsible, and not the Society publis.h.i.+ng the pamphlet.
Vegetarians, generally, place the humane as the highest reason for their practice, though the determining cause of the change from a flesh diet has been in most cases bad health.
A vegetarian may be defined as one who abstains from all animals as food.
The term animal is used in its proper scientific sense (comprising insects, molluscs, crustaceans, fish, etc.). Animal products are not excluded, though they are not considered really necessary. They are looked upon as a great convenience, whilst free from nearly all the objections appertaining to flesh food.
A.W.D.
The Chemistry of Food and Nutrition
By A.W. DUNCAN, F.C.S.
We may define a food to be any substance which will repair the functional waste of the body, increase its growth, or maintain the heat, muscular, and nervous energy. In its most comprehensive sense, the oxygen of the air is a food; as although it is admitted by the lungs, it pa.s.ses into the blood, and there re-acts upon the other food which has pa.s.sed through the stomach. It is usual, however, to restrict the term food to such nutriment as enters the body by the intestinal ca.n.a.l. Water is often spoken of as being distinct from food, but for this there is no sufficient reason.
Many popular writers have divided foods into flesh-formers, heat-givers, and bone-formers. Although attractive from its simplicity, this cla.s.sification will not bear criticism. Flesh-formers are also heat-givers. Only a portion of the mineral matter goes to form bone.
Cla.s.s I.--INORGANIC COMPOUNDS.
Sub-cla.s.s 1. Water. 2. Mineral Matter or Salts.
Cla.s.s II--ORGANIC COMPOUNDS.
1. Non-Nitrogeneous or Ternary Compounds. _a_ Carbohydrates.
_b_ Oils. _c_ Organic Acids.
2. Nitrogenous Compounds. _a_ Proteids. _b_ Osseids.
Cla.s.s III.--NON-NUTRITIVES, FOOD ADJUNCTS AND DRUGS.
Essential Oils, Alkaloids, Extractives, Alcohol, &c.
These last are not strictly foods, if we keep to the definition already given; but they are consumed with the true foods or nutrients, comprised in the other two cla.s.ses, and cannot well be excluded from consideration.
Water forms an essential part of all the tissues of the body. It is the solvent and carrier of other substances.
Mineral Matter or Salts, is left as an ash when food is thoroughly burnt. The most important salts are calcium phosphate, carbonate and fluoride, sodium chloride, pota.s.sium phosphate and chloride, and compounds of magnesium, iron and silicon.
Mineral matter is quite as necessary for plant as for animal life, and is therefore present in all food, except in the case of some highly-prepared ones, such as sugar, starch and oil. Children require a good proportion of calcium phosphate for the growth of their bones, whilst adults require less. The outer part of the grain of cereals is the richest in mineral const.i.tuents, white flour and rice are deficient. Wheatmeal and oatmeal are especially recommended for the quant.i.ty of phosphates and other salts contained in them. Mineral matter is necessary not only for the bones but for every tissue of the body.