Lessons in Food Values

Ladies' Mirror, Volume 5, Issue 3, 1 September 1926, Page 60

Lessons in Food Values

The subject of food values proves a fascinating one to most people ; to certain individuals the length and composition of their dinner is an all-important problem, while to the harassed housewife tin: part of her duties is a continual source of worry. Let us look at this question from a scientific point of view, and see if we cannot reduce the trials of the hard-working mother to a minimum, at the same time providing interesting and varied menus. What should we cat? is a question that one hears very frequently. What arc we going to consider the most fundamental points in connection with our food? The gourmet would probably be most concerned with the actual flavour, while the poorer members of the community would be more likely to consider the cost, and it is quite true that both these points have to be considered. The

taste of food is important, because a meal which is palatable is digested more readily than one that is not, and is, therefore, of greater use to the body. The cost of food is certainly of great importance, too. The most important consideration of all. however, is the composition of food, and this is a subject which should be of great interest to every housewife. As the result of many years’ work, physiologists arc now able to tell us of what the diet should consist, and can give us quite a short list of essential constituents.

/ "T~'hc diet should consist of the -*■ following: Protein (e.g., lean meat, fish, white of egg). Fat (e.g., butter, meat fat, etc.). Carbohydrate (e.g., starch in potatoes and bread, sugar). Water. Mineral salts (e.g., lime, etc.). Roughage (found in vegetables, and needed to give bulk to food). Vitamins. Let us take each one of these constituents separately and consider their different functions carefully. It is difficult to know which should come first on the list. We put vitamins last, merely because these elusive substances have been discovered more recently than any of the others, not because they arc the least important. We shall see that there are at any rate three vitamins, all equal -

ly essential and necessary for bodily well-being. To some extent we can replace fats in our diet by carbohydrates and vice-versa, but it is only to a slight degree that we. can substitute cither of these groups of food for protein. We may, therefore, consider the protein of the diet to be of primary importance, and hence we will deal with this class first. Proteins. —lt is not within the scope of this article to give a long chemical dissertation on proteins,

Tjj' (its, like carbohydrates, are sources -*■ of energy, although, as a given weight of fat produces more than twice as much energy as the same weight of carbohydrate, they may be regarded as better sources. Against this, however, we must place the greater cost of fat, and also the fact that some people cannot digest it very well. Fats arc specially good sources of heat. In the winter, therefore, we naturally take more fat than in the summer-time : a slice of buttered toasts, for instance, or a muffin, is very attractive on a cold winter’s day, while in the hot weather we should not appreciate it. Yet another value is the fact that in many foods, e.g„ butter, beef, and mutton, fats are associated with one of the vitamins, vitamin A. A /T literal Salts, although absolutely essential to life, hold quite a different position from carbohydrates, fat. and protein: they are of no use as sources of energy, but may be regarded solely as body-builders, livery cell in the body contains mineral salts, and the necessity for lime salts in the process of bone and tooth formation is well known. Then again, mineral salts are used in the manufacture of the digestive juices, and the red cells in our blood contain iron. The best sources of these salts arc the fruit and vegetables of our diet, and in this respect we should be careful to cook our vegetables in such a way that we do not lose most of the mineral salts in the water which we throw away. ID onghage. —By this term we mean the fibres of vegetables and fruits (made of cellulose —a kind of carbohydrate not digested by human beings), which give ballast to our food, and arc necessary to keep our internal organs in good workingorder. In cases of constipation the doctor frequently recommends more fresh fruit and vegetables, be., he is adding more roughage to the patient’s diet. '\7itainins. —There arc at least three * vitamins known at the present time, all possessing special properties, and found in different foods. Each is essential for health and bodily welfare, and the three arc known as vitamin A. vitamin B, and vitamin C. The existence of these interestingsubstances is a comparatively recent discovery. Until about twenty years ago we knew nothing of them, and were taught that the constituents of a diet should be fat, carbohydrate, protein, mineral salts, roughage, and water. It was then found that animals could not live on a diet composed of these purified constituents: research work led on to the discovery of the three vitamins. Americans already claim that there arc five vitamins, but at the moment we will he content to recognise three of these interesting substances, and proceed to consider each one separately.

\7ilaniin A. This vitamin is fre- * quently called the anti-rachitic vitamin, because its absence from an infant’s diet results in the baby developing rickets. Its absence also leads to bad eye trouble, in adults as well as in children, and it is important, therefore, that the supply should be very carefully safeguarded. Unfortunately, this vitamin occurs in rather expensive foods, so that the babies of poor mothers may suffer from lack of it, but in England, at any rate, the average individual should receive a good supply. Large quantities of this food factor arc found in cod-liver oil, herring and mackerel also being good sources, while butter, milk, cheese, egg-yolk, and animal fats provide us with this most necessary vitamin. From these facts it is seen that vitamin A is found closely associated with fats, but not with vegetable fats —margarine, for instance, if made from vegetable fats, contains none. It also occurs in tomatoes, and green vegetables, e.g., lettuce, cabbage and water-cress. On an ordinary mixed diet, it is unlikely that any one suffers from lack of vitamin A, but there is a possibility that those who cut down the fat in their diet, to a minimum should be very careful to eat tomatoes and green foods. The lack of vitamin A does not appear to lead to such drastic results in an adult as in a baby, yet it is highly probable that living on a minimum of this food factor results in a general state of feeling “not very well.’’ and leads to a decreased resistance to disease. People, for example with a low vitamin A diet may be more susceptible to colds. \7ilaniin —For us in New Zea- * land this vitamin has very little interest. Its distribution is much wider than that of any other vitamin ; in fact it is difficult to find even one food which contains none. A deficiency of vitamin B in the diet leads to a nervous disorder known as beri-beri; this disease, however, is only met with in countries where the diet is of a very restricted nature — for example, when the food consists almost entirely of polished rice (the vitamin having been removed by polishing, as it is present in the outer part of the rice grain). '\Tilamin C. — This vitamin is the * most important so far as we are concerned. Its absence from the diet results in the development of scurvy, a disease which attacks adults as well as children. Vitamin C has not nearly such a wide distribution as Vitamin A, and possesses the further drawback of being easily destroyed by heat; a large proportion therefore, is lost- during cooking. Consequently, it is of the greatest importance that every housewife should know what foods contain this vitamin, and should take special precautions to ensure that every member of her household receives a liberal supply.

From the point of view of obtaining sufficient of the anti-scorbu-tic vitamin, raw fruit should be included in the diet whenever possible. The more vegetables we consume, the more chance we have of obtaining the necessary ration of vitamin C, even if a certain proportion is destroyed in the cooking. This question obviously presents more difficulties to the town housewife than to the country one, as in towns, where most vegetables have to be bought, the portion for each individual is necessarily smaller. All town dwellers, therefore, should eat oranges, tomatoes, etc., as an essential part of the diet, and not as “extras.” Institutional catering is often very bad in this respect; in many cases no raw fruit is given at all. Tinned fruits are obviously useless as sources of vitamin C, because the temperature used in canning destroys the vitamin. There are many ways of remedying this defect —for instance, the food value of a fruit salad made from tinned fruit is greatly increased by the addition of a raw orange or, in the case of a very sweet syrup, some lemon-juice. In winter, a roll and cheese with an orange provides an excellent substitute for a pudding,—From Good Housekeeping.

yet we must try to grasp one or two fundamental points in order to have a clear understanding of the problems of the correct diet. Proteins are very complex chemical substances, differing from carbohydrates and fats in that they contain nitrogen. Furthermore, the nitrogen is there in such a form that it is of use to the body. The air around us contains as much as four-fifths of its volume of nitrogen, yet this nitrogen is absolutely no good to us as food. We must have nitrogen in the form of protein from which to build our tissues, and it is for this reason that proteins are frequently called “body builders.”

No food is entirely composed of protein, hut lean meat, fish, and white of egg consist largely of protein, and arc perhaps the best examples, while milk and cheese also contain a high percentage of protein. Vegetables and fruit, on the other hand, although they contain protein, possess only small amounts of it.

We know also that there are different kinds of protein, some of much better quality than others. On

the whole, proteins of animal origin (meat, fish, milk, cheese) are thought to be of better quality than plant proteins, although some vegetable proteins, c.g., potato protein, arc quite good. Vegetables, however, cannot he regarded as an adequate source, as the proportion of protein compared to other constituents is so low (hat an enormous bulk has to he eaten to obtain sufficient. During digestion the proteins of our food are broken up into their constituent parts. The body chooses what it needs for its own building processes and discards the remainder. From this it follows that we should eat a variety of foods in order to obtain different kinds of proteins, and allow our internal organs to have a chance to select what is necessary. If we reduce our protein food to one or two varieties, we may he

limiting ourselves in respect of something essential to the welfare of the body, for not only do we need proteins to provide the necessary materials for growth, but also for general bodily functions. For example, throughout life the thyroid gland (disease of which causes goitre) acts as a chemical factory, manufacturing a special secretion which is absolutely essential for health. Proteins may be regarded as part of the raw material from which the thyroid gland manufactures this secretion. Thus we see that proteins are an essential in any diet, and the more varied the protein ration, the more chance we have of obtaining what is necessary. (Carbohydrates are much more homely substances than proteins ; starches and sugars forming the chief carbohydrates of our diet. We arc all accustomed to meeting starch, though we may be more inclined to regard it as of use in laundrywork than as a source of food.

Therp are several different kinds of starch —rice starch, for instance, the variety found in the rice grain, potato starch, and maize starch, which is found in cornflour —but all varieties are useful food. Potatoes, bread flour, cereals (rice, etc.), and pulses (peas and beans) are the best examples of food containing starch. Another carbohydrate, sugar, is also a very familiar substance, and here again there arc several different varieties —cane sugar, which is either loaf or granulated, glucose, the variety we find in honey and fruits, and lactose or the sugar in milk. Now let us consider the use of these carbohydrates in our diet. Speaking briefly, we can say that our food is utilised within our bodies for two main functions : (1) To provide for growth. (2) To provide energy to do work and keep us warm. Carbohydrates are burnt in the tissues and are an excellent source of energy; anybody engaged in heavy manual labour, therefore, should have an extra large supply of these substances. When taking long walks, people frequently like to eat sweets on the way, and this is a very reasonable proceeding, for they are merely providing themselves with a source from which to obtain the necessary energy. Sweets are so often regarded as an extra and not as a food, but this is entirely wrong, for sweets arc food. Another function of carbohydrates is that in some peculiar way theyj assist us to burn our fatty food*' from which we also obtain energy). It is a known fact that fats cannot be burned properly within the body unless carbohydrates are being burned at the same time, and from this point of view carbohydrates arc essential and irreplaceable. Thus we sec that there is a physiological reason for eating sugar with our straw- j berries and cream, and golden syrup j or jam (sugar) with our suet pud-j ding (fat). |