Foods and Their Functions
ost of us eat for pleasure and to satisfy the appetite with the greatest joy to the palate. We should also eat with an understanding of the functions of our food. From food, and food alone, we daily must get materials which make us grow, which build our tissues, which regulate our body functions, and which provide energy for our activities. If our diet lacks the food materials for any of these important requirements the journey toward Wellville is certain to be interrupted.The body has been likened to a machine which must continue to function. Even when we are asleep or perfectly quiet, the heart, in beating, uses in a single day energy sufficient to lift an average man some twenty-five hundred feet in the air. Respiration and digestion continue. Tissue building goes on. When we are up and about, exercise brings muscles into play, and energy is expended in proportion to our activity.
Thus it may be seen what a constant necessity we have for the various materials different foods supply us, and how important it is that we do not neglect to provide ourselves with any single class of these materials in our daily meals.
Body Building Material: Proteins, Minerals, WaterThe body builders are the proteins, mineral salts, and water. They are the substances from which the body’s tissues are made. The body’s tissues include all the materials of the body. Muscles, nerves, bones, and blood are body tissues. Therefore it is imperative that protein, mineral salts, and water be supplied by food, in amounts large enough to make up for that used each day.
ProteinsThe proteins are complex, nitrogenous substances. They are absolutely essential to the growth and maintenance of our body tissues. Some of them have a greater potential building and repair value than others, so they must be selected with care.
All living tissue, whether of plants or animals, contains protein. Consequently, all foods not too thoroughly refined in manufacture possess protein in varying amounts.
But it is from animal sources that we obtain foods with proteins in largest amounts and in the form to do us the most good. Proteins in milk, eggs, meat, and fish are much like those in the human body, and so we can build proteins from these foods easiest into our own body tissues. However, plant proteins may be used to supplement proteins from animal sources.
An excellent source of plant proteins is found in cereals, especially in wheat.
Proteins cannot be stored up in the body to be requisitioned as needed. If there is no work for them to do, they are immediately rejected. This increases the burden upon the kidneys and may promote intestinal putrefaction. So it should be the aim to have enough, but not too much, protein, and to give due attention to the quality of the protein.
Mineral salts, while required in small quantities, are of enormous importance to our health.
CalciumCalcium and phosphorus are needed to build strong teeth and bones. They are the prime mineral elements in these tissues. Milk is by far the best source of calcium.
PhosphorusPhosphorus is part of every active body cell and, with calcium, gives rigidity to teeth and bones. Nerve and gland tissues especially demand it.
IronIron is another food essential. It enters into the composition of the red corpuscles of the blood and also is an element in the structure of all active cells. It is especially important that infants and adolescent boys and girls get an adequate iron supply. Spinach, egg yolk, green vegetables, and the outer layers of the grains provide iron in best quantities.
WaterThese are the important building materials for the body. To them, of course, must be added water, of which more than two-thirds of our body is composed.
The RegulatorsEven with all the building material ready at hand, there can be no satisfactory work accomplished within the body without proper regulation of the body machinery and a prompt disposition of its waste matter.
Minerals, water, and bulk must be provided in right amounts if the various body functions are to be kept on an uninterrupted schedule. The efficiency of each of these body regulators is increased by the use of right proportions of the others. They supplement each other’s efforts like partners in a well organized business enterprise, each with its particular function and responsibility.
Calcium and PhosphorusCalcium regulates the heart’s action and tends to keep the balance among other minerals. It helps the blood to maintain its neutrality and gives it its power to coagulate. Phosphorus is essential to nerve action. It is involved in all cell multiplication. It is important in maintaining the right liquid content of the tissues as well as in absorption and secretion.
IronWithout iron the energy would flag and body warmth decrease, because the oxygen needed for energy-yielding processes could not be carried through the body by the blood stream.
IodineIodine is so necessary to the thyroid gland that goiter occurs frequently in those sections where there is a lack of iodine in the food or water supply. Iodine is present in most sea foods and is found in the vegetation and water along the seaboard of the country. In certain sections known as “goiter belts,” iodine must be supplied medicinally. It is now available in an iodinized table salt.
WaterWater helps to regulate the concentration of the minerals in the body and carries food to the tissues by holding the food materials in solution in the body fluids. It also is invaluable in helping to carry off the body’s wastes and assists in regulating the body temperature. Four to eight glasses of pure water every day make for health. Most of it should be taken between meals.
BulkBulk in food is necessary to the successful action of the intestine and is an aid to digestion also. Bulk (indigestible roughage) is necessary to carry needed moisture through the intestinal tract, as well as to give bulk to the food residues, so that the intestinal muscles will get the stimulation necessary to move the food along.
Primitive man developed an intestine large enough to accommodate a coarse diet of unground grain, half-cooked meat, and raw vegetables. We retain this inheritance in the midst of a sedentary civilization. Thus the addition to the diet of a regular amount of roughage, in appetizing form that does not tire the taste and so may be taken regularly enough to do good, is of prime importance to those of us who would keep our eyes fixed on Wellville’s spires.
Foods for Growth and HealthThese are the all-important vitamins. We do not know what vitamins are. We only know them by their works. They are absolutely necessary to health and growth and are present in various foods in minutest quantities.
Experimentation has shown striking disaster resulting from diets entirely lacking in vitamins. But diets only slightly lacking in any one of the vitamins are even more dangerous. First, because such deficient diets are a great deal more prevalent. And second, because they produce just as serious consequences but in a more obscure and subtle way.
One who habitually gets an under-supply of vitamins in his food will suffer from general debility, will be easy prey to infections, and will fall heir to the common languors and inefficiencies accepted by many persons as inevitable.
Vitamin AVitamin A is particularly important to general well-being. It is stored in the body and seems to build a positive resistance to disease. Recent experiments have shown the importance of carrying a wide margin of insurance in the consumption of foods containing good supplies of vitamin A. Children lacking a sufficient amount of this important vitamin, while displaying an appearance of good health while young, at adolescence revealed marked tendencies toward lung disease, and their general resistance to infections was extremely low.
A serious eye trouble with a very long name (xerophthalmia) results from lack of vitamin A. The traveler along Wellville’s trouble-free road will not neglect this important food element, which builds his resistance to bodily ills. The best sources of vitamin A are butter, cream, milk, egg yolk, and spinach.
Vitamin BLack of vitamin B in the day’s food supply causes loss of appetite, poor digestion, and faulty nutrition. In fact, without an adequate supply of this important vitamin, one’s entire bodily vigor is lowered, growth is retarded, and the system is left easy prey to disease. Diets totally lacking in vitamin B cause a nerve disease named “beriberi,” and it is, therefore, called the “antineuritic” vitamin. It is not stored in the system for use when wanted, and therefore it is important, if we would travel to Wellville, to get an adequate amount of vitamin B in our food each day. Fortunately this is easy to do, for vitamin B Is widely distributed by nature in our foods and is not easily destroyed by heat in cooking processes. The best sources of vitamin B are milk, whole wheat cereals, and bran, vegetables, especially spinach, cabbage, tomatoes, and navy beans.
Vitamin CAbsence of vitamin C causes scurvy. But if the supply is deficient, there will result irritability, stunted growth, and lack of stamina. Vitamin C is the vitamin easiest to miss, because it is so easily destroyed by heat and is found less generally in foods than the other vitamins. It is not enough barely to escape scurvy. We need an abundance of vitamin C to insure vigorous health, and it is extremely necessary for mothers, both before and after baby’s arrival. It is found in good quantities in oranges, lemons, grape fruit, tomatoes, fresh or canned, raw cabbage, raw onions, lettuce, and rutabagas. We should eat at least one of these every day to be certain of getting a good supply of vitamin C.
Anti-rachitic Factor, Vitamin DAnother food element is vitamin D, the absence of which, especially in infants’ food, is one of the causes of that prevalent form of malnutrition called rickets—the failure of the bones to deposit calcium and phosphorus properly and to harden normally. Once rickets has fastened itself upon the child, the little victim becomes more susceptible to other diseases, especially those of the respiratory tract. A deficiency of vitamin D also causes poor development of the teeth. Egg yolk and cod liver oil are the best sources of the anti-rachitic factor and therefore should be used to keep rickets at bay.
Vitamins Extremely Important to YoungThe young must have all these important vitamins to build healthy bodies with strong resistance. But the adult, subjected to the strains and artificialities of modern life, needs them also. Vitamin-bearing foods there must be in right quantities each day to aid both old and young along the Road to Wellville.
Foods for EnergyFood for body fuel, to give it energy for maintaining its warmth and for providing it power to work, must be had in adequate amounts each day. The body is dependent upon protein, fat, and carbohydrates (starches and sugars) for its energy supply. Protein foods, selected primarily for building purposes, supply some of this energy, but it is inadvisable to take more protein into the body than is required each day to build needed tissues or repair worn tissues. Considerable energy may also be had from the fruits and vegetables selected primarily to supply mineral salts or vitamins and from fats chosen chiefly for the vitamins they possess. Under normal conditions, however, the amount of energy obtained from these foods will not be sufficient for the day’s requirement, and they must be supplemented by carbohydrate foods if the body’s energy demands are to be thoroughly satisfied.
For every motion we make, from turning the head to the most violent exercise, and for all the internal workings of the body in digestion and assimilation, tearing down old tissues, building up new ones, and eliminating waste—for all this we need energy. And we get energy from the food we put into our bodies, as we get warmth for the house from the wood and coal we put into the furnace.
The fats yield two and one-quarter times as much energy for a given weight as do the starches and sugars. But they are more costly and more difficult to digest, more concentrated, and so we can use less of them, about one-quarter to one-third of our food being fats. Three-fifths of the ration should be from sugars and starches, the latter being our leading body fuel.
The grains lead as a starch supply, as they are three-fourths carbohydrates; the beans and peas come next with three-fifths, and the potato, as eaten, has one-fifth.
Another point to remember is that unless we have enough of the fuel foods (starches, sugars, and fats), the body will eventually burn its protein to get enough energy and warmth. So undernourishment, stunted growth, and general disability may all result indirectly from having too little of the fuel foods, as well as from having too few of the building proteins, vitamins, or minerals.
And whether we use the fuel foods for energy for doing work, or store them in the body in the form of fat, depends on our activities in relation to the amount of food eaten. The same amounts of sugar, butter, cereals, and breads may spell energy and muscle for the athlete, and dullness and fat for the Lady of the Hammock or for the Man-Behind-the-Desk who exercises his brains only!