Synopsis
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Extrait
Chapter 1
FOODS WE EAT
Put this puzzle together and you will find milk, cheese and eggs, meat, fish, beans and cereals, greens, fruits and root vegetables -- foods that contain our essential daily needs.
Exactly how they interlock and in what quantities for the most advantageous results for every one of us is another puzzle we must try to solve for ourselves, keeping in mind our age, body type, activities, the climate in which we live, and the food sources available to us. How we wish someone could present us with hard and fast rules as to how and in what exact quantities to assemble the proteins, fats and carbohydrates as well as the small but no less important enzyme and hormone systems, the vitamins, and the trace minerals these basic foods contain so as best to build body structure, maintain it, and give us an energetic zest for living!
Where to turn? Not to the sensational press releases that follow the discovery of fascinating bits and pieces about human nutrition; nor to the oversimplified and frequently ill-founded dicta of food faddists that can lure us into downright harm. First we must search for the widest variety of the best grown unsprayed foods we can find in their freshest condition, and then look for foods with minimal but safe processing and preservatives and without synthetic additives. While great strides have been made in the storage of foods commercially and in the home, if fresh foods in good condition are available to you, choose them every time. To compare the nutritive values in frozen, canned and fresh vegetables, see 798.
Next we can find in the U.S. Handbook on the Composition of Foods some of the known calorie, protein and other values based on the edible portions of common foods. Recent mandatory labeling information, 7, is of some help, although the U.S. Recommended Daily Allowances are based on information from a nongovernmental agency, the National Research Council, a source not acceptable to some authorities. But no one chart of group of charts is the definitive answer for most of us, who are simply not equipped to evaluate the complex relationships of these elements, or to adapt them to the practicalities of daily living. Such studies are built up as averages, and thus have greater value in presenting an overall picture than in solving our individual nutrition problems.
Nevertheless, by applying plain common sense to available mass data, we as well as the experts are inclined to agree that many Americans are privileged to enjoy superabundance and that our nutritional difficulties have to do generally not with under- but with overeating. Statistics on consumption also bear out other trends: first, that we frequently make poor choices and eat too much of the wrong kinds of foods; second, that many of us overconsume drugs as well as foods. Medication, often a lifesaver, may, when used habitually, induce ah adverse effect on the body's ability to profit fully from even the best dietary intake.
Individually computerized diagnoses of our lacks may prove a help in adjusting our deficiencies to our needs. But what we all have in our bodies is one of the greatest of marvels: an already computerized but infinitely more complex built-in system that balances and allocates with infallible and almost instant decision what we ingest, sending each substance on its proper course to make the most of what we give it. And since nutrition is concerned not only with food as such but with the substances that food contains, once these essential nutrients ate chosen, their presentation in the very best state for the body's absorption is the cook's first and foremost job. Often taste, flavor and color at their best reflect this job well done. Read The Foods We Heat, 145, and follow our pointers to success for effective ways to preserve essential nutrients during cooking. And note at the point of use recommendations for optimum storage and handling conditions, for one must always bear in mind the fragility of foods and the many ways contaminants can affect them, and consequently us, when they are carelessly handled or even when such a simple precaution as washing the hands before preparing foods is neglected.
But now let's turn to a more detailed view of nutritional terms: calories, proteins, fats, carbohydrates, accessory factors like vitamins, minerals, enzymatic and hormonal fractions -- all of which are needed -- and see how they interact to maintain the dietary intake best suited to our individual needs.
ABOUT CALORIES
A too naïve theory used to prevail for explaining regeneration through food. The human system was thought of as an engine, and you kept it stoked with foods to produce energy. Food can be and still is measured in units of heat, or calories. A Calorie, sometimes called a kilocalorie or K Calorie, is the amount of heat needed to raise one kilogram of water one degree Centigrade. Thus translated into food values, each gram of protein in egg, milk, meat or fish is worth four calories; each gram of carbohydrate in starches and sugars or in vegetables, four calories; and each gram of fat in butters, in vegetable oils and drippings, and in hidden fats, 5, about nine calories. The mere stoking of the body's engine with energy-producing foods may keep life going in emergencies. But to maintain health, food must also have, besides its energy values, the proper proportions of biologic values. Proteins, vitamins, enzymes, hormones, minerals and their regulatory functions are still too complicated to be fully understood. But fortunately for us the body is able to respond to them intuitively.
What we really possess, then, we repeat, is not justa simple stoking mechanism, but a computer system far more elaborate and knowledgeable than anything that man has been able to devise. Our job is to help it along as much as possible, neither stinting ir nor overloading it. Depending on age, weight and activity the following is a rough guide to the favorable division of daily caloric intake: a minimum of 15% for proteins, under 25% for fats, and about 60% for carbohydrates. These percentages are relative: some people with highly efficient absorption and superior metabolism require both lower intake and the lesser amount of protein. No advice for reducing is given here, nor are the vaunted advantages of unusually high protein intake considered -- as again such decisions must be highly individual, see About Proteins, at right. In general, and depending also on age, sex, body type and amount of physical activity, adults can use 1700 to 3000 calories a day. Adolescent boys and very active men under fifty-five can utilize close to 3000 calories a day. At the other extreme, women over fifty-five need only about 1700 calories. Women from eighteen to thirty-five need about 2000 calories daily. During pregnancy they can add 200 calories and, during lactation, an extra 1000 calories. Children one to six need from 1100 to 1600. Before a baby's first birthday, his diet should be closely watched, and parents should ask their pediatricians about both the kinds and the amounts of food to give their baby.
Given your present weight, perhaps a more accurate way to calculate your individual calorie requirement is to consider your activity rate. If you use a car to go to work and have a fairly sedentary job, or even if you are a housewife with small children, your rate is probably only 20%; 30% if you are a delivery man of patrolman working out of doors, and 50% if you are a dirt farmer, construction worker or athlete in training. If you multiply your weight by 14 calories, you will get your basal need, that is, the calories you would require if you were completely inactive. When you multiply this amount by your own activity factor and add it to your basal needs, you should get ah approximation of your required daily caloric intake. If you reduce your caloric intake much below this approximate norm, you may be lacking in your mineral, vitamin and protein requirements. Whatever your caloric intake, distribute your choices properly among protein, fat and carbohydrate values.
ABOUT PROTEINS
On our protein intake depends the constant virtual replacement of self. And nowhere in the diet is the relation of quantity to quality greater. The chief components of proteins are 22 amino acids. They form an all-or-nothing team, for food is utilized by the body only in proportion to the presence of the scarcest of them. Fourteen of the 22 aminos are both abundant and versatile. If they are not present when food is ingested, the body is able to synthesize the missing ones from those present. The remaining 8 aminos, however, cannot be synthesized and must be present in the food when ingested. These eight are known as the essential aminos. Four of them -- leucine, valine, phenylalanine and threonine -- are relatively abundant in foods, but the other four -- isoleucine, lysine, methionine and tryptophan -- are more scarce. And because utilization of protein by the body depends in each instance on the least abundant member of the essential aminos, these latter four are known as the key aminos.
Generally speaking, proteins from animal sources like egg? meat, fish, and dairy products are valued because their total protein content is high, and they are referred to as complete because they are rich in the essential aminos, and therefore more of the total protein present is utilizable. Those from vegetable sources such as whole grains, nuts, seeds, and legumes -- with the exception of soybeans -- are less valuable because their total protein content is low. They are referred to as incomplete because they are also Iow in one or more of the eight essential amino acids, meaning that less of their total protein can be utilized by the body. The terms "complete" and "incomplete" ate somewhat misleading, however, because of their absolute connotations. It is still possible to fulfill your daily requirements for protein from incomplete vegetable sources, provided you are willing and able to consume large enough quantities of the incomplete protein item in question. But the utilizable protein content of most cereals is so poor that consuming enough to satisfy protein requirements would be a practical impossibility.
Take corn, for example. It has little protein and many starch calories. A diet based exclusively on corn would require consumption of enormous quantities of com to establish the needed essential aminos. A complete protein source like eggs would therefore be more realistic and desirable in satisfying the same protein requirement with far less caloric intake. In fact, for 10 grams of egg protein at 125 calories, you would have to eat 16.5 grams of corn protein at 500 calories to get ah equivalent amount of usable protein. But since no one wants to live on corn or eggs alone, a more reasonable way to approach the problem is to note how complete and incomplete proteins complement each other.
There are various ways of expressing protein values -- net protein utilization, of NPU; protein efficiency ratio, of PFR; and biologic value, or BV. Another unit of measure used on product labels is protein value in relation to casein, 7. Although these terms are all derived by different methods, they correlate well with each other. Whatever the method of expressing this utilization efficiency, one fact remains: that is, the body requires certain kinds and amounts of essential amino acids which must be supplied each day.
Any excess intake of amino acids not compensated for is metabolized away and thus not used for growth or maintenance of the body. Eggs, with a BV of 94, may be considered the most ideal protein from the point of view of utilization to replace body protein. But we can't survive on one food alone.
If we combine durum wheat, with a BV of 60, and lima beans, with a BV of 50, we get through their complementarity of utilizable protein a score of 60. But a BV of 60 is marginal for body replacement, and so a more complete protein such as that contained in milk of eggs should be added to such a meal. Combine, for instance, I tablespoon of peanut butter, with a BV of 43, and one slice of white bread, with a BV of 52. If you add 4 ounces of milk, with a BV of 86, the combination stabilizes at a BV of approximately 80.
In countries dependent mainly on beans and rice of other cereal combinations, the beneficial effects of adding to the diet even small amounts of meat, fish, eggs or dairy products is well recognized. And when various pastas are the staple foods, the inclusion of at least one-third in the form of a complete protein is considered the minimal amount to bring the meal up to acceptable levels. Furthermore, it should be stressed that any meal of snack which fails to include sufficient complete protein, although it may temporarily stay one's hunger, will not replenish all of the metabolic Iosses of the body.
In regions where only vegetable protein is available, grains combined with pulses such as beans and peas ate classic. It has been found that increments of about one-third complete protein reinforce incomplete protein to form a total that is greater than the sum of its parts.
Even more significant differences ate found between processed and unprocessed foods. Brown rice has a BV of 75, as opposed to white rice with a BV of 65. Whole wheat bread has a BV of 67; white bread, 52.
To meet the needs of underdeveloped areas and the threat of worldwide protein shortages, in recent years experiments involving grain, seed and legume combinations, 198, have been undertaken which may one day prove valuable to all of us. Gross nutritional deficiencies ate more conspicuous in areas where protein imbalances are drastic and prolonged, and the effects of improved diet are easier to evaluate than in areas like ours, where such deficiencies are less severe and thus harder to detect. Until recently, we have relied on animal experimentation, and although dietary results thus achieved are valuable, they are not always applicable to man, and, for the most reliable results, data must be based on human reactions.
Since vegetable proteins are incomplete except as noted above, ir is wise to draw two-thirds of the daily protein intake of 10% of your caloric intake from animal sources. Preferably, meats should be fresh -- not pickled, salted or highly processed. Protein foods when cooked should not be subjected to too high heat, for then they lose some of their nutrients. Familiar clanger signals are curdling in milk, "stringiness" in cheese and dryness in meat and fish.
Protein requirements generally are slightly higher in colder climates but no matter what the climate, growing children, pregnant women and nursing mothers need a larger proportion of protein than the average adult. The elderly, whose total caloric intake often declines with age, should consume a relatively larger percentage of protein to reinforce their body's less efficient protein metabolism. Again, absolute amounts cannot be given, because needs will depend on the efficiency of utili...
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