FOOD SCIENCE. — It is the study of human nutritional needs and, in a broader sense, those of animals and plants, as well as the means to adequately satisfy them.
I. HISTORICAL BACKGROUND
From the very appearance of man on earth, the determining factor in human actions must have been the reproduction and preservation of the species, the search for daily sustenance; hence an uninterrupted succession of migrations, wars, revolutions, etc. The principal aspects of primitive civilizations were shaped by the activities undertaken by man to procure food: hunting, fishing, gathering wild plant foods first; then pastoralism and agriculture. Many centuries, however, were required before his nutritional needs were scientifically defined.The earliest evidence demonstrating man’s interest in the nutritive qualities of foods comes from Egypt and Babylon, dating back 4,000 to 5,000 years. Later, in 460 B.C., in Greece, Hippocrates was the first to link the study of medicine with that of nutrition; it was only after the beginning of the Christian era, with Galen, that this association bore practical fruit.
The first information regarding the transformations food undergoes in the organism is owed to Fernel (1543), van Helmont (1577), and Sanctorius (1614); but great progress came after the discovery of oxygen. It was Lavoisier (1777) who explained the importance of this gas for living organisms and measured the degree of combustion in human subjects, thereby laying the foundations of animal calorimetry. The relationship between combustion and foods was later established more precisely with the detailed knowledge of the chemical composition of the latter, to which Beccari (1728) and Liebig (1842) with his school contributed. One of Liebig’s students, Voit (1866–73), established that protein requirements depend on the mass of organized tissue, while lipid and carbohydrate requirements depend on the organism’s activity. The foundations of food science were thus laid; its further development was advanced by scientists such as Rubner, Atwater, Müller, Lusk, Chittenden, Mendel, Sherman, McCollum, Albertoni, Rose, and others.
II. CURRENT CONCEPTIONS
The aims of food science are pursued through research: 1) on the composition and function of foods; 2) on the energetic and material transformations (metabolism) that occur in the organism in relation to its various functional states.1. Chemical and functional study of foods
This has made it possible to identify and group the following nutrients in foods:a) energy-yielding nutrients, which provide chemical energy usable by the organism and primarily convertible into heat and work (including carbohydrates and lipids; proteins only secondarily);
b) structural nutrients, which provide the material essential for growth and maintenance of tissues (represented by proteins and their amino acids, though carbohydrates, lipids, and mineral elements also serve this purpose, albeit in limited quantities);
c) nutrients that maintain the integrity and efficiency of vital processes as a whole (this group includes vitamins and mineral salts).
d) To these nutrients must be added water and oxygen, indispensable for all reactions to occur.
2. Study of energetic and material metabolism
This has made it possible to consider the food reaction from two aspects which, though conveniently treated separately, must nonetheless be regarded as a unity:a) Energetic aspect. Every vital activity requires an expenditure of energy derived from the chemical energy of foods, which corresponds to the energy released when foods are utilized by the organism. This energy amounts to 4.1, 9.3, and 4.1 calories per gram of carbohydrates, lipids, and proteins, respectively. It is this energy that, during vital activity, is converted into internal work, defined as basal metabolism, and into external or muscular work, which, when added to the former, expresses the total energy metabolism. The values of this metabolism have been determined in various functional states; they are expressed in calories and define the energetic aspect of nutritional requirements, which vary with age, sex, work, etc.
b) Qualitative aspect. However, equal energy value does not correspond to equal biological value of a diet, which is conditioned by various indispensable factors linked to the law of the minimum.
It is always necessary to introduce with foods a minimum of proteins, or rather of certain essential amino acids that the organism cannot synthesize. To appreciate the importance of the protein aspect of nutrition, it suffices to recall the highly variable structure of proteins (which accounts for their high specificity), and the fact that enzymes, numerous hormones, viruses, antibodies, etc., are of a protein nature. Lipids and carbohydrates also fall among the factors for which a minimum cannot be exceeded below which metabolism is impaired.
Since numerous inorganic elements are found in the organism in the form of soluble and insoluble salts, they must be introduced from outside.
It is scientifically justified to believe that, to ensure the organism’s mineral requirements (including those of elements that, even in trace amounts, perform important functions), it is sufficient to ensure the ingestion, in adequate quantities, of four elements—calcium, phosphorus, iron, and iodine—whose deficiency alters many vital processes.
Vitamins are substances of the most varied structures which, even in minute quantities, regulate the course of highly delicate physiological processes; many of them are part of enzymes (complex substances that catalyze the countless chemical transformations occurring in the organism). Not all vitamins, once isolated and chemically identified, are recognized as important for human nutrition; the best known are: vitamin A or axerophthol, vitamin B1 or aneurin, vitamin B2 or riboflavin, vitamin PP or niacin, vitamin C or ascorbic acid, the anti-anemic vitamin or folic acid, vitamin D or the antirachitic factor, vitamin E or tocopherol, vitamin K or the antihemorrhagic factor, and vitamin P or the permeability factor.
The human organism does not synthesize them, so they must be supplied through food. Chronic deficiency of one or more of these limited factors leads to specific morbid forms due to nutritional deficits, known as deficiency diseases.
It is now fully demonstrated how and to what extent abnormalities of development, growth defects, and intellectual retardation are linked to qualitatively and quantitatively insufficient diets. It is a diet balanced in all its constituents that enables the organism to function at the highest level of efficiency and performance. The advances in the field of food science also influence the agricultural and commercial activities of every country with a view to the production, distribution, and preservation of foodstuffs, with consequences no less profound than those achieved in the fields of medicine, individual hygiene, and social welfare.