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Food and Feeding
- Johns Hopkins University Press
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3 Food and Feeding Dis-moi ce que tu manges, je te dirai qui tu es. — brillat-savarin, 1825 THE FAMED FRENCH POLITICIAN and gourmet Jean-Anthelme Brillat-Savarin wrote in La physiologie du goût, “Tell me what you eat, I will tell you who you are.” One can only guess whether the similar wording of Cuvier’s statement, “Show me your teeth, and I will tell you who you are,” is coincidental. Whether these statements are connected or not, it is clear that teeth are important to mammals principally because of their role in procuring and processing food. And it is the interaction between teeth and foods, as much as anything else, that puts Mammalia in a class of its own. If we do not occasionally remind ourselves of this, we can easily lose sight of the big picture when considering the details of mammalian tooth form. Mammals must fuel their bodies and provide themselves with the necessary raw materials for maintenance, growth, development, and reproduction. Diet is key to the role of an individual in its biotic community. The connection between an animal and what it consumes is fundamental to ecology, the study of the relationship between an organism and its environment. It should come as no surprise, then, that, as Rozin and Rozin (1981:209) have written, “the structure and the behavior of most animals are shaped and characterized in very large measure by the nature of the foods consumed, and the ways in which those foods are obtained.” We cannot fully appreciate teeth without considering foods and feeding. This chapter presents a review of the dietary requirements of mammals and the many different ways in which they obtain or make the nutrients they need to survive and flourish. Some physical properties of foods are also described, as these are especially important in the context of the role of teeth in food acquisition and processing. An appreciation for the challenges that teeth face during feeding is necessary if we are to understand dental form-function relationships and the adaptive radiation of mammalian tooth form. NUTRIENT REQUIREMENTS Mammals must consume and assimilate complex organic molecules in order to sustain themselves. Our nourishment depends ultimately on beneficial microorganisms and green plants, which manufacture these organic molecules. Green plants, for example, turn inorganic materials into monosaccharides, amino acids, and fatty acids. These simple organic molecules are the building blocks used to make larger, more complex molecules; monosaccharides are assembled polysaccharides, amino acids are bonded to form proteins, and fatty acids are combined with glycerol as oils f o o d a n d f e e d i n g 27 Carbohydrates Carbohydrates are the principal source of energy for the body. These organic compounds typically consist of a chain of carbon atoms to which hydrogen and oxygen are attached . Most come from plants, which use solar energy to make them from carbon dioxide and water during the process of photosynthesis. If the radiant energy of sunlight is applied to six molecules each of CO2 and H2 O, for example, a simple hexose sugar molecule (C6 H12 O6 ) and six O2 molecules can result. The length of a carbon chain can vary among simple sugars, typically comprising five or six atoms, but all are monomers called saccharides, which cannot be hydrolyzed, or cleaved in two by the addition of a water molecule. On the other hand, these monomers can be bonded together to form polymers by releasing water (Fig. 3.1). Indeed, carbohydrates are classified according to the number of saccharides, or sugar units, they contain. According to one common scheme, those with only one sugar unit are called monosaccharides ; those with two, disaccharides; those with three to nine, oligosaccharides; and those with ten or more, polysaccharides (Asp 1996; Englyst and Hudson 1996; Cummings et al. 1997; W. G. Pond et al. 2005). (neutral fats). These processes, especially the photosynthesis of carbohydrates, are considered below. Digestion occurs when animals take these complex molecules and break them back down into their simple constituent parts. The resulting smaller, simpler molecules are then absorbed into the bloodstream and reassembled according to the needs of the consumer. This dismantling of complex molecules that plants (or animals, for that matter) have assembled occurs by both mechanical and chemical preparation . Mechanical preparation includes chewing and muscular contractions of the gastrointestinal (GI) tract. Chemical preparation includes dissolution by hydrochloric acid in the stomach or bile in the small intestine, hydrolysis by enzymes produced and released into...