Two of the major nutritional roles of oral sensory mechanisms are to initiate eating and to ensure reliable control of nutrient intake. Lepkovsky stated that the "universality of the chemical senses is best explained by the fact that in order to eat, the organism must possess some chemical knowledge" (I ). Studies have demonstrated that experimental animals, under some circumstances, are able to associate the sensory qualities of foods with their postabsorptive consequences, allowing the animals to select nutrients according to their physiological needs ( 2 4 ) . This suggests survival value of the chemical senses in governing selection of nutrients. However, at least in the industrialized nations, humans select and consume nutrients from among foods which are available in excess of survival needs. Additionally, taste experiences and cultural factors produce new eating patterns and nutritional consequences. Thus, the role played by the chemical senses during the over-consumption of high-salt, high-fat, and high-sugar foods becomes an obvious aim of nutritional studies.ntmuse oral stimulatiun cnn initiate exucrine and endwrine sca:rrtions invdvrd in dinestion and metabulism ( 5 61, at-" tention is currently being given to the nutritional conseouences of these nhvsioloeical secretions. In this paver, we . " discuss possible nutritional applications of the interrelationshios of the chemical senses with eating behavior, digestion, and metabolism.
The Role ot the Chemical Senses in Regulating the Selection of NutrientsIt is apparent that the chemical senses play a significant role in food choices. The fact that newborn infants with no prior taste experience prefer sugar solutions over water in a pattern similar to that of adults, coupled with the fact that newborns show no preference for othertaste stimuli (9, lo), suggests that the human preference for sweet tastes is probably innate. The avid selection of sugar solutions by the human newborn complements their continuing caloric need. On the other hand, there is no apparent selection of sodium chloride solutions presumably because maternal milk is well supplied with sodium chloride.The newborn has a narrow margin of safety from dehydration stemming from the high ratio of surface area to body mass. Further, the ability to handle salt is limited because of the immature kidnev. A few vears later the child will select salty foods; however, by thattime the threat of dehydration is reduced and kidneys are fully functional. It would appear that, in the newborn, taste for sugar and for salt functions in the interest of the baby's welfare.When given a choice of novel foods, rats initially select diets having flavors known to appeal to humans in preference to diets containing tastes considered to he aversive. This unlearned discrimination may have survival value in mammals, since appealing tastes are associated with nutritious foods and many toxic compounds are bitter. The physiological state of an animal may induce altered behavioral patterns in food selection. For example, ...