THE ROLE OF TASTE AND SMELL 



IN THE REGULATION OF FOOD 



AND WATER INTAKE 



P. Teitelbaum and A. N. Epstein 

 Departments of Psychology and Zoology, University of Pennsylvania 



It is commonly assumed that taste and smell play little or no role in the 

 long-term quantitative regulation of food and water intake. This view is 

 based on a variety of different kinds of evidence. 



First, animals regulate their caloric intake over a wide range of dietary 

 adulterations. If the nutrient content of a solid powdered diet is decreased 

 by mixing it with cellulose (Teitelbaum, 1955) or with kaohn (Adolph, 

 1947 ; Kennedy, 1950) up to as much as 75 per cent, the animals main- 

 tain appreciable intake. It is only when the bulk of the diet becomes 

 tremendous that the animal will fail to eat enough to survive (Smith, 

 Pool and Weinberg, 1962). If water is added to a Hquid diet, normal intake 

 is maintained when as little as 2 per cent nutrient is present (Adolph, 1947). 

 Normal animals will thus face extreme overhydration to maintain their 

 caloric intake. 



Second, direct manipulation of the taste of the diet seems not to affect 

 caloric intake at all. If food is sweetened by mixing it with dextrose 

 (Teitelbaum, 1955) caloric regulation is maintained at the same level. If 

 the diet is made quite bitter by mixing it with up to 1.25 per cent quinine 

 hydrochloride, rats continue to regulate caloric intake (Teitelbaum and 

 Epstein, 1962). For water intake, the picture is quite similar. When 

 quinine hydrochloride is added to their water, rats continue to drink it 

 up to a concentration of 1 per cent (Teitelbaum and Epstein, 1962). This 

 is close to the maximum amount of quinine that will dissolve in water and 

 it is the point at which the fluid becomes lethal if ingested in normal 

 quantity. Therefore, the animals continue to drink quinine solutions until 

 they become actually poisonous. 



Third, regulation continues in the absence of taste and smell. Several 

 attempts have been made to achieve complete surgical denervation of taste 

 and to study the regulation of food and water intake in its absence. In 

 dogs, Bellows and Van Wagenen (1939) sectioned the fifth cranial nerve to 

 denervate the buccal cavity. In other dogs, they cut the chorda tympani 



347 



