Appetite, 1990,24,159-161

What Do We Mean When We Say “Palatable

food”?

ISRAEL RAMIREZ Monell Chemical Senses Center Philadelphia

The word palatability and related words have not been used in a consistent way. Palatability may be a property of a food, of the organism eating the food, or both.

Investigators have failed to distinguish different possible meanings of the statement: “palatable foods increase intake”. This may indicate: (1) a simple observation that some foods stimulate more intake than others, (2) an innate response to the taste of foods that alters appetite, (3) a correlate of food intake that does not itself affect intake, and (4) a link in a causal chain involving prior associations between foods and their postingestive consequences.

WHATDO

WEMEANWHEN

WESAY~PALATABLEFOOD"?

Palatability is one of the most commonly mentioned concepts in the field of appetitive behavior. It goes by many names, may be studied in many ways, and can influence food intake in any species. Palatability plays a critical role in theories of obesity and food choice. So many discussions of what the concept is and what influences it have been published (e.g. Young, 1967; Grill & Bet-ridge, 1985; Le Magnen, 1987) that one would think that it should not be necessary for someone to raise the question posed in the title. The question arose when the author began asking why certain diets produce obesity. Discussions and correspondence with colleagues as well as a survey of the literature led to several suggestions, but the most common was that some foods taste better. Although some dissenting opinions were offered, the popularity of this view is remarkable in light of the limited evidence for it (see Naim et al., 1985; Ramirez et al., 1989). It is noteworthy that most investigators employing cafeteria diets describe the foods as “palatable” without providing any information about how it is determined that foods such as cookies and salami are palatable to rats. The source of the problem is that in colloquial usage the word is vague. Dictionaries generally define “palatable” using some variant of the phase “agreeable to the palate or taste” (e.g. Gove, 1967): this does not tell us if palatability is a property of the person, the food or both. Some theorists (e.g. Kissileff, 1986) have argued that palatability is an objective property of foods. According to this view, there is a correct answer to the question “which is more palatable, vanilla or chocolate ice cream?’ , just as a red traffic light is still red, even if seen as green by a color-blind person. Other theorists have argued that palatability should be defined as the hedonic response of an animal or human to sensory stimuli (e.g. Young, 1967; Grill & This work was supported by a National Science Foundation grant (BNS 87-19309) and the Monell Chemical Senses Center. Highly skilled technical assistance was provided by Charlene Connelly. Conversations with scientists at Monell, especially M. Naim and M. Tordoff, stimulated my thinking. Anne Ramirez made the text more readable. Address reprint requests to: I. Ramirez, Monell Chemical Senses Center, 3500 Market St., Philadelphia, PA 19104-3308, U.S.A. 01956663/90/030159+03

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I.RAMIREZ

Berridge, 1985; Le Magnen, 1987). According to this view, one cannot say that a food is palatable but should say instead that a food is palatable to any individual under defined circumstances. Vague and inconsistent meanings create a severe problem for causal analysis. Some researchers seem to use the word palatable as a purely descriptive term meaning that organisms eat more of some foods than others. This is undesirable because it insinuates a mechanism without actually providing one. The following causal sequence seems to be what many researchers mean when they do refer to palatability as a cause. Food eaten-palatability

response+More

food eaten

Presumably, the palatability of ice cream and soft drinks reflects an innate response of humans and rats. This sequence makes sense only if one assumes that palatability is a property of the food and not of the organism eating the food. However, an alternative sequence is plausible. Food eaten-+Palatability response-+No effect on intake LGastrointestinal and metabolic effects-More food eaten In the second causal sequence, palatability is merely correlated with ingestion. The nature of the gastrointestinal and metabolic effects involved is left open for the sake of simplicity. Some specific possibilities are discussed elsewhere (Ramirez et al., 1989). A third plausible causal sequence involves learning. Food eaten-+Gastrointestinal

and metabolic e&cts+Palatability

Food sampled again-+Palatability

response-+More

increased

food eaten

In this third sequence, palatability is a link in a causal chain but cannot be considered the ultimate cause. Again, for the sake of simplicity, the time between the first and second occasions the food is eaten is undefined but could be anything from minutes to months. It is not necessary for the foods to be identical on both occasions: the foods can merely share a common taste or smell. The third causal sequence requires one to treat palatability as the response of an organism to food rather than a property of the food itself. The three causal sequences could occur concurrently. For example, intake of sucrose by rodents is partly innate (sequence 1) (Ramirez & Fuller, 1976) and partly learned (sequence 3) (Booth et al., 1972). However, analysis of the role of palatability in appetite cannot proceed unless the three possibilities are conceptually distinguished. This is not generally done. Nearly every discussion of the role of palatability in dietary obesity has assumed the first sequence. A striking exception is Le Magnen (1987), who described the third sequence but then proceeded to treat palatability as the ultimate cause of dietary obesity. It should be emphasized that this problem applies equally to humans and rats. One cannot assert that palatability makes a human eat more chocolate than spinach merely because the person says that chocolate is more palatable, pleasant, delicious, etc. Studies in which such introspective reports are uncritically accepted are common; attempts to understand the causes of preferences are uncommon. One way out of this muddle is to banish the word palatability entirely and stick with concepts whose meaning everyone can agree on. Many will find this alternative unpalatable.

PALATABILITY

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REFERENCES

Booth, D. A., Lovett, D. & McSherry, G. M. 0972) Postingestive modulation of the sweetness preference gradient in the rat. Journal of Comparativeand Physiological Psychology, 78, 485-5 12. Gove, P. B. (Ed.) (1967) Webster’s seventh new collegiate dictionary. G. and C. Merriam Co.,

Springfield, M.A., p. 606. Grill, H. J. & Berridge, K. C. (1985) Taste reactivity as a measure of the neutral control of palatability. Progress in Psychobiology and Physiological Psychology, II, I-61. Kissileff, H. R. (1986) Quantitative relationship between palatability and food intake in man. In M. R. Kare and J. G. Brand (Eds), Interaction of the chemical senses with nutrition. Pp. 293-317. NY: Academic Press. Le Magnen, J. (1987) Palatability: concept, terminology, and mechanisms. In: R. A. Boakes, D. A. Popplewell & M. J. Burton (Eds.) Eating habits. Pp. 131-154. Chichester, England: Wiley. Naim, M., Brand, J. G., Kare, M. R. & Carpenter, R. G. (1985) Energy intake, weight gain and fat deposition in rats fed flavored, nutritionally controlled diets in a multichoice “cafeteria” design. Journal of Nutrition, 115, 1447-1458. Ramirez, I. & Fuller, J. L. (1976) Genetic influence on water and sweetened water consumption in mice. Physiology and Behavior, 16, 163-168. Ramirez, I., Tordoff, M. G. & Friedman, M. I. (1989) Dietary obesity and hyperphagia: what causes them? Physiology and Behavior, 45, 163-168. Young, P. T. Palatability: the hedonic response to foodstuffs. In C.F. Code (Ed.), Section 6. Alimentary Canal. Vol. 1. Pp. 353-366. Washington D.C.: American Physiological Society. Received 14 July 1988, revision 1 December 1988

What do we mean when we say "palatable food"?

The word palatability and related words have not been used in a consistent way. Palatability may be a property of a food, of the organism eating the f...
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