ArticlesDo Chemosensory Changes Influence Food Intake in the Elderly?
Section snippets
Aging and Food Intake and Preference
Nutritional surveys have shown a low to moderate prevalence of frank nutrient deficiencies and an increased risk of deficiencies in both institutionalized and noninstitutionalized elderly groups. Based on a single 24-h diet recall, the National Health and Nutrition Examination Survey III (1988–1991) showed that the reported macronutrient composition of the energy content of the diet was similar to the population as a whole (50% carbohydrate, 16% protein, and 34% fat). However, the median daily
Effects of Changes in Taste Systems on Food Preference and Intake
Sensitivity to taste stimuli can decline with age, and although the magnitude of the change is often small (32), it can affect a number of older individuals (31). However, studies on taste acuity do not give an indication of how aging may affect taste preferences. It seems likely that taste preferences, not taste acuity, will affect food preferences and food intake. Two recent studies have examined the link between taste perception, taste preference, and food intake in young and elderly
Changes in Olfactory Function and Food Intake
The decline in olfactory function seen with aging is often more severe and more pervasive than that seen for taste systems 6, 32. Aging is associated with increases in the threshold for odor detection (29), lower perceived odor intensity, and a decreased ability to identify food-related odors (28). The key question is whether impairments of smell in the elderly have a measurable impact on food selection.
There is evidence that sensory factors related to olfaction play a role in diet choice. To
Variety in the Diet
In young individuals an important determinant of both the amount consumed and the variety in the diet is sensory-specific satiety. Normally, following consumption of a particular food, the rated pleasantness of the taste, smell, appearance, and texture of that food declines. This change in the hedonic response to the food, called sensory-specific satiety, is associated with decreased consumption of the previously eaten food and a shift in consumption to other food choices during a meal (21).
Aging and Fat Intake
Many elderly individuals are being advised to cut back on both sodium chloride and dietary fat to reduce their risk for cardiovascular disease. Recent surveys of dietary practices indicate that the elderly are using this advice to guide their diet choices. Food frequency questionnaires filled out by 7,419 women aged 50 to 79, indicated that low-fat diet practices such as trimming the fat from meat, and using reduced-fat spreads, dairy products, and snacks were widespread (17). In a recent
Regulation of Food Intake in the Elderly
Aging is associated with changes not only in chemosensory systems, but also in those that regulate appetitive behaviors such as eating 22, 23, 24, 25 and drinking (19). Several recent studies suggest that the dysregulation of food intake could put the elderly at high risk for nutritional disorders. One study (20) demonstrated that the elderly do not adjust their food intake following periods of over- or underfeeding. During a period of ad lib intake following 21 days of overfeeding, younger men
Conclusions
Although there are changes in chemosensory systems with aging, it is not clear how such dysfunction influences food preference or nutritional status. Indeed, several studies indicate that precise laboratory tests of smell and taste function may give limited insight into the habitual intake of the elderly. Their loss of chemosensory function may be so gradual that it has little impact on intake. Also, their food choices may be largely determined by habit and by beliefs about foods, for example,
Acknowledgements
This work was supported by DK50156 and DK39177.
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