THE DEGENERATION OF TASTE AND SMELL IN ELDERLY ADULTS AND HOW IT NEGATIVELY AFFECTS THEIR EATING HABITS AND NUTRITIONAL STATUS.

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1 THE DEGENERATION OF TASTE AND SMELL IN ELDERLY ADULTS AND HOW IT NEGATIVELY AFFECTS THEIR EATING HABITS AND NUTRITIONAL STATUS. ABSTRACT The purpose of this paper is to investigate the effect that the loss of two senses, taste and smell, have on the eating habits and nutritional status of the elderly. Smell and taste are largely connected pathways. The loss of smell almost always results in a loss or alteration in taste. The loss of taste and/or smell can affect a person s eating habits in two ways, by causing them to undereat due to lack of appetite or by causing them to overeat by consuming high fat foods to make up for the blandness in their diet. Both of these results are detrimental to the health of the person. There is also substantial evidence that the degeneration of smell leads to dislike or disinterest in certain foods, many of which contain essential nutrients, leading to nutrient deficiencies. It has also been proposed that the elderly eat a smaller variety of foods. There is conflicting evidence making it difficult to form a conclusion on whether the elderly consume a smaller variety than young adults. Various methods were used to test olfactory perception, including odor and flavor tests. Data was also collected through surveys of food preferences and habits. 0

2 INTRODUCTION Aging is a natural process and many changes occur during this stage of life, including changes in the senses of taste and smell. Taste and smell usually work together to give a person the fullest sensations while eating. 1 However, when one or both of these senses are damaged, the eating eperience is transformed into a less enjoyable eperience. 1 This paper investigates and discusses how the changes in taste and smell affect a person s eating habits and nutritional status. In order to understand the impact that the loss of taste and/or smell has on an individual, it is first important to understand the normal functions of these senses. The sense of taste begins with the many taste buds on the human tongue. 1 These taste buds send nerve impulses to the brain that are interpreted as taste. 1 The sense of smell starts with olfactory cells in the nasal cavity. 1 These cells also cause nerve impulses that are interpreted by the brain as odors. 1 Through physiological evidence, scientists know that flavors result from both taste bud and olfactory receptor stimulation. 1 Without a sense of smell, it is much harder to detect taste. 1 Pinching the nose closed while eating can provide an appreciation of the difference that smell makes in the taste of food and stimulation of appetite. 2 The sense of smell is linked so closely with taste that with loss of smell comes loss or at least alteration of taste, though the opposite is not always true. 2 This paper will discuss the current research on the effects that the loss of taste and smell has on an aging adult, specifically pertaining to their eating habits and nutritional status. METHODS The articles that will be reviewed in the Results and Discussion sections of this paper were found through various database websites. First Pubmed was used to find five articles. The key words sensory loss and nutrition were searched and the articles were limited to those using human trials within the last 10 years. The articles were chosen because they were relevant and recent. Net, the key words were changed to taste and smell. With the same parameters, this resulted in three useful articles. Third, Web of Science was used with the key words of elderly nutrition and sensory loss. This search resulted in two useful articles, also chosen because of relevance. RESULTS To understand how loss of smell affects an individual, it is necessary to understand the normal process of losing the ability to smell. According to a study that measured the smell identification ability of people from ages 5-99, the ability to identify odors peaks between ages and slowly declines from there. 3-4 Usually, however, it is hardly noticeable until about age One difficulty in testing normal degeneration of smell is that there are numerous outside factors that can affect it. For eample, over 250 different medications alter the human s sense of smell. 2 It is also difficult to differentiate between sensory loss caused by normal aging and sensory loss caused by other means such as smoking, radiation therapy, or neurological conditions. 4 Regardless of cause, 50% of those between ages years have major olfactory impairment and more than 75% of those over 80 years of age have major olfactory impairment. 3 Similarly, at least 70% of the people over 80 years old have some reduction in their sense of 1

3 smell severe enough to adversely affect their nutritional status. 4 Sensory loss clearly affects a large portion of the elderly population increasing the importance of good nutritional status and healthy eating habits. 3-4 Aging is also associated with impaired ability to regulate food intake. 2 A major component of this inability to regulate food intake is the degeneration of taste and smell. 2 Another factor, related to the first, is the enhanced pleasure observed when eating with the senses of taste and smell as opposed to eating with one or neither. 2 An elderly person who is already eperiencing less frequent modes of gratification may allow this loss of pleasure in eating to adversely affect their body weight. 2 Studies suggest that the thresholds for salt recognition and detection increases with age, meaning that as a person gets older, it is harder to taste salt. 2 This may be true of other tastes, as well as salt. It is also interesting to note that this change in taste threshold is not due to a decreased number of taste buds, it is due to a loss of function of the taste buds. 2 It is also hypothesized that perhaps the taste bud turnover rate decreases with age which leads to a decreased ability to taste and potentially a jeopardized nutritional status. 2 According to research, women seem to retain their sense of smell better than men do. 5 However, there seems to be more research done on women than men, so this may not be conclusive. In one study that involved only women, elderly women had about 10% of the olfactory function, 50% of ability to taste sweetness, and 72% of the ability to taste salt as compared to young women when similarly tested. 5 This shows that even with a decreased sensitivity to taste, some flavors, such as salt, are still easier to taste than others, such as the flavors of sweet things. 5 Because such flavors are harder to taste, people say that the food tastes bland which often leads to unhealthy eating habits due to dislike of bland food. 5 The articles reviewed for this paper provided two potential nutritional concerns arising from a diet of seemingly bland food which is what an elderly person eating without the sense of smell would eperience. 6 The first outcome is decreased appetite and variety in the diet resulting in weight loss and other adverse effects. 6 This can be damaging to the health of the individual because even though early detection and treatment of anoreia may prevent weight loss, improve health outcomes, and reduce mortality, most providers only give nutritional intervention after weight loss has occurred. 7 If a provider can notice the lack of appetite or decreased consumption before weight loss occurs, the health of the individual could be improved early on, preventing detrimental outcomes. 7 More vigilant and prepared providers could improve the nutritional outcomes of many elderly adults struggling with this problem of weight loss. 7 The other outcome of a bland diet is increased consumption, not due to increased hunger, but because the elderly shift their focus to the nonolfactory components of food. 6 One article stated that the higher nutritional risk occurs when a person adds high salt and high sugar foods to their diet. 6 These foods provide ecess energy from fat instead of other, healthier sources, resulting in unnecessary weight gain. 6 However, a conflicting article stated the opposing opinion that the greater nutritional risk lies with the weight loss that follows loss of appetite due to sensory loss. 8 More research is necessary to conclude which outcome is more nutritionally dangerous. A study by Duffy eamined the nutritional habits of free-living, elderly women in relation to olfactory dysfunction. This study measured olfactory dysfunction and surveyed food behaviors and preferences to find any correlations. 6 Many women in this study increased food 2

4 intake to compensate for olfactory loss which resulted in a higher prevalence of obesity. 6 Women with lower odor perception scores also had lower scores on the food interest tests. 6 Not surprisingly higher food interest and involvement were associated with formal education and higher overall functioning. 6 This study also ehibited major nutritional concerns for those with olfactory dysfunction. The researchers found through statistical analysis that the women with lower odor perception scores also reported lower preferences in food groups that contained essential vitamins A and C. 6 Other foods that were reported hardly ever eaten included milk, fried foods, processed meats, organ meats, and alcoholic beverages. 6 Milk is the largest problem on this list because older women are already at risk for osteoporosis and decreasing calcium intake can put a woman at even higher risk. Lower flavor perception was also associated with less preference for whole grains. 6 Once again, this puts those with olfactory dysfunction at greater risk for other diseases due to the changes in their food preferences. It is hypothesized by some that the variety in diet decreases with age and sensory loss. 2, 9 However, some studies found that adults 61 years of age or older consumed a greater total food variety compared with adults 60 years or younger. 2 Despite their age, financially secure, freeliving individuals seem to consume as much variety and sometimes even more variety than their young adults. 9 However, other studies have reported the opposite, so it is hard to come to a firm conclusion. DISCUSSION As shown by the cited articles, the degeneration of smell and taste are cause for concern in the nutritional status of an elderly person. Smell declines faster and more severely than taste, but because it affects taste so directly, it is more concerning than the loss of taste. 10 The taste system declines at a slower rate and with less severity. 10 Taste also maintains a lower threshold than smell throughout the aging process. 10 The degeneration of these senses is linked to the nutritional status of elderly individuals. Multiple studies show that dysfunctional olfactory system relates to both undereating and overeating. 6 Both of these practices are damaging to the health on an individual, but this paper was unable to define which is more detrimental, due to conflicting evidence. 6-8 However, both unnecessary weight gain and weight loss are hazardous to the health of an aging person and should be avoided. 6 This paper also concludes that a variety of foods is needed in the diet to maintain a healthy lifestyle. 2, 9 Studies show that the elderly population does not necessarily eat a smaller variety of food than young adults, but sometimes loss of smell can affect the desire to eat certain food groups that can lead to a decreased variety and eventually nutrient deficiencies. 6 The people struggling to eat certain essential food groups should find foods that they can tolerate and eat these foods to avoid deficits of essential vitamins and minerals. 6 Clearly the loss of smell and taste are important factors in the nutritional status of the aging population. 6-8 Further research may provide more information on how to can prevent loss of taste and smell or how to combat the nutritional risks that accompany the degeneration of these senses. 3

5 REFERENCES 1. Hendry C, Farley A, McLafferty E. Anatomy and physiology of the senses. Nurs Stand. 2012;27(5): Hays NP, Roberts SB. The anoreia of aging in humans. Physiol Behav. 2006;88(3): Doty RL, Shaman P, Applebaum SL, Giberson R, Siksorski L, Rosenberg L. Smell identification ability: Changes with age. Science. 1984;226(4681): Lafreniere D, Mann N. Anosmia: Loss of smell in the elderly. Otolaryngol Clin North Am. 2009;42(1): Yen PK. Nutrition and sensory loss. Geriatr Nurs. 2004;25(2): Duffy VB, Backstrand JR, Ferris AM. Olfactory dysfunction and related nutritional risk in free-living, elderly women. J Am Diet Assoc. 1995;95; Wilson MM, Thomas DR, Rubenstein LZ, Chibnall JT, Anderson S, Bai A, Diebold MR, Morley JE. Appetite assessment: Simple appetite questionnaire predicts weight loss in community-dwelling adults and nursing home residents. Am J Clin Nutr. 2005;82(5): Donini LM, Savina C, Cannella C. Eating habits and appetite control in the elderly: The anoreia of aging. Int Psychogeriatr. 2003;15(1): Rolls BJ. Do chemosensory changes influence food intake in the elderly? Physiol Behav. 1999;66: Murphy C. The chemical senses and nutrition in older adults. J Nutr Elderly. 2008;27:

6 BE SURE TO SUBMIT THIS FORM WITH EVERY PAPER DRAFT SUBMITTED ON LEARNING SUITE Research Review Paper Submission Checklist Please use the following checklist to ensure that you addressed the items students commonly miss from the instructions sheet (put an in each bo to confirm that you met this requirement): Is your paper formatted correctly? (Single-spaced, left-justified with 0.5 to 1-inch margins, 12- point type in Times New Roman, and pages numbered and include line numbers) Is your research paper 3-pages in length? (ecluding the Author/Title page, Abstract, and References) Is your title less than 200 characters? Does your abstract contain these elements: topic and primary objective of the review, methods of data sourcing and etraction, and results/conclusions (with no references cited)? Is your abstract 250 words or less? Did you clearly state the purpose of your research review paper in the introduction? Did you choose primary research articles not review articles in your paper? Are 80% of your references from peer-reviewed journals? Are no more than 20% of your references from Internet sources? Are only credible Internet sources listed? Are references numbered sequentially upon first appearance in the tet? Are references typed as superscripts and placed after commas and periods but before colons and semicolons? Is the reference list formatted according to AMA style? 5