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PubMedDate not supplied

Taste and smell losses in normal aging and disease.

OBJECTIVE: To review the scientific literature on the alterations in the senses of taste and smell in the elderly, including causes, diagnosis, prognosis, and treatment. DATA SOURCES: Original reports and reviews obtained through MEDLINE searches from 1966 through June 1997 using the MeSH headings of "taste," "taste buds," "taste disorders," "taste thresholds," "smell," "odors," "aged," and "aging." Articles frequently cited in reference lists were also included. STUDY SELECTION: All articles were reviewed, tabulated, and summarized. DATA EXTRACTION: Criteria for extraction included data quality and validity, statistical treatment of the data, venue of publication, and relevance to clinical care. CONCLUSION: Losses of taste and smell are common in the elderly and result from normal aging, certain disease states (especially Alzheimer disease), medications, surgical interventions, and environmental exposure. Deficits in these chemical senses cannot only reduce the pleasure and comfort from food, but represent risk factors for nutritional and immune deficiencies as well as adherence to specific dietary regimens. Chemosensory decrements can lead to food poisoning or overexposure to environmentally hazardous chemicals that are otherwise detectable by taste and smell. Use of flavor-enhanced food can increase enjoyment of food and have a positive effect on food intake and immune status.

Aged↗
PubMed1989

Phenylthiocarbamide taste sensitivity revisited: complete sorting test supports residual family resemblance.

Phenylthiocarbamide (PTC) taste thresholds were determined in 100 nuclear families using the complete sorting test. Segregation analysis using the mixed model suggested that the variability in PTC thresholds is controlled by a major locus with incomplete dominance as well as by a multifactorial component with significant residual heritability. Such a model explained nearly 96% of the variance, leaving only 4% of the variance in thresholds arising from measurement error and other environmental factors.

Adolescent↗
PubMed1996

Altered taste sensation in newly-diagnosed NIDDM.

OBJECTIVE: To assess gustatory appreciation in newly diagnosed NIDDM patients and to determine whether it altered with the improvement of glycemic control after treatment with diet and oral hypoglycemic drugs. RESEARCH DESIGN AND METHODS: Assessments of taste, peripheral and autonomic neural function, diet, and oral microbiological flora were performed in 20 patients before and after treatment of hyperglycemia, 20 matched nondiabetic control subjects, and 11 patients with long duration of diabetes and advanced peripheral neuropathy. RESULTS: Median total HbA1 fell from 12.6 to 8.8% in new diabetic patients after 3-5 months of treatment. Electrical taste thresholds, detection threshold for glucose, and recognition threshold for glucose and salt were increased in newly-diagnosed NIDDM patients compared with the control subjects. The dose-response curve to glucose (using a visual analogue scale [VAS]) of newly-diagnosed NIDDM patients was significantly impaired and improved after treatment. By contrast, newly-diagnosed NIDDM patients had normal VAS taste responses to fructose, salt, and urea. Measurements of somatic and autonomic nerve function did not correlate with electrical or chemical taste function. CONCLUSIONS: Newly-diagnosed NIDDM patients have a blunted taste response, which displays a degree of specificity to glucose, is partially reversed after correction of hyperglycemia, and is independent of somatic or autonomic nerve function. This taste abnormality may influence the premorbid choice of nutrients, with a preference for sweet-tasting foods, thereby exacerbating hyperglycemia.

Autonomic Nervous System Diseases↗
PubMed1978

Salt taste and disease.

Sodium appetite reflects the importance of sodium homeostasis and the relative scarcity of sodium for many terrestrial animals. Man, for various reasons, also seems to have a specific preference for salt which he consumes in excess of need, and this has been characterized as an important contributor to hypertension. Gustatory sensibility is necessary for the development of sodium appetite. Thus, research on the possible role salt taste sensitivity plays in controlling NaCl consumption in the sodium deficient rat was reviewed as a potential model for the study of salt taste and hypertension in man. Taste acuity experiments began first by examining salt taste thresholds. These studies found that thresholds were not altered by sodium deficiency in rat and the results in hypertensive humans were inconclusive. Threshold determinations may not reveal true sensitivity differences because they varied significantly across experiments and because they are restricted to a small portion of the intensity domain. When research was directed to suprathreshold stimuli, concentrations a rat or man might normally experience, the evidence suggested that hypertensive humans, like sodium-deficient rats, were less sensitive to the taste of salt. This reduced sensitivity may account, in part, for the fact that these two groups consume more salt.

Adrenal Glands↗
PubMed2001

Characterization of an intense bitter-tasting 1H,4H-quinolizinium-7-olate by application of the taste dilution analysis, a novel bioassay for the screening and identification of taste-active compounds in foods.

Thermal treatment of aqueous solutions of xylose and primary amino acids led to rapid development of a bitter taste of the reaction mixture. To characterize the key compound causing this bitter taste, a novel bioassay, which is based on the determination of the taste threshold of reaction products in serial dilutions of HPLC fractions, was developed to select the most intense taste compounds in the complex mixture of Maillard reaction products. By application of this so-called taste dilution analysis (TDA) 21 fractions were obtained, among which 1 fraction was evaluated with by far the highest taste impact. Carefully planned LC-MS as well as 1D and 2D NMR experiments were, therefore, focused on the compound contributing the most to the intense bitter taste of the Maillard mixture and led to its unequivocal identification as the previously unknown 3-(2-furyl)-8-[(2-furyl)methyl]-4-hydroxymethyl-1-oxo-1H,4H-quinolizinium-7-olate. This novel compound, which we name quinizolate, exhibited an intense bitter taste at an extraordinarily low detection threshold of 0.00025 mmol/kg of water. As this novel taste compound was found to have 2000- and 28-fold lower threshold concentrations than the standard bitter compounds caffeine and quinine hydrochloride, respectively, quinizolate might be one of the most intense bitter compounds reported so far.

Caffeine↗
PubMed1989

Quality-specific effects of aging on the human taste system.

Elderly persons are known to have elevated taste thresholds, with those for bitter more affected by age, for example, than those for sweet. Do analogous quality-specific effects occur at suprathreshold levels? Young (mean age = 20.3 years, SD = 2.99) and elderly (mean age = 72.5 years, SD = 4.58) subjects made magnitude estimates of sweetness, bitterness, sourness, and saltiness for the unmixed components sucrose, caffeine, citric acid, and NaCl at three concentration levels for each. They also made magnitude estimates of the separate taste qualities in two-component mixtures of sucrose with each of the other three qualities, at various levels of the two components in each mixture. Magnitude estimates of taste intensity were interweaved with magnitude estimates of the heaviness of six weights, which subjects were to judge on the same subjective intensity scale: This is the calibration feature of the method of magnitude matching, and permits the comparison of elderly and young subjects on the absolute intensity of tastes. When unmixed components were judged, elderly subjects found the characteristic tastes of caffeine and citric acid less intense than, but those of sucrose and NaCl as intense as, younger subjects did. In judging mixtures, the elderly found bitterness, but not the other three qualities, less intense than did the young subjects.

Adult↗
PubMed1992

Phenylthiocarbamide (PTC) tasting in paranoid and nonparanoid schizophrenic patients.

The present study reports on the association between Phenylthiocarbamide tasting for paranoid and nonparanoid schizophrenic patients. The incidence of PTC tasting is highly variable, and tasters and nontasters are frequently associated with some pathological states. 25 paranoid and 25 nonparanoid schizophrenic patients were examined for their PTC taste sensitivity. Frequency of paranoid tasters resembles the distribution of the normal population, whereas the nonparanoid patients are significantly different in their taste thresholds, with a higher incidence of nontasters. The members of this latter group have twice the incidence of psychiatric illness in their family histories as those of the former group. The significance of these findings is discussed as related to vulnerability for schizophrenia.

Arousal↗
PubMed1989

[Factors of quantitative variation in taste sensitivity].

Under well controlled experimental conditions, it is possible to accurately and reproducibly measure taste thresholds as well as supraliminal intensity matches in individual subjects. It is therefore possible to evaluate interindividual differences. Some factors influencing sweetening potencies remain obscure unless individual data are processed. Sweetening potency depends on the taster, the stimulus concentration, pH and temperature, but also on all the components of the mixture into which the sweetener is incorporated.

Humans↗
PubMed1982

Serum zinc and taste acuity in Tel-Aviv patients with inflammatory bowel disease.

Serum zinc levels and taste acuity were determined in patients with Crohn's disease, those with ulcerative colitis, and normal controls. All serum zinc values were within the normal range but significantly lower in the Crohn's disease patients as compared with controls. The taste threshold for salt was significantly impaired in patients with inflammatory bowel disease. These findings were less than expected and may be explained by the relatively high zinc intake normal for the Tel-Aviv population and relate indirectly to the high intake of refined carbohydrate that occurs in Crohn's disease patients.

Adolescent↗
PubMed1990

Circadian rhythm in recognition threshold of salt taste in healthy subjects.

The circadian rhythm in recognition threshold of salt taste was examined in six healthy young subjects. Plasma aldosterone (PA) and cortisol concentrations, plasma renin activity (PRA), salivary sodium concentration, and salt recognition thresholds were measured every 3 h for a 24-h period. The salt recognition threshold and salivary sodium concentration exhibited similar circadian rhythms, with the lowest values recorded in the afternoon. Positive correlations were observed between the recognition threshold and salivary sodium (P less than 0.001) and between cortisol and PA (P less than 0.001). There was no correlation between PRA and PA. A negative correlation was observed between PA and salivary sodium concentration (P less than 0.01). These data indicate that the recognition threshold for salt taste has a circadian rhythm in young healthy subjects. This rhythm appears to be related to daily variations in the plasma aldosterone concentration and its subsequent effects on salivary sodium concentration.

Adult↗
PubMed1992

Changes in gastrointestinal function attributed to aging.

There are numerous reports in the literature of impaired gastrointestinal function with aging. However, most gastrointestinal functions remain relatively intact because of the large reserve capacity of the intestine, pancreas, and liver. Clinically important changes in gastrointestinal function with aging in human include decreased taste thresholds, hypochlorhydria due to atrophic gastritis, and decreased liver blood flow and size. Increased absorbability of lipids and large size molecules has been demonstrated in aging animals, but this has not been studied in humans. Nutrients with impaired gastrointestinal bioavailability in aging include dietary B-12, calcium carbonate, and ferric iron in atrophic gastritis; calcium, zinc, and possibly carbohydrate in a mixed meal. The implications of these changes for health maintenance and chronic disease in elderly people are in need of study.

Aging↗
PubMed1980

Taste hedonics and thresholds in obesity.

Previous investigations of the relation of taste to obesity have focused on sweet taste, with inconclusive results. This study compared adult-onset obese, juvenile-onset obese, and never-obese females on sensitivity and hedonic (preference) responses to sweet, salty, sour, and bitter solutions. On no taste did the groups differ on detection or recognition thresholds or on hedonic ratings of supra-threshold concentrations. Two patterns of individual hedonic responses to increasing concentrations were identified with supra-threshold sucrose solutions, as in previous work, but not with the other solutions. There were no reliable relations across tastes on detection or recognition thresholds or supra-threshold hedonic ratings. Hedonic ratings of the lowest (below detection threshold) concentrations of each taste solution were examined as indices of cognitive and affective responses to the expected properties of the taste. Adult-onset obese subjects assigned higher expectancy hedonic ratings for sour and sweet than did juvenile-onset obese or never-obese subjects. The same trend held, nonsignificantly, for salty. Discussion focuses on the nature of expectancy ratings and implications of findings for future investigations of the role of taste in obesity within different obese populations.

Adolescent↗
PubMed1990

Interaction of saliva and taste.

In spite of the coexistence of saliva and taste in the oral cavity, an understanding of their interactions is still incomplete. Saliva has modulating effects on sour, salt, and the monosodium-glutamate-induced savory or umami taste. It has a diminishing effect on sour taste as a result of the buffering by salivary bicarbonate. It probably also contributes to the umami taste with endogenous salivary glutamate levels. Salt taste is detected only when above salivary sodium-chloride concentrations; thus saliva influences salt taste threshold levels. It also provides the ionic environment for taste cells, probably critical in signal transduction. Salivary flow rate and composition are influenced by the type of taste stimuli. In general, sour taste, elicited by citric acid or sour food, induces the highest flow rate and Na+ concentrations, while salt gives rise to high protein and Ca2+ concentrations. Stimulation with the four basic taste modalities (sour, sweet, salty, and bitter), however, does not increase the relative proportion of any of the salivary proteins. This review examines the literature on the interactions of saliva with taste, and the effect of taste on salivary composition. The possible role of the von Ebner's salivary glands and the role of saliva as a chemical cue are also discussed.

Humans↗
PubMed1993

Nutrition and chemosensory perception in the elderly.

The elderly person's perception of foods and food flavor is affected by age-associated changes in the chemical senses (taste, smell, and trigeminal sensation). Both classic and modern psychophysical techniques have been applied to achieve some understanding of these changes. Taste threshold sensitivity declines with age; however, the magnitude of the decline and the degree to which taste qualities are differentially affected remains to be understood. Suprathreshold taste intensity perception is affected by age, but there is a differential effect of taste quality. Experiments with blended foods have indicated that both olfactory and taste deficits contribute to older people's difficulty with food identification. Experiments assessing threshold sensitivity, suprathreshold intensity, and suprathreshold identification have all demonstrated significant impairment in olfaction in old age. In fact, these effects are far greater than in the taste system. Patients with Alzheimer's disease show even greater olfactory deficits than normal elderly and the effect is related to the degree of dementia. We have ruled out nasal disease in these patients as the primary causes of olfactory insensitivity, because significant impairment remains when the influence of nasal airflow and nasal cytology has been removed statistically. Both normal elderly and patients with Alzheimer's disease show impairment in odor memory. Sensitivity to, familiarity with, and identifiability of the odors all play a role in odor memory performance. Flavor preference also changes over the lifespan. Older subjects, for instance, rate high concentration of sugar and salt as pleasanter than young subjects do. Multiple influences contribute to this phenomenon. Elderly persons and those of lower nutritional status have shown preferences for higher concentrations of casein hydrolysate than young persons and those of higher nutritional status, suggesting that dietary preference can be related to chemosensory cues. There are significant age-associated changes in chemosensory perception that have the potential to interact with dietary selection and nutrition in the elderly. A better understanding of these phenomena may promote health and well-being in the elderly.

Aged↗
PubMedDate not supplied

Olfactory dysfunction in Down's Syndrome.

Down's Syndrome subjects over 40 years old show neuropathology similar to that of Alzheimer's disease. The olfactory system is particularly vulnerable in Alzheimer's disease, both anatomically and functionally. Several measures of sensory and cognitive functioning were studied in the older Down's Syndrome patient, with the hypothesis of significant olfactory dysfunction. Participants were 23 Down's subjects, and 23 controls. The Dementia Rating Scale showed mean scores of 103 for Down's subjects and 141 for controls. Down's subjects showed significant deficits in odor detection threshold, odor identification, and odor recognition memory. Normal performance in a taste threshold task, similar to the olfactory threshold task in subject demands, suggested that the Down's syndrome subjects' poor performance was not due to task demands. Deficits in olfaction may provide a sensitive and early indicator of the deterioration and progression of the brain in older subjects with Down's Syndrome.

Adult↗
PubMed1989

ACE inhibitors in hypertension: assessment of taste and smell function in clinical trials.

Taste and smell disturbances are infrequently reported adverse effects of treatment with captopril and are even less frequently reported with other ACE inhibitors. These adverse effects have been attributed to the chemical structure of the drugs used, although this relationship is the matter of some debate. A link between the taste disturbance associated with ACE inhibitors and changes in plasma zinc concentration has also been suggested, but again the evidence for this relationship is equivocal. One problem facing research in this area has been the lack of reliable assessment techniques for the quantitative evaluation of smell and taste function. Three quantitative methods for evaluating taste and smell function are described, together with the results of a pilot study aimed at evaluating the potential ease of application of these techniques in a larger group of patients. In this double-blind, crossover pilot study, 8-week treatment with lisinopril (20-40 mg once daily) was compared with captopril (25-50 mg twice daily) in 12 hypertensive patients. The two drugs produced similar falls in lying and standing blood pressure and neither drug produced a significant alteration in smell recognition, or olfactory or taste threshold. None of the minor changes observed appeared to correlate with either plasma zinc concentrations or intra-erythrocyte zinc levels. This study provides important observations on the use of these new techniques. Based on the wide variability of results obtained, the design of further clinical studies must address and overcome the many factors (age, sex, smoking, etc.) which may confound the study of drug effects on taste and smell.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Structural and sensory characterization of compounds contributing to the bitter off-taste of carrots (Daucus carota L.) and carrot puree.

Sequential application of solvent extraction, gel permeation chromatography, and HPLC in combination with taste dilution analyses revealed that not a sole compound but a multiplicity of bitter tastants contribute to the bitter off-taste of cold-stored carrots and commercial carrot puree, respectively. Among these bitter compounds, 3-methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin (6-methoxymellein), 5-hydroxy-7-methoxy-2-methylchromone (eugenin), 2,4,5-trimethoxybenzaldehyde (gazarin), (Z)-heptadeca-1,9-diene-4,6-diin-3,8-diol (falcarindiol), (Z)-heptadeca-1,9-diene-4,6-diin-3-ol (falcarinol), and (Z)-3-acetoxy-heptadeca-1,9-diene-4,6-diin-8-ol (falcarindiol 3-acetate) could be identified on the basis of MS as well as 1D- and 2D-NMR experiments. Due to the low concentrations of <0.1 mg/kg and the high taste thresholds found for eugenin and gazarin, these compounds could be unequivocally excluded as important contributors to the bitter taste of carrots. Calculation of bitter activity values as the ratio of their concentration to their bitter detection threshold clearly demonstrated that neither in fresh and stored carrots nor in commercial carrot puree did 6-methoxymellein contribute to the bitter off-taste. In contrast, the concentrations of falcarindiol in stored carrots and, even more pronounced, in carrot puree were found to be 9- and 13-fold above its low bitter detection concentration of 0.04 mmol/kg, thus demonstrating that this acetylenic diol significantly contributes to the bitter taste of the carrot products investigated.

Alkynes↗
PubMed1990

Phenylthiocarbamide taste sensitivity in chronic peptic ulcer.

Ability to taste phenylthiocarbamide is genetically determined and has been investigated as a possible genetic marker for disease. This study examined phenylthiocarbamide taste sensitivity in gastric and duodenal ulcer disease. The study sample included 164 patients with gastric ulcer, 134 with duodenal ulcer, and 299 community controls. Eight concentrations of phenylthiocarbamide in distilled water were obtained by binary serial dilution. The lowest concentration distinguished by taste from distilled water defined taste threshold. Bimodality of threshold distributions distinguished nontasters from tasters. Comparisons of patients with controls gave odds ratios of nontaste in gastric ulcer and duodenal ulcer of, respectively, 0.7 (P greater than 0.1) and 1.3 (P greater than 0.03). The power of detecting at least a twofold difference between patients and controls in the odds of nontaste was 80%. Nontaste was more common in duodenal than in gastric ulcer patients (odds ratio = 2.0, P = 0.02). Taste sensitivity was unassociated with other genetic factors related to ulcer--ABO blood group, secretor status, and serum pepsinogen 1 level. The difference between gastric and duodenal ulcer patients in the ability to taste phenylthiocarbamide may be genetic; however, this study's inability, despite substantial power, to detect at least a twofold difference between patients and controls suggests that if phenylthiocarbamide taste sensitivity is a genetic factor in peptic ulcer, the relationship is weak.

Adult↗