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In two groups of 15-year-olds--50 with a high and 50 with a low caries experience--recognition thresholds were determined for sweet, salty, sour, and bitter tastes and preferences for sweet taste, using a full-mouth technique. No statistically significant difference in thresholds could be found between the groups. No correlation between threshold values and preferences for sucrose could be established.
Taste threshold for phenylthiocarbamide (PTC) was measured in 393 offspring from the families of 85 monozygotic (MZ) twin pairs. PTC scores were bimodally distributed with modes at one and eight and the antimode at five. Because of the non-normality of the distribution, a jackknife procedure was used to obtain 95% confidence intervals for the estimates of genetic, maternal, and environmental parameters. Analyses which assumed no epistasis and which included additive genetic effects revealed that 37.9% of the observed variation in PTC threshold was due to additive genetic effects, 16.6% was due to dominance effects, 14.2% was due to maternal effects, 13.7% was due to a common sibship environment, and 17.6% was due to random environmental effects, yielding a broad sense heritability of 0.55 for the threshold ability to taste PTC. Analyses which did not include additive genetic effects revealed 26.6% of the observed variance was due to dominance effects, 23.6% to maternal effects, and 49.8% to environmental effects at the 0.67 confidence levels, but that environmental factors accounted for 72.4% and dominance effects for 23.6% of the observed variation at the 95% level.
The conditioned taste aversion (CTA) threshold for either citric acid (CA) or HCl solutions and the two-bottle taste preference (TBP) threshold were determined in rats that are familiarized to the odor of conditioning solutions or that are naive. The CTA method appeared to be more sensitive than the TBP test, particularly when rats were not familiarized to the odor of the conditioning solution. The CTA threshold for HCl-conditioned rats and familiarized to the odor of conditioning solution lies between 1.00 and 2.00 mmol; in unconditioned rats, it lies between 4.00 and 5.00 mmol. In CA-conditioned and odor-familiarized rats, the threshold lies between 0.09 and 0.20 mmol; in unconditioned rats, it lies between 7.00 and 10.00 mmol. In rats not familiarized to the odor of the conditioning solution, the threshold for HCl-conditioned rats lies between 0.90 and 1.00 mmol; in unconditioned rats, it lies between 2.00 and 3.00 mmol. In CA-conditioned rats, the CTA threshold lies between 0.03 and 0.05 mmol; in unconditioned rats, it lies between 4.00 and 7.00 mmol. The two-bottle test is less sensitive than the CTA method. The TBP threshold lies between HCl 4.00 and 5.00 mmol, and between CA 4.00 and 7.00 mmol. The odor of a solution may potentiate the ability of rats to detect the concentration of CA and HCl solutions.
Taste responses to fructose and tannic acid were compared between great apes using the 'two-bottle test' with tests of brief duration. The taste thresholds for fructose were [10-20] mM in Pongo pygmaeus, [40-50] mM in Pan troglodytes, and [70-80] mM in Gorilla gorilla. Inhibition thresholds for tannic acid were [2.9-3.5] mM in Pongo and [2.9-5.9] mM in Pan. Gorillas apparently significantly preferred tannins at low concentrations ([0.59-5.9] mM) but rejected concentrations above [8.8-14.7] mM. These results are discussed in relation to the effects of phylogenetic inertia and biological adaptation.
Taste threshold levels for the four basic taste modalities were determined in 30 male lung cancer subjects and 30 male control subjects who had no history of malignant disease. Lung cancer patients demonstrated significant alteration in taste recognition for sour but not for bitter, sweet, or salt. There were, however, quantitative differences between cancer patients and control subjects in recognition thresholds for the sweet taste modality. Some of the lung cancer subjects had demonstrated greater sensitivity to the taste of bitter than the control subjects and others were less sensitive. These alterations may account in part for the reduction of intake and for the aviodance of certain food items by lung cancer subjects. Dietary histories should be taken on all cancer patients in order to individualize dietary management, thereby improving the nutritional intake.
The aim of the present investigation was to study the relationship between taste acuity and dental caries. The material consisted of 26 15-year-olds. Twelve (7 girls and 5 boys) had a high prevalence of dental caries and 14 (6 girls and 8 boys) had a low prevalence. The average DFS in the two groups was 26.9 (range 19-39) ad 1.5 (range 0-4) respectively. Recognition thresholds were determined for sweet and, as a control, for salty, sour and bitter taste using a full-mouth technique. A modified method of limit was used. No significant difference in thresholds could be found between the different caries groups. Preferences for sweet taste were also determined in 14 of the subjects. They were asked to indicate the preferred solution of sucrose (.15, .30, .60 and 1.20M), presented randomly. The groups did not differ markedly in this test either. No correlation between threshold values and preferences for sucrose could be established.
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Twelve patients with untreated cancer of the esophagus and 14 control subjects matched for age, smoking, and alcohol consumption were tested for taste thresholds. Taste acuity for the four basic tastes was evaluated by three stimulus forced choice techniques (Henkin). There were no significant differences between the groups for detection and recognition thresholds for sour, salty, sweet, or bitter taste stimuli. Comparison of patients' detection and recognition thresholds with those of eight young healthy nonsmokers showed marked differences. Salivary urea nitrogen concentration was not different between patients and matched controls and did not correlate with bitter taste thresholds. Variable results have been reported for taste sensitivity in patients with malignant disease. In view of the results of this study and the many factors which influence taste acuity, it appears that a general statement regarding taste alterations in cancer patients cannot be made. Choice of appropriate control groups to correct for factors known to affect taste but not related to cancer per se is important for proper interpretation of taste testing results.
Circumstances in which serotonin (5-HT) and noradrenaline (NA) are altered, such as in anxiety or depression, are associated with taste disturbances, indicating the importance of these transmitters in the determination of taste thresholds in health and disease. In this study, we show for the first time that human taste thresholds are plastic and are lowered by modulation of systemic monoamines. Measurement of taste function in healthy humans before and after a 5-HT reuptake inhibitor, NA reuptake inhibitor, or placebo showed that enhancing 5-HT significantly reduced the sucrose taste threshold by 27% and the quinine taste threshold by 53%. In contrast, enhancing NA significantly reduced bitter taste threshold by 39% and sour threshold by 22%. In addition, the anxiety level was positively correlated with bitter and salt taste thresholds. We show that 5-HT and NA participate in setting taste thresholds, that human taste in normal healthy subjects is plastic, and that modulation of these neurotransmitters has distinct effects on different taste modalities. We present a model to explain these findings. In addition, we show that the general anxiety level is directly related to taste perception, suggesting that altered taste and appetite seen in affective disorders may reflect an actual change in the gustatory system.
A special "gustometer" has been built, which permits continuous measurement of the threshold of taste sensations. Taste sensations show strong adaptation even at the threshold level. The adaptation was much the same for the four primary tastes, but there were large individual differences. Of theoretical interest is the finding that adaptation to a taste can occur even with subliminal stimuli.
Copper effects on human health represent a relevant issue in modern nutrition. One of the difficulties in assessing the early, acute effects of copper ingested via drinking water is that the taste of copper may influence the response and the capacity to taste copper in different waters is unknown. The purpose of the study was to determine the taste threshold of copper in different types of water, using soluble and insoluble salts (copper sulfate and copper chloride). Copper-containing solutions (range 1.0-8.0 mg/l Cu) were prepared in tap water, distilled deionized water and uncarbonated mineral water. Sixty-one healthy volunteers (17-50 years of age), with no previous training for sensory evaluation, participated in the study. A modified triangle test was used to define the taste threshold value. The threshold was defined as the lowest copper concentration detected by 50% of the subjects assessed. To evaluate the olfactory input in the threshold value obtained, 15 of 61 subjects underwent a second set of triangle tests with the nose open and clamped, using distilled water with copper sulfate at a concentration corresponding to the individual's threshold. The taste threshold in tap water was 2.6 mg/l Cu for both copper sulfate and copper chloride. The corresponding values for distilled deionized water were 2.4 and 2.5 mg/l Cu for copper sulfate and copper chloride, respectively. In uncarbonated mineral water the threshold values were slightly higher, 3.5 and 3.8 mg/l Cu for copper sulfate and for copper chloride, respectively, which are significantly higher than those observed in tap and distilled waters (P < 0.01, Kruskal-Wallis test). The taste threshold did not change significantly when the nose was clamped. In conclusion, the median values for copper taste threshold were low, ranging between 2.4 and 3.8 mg/l Cu, depending on the type of water.
Taste threshold detection and recognition were determined on 46 dyspeptic patients and on 42 blind controls. Among the dyspeptic patients 60% suffered from different taste disorders. Among the blind controls the frequency of taste disorder was 41%. Among the dyspeptic patients heterogeusia and dysgeusia dominated, threefold compared to the control blind persons. A mild hypergeusia appeared among the patients in 21%, among the blind in 8%. There was an enhanced hypergeusia in the group of blind persons (16%), but this was found in the group of dyspeptic patients in only 4%. It is suggested that the hypergeusia may also be a compensatory function, a consequence of the loss of seeing. There was an inverse ratio between the taste acuity and taste preference. The taste threshold to the preferred taste in both groups was higher, therefore more food was needed to stimulate the taste nerves.
Taste threshold for the four basic tastes were determined to assess taste impairments in 11 children with acute leukemia undergoing marrow transplantation and in 20 normal children. Thresholds were measured on admission, 2 days, and 45 days after transplant using the Up-Down Staircase method. No significant difference was noted between patients at admission and the control group for sweet, bitter, or salt. There was a significant difference between patients and controls for the sour threshold (p = 0.006). Patient threshold values on day 2 and day 45 (posttransplant were compared with admission values. No significant differences were seen, except for the salt threshold which was increased at day 2 posttransplant when compared with the admission values. We conclude that only minor changes in taste thresholds were demonstrated in this study. These changes probably do not account for abnormal food tastes reported by patients.
Taste thresholds for phenylthiourea were measured for 244 Ashkenazic Jews. The frequency of nontasters was 27.86 percent. In the sample, 102 individuals were of pure Polish ancestry, and the frequency of nontasters among these was significantly different from the frequencies of nontasters among Europeans and Mongoloids.
The role of salt in the genesis of hypertension has been well documented. Earlier studies have demonstrated higher salt taste threshold among hypertensives compared to normotensives. The aim of this study is to compare the salt taste thresholds of normotensive relatives of hypertensive patients with those of normotensives without family history of hypertension. Twenty-one hypertensives, 52 first degree relatives of these hypertensives and 99 normotensives without family history of hypertension were studied. They were made to taste different concentrations of solution from distilled water to 280 mmol of saline. The results showed that hypertensives had higher salt taste thresholds--detection (p < 0.0001), recognition (p < 0.0001) and maximum tolerable threshold (p < 0.05)--compared with normotensive relatives. The normotensive relatives of hypertensive patients in turn had higher salt taste thresholds--detection (p < 0.01), recognition (p < 0.0001) and maximum tolerable threshold (p < 0.001)--compared with normotensive controls; they also had significantly higher mean arterial pressure (p < 0.001). Health education with intervention directed at the hypertensives and their first degree normotensive relatives to willfully modify their desire and appetite for salt is of paramount importance.
Taste thresholds and consumption responses to above-threshold concentrations of fructose solutions were determined in eight callitrichid primate species using the "two-bottle preference test". Although taste thresholds are relatively similar across species, above-threshold responses may differ considerably between marmosets and tamarins. As fructose concentration increases, the rate of consumption increases less for most marmoset species (Cebuella and Callithrix spp.) than for Goeldi's monkey (Callimico) and tamarins (Saguinus and Leontopithecus spp.). It is proposed that distinct shapes of the curves illustrating these responses characterize species in terms of global taste system adaptations to different diets.
How accurately can the electrically evoked taste threshold be determined? Why have standards of normal values not yet been generally accepted? In order to answer these questions, 80 normal subjects were examined by means of the method of adjustment. The results showed a greater variability of threshold values and side differences than found by other authors. In explanation, it is suggested that the method of adjustment minimizes the biasing effect of the examiner, which normally leads to an underestimation of the threshold variability as well as of the side differences. The method of adjustment is therefore suitable for certain experimental purposes. For clinical use, a simple procedure like Krarups should be preferred. Due to its limited validity, however, only side differences of 100% or more should be considered pathological. A log-scale with rather large units (25% increment steps) is recommended.
The main purpose of this study was to determine the relationship between the number of circumvallate papillae and the bitter taste threshold with age. The study group consisted of 10 women (age range, 60-80) and 14 men (age range, 60-85) and the control group of 15 young women (age range, 18-25) and 15 young men (age range, 17-20); the total number of subjects was 54. The number of circumvallate papillae was counted by direct observation with the naked eye; bitter taste thresholds were evaluated by the three drop forced-choice method with an ascending series, using quinine sulfate dehydrate as the bitter agent. We observed that while the number of circumvallate papillae did not increase with age, the bitter taste threshold changed significantly with age.