Bitter taste markers explain variability in vegetable sweetness, bitterness, and intake

Food bioactive peptides: functionality beyond bitterness

Bitter taste is an aversive taste because it is unconsciously associated with toxic compounds. However, a considerable variability in bitter sensitivity exists in those who have the genetic polymorphism for bitter taste receptors (TAS2Rs). Besides the oral cavity, TAS2Rs are present in many body tissues, including the gastrointestinal tract; therefore, they are crucial players both in the gustatory/hedonic system and in the homeostatic system, triggering numerous biological responses, including adipogenesis, carcinogenesis, or immunity. Bitter-tasting compounds are widely distributed in plant and animal foods and belong to many chemical classes. In this study, the evidence was reviewed on bitter peptides, considering the food sources, their formation in food under different processing and storage conditions and in the gastrointestinal tract during digestion, as well as their biological activities. Bitterness associated with peptides is due to the presence of hydrophobic amino acids in the C-terminus. The current literature mainly explores the enzymes and hydrolysis conditions, with the aim of reducing the formation of bitter peptides in hydrolysate preparation or food. Few studies highlight the bioactivity (namely, antihypertensive, antidiabetic, antioxidant, or immunity boosting), besides the bitterness. However, encapsulation of bitter peptides has been tentatively used to develop antihypertensive and antidiabetic supplements. In the era of personalized nutrition and precision medicine, the evidence available suggests the opportunity to use bitter bioactive peptides as functional ingredients in food. Such types of food may modulate a plethora of physiological mechanisms by targeting TAS2Rs in the gastrointestinal tract, thus modulating appetite sensations or gastrointestinal motility and discomfort according to individual nutritional needs and goals. More studies are needed to optimize the technological strategies to target TAS2Rs by bitter bioactive peptides, improve their stability in food, and validate the biological efficacy through well-designed in vivo studies.

Taste and oral somatosensation: Role of PTC bitter sensitivity, gender, and age

Sensitivity to the bitterness of phenylthiocarbamide (PTC) is considered to be linked to general taste perception, which is higher in women, and exhibits a slight decrease with age. Additionally, PTC sensitivity may contribute to somatosensory perception of spiciness and astringency. However, controversial data have been reported. This study investigates the relation between PTC perception, age, and gender on taste and somatosensory sensitivity using the Seven-iTT. A total of 200 healthy participants were classified based on their PTC perception, and subjects underwent an extended version of Seven-iTT to identify and rate the intensity of twelve stimuli. Results indicated that individuals classified as Tasters (T) exhibited higher taste scores compared to Non-Tasters (NT) for PTC, with age serving as a significant factor (p ≤ 0.009). Women outperformed men only among NT (p = 0.019). Older T demonstrated higher taste sensitivity than NT, suggesting that PTC status might act as a protective factor of gustatory function in aging. While PTC taster status significantly affected the intensity of sweet, salty, and bitter sensations (p ≤ 0.032), it had minimal impact on the intensity of somatosensory sensations (capsaicin and tannins). The combined use of Seven-iTT and the investigation of PTC status show promise for applications in research and clinical practice, offering a comprehensive approach to understanding taste perception and its implications for diet, nutrition, and aging.

Exploring consumer acceptability of leafy greens in earth and space immersive environments using biometrics

Novel research on food perception is required for long-term space exploration. There is limited research on food/beverage sensory analysis in space and space-simulated conditions, with many studies presenting biases in sensory and statistical methods. This study used univariate and multivariate analysis on data from pick-and-eat leafy greens to assess self-reported and biometric consumer sensory analysis in simulated microgravity using reclining chairs and space-immersive environments. According to ANOVA (p < 0.05), there were significant differences between interaction room × position for head movements; besides, there were non-significant differences in the interaction samples × environment. On the other hand, there were significant differences in the sample×position interaction for all liking attributes. Results from multivariate analysis showed effects on self-reported, physiological, and emotional responses of samples in space-related positions and environments related to sensory perception changes. Non-invasive biometrics could offer a powerful tool for developing digital twins to assess genetically modified plants and plant-based food/beverages for long-term space exploration.

A method to "gamify" exposure to vegetable flavor and its potential influence on liking

Unpleasant flavor is a commonly stated reason for avoiding vegetables. However, repeated exposure to flavors, even unpleasant vegetable flavors, improves acceptability. Yet, increasing exposure to vegetables is difficult, as vegetables can be less convenient, available, and affordable than other foods. This study describes a method to circumvent these barriers to repeated flavor exposure. We designed a game with vegetable- or control-flavored gummies, where players (N = 34) were challenged to identify the flavors over 2 weeks. One round was played per day, and the questions and gummies were designed to make it harder to identify the flavors as the game progressed. At screening, qualified subjects needed to consume <2.5 servings of nonstarchy vegetables per day as well as dislike at least one "target" and one "non-target" vegetable. The "target" vegetables (kale and broccoli) were included in the game and the "non-target" vegetables (asparagus and spinach) were included in sensory tests but not the game. Vegetable liking ratings were measured at baseline (before gameplay), after 1 week of gameplay, and after 2 weeks of gameplay. Pilot data indicate one target vegetable (kale) increased in liking after 1 and 2 weeks of gameplay among the vegetable group, but not the control group. Liking for broccoli (other target vegetable), as well as asparagus and spinach (nontarget vegetables), did not significantly change for either group. Thus, our "gamified" approach to vegetable flavor exposure may be useful in increasing acceptance of some vegetables, but additional work to identify why the game improved liking for kale but not broccoli is needed.

Distinct Sensory Hedonic Functions for Sourness in Adults

Over the last half-century, variable responses to sweetness have repeatedly been shown to fall into a small number of hedonic responses, implying that looking only at group means may can obfuscate meaningfully different response patterns. Comparative data for sourness is quite sparse, especially in adults. While increased liking with higher acid concentration has been reported for some children, in adults, sourness is classically assumed to be aversive, with a monotonic drop in liking with increasing sourness. Here, we test this assumption using a simple model system or experimental beverage in convenience samples of adults from the United States (increasing citric acid in water) and Italy (increasing citric acid in pear juice). Participants rated intensity and liking of sampled stimuli. For both cohorts, we find clear evidence of three distinct patterns of responses: a strong negative group where liking dropped with increased sourness, an intermediate group who showed a more muted drop in liking with more sourness, and a strong positive group where liking increased with more sourness. Strikingly, both cohorts showed similar proportions of response patterns, with ~63-70% in the strong negative group, and 11-12% in the strong positive group, suggesting these proportions may be stable across cultures. Notably, the three groups did not differ by age or gender. These data support the existence of different hedonic response profiles to sour stimuli in adults, once again highlighting the importance of looking at individual differences and potential consumer segments, rather than merely averaging hedonic responses across all individuals within a group.

Temporal patterns in taste sensitivity

Individuals vary in their ability to taste, and some individuals are more sensitive to certain tastes than others. Taste sensitivity is a predictor of various factors, such as diet, eating behavior, appetite regulation, and overall health. Furthermore, taste sensitivity can fluctuate within an individual over short to long periods of time: for example, in daily (diurnal) cycles, monthly (menstrual) cycles (in females), and yearly (seasonal) cycles. Understanding these temporal patterns is important for understanding individual eating habits and food preferences, particularly in the context of personalized and precision nutrition. This review provides a summary of the literature on taste sensitivity patterns across 3 temporal dimensions: daily, monthly, and yearly. Good evidence for diurnal patterns has been observed for sweet taste and fat taste, although the evidence is limited to rodent studies for the latter. Obese populations showed limited variation to sweet and fat taste sensitivities over a day, with limited variation in sweet taste sensitivity being linked to insulin resistance. There were mixed observations of temporal variation in sensitivity to sour and umami tastes, and there were no patterns in sensitivity to bitter taste. Menstrual patterns in sweet taste sensitivity were consistent with patterns in food intake. Other taste modality investigations had mixed findings that had little agreement across studies. Hormonal changes in females influence taste sensitivity to some degree, although the overall patterns are unclear. Seasonal patterns have been less well studied, but there is weak evidence that sweet, salty, and bitter taste sensitivities change across seasons. Differences in seasonal taste patterns have been observed in subgroups susceptible to mental health disorders, requiring further investigation. Patterns of taste sensitivity are evident across multiple temporal dimensions, and more research is needed to determine the influence of these patterns on food intake. Dysregulation of these patterns may also be a marker of certain diseases or health conditions, warranting further investigation. Notably, the alimentary tastes (umami, fat, and carbohydrate) are underrepresented in this research area and require additional investigation.

Interventions based on sensory-hedonic strategies and on nudging to facilitate vegetable and pulses consumption in the school environment

Childhood and adolescence shape lifelong taste preferences and dietary habits, making them crucial periods for promoting healthy and sustainable eating. As students consume up to half of their daily energy intake at school, school interventions can have a significant impact on promoting plant-based diets. Although the benefits of promoting plant-based diets on children's and adolescents' health and environmental sustainability are well established and various studies report promising effects of interventions based on sensory-hedonic strategies and on nudging in promoting vegetables and pulses in schools, a comprehensive collection of those reports is lacking. Therefore, this systematic review aims to collect published literature on the above interventions in schools that focus on promoting the consumption of vegetables and pulses to children and adolescents. Three databases-PubMed, Scopus, and Web of Science-were searched over all years until March 2022 using pre-specified terms. From the 10.488 studies identified, a total of 57 studies reporting sensory-hedonic (e.g., manipulating food sensory properties or their hedonic value) or nudging (e.g., changing the presentation) interventions targeting children and/or adolescents in schools and aiming at promoting vegetables and/or pulses were included. Overall, interventions based on sensory-hedonic strategies (either enhancing the perception of well-accepted flavor and texture or manipulating their hedonic value) and on nudging (through incentives and prompts) are effective in promoting vegetables and pulses. A gap in the literature was identified for interventions targeting adolescents and promoting pulses. Finally, multicomponent interventions, rather than using one strategy alone, could be more successful.

The Effects of Artificial Sweeteners on Intestinal Nutrient-Sensing Receptors: Dr. Jekyll or Mr. Hyde?

The consumption of artificial and low-calorie sweeteners (ASs, LCSs) is an important component of the Western diet. ASs play a role in the pathogenesis of metabolic syndrome, dysbiosis, inflammatory bowel diseases (IBDs), and various inflammatory conditions. Intestinal nutrient-sensing receptors act as a crosstalk between dietary components, the gut microbiota, and the regulation of immune, endocrinological, and neurological responses. This narrative review aimed to summarize the possible effects of ASs and LCSs on intestinal nutrient-sensing receptors and their related functions. Based on the findings of various studies, long-term AS consumption has effects on the gut microbiota and intestinal nutrient-sensing receptors in modulating incretin hormones, antimicrobial peptides, and cytokine secretion. These effects contribute to the regulation of glucose metabolism, ion transport, gut permeability, and inflammation and modulate the gut-brain, and gut-kidney axes. Based on the conflicting findings of several in vitro, in vivo, and randomized and controlled studies, artificial sweeteners may have a role in the pathogenesis of IBDs, functional bowel diseases, metabolic syndrome, and cancers via the modulation of nutrient-sensing receptors. Further studies are needed to explore the exact mechanisms underlying their effects to decide the risk/benefit ratio of sugar intake reduction via AS and LCS consumption.

Responsiveness to warning sensations and anxiety-related psychological traits modulate individual differences in preference for vegetable foods with varied sensory properties

The innate aversion to warning sensations is an important barrier to the acceptance of vegetable food often characterized by bitter and sour tastes, and astringency. Large individual variations exist in preference for this food category. The present study aimed at exploring differences in demographics, anthropometrics, taste responsiveness, personality traits and attitudes in consumers differing in their preference for vegetable food with varied levels of warning sensations. A panel of Italian consumers (n = 718; 53.6% women, age 18-74 years) self-reported familiarity with, preference for and choice of vegetables with high and low levels of warning sensations. Two clusters were identified: High Warning-Vegetable Consumers (HWVC, n = 464) and Low-Warning Vegetable Consumers (LWVC, n = 254). HWVC showed higher familiarity with and preference for vegetables as a whole and higher choice of vegetables characterized by warning sensations than LWVC. HWVC were more represented by older and normal weight individuals as compared to LWVC. Differences among clusters in liking for and perception of a phenol-enriched plant-based food model specifically developed to induce different levels of bitterness, sourness and astringency were found. HWVC rated bitterness, sourness, and astringency lower and liking higher than LWVC. Scores in anxiety-related psychological traits were lower while attitudes to healthy and high-quality food choice were higher in HWVC than in LWVC. The results of the present study depicted a coherent interplay among several person-related dimensions in modulating preference for vegetable foods. Higher responsiveness to warning sensations, higher level of anxiety-related traits, lower importance assigned to food healthy/quality aspects and younger age all acted as barriers to exposure and acceptance of vegetable food and call for a multidimensional approach to promote the consumption of this food category.

Child characteristic correlates of food rejection in preschool children: A narrative review

Dietary habits formed in early childhood are key for establishing a healthy diet later in life. Picky eating and food neophobia - the two main forms of food rejection in young children - form an important barricade to establishing such healthy habits. Understanding these types of food rejection is thus essential for promoting healthy eating behaviour in both children and adults. To this end, the present narrative review aims to provide an overview of food rejection research in preschool-aged children, focusing on recent advances in the cognitive literature. Specifically, we evaluate the link between children's cognitive development, chemosensory perception and affective evaluation of food, food knowledge, decision-making strategies, anxiety and disgust sensitivity, and food rejection behaviour. Longitudinal and experimental studies are necessary to establish how the relationships between food rejection and cognitive processes develop over time and to determine their causal directions.

Bitter taste sensitivity, cruciferous vegetable intake, obesity, and diabetes in American adults: a cross-sectional study of NHANES 2013-2014

Objective: To examine the associations between bitter taste sensitivity, cruciferous vegetable consumption, and likelihood of obesity and diabetes among American adults. Research design and method: Cross-section observation of 2129 adults aged 40-80 years of the National Health and Nutrition Examination Survey (NHANES) 2013-2014. Bitter taste sensitivity was estimated by the generalized labeled magnitude scale (gLMS) rating for bitterness (non-tasters: the lowest 25%, the others were tasters). Consumption of cruciferous vegetables was recorded by the 2 day 24 hours dietary records. Obesity was defined as body mass index (BMI) ≥30 kg m-2. Diabetes was defined as self-reported physician-diagnosed diabetes, or who reported taking diabetes medication or individuals with a fasting plasma glucose (FPG) ≥ 126 mg dL-1 or Hemoglobin A1c ≥ 6.5%. Results: The proportion of participants who ate cruciferous vegetables over the two days was 29.5% among bitter tasters, significantly lower than that (35.7%) among non-tasters (P = 0.04) after adjustment of age, gender, race/ethnicity, dietary energy intake, physical activity, education, smoking and income levels. Among participants who ate cruciferous vegetables, bitter tasters on average consumed 15.5 g (±7.0) grams less cruciferous vegetables per day compared to non-tasters. The multi-variates adjusted odds ratio of obesity was 1.29 (95% confident interval (CI): 0.76-2.17), 1.40 (95% CI: 0.90-2.18) and 1.68 (95% CI: 1.05-2.67) among bitter tasters who ate cruciferous vegetables, among non-tasters who did not ate cruciferous vegetables, and among bitter tasters who did not eat cruciferous vegetables, respectively, as compared with non-tasters who ate cruciferous vegetables. The prevalence of diabetes was 17.3% and 13.0% among bitter tasters and non-tasters, respectively, with a multi-adjusted odds ratio of 1.32 (95% CI: 1.02-1.69, P = 0.033) for diabetes comparing bitter tasters with non-tasters, which was attenuated to 1.26 (95% CI: 0.95-1.67, P = 0.108) by further adjustment of cruciferous vegetables consumption and obesity, with a mediation effect of 17.8% (95% CI: 2.9%-60.9%; P = 0.069). Conclusion: Bitter taste sensitivity was associated with less consumption of cruciferous vegetables and a high likelihood of obesity, which may mediate its association with diabetes.

Assessing Food Preferences and Neophobias among Spanish Adolescents from Castilla-La Mancha

Food neophobia is a reaction of dislike or fear of food, which may be due to a wide variety of factors (taste, texture, exposure at an early age, genetics, or diversity in feeding practices and food consumption). The aim of this study was to assess the preferences for tastes and foods and food neophobias among Spanish adolescents and to compare the differences between boys and girls. This was a cross-sectional observational study on 11-18-year-old healthy adolescents (n = 600; 50% female) recruited in the Castilla-La Mancha region (central Spain). Information on taste preferences, food neophobias, anthropometric measurements, and sociodemographic data was recorded. The highest taste preference was found for sweet, salty, and umami. Most adolescents usually did not try new foods outside the home, nor did they like to try foods from other countries. More than half of them also acknowledged being selective eaters or were very particular about the foods they ate. There were no significant associations between taste preference and neophobias with obesity, waist-to-height ratio (WtHR), sleep, and smoking. Adolescents showed a high unwillingness to change food habits, and most of the food neophobias found in the current study were related to new, novel, or previously unknown foods. Spanish adolescents from central Spain (Castilla-La Mancha region) showed a preference for sweet, salty, and umami tastes of foods, as well as food neophobia towards foods that they do not regularly consume, mainly those with a bitter taste. Gender and body weight showed little influence, and age had a moderate influence on food neophobias. Familiarity with foods, as well as educational activities, are suggested as useful to decrease food neophobias among adolescents.

Consumer Liking of Turnip Cooked by Different Methods: The Influence of Sensory Profile and Consumer Bitter Taste Genotype

Brassica vegetables are bitter, predominantly because they contain bitter-tasting glucosinolates. Individuals with high bitter taste sensitivity are reported to have lower consumption of bitter vegetables. Studies reported that cooking methods can alter the sensory characteristics of vegetables, increasing acceptability. This study investigated consumer liking of turnip cooked by four methods (boiled-pureed, roasted, steamed-pureed and stir-fried) and related this to sensory characteristics. Additionally, this study examined the effect of the bitter taste genotype on taste perception and liking of the cooked turnip samples. Participants (n = 74) were recruited and the TAS2R38 genotype was measured. Liking, consumption intent, perception of bitterness and sweetness of turnip were evaluated. A sensory profile of the cooked turnip variants was also determined by a trained sensory panel. There were significant differences in the overall (p = 0.001) and taste (p = 0.002) liking between cooking methods. Turnip liking was increased when preparation led to sweeter taste profiles. The TAS2R38 genotype had a significant effect on bitter perception (p = 0.02) but did not significantly affect taste liking. In conclusion, the cooking method affected turnip liking, and the bitter perception in turnip was influenced by the TAS2R38 genotype. However, taste sensitivity did not predict turnip liking in this UK adult cohort.

Change in preference for vegetables and their perceptual attributes as a function of age and pickiness

Preference for vegetables is influenced by various factors, including demographic, psychological, socio-environmental, and genetic factors. This study confirmed that age, pickiness, and perceptual attributes were predictors of preference for vegetables and examined how preference for vegetables and their perceptual attributes varies with age and pickiness. Children (8-14 years, n = 420), youth (15-34 years, n = 569), middle-aged adults (35-64 years, n = 726), and older adults (65-85 years, n = 270) were asked which vegetables they liked (or disliked) and which perceptual attributes of each vegetable they liked (or disliked). On the basis of their responses, an overall preference score and a preference sub-score for each perceptual attribute were calculated. Participants in each age group were classified into four statuses (non-, mild, moderate, and severe) according to their pickiness scores. Multiple regression analysis revealed that age and preference sub-scores for eight perceptual attributes (sweetness, sourness, bitterness, umami, pungency, orthonasal aroma, texture, and appearance) were positive predictors of overall preference score and that pickiness score and four perceptual attributes (saltiness, astringency, retronasal aroma, and aftertaste) were negative predictors. In addition, overall preference score and preference sub-scores for perceptual attributes other than saltiness increased with increasing age group and decreasing picker status; however, preference sub-scores for at least one of the six perceptual attributes (bitterness, astringency, pungency, orthonasal aroma, retronasal aroma, and aftertaste) exhibited negative values in children, youth, and pickers (mild, moderate, and severe). The increase in preference for these perceptual attributes might be an indicator of the adultization of food perception and the expansion of food acceptance.

A Supervised Learning Regression Method for the Analysis of the Taste Functions of Healthy Controls and Patients with Chemosensory Loss

In healthy humans, taste sensitivity varies widely, influencing food selection and nutritional status. Chemosensory loss has been associated with numerous pathological disorders and pharmacological interventions. Reliable psychophysical methods are crucial for analyzing the taste function during routine clinical assessment. However, in the daily clinical routine, they are often considered too time-consuming. We used a supervised learning (SL) regression method to analyze with high precision the overall taste statuses of healthy controls (HCs) and patients with chemosensory loss, and to characterize the combination of responses that would best predict the overall taste statuses of the subjects in the two groups. The random forest regressor model allowed us to achieve our objective. The analysis of the order of importance of each parameter and their impact on the prediction of the overall taste statuses of the subjects in the two groups showed that salty (low-concentration) and sour (high-concentration) stimuli specifically characterized healthy subjects, while bitter (high-concentration) and astringent (high-concentration) stimuli identified patients with chemosensory loss. Although the present results require confirmation in studies with larger samples, the identification of such distinctions should be of interest to the health system because they may justify the use of specific stimuli during the routine clinical assessments of taste function and thereby reduce time and cost commitments.

Metabolome and Transcriptome Integrated Analysis of Mulberry Leaves for Insight into the Formation of Bitter Taste

Mulberry leaves are excellent for health care, confirmed as a 'drug homologous food' by the Ministry of Health, China. The bitter taste of mulberry leaves is one of the main problems that hinders the development of the mulberry food industry. The bitter, unique taste of mulberry leaves is difficult to eliminate by post-processing. In this study, the bitter metabolites in mulberry leaves were identified as flavonoids, phenolic acids, alkaloids, coumarins and L-amino acids by a combined analysis of the metabolome and transcriptome of mulberry leaves. The analysis of the differential metabolites showed that the bitter metabolites were diverse and the sugar metabolites were down-regulated, indicating that the bitter taste of mulberry leaves was a comprehensive reflection of various bitter-related metabolites. Multi-omics analysis showed that the main metabolic pathway related to bitter taste in mulberry leaves was galactose metabolism, indicating that soluble sugar was one of the main factors of bitter taste difference in mulberry leaves. Bitter metabolites play a great role in the medicinal and functional food of mulberry leaves, but the saccharides in mulberry leaves have a great influence on the bitter taste of mulberry. Therefore, we propose to retain bitter metabolites with drug activity in mulberry leaves and increase the content of sugars to improve the bitter taste of mulberry leaves as strategies for mulberry leaf food processing and mulberry breeding for vegetable use.

Association between Genetic Variation in the TAS2R38 Bitter Taste Receptor and Propylthiouracil Bitter Taste Thresholds among Adults Living in Japan Using the Modified 2AFC Procedure with the Quest Method

Individual taste sensitivity influences food preferences, nutritional control, and health, and differs greatly between individuals. The purpose of this study was to establish a method of measuring and quantifying an individual's taste sensitivity and to evaluate the relationship between taste variation and genetic polymorphisms in humans using agonist specificities of the bitter taste receptor gene, TAS2R38, with the bitter compound 6-n-propylthiouracil (PROP). We precisely detected the threshold of PROP bitter perception by conducting the modified two-alternative forced-choice (2AFC) procedure with the Bayesian staircase procedure of the QUEST method and examined genetic variation in TAS2R38 in a Japanese population. There were significant differences in PROP threshold between the three TAS2R38 genotype pairs for 79 subjects: PAV/PAV vs AVI/AVI, p < 0.001; PAV/AVI vs AVI/AVI, p < 0.001; and PAV/PAV vs PAV/AVI, p < 0.01. Our results quantified individual bitter perception as QUEST threshold values: the PROP bitter perception of individuals with the PAV/PAV or PAV/AVI genotypes was tens to fifty times more sensitive than that of an individual with the AVI/AVI genotype. Our analyses provide a basic model for the accurate estimation of taste thresholds using the modified 2AFC with the QUEST approach.

Automated identification of the genetic variants of TAS2R38 bitter taste receptor with supervised learning

Several studies were focused on the genetic ability to taste the bitter compound 6-n-propylthiouracil (PROP) to assess the inter-individual taste variability in humans, and its effect on food predilections, nutrition, and health. PROP taste sensitivity and that of other chemical molecules throughout the body are mediated by the bitter receptor TAS2R38, and their variability is significantly associated with TAS2R38 genetic variants. We recently automatically identified PROP phenotypes with high precision using Machine Learning (mL). Here we have used Supervised Learning (SL) algorithms to automatically identify TAS2R38 genotypes by using the biological features of eighty-four participants. The catBoost algorithm was the best-suited model for the automatic discrimination of the genotypes. It allowed us to automatically predict the identification of genotypes and precisely define the effectiveness and impact of each feature. The ratings of perceived intensity for PROP solutions (0.32 and 0.032 mM) and medium taster (MT) category were the most important features in training the model and understanding the difference between genotypes. Our findings suggest that SL may represent a trustworthy and objective tool for identifying TAS2R38 variants which, reducing the costs and times of molecular analysis, can find wide application in taste physiology and medicine studies.

Variations in the TAS2R38 gene among college students in Hubei

BACKGROUND

The bitter taste receptor gene TAS2R38 is a member of the human TAS2R gene family. Polymorphisms in TAS2R38 affect the ability to taste the bitterness of phenylthiourea (PTC) compounds, thus affecting an individual's food preference and health status.

METHODS

We investigated polymorphisms in the TAS2R38 gene and the sensitivity to PTC bitterness among healthy Chinese college students in Hubei province. The association of TAS2R38 polymorphisms and PTC sensitivity with body mass index (BMI), food preference, and health status was also analyzed. A total of 320 healthy college students were enrolled (male: 133, female: 187; aged 18-23 years). The threshold value method was used to measure the perception of PTC bitterness, and a questionnaire was used to analyze dietary preferences and health status. Polymerase chain reaction (PCR) was used to analyze polymorphisms at three common TAS2R38 loci (rs713598, rs1726866, and rs10246939).

RESULTS

In our study population, 65.00% of individuals had medium sensitivity to the bitterness of PTC; in contrast, 20.94% were highly sensitive to PTC bitterness, and 14.06% were not sensitive. For the TAS2R38 gene, the PAV/PAV and PAV/AAI diplotypes were the most common (42.19% and 40.63%, respectively), followed by the homozygous AVI/AVI (8.75%) and PAV/AVI (5.00%) diplotypes.

CONCLUSION

There was a significant correlation between the sensitivity to PTC bitterness and sex, but there was no correlation between the common diplotypes of TAS2R38 and gender. Polymorphisms in the TAS2R38 gene were associated with the preference for tea, but not with one's native place, BMI, health status, or other dietary preferences. There was no significant correlation between the perception of PTC bitterness and one's native place, BMI, dietary preference, or health status. We hope to find out the relationship between PTC sensitivity and TAS2R38 gene polymorphisms and dietary preference and health status of Chinese population through this study, providing relevant guidance and suggestions for dietary guidance and prevention of some chronic diseases in Chinese population.

A Cross-Sectional Analysis of Food Perceptions, Food Preferences, Diet Quality, and Health in a Food Desert Campus

The sensory properties of foods guide food choices and intake, importantly determining nutritional and health status. In communities that have inconsistent access to nutritious foods, such as food deserts, food taste perceptions and preferences have yet to be explored. The purpose of this study was to examine how taster status (supertaster vs. non-taster) and food security status (high or marginal vs. low or very low) influences food taste intensities, food preferences and perceptions, and diet quality in a cohort of students from a food desert campus in the Central Valley of California. Moreover, the complex relationship of socioeconomic status, race/ethnicity, and sex on cardiometabolic and cognitive health warrants further examination. Two hundred fifty participants (aged 18-24 years) living in a food desert campus were recruited in 2018 for this cross-sectional study where participants underwent taste tests on selected fruits, vegetables, and nuts, and clinical tests (anthropometrics, blood glucose, blood pressure, and endothelial function), cognitive function tests (memory and attention), diet quality assessment (Healthy Eating Index (HEI)), and food preference and perception assessments. Food taste intensities were influenced by sex with bitter and umami taste intensities of several foods being perceived more intensely by males. Moreover, food liking was largely influenced by ethnicity with Hispanics having higher liking ratings for several foods compared with non-Hispanics. Both, Hispanics and females, had higher total fruit HEI scores and lower attention scores than non-Hispanics and males, respectively. Females also had lower blood pressure, reactive hyperemia index, and fasting blood glucose. Food-insecure individuals rated cost and convenience as more important factors for overall food consumption and had lower attention scores than those with higher food-security status. Future research should consider the complex interactions of factors such as taste and flavor perception, sex, ethnicity, prior exposure to foods, and other environmental factors when studying food preferences and health in young adults.

Associations between Sweet Taste Sensitivity and Polymorphisms (SNPs) in the TAS1R2 and TAS1R3 Genes, Gender, PROP Taster Status, and Density of Fungiform Papillae in a Genetically Homogeneous Sardinian Cohort

Individual differences in sweet taste sensitivity can affect dietary preferences as well as nutritional status. Despite the lack of consensus, it is believed that sweet taste is impacted by genetic and environmental variables. Here we determined the effect of well-established factors influencing the general taste variability, such as gender and fungiform papillae density, specific genetic variants (SNPs of TAS1R2 and TAS1R3 receptors genes), and non-specific genetic factors (PROP phenotype and genotype), on the threshold and suprathreshold sweet taste sensitivity. Suprathreshold measurements showed that the sweet taste response increased in a dose-dependent manner, and this was related to PROP phenotype, gender, rs35874116 SNP in the TAS1R2 gene, and rs307355 SNP in the TAS1R3 gene. The threshold values and density of fungiform papillae exhibited a strong correlation, and both varied according to PROP phenotype. Our data confirm the role of PROP taste status in the sweet perception related to fungiform papilla density, show a higher sweet sensitivity in females who had lower BMI than males, and demonstrate for the first time the involvement of the rs35874116 SNP of TAS1R2 in the sweet taste sensitivity of normal weight subjects with body mass index (BMI) ranging from 20.2 to 24.8 kg/m2. These results may have an important impact on nutrition and health mostly in subjects with low taste ability for sweets and thus with high vulnerability to developing obesity or metabolic disease.

Variation in TAS2R receptor genes explains differential bitterness of two common antibiotics

For pharmaceuticals to deliver their full benefits with maximum efficacy, patients need to follow recommended dosing schedules, in terms of amount and frequency. Unfortunately, the aversive taste of many drugs, especially bitterness, can reduce patient compliance in oral liquid formulations. Given common genetic differences in bitter taste receptor genes (TAS2Rs), some individuals may be at increased risk for poor compliance due to heightened bitterness that becomes a barrier to proper use. Here we report on the sensory profile of two antibiotics, chloramphenicol and ofloxacin, investigating whether bitterness intensity associates with nominally functional TAS2R variants. Participants (n = 143) rated suprathreshold intensity on a general Labeled Magnitude Scale (gLMS) for chloramphenicol and ofloxacin; propylthiouracil (PROP) was included as a control, given robust prior associations with TAS2R38 variants. The dominant sensation from chloramphenicol and ofloxacin was bitterness, falling just below "moderate" on a gLMS. TAS2R38 diplotype associated with variable bitterness of chloramphenicol and PROP, but not ofloxacin. The bitterness of ofloxacin associated with a TAS2R9 SNP (V187A). This pilot study provides novel evidence on differences in the bitterness from two antibiotics, which are associated with TAS2R variants. Improved understanding of individualized barriers to patient compliance, especially for oral formulations, can guide future efforts to optimize delivery systems for improved compliance.

Application of a salt substitute in bitter taste suppression and toward better acceptance of cruciferous vegetables in diet

The addition of table salt has been reported to enable better acceptance when consuming the least preferred vegetables belonging to the Cruciferae family. Considering the adverse effect of excessive table salt intake on incidence of hypertension and cardiovascular diseases, it is essential to explore an alternative healthier option for better acceptance and to encourage consumption of these vegetables. In this study, 261 adult participants were evaluated for their preferences toward basic tastes and food as well as sensory evaluation of a meal prepared from cruciferous vegetables with the addition of two different salts, sodium chloride and salt substitute containing a blend of potassium and sodium salts. A general questionnaire was used to assess taste and food preferences, while the Cruciferous Vegetable Food Frequency Questionnaire (CVFFQ) was used for vegetable intake assessment. The Labeled Magnitude Scale (LMS), Just About Right (JAR) scale, and several hedonic scales were used to determine taster status and sensory evaluation. The results show that a low concentration of the salt substitute did not impact bitterness suppression but did result in higher preference of the cruciferous vegetable meal. Although, subjects self-reported to have salty taste preferences were more sensitive to bitter taste, they did not perceive samples as less salty and less acceptable than subjects with lower sensitivity. The results show the necessity for further examination of the effectiveness of different concentrations of the assessed salt substitute in suppressing perceived bitterness of cruciferous vegetables and regarding their overall acceptance for inclusion in diets.

Sensory Capacities and Eating Behavior: Intriguing Results from a Large Cohort of Italian Individuals

Eating behavior (EB) is a complex system influenced by many factors, but an undisputed role is played by the senses. In this work, we examined the effect of the sensory capacities on EB in 1152 Italian adult individuals. After administering a questionnaire on EB and assessing sensory performance through standard audiometric, olfactory, and taste tests, the prevalence of reduced sensory capacities (RSCs) and the correlation with selected risk factors were calculated. Regression models, structural equation modelling, and conditional recursive partitioning were used to investigate the relationship between variables. Around 70% of the subjects show reduced capacities in at least one sense, with taste being the most prevalent (55.21%). Male sex, aging, and low educational level are risk factors for RSCs. The increased number of senses with reduced capacities is a predictor of diminished food adventurousness and lower liking for vegetables, fish, and alcoholic beverages, while reduced capacities (RCs) in taste is a predictor of lower liking for alcoholic beverages and sweets. Overall, in addition to providing an overall picture of RSCs in Italian samples, our study reveals the association of RSCs with EB variables. This finding could have a relevant role in influencing individuals’ dietary habits and, therefore, health status.

Racial Differences in Pain, Nutrition, and Oxidative Stress

Investigating the disproportionate rates of chronic pain and their related comorbidities between Black and non-Hispanic White (White) individuals is a growing area of interest, both in the healthcare community and in general society. Researchers have identified racial differences in chronic pain prevalence and severity, but still very little is known about the mechanisms underlying them. Current explanations for these differences have primarily focused on socioeconomic status and unequal healthcare between races as causal factors. Whereas these factors are informative, a racial gap still exists between Black and White individuals when these factors are controlled for. One potential cause of this racial gap in chronic pain is the differences in nutrition and dietary intake between groups. Certain foods play a key role in the inflammatory and oxidative stress pathways in the human body and could potentially influence the severity of the pain experience. Here, we review the previous literature on the surrounding topics and propose a potential mechanism to explain racial differences in the chronic pain population, based on established racial differences in diet and oxidative stress.

Are taste variations associated with the liking of sweetened and unsweetened coffee?

OBJECTIVE

In this study, we evaluated the influence of taste phenotypes and genotypes on the hedonics of sweetened and unsweetened coffee.

METHODS

Liking of espresso coffee from food questionnaire and of a ready-to-drink unsweetened coffee beverage was measured using a 9-point hedonic scale in 1551 Italian individuals. Perception and liking for different bitter and sweet compounds were also collected. Genotyping of selected Single Nucleotide Polymorphisms (SNPs) in five taste genes (TAS1R3, GNAT3, TAS2R14, TAS2R19, TAS2R38) was performed. Linear and logistic regression models, including sex and gender as covariates, were used to test the relationship of taste phenotypes and selected SNPs with coffee liking.

RESULTS

We found that increased caffeine bitterness perception was associated with an increasing liking for sweetened coffee (p-value = 0.018) and decreased liking of unsweetened coffee (p-value = 0.034). The liking of unsweetened coffee beverage was also negatively associated with sweet intensity perception (p-value = 0.03). Analysis of SNPs in taste-related genes showed that rs6467192 G allele (intron 4 variant) in GNAT3 sweet taste gene was associated with higher liking of sweetened coffee (p-value = 0.002) and lower liking of unsweetened coffee (p-value = 0.01). An association also emerged between unsweetened coffee and SNPs in bitter receptor genes, with rs2597979 in TAS2R14 gene associated with liking of unsweetened coffee (p-value = 0.004) and rs10772420 in TAS2R19 gene associated with liking of both unsweetened espresso coffee and coffee beverage (p-value = 0.04 and p-value = 0.03, respectively).

CONCLUSION

These findings suggested that individual preference for sweetened and unsweetened coffee may be influenced by both phenotypic and nucleotide variations in bitter and sweet taste sensitivity.

Re-evaluating how sweet-liking and PROP-tasting are related

Past research has identified distinct phenotypic differences in responses to sweet taste, although the origins of these differences remain unclear. One possibility is that these individual differences in sweet-liking are a manifestation of the more widely known differences in sensitivity to the bitter tastant 6-n-propylthiouracil (PROP), which has been related to wider differences in food liking and preference. However, previous studies exploring the relationship between sweet-liking and PROP-tasting have had mixed outcomes. This is possibly due to older studies using a more simplistic dichotic characterisation of sweet likers, whereas recent research suggests three sweet-liking phenotypes (extreme sweet likers, ESL; moderate sweet likers, MSL; and sweet dislikers, SD). To re-assess how sweet-liking and PROP tasting are inter-related, 236 volunteers evaluated their liking for 1.0 M sucrose and the intensity of three concentrations of each NaCl and PROP. Using three different methods for classifying PROP taster status, our analysis confirmed that all three sweet-liking phenotypes were represented in all three PROP taster groups (super-tasters, ST; medium tasters, MT; and non-tasters, NT), but relatively few ESL were classified as ST, or SD as NT. Overall, these data suggest that while PROP tasting and sweet-liking are not causally related, the SD phenotype may partly be explained by a broader tendency for anhedonia.

Automated Classification of 6-n-Propylthiouracil Taster Status with Machine Learning

Several studies have used taste sensitivity to 6-n-propylthiouracil (PROP) to evaluate interindividual taste variability and its impact on food preferences, nutrition, and health. We used a supervised learning (SL) approach for the automatic identification of the PROP taster categories (super taster (ST); medium taster (MT); and non-taster (NT)) of 84 subjects (aged 18-40 years). Biological features determined from subjects were included for the training system. Results showed that SL enables the automatic identification of objective PROP taster status, with high precision (97%). The biological features were classified in order of importance in facilitating learning and as prediction factors. The ratings of perceived taste intensity for PROP paper disks (50 mM) and PROP solution (3.2 mM), along with fungiform papilla density, were the most important features, and high estimated values pushed toward ST prediction, while low values leaned toward NT prediction. Furthermore, TAS2R38 genotypes were significant features (AVI/AVI, PAV/PAV, and PAV/AVI to classify NTs, STs, and MTs, respectively). These results, in showing that the SL approach enables an automatic, immediate, scalable, and high-precision classification of PROP taster status, suggest that it may represent an objective and reliable tool in taste physiology studies, with applications ranging from basic science and medicine to food sciences.

Associations between Taste Perception Profiles and Empirically Derived Dietary Patterns: An Exploratory Analysis among Older Adults with Metabolic Syndrome

Taste perception is a primary driver of food choices; however, little is known about how perception of all five tastes (sweet, salt, sour, bitter, umami) collectively inform dietary patterns. Our aim was to examine the associations between a multivariable measure of taste perception—taste perception profiles—and empirically derived dietary patterns. The cohort included 367 community-dwelling adults (55–75 years; 55% female; BMI = 32.2 ± 3.6 kg/m²) with metabolic syndrome from PREDIMED-Plus, Valencia. Six taste perception profiles were previously derived via data-driven clustering (Low All, High Bitter, High Umami, Low Bitter and Umami, High All But Bitter, High All But Umami); three dietary patterns were derived via principal component analysis (% variance explained = 20.2). Cross-sectional associations between profiles and tertials of dietary pattern adherence were examined by multinomial logistic regression. Overall, there were several significant differences in dietary pattern adherence between profiles: the vegetables, fruits, and whole grains pattern was significantly more common for the High All But Umami profile (OR range for high vs. low adherence relative to other profiles (1.45–1.99; 95% CI minimum lower, maximum upper bounds: 1.05, 2.74), the non-extra virgin olive oils, sweets, and refined grains pattern tended to be less common for Low All or High Bitter profiles (OR range: 0.54–0.82), while the alcohol, salty foods, and animal fats pattern tended to be less common for Low Bitter and Umami and more common for High All But Bitter profiles (OR range: 0.55–0.75 and 1.11–1.81, respectively). In conclusion, among older adults with metabolic syndrome, taste perception profiles were differentially associated with dietary patterns, suggesting the benefit of integrating taste perception into personalized nutrition guidance.

An update on extra-oral bitter taste receptors

Bitter taste-sensing type 2 receptors (TAS2Rs or T2Rs), belonging to the subgroup of family A G-protein coupled receptors (GPCRs), are of crucial importance in the perception of bitterness. Although in the first instance, TAS2Rs were considered to be exclusively distributed in the apical microvilli of taste bud cells, numerous studies have detected these sensory receptor proteins in several extra-oral tissues, such as in pancreatic or ovarian tissues, as well as in their corresponding malignancies. Critical points of extra-oral TAS2Rs biology, such as their structure, roles, signaling transduction pathways, extensive mutational polymorphism, and molecular evolution, have been currently broadly studied. The TAS2R cascade, for instance, has been recently considered to be a pivotal modulator of a number of (patho)physiological processes, including adipogenesis or carcinogenesis. The latest advances in taste receptor biology further raise the possibility of utilizing TAS2Rs as a therapeutic target or as an informative index to predict treatment responses in various disorders. Thus, the focus of this review is to provide an update on the expression and molecular basis of TAS2Rs functions in distinct extra-oral tissues in health and disease. We shall also discuss the therapeutic potential of novel TAS2Rs targets, which are appealing due to their ligand selectivity, expression pattern, or pharmacological profiles.

Bitter taste receptors: Genes, evolution and health

Bitter taste perception plays vital roles in animal behavior and fitness. By signaling the presence of toxins in foods, particularly noxious defense compounds found in plants, it enables animals to avoid exposure. In vertebrates, bitter perception is initiated by TAS2Rs, a family of G protein-coupled receptors expressed on the surface of taste buds. There, oriented toward the interior of the mouth, they monitor the contents of foods, drinks and other substances as they are ingested. When bitter compounds are encountered, TAS2Rs respond by triggering neural pathways leading to sensation. The importance of this role placed TAS2Rs under selective pressures in the course of their evolution, leaving signatures in patterns of gene gain and loss, sequence polymorphism, and population structure consistent with vertebrates' diverse feeding ecologies. The protective value of bitter taste is reduced in modern humans because contemporary food supplies are safe and abundant. However, this is not always the case. Some crops, particularly in the developing world, retain surprisingly high toxicity and bitterness remains an important measure of safety. Bitter perception also shapes health through its influence on preference driven behaviors such as diet choice, alcohol intake and tobacco use. Further, allelic variation in TAS2Rs is extensive, leading to individual differences in taste sensitivity that drive these behaviors, shaping susceptibility to disease. Thus, bitter taste perception occupies a critical intersection between ancient evolutionary processes and modern human health.

QTL Mapping and GWAS Reveal the Genetic Mechanism Controlling Soluble Solids Content in Brassica napus Shoots

Oilseed-vegetable-dual-purpose (OVDP) rapeseed can effectively alleviate the land contradiction between crops and it supplements vegetable supplies in winter or spring. The soluble solids content (SSC) is an important index that is used to evaluate the quality and sugar content of fruits and vegetables. However, the genetic architecture underlying the SSC in Brassica napus shoots is still unclear. Here, quantitative trait loci (QTLs) for the SSC in B. napus shoots were investigated by performing linkage mapping using a recombinant inbred line population containing 189 lines. A germplasm set comprising 302 accessions was also used to conduct a genome-wide association study (GWAS). The QTL mapping revealed six QTLs located on chromosomes A01, A04, A08, and A09 in two experiments. Among them, two major QTLs, qSSC/21GY.A04-1 and qSSC/21NJ.A08-1, accounted for 12.92% and 10.18% of the phenotypic variance, respectively. In addition, eight single-nucleotide polymorphisms with phenotypic variances between 5.62% and 10.18% were identified by the GWAS method. However, no locus was simultaneously identified by QTL mapping and GWAS. We identified AH174 (7.55 °Brix and 7.9 °Brix), L166 (8.9 °Brix and 8.38 °Brix), and L380 (8.9 °Brix and 7.74 °Brix) accessions can be used as superior parents. These results provide valuable information that increases our understanding of the genetic control of SSC and will facilitate the breeding of high-SSC B. napus shoots.

Infant and Toddler Responses to Bitter-Tasting Novel Vegetables: Findings from the Good Tastes Study

BACKGROUND

Infants are born with the biological predisposition to reject bitterness. Dark green vegetables contain essential nutrients but also bitter compounds, making them more difficult to like.

OBJECTIVE

The Good Tastes Study was designed to determine whether reducing bitterness by adding small amounts of sugar or salt would alter infant acceptance of kale purées.

METHODS

Caregivers (n = 106, 94% mothers, 82% Non-Hispanic White) and children (53% male, aged 6-24 mo) participated in a videorecorded laboratory visit during which infants were offered 4 versions of puréed kale: plain, 1.2% or 1.8% added sugar, or 0.2% added salt. Caregivers rated their children's liking for each kale version. Videos were coded for the number of tastes accepted and for children's behaviors and acceptance of each kale version. A multilevel ordered logistic model was fit for the number of accepted tastes and caregiver ratings of child liking of kale versions with age, breastfeeding history, order effects, and kale version as predictors.

RESULTS

Infants 6 to <12 mo accepted more tastes (b = 2.911, P < 0.001) and were rated by caregivers as liking the kale more than older toddlers (≥18 mo; b = 1.874, P = 0.014). The plain kale was more likely to be accepted (P < 0.001); also, the first version offered was more likely to be rejected (b = -0.586, P < 0.007). Older infants (≥18 mo) exhibited more avoidant behaviors (b = 1.279, P < 0.001), more playing (b = 2.918, P < 0.001), and more self-feeding (b = 1.786, P = 0.005) than younger infants (6 to <12 mo). Children who were reported to have been breastfed more in the last 7 d were more likely to self-feed (b = 0.246, P < 0.001) and play with food (b = 0.207, P < 0.005).

CONCLUSIONS

Our findings support that there may be a sensitive period, during the early phase of complementary feeding, to improve success of introducing a novel, bitter, more difficult-to-like food. When low levels of sugar or salt were added, no advantage of bitterness reduction was observed. This study has been registered with ClinicalTrials.gov as NCT04549233.

Taste perception and expression in stomach of bitter taste receptor tas2r38 in obese and lean subjects

Differences in taste perception have been related to eating behavior, nutritional status, and diseases. Recently, taste receptors have been identified in several extra-oral tissues, such as the gastrointestinal tract, where they seem to influence processes like digestion, sense of satiety as well as energy balance and intraluminal changes occurring in obesity. Our study aims to analyze differences in taste perception among 42 obese patients (OB) and 41 normal-weight subjects (LEAN). Polymorphisms in the gene codifying for the bitter taste receptor TAS2R38 and its expression on the surface of the gastric mucosa were tested and compared among OB and LEAN. Taste intensity of PROP (6-n-propylthiouracil), quinine, sucrose, citric acid and NaCl were measured on a labeled magnitude scale. DNA from peripheral whole blood was extracted and three polymorphisms in the TAS2R38 gene (rs713598, rs1726866, rs10246939) analyzed. Gastric biopsies were collected during bariatric surgery in OB and during endoscopy in LEAN. RNA was extracted and TAS2R38 gene expression assessed by RT-Real-Time qPCR. Anamnestic and anthropometric data were recorded in all participants during baseline visits. Logistic regression analysis showed that OB perceives sweet (sucrose) and bitter (PROP or 6-n-propylthiouracil) taste more intensely than LEAN (p-value = 0.02 and p-value = 0.005, respectively). While polymorphisms in TAS2R38 gene did not differ among OB and LEAN, we observed a significant increase of TAS2R38 mRNA levels in the stomach of OB compared to LEAN (p = 0.01). Our results provide new evidence of a link between obesity and altered taste perception as well as TAS2R38 expression in the stomach.

Consumption of a Variety of Vegetables to Meet Dietary Guidelines for Americans' Recommendations Does Not Induce Sensitization of Vegetable Reinforcement Among Adults with Overweight and Obesity: A Randomized Controlled Trial

BACKGROUND

Food reinforcement, or the motivation to obtain food, can predict choice and consumption. Vegetable consumption is well below recommended amounts for adults, so understanding how to increase vegetable reinforcement could provide valuable insight into how to increase consumption.

OBJECTIVES

We sought to determine whether daily consumption of the Dietary Guidelines for Americans (DGA) recommendations for vegetable intake induces sensitization of vegetable reinforcement in adults with overweight and obesity.

METHODS

Healthy adults with a BMI ≥ 25 kg/m2 who consumed ≤1 cup-equivalent of vegetables/day were randomly assigned to a vegetable intervention (VI; n = 55) or an attention control (AC; n = 55) group. The VI consisted of the daily provision of vegetables in the amounts and types recommended by the DGA (∼270 g/day) for 8 weeks. Participants were followed for an additional 8 weeks to assess sustained consumption. Compliance was measured weekly by resonance Raman light-scattering spectroscopy (RRS). Vegetable reinforcement was tested at weeks 0, 8, 12, and 16 using a computer choice paradigm.

RESULTS

In the VI group, RRS intensity increased from week 0 to 8 (from 22,990 to 37,220), returning to baseline by week 16 (27,300). No change was observed in the AC group. There was no main effect of treatment (P = 0.974) or time (P = 0.14) and no treatment x time interaction (P = 0.44) on vegetable reinforcement. There was no moderating effect of sex (P = 0.07), age (P = 0.60), BMI (P = 0.46), delay discounting (P = 0.24), 6-n-propylthiouracil taster status (P = 0.15), or dietary disinhibition (P = 0.82) on the change in vegetable reinforcement.

CONCLUSIONS

These findings suggest no effects of the provision of a variety of vegetables to meet DGA recommendations for 8 weeks on vegetable reinforcement and highlight the difficulty in increasing vegetable consumption in adults. This trial was registered at clinicaltrials.gov as NCT02585102.

Predominant Qualities Evoked by Quinine, Sucrose, and Capsaicin Associate With PROP Bitterness, but not TAS2R38 Genotype

Genetic variability in the ability to taste thiourea compounds has been studied for 80+ years. Over the last 3 decades, many studies have reported perceived intensity of concentrated propylthiouracil (PROP) associates with greater intensity from a broad range of stimuli, including nonbitter tastants, irritants, and retronasally delivered odorants. Thus, PROP phenotype has become a common measure of individual differences in orosensation. Much, but not all, of the phenotypic variation in PROP bitterness is explained by TAS2R38 polymorphisms. While differences in PROP bitterness are clearly due to genetic variation, mechanistically it is challenging to envision how this receptor (narrowly tuned to the N-C=S moiety) relates to overall orosensory response. Here, we report data for 200+ individuals who had been genotyped for TAS2R38 and phenotyped for PROP in a laboratory setting. Participants also reported the intensity of quinine, capsaicin, and sucrose on a general Labeled Magnitude Scale. Our data recapitulate earlier reports associating PROP bitterness with the intensity of the predominant qualities of sucrose, quinine, and capsaicin; however, we also find correlations between the intensities of sucrose, quinine, and capsaicin were much stronger with each other than with PROP. As expected, TAS2R38 diplotype did not associate with the intensity of sucrose, quinine, or capsaicin. The strength of PROP-capsaicin and PROP-sucrose relationships increased after grouping participants by TAS2R38 diplotype, with the greatest increases in association observed within homozygotes. Collectively, this suggests the suprathreshold intensity of PROP is a confounded phenotype that captures both genetic variation specific to N-C=S compounds and overall orosensation.

Taste Sensitivity and Taste Preference among Malay Children Aged 7 to 12 Years in Kuala Lumpur-A Pilot Study

The taste and food preferences in children can affect their food intake and body weight. Bitter and sweet taste sensitivities were identified as primary taste contributors to children's preference for consuming various foods. This pilot study aimed to determine the taste sensitivity and preference for bitter and sweet tastes in a sample of Malaysian children. A case-control study was conducted among 15 pairs of Malay children aged 7 to 12 years. Seven solutions at different concentrations of 6-n-propylthiouracil and sucrose were prepared for testing bitterness and sweet sensitivity, respectively. The intensity of both bitter and sweet sensitivity was measured using a 100 mm Labelled Magnitude Scale (LMS), while the taste preference was rated using a 5-point Likert scale. The participants were better at identifying bitter than sweet taste (median score 6/7 vs. 4/7). No significant differences were detected for both tastes between normal-weight and overweight groups (bitter: 350 vs. 413, p = 0.273; sweet: 154 vs. 263, p = 0.068), as well as in Likert readings (bitter 9 vs. 8: p = 0.490; sweet 22 vs. 22: p = 0.677). In this sample of Malay children, the participants were more sensitive to bitterness than sweetness, yet presented similar taste sensitivity and preference irrespective of their weight status. Future studies using whole food samples are warranted to better characterize potential taste sensitivity and preference in children.

Association of single nucleotide polymorphisms with taste and food preferences of the Hungarian general and Roma populations

It is reasonable to suppose that poor diet underlies the unfavorable health status of the Roma population of Europe. Previously in the framework of a complex health survey, fruit and vegetable consumption, quantity of sugar added, salting frequency; bitter, salty, sweet and fat taste preferences were evaluated of Hungarian (HG, n = 410) and Roma (HR, n = 387) populations. In the present study the associations of taste and food preferences with TAS1R3, CD36, SCNN1B, TRPV1, TAS2R38, TAS2R19 and CA6 polymorphisms were tested in the same samples. Genotype frequencies did not differ significantly between the two populations. Although we initially observed associations between certain genetic polymorphisms and taste and food preferences in our study samples, none of the p values remained significant after the multiple test correction. However, some of our results could be considered promising (0.05<corrected p < 0.20), which showed potential ethnicity-specific effects (CA6 rs2274333 with salty taste and raw kohlrabi preference, CD36 rs1527483 with fat taste preference, TAS2R19 rs10772420 with grapefruit preference, and TAS2R38 rs713598 with quantity of sugar added). Our results may suggest that genetics may mediate food preferences, and individuals with different ethnic background may require personalized interventions to modify diet. Further investigations with greater sample sizes are essential to explore the effect of these genetic variants on taste and food preferences.