The human sweet tooth

Understanding the determinants of sweet taste liking in the African and East Asian ancestry groups in the U.S.-A study protocol

BACKGROUND

The liking for sweet taste is a powerful driver for consuming added sugars, and therefore, understanding how sweet liking is formed is a critical step in devising strategies to lower added sugars consumption. However, current research on the influence of genetic and environmental factors on sweet liking is mostly based on research conducted with individuals of European ancestry. Whether these results can be generalized to people of other ancestry groups warrants investigation.

METHODS

We will determine the differences in allele frequencies in sweet-related genetic variants and their effects on sweet liking in 426 adults of either African or East Asian ancestry, who have the highest and lowest average added sugars intake, respectively, among ancestry groups in the U.S. We will collect information on participants' sweet-liking phenotype, added sugars intake (sweetness exposure), anthropometric measures, place-of-birth, and for immigrants, duration of time living in the U.S. and age when immigrated. Ancestry-specific polygenic scores of sweet liking will be computed based on the effect sizes of the sweet-related genetic variants on the sweet-liking phenotype for each ancestry group. The predictive validity of the polygenic scores will be tested using individuals of African and East Asian ancestry from the UK Biobank. We will also compare sweet liking between U.S.-born individuals and immigrants within each ancestry group to test whether differences in environmental sweetness exposure during childhood affect sweet liking in adulthood.

DISCUSSION

Expanding genetic research on taste to individuals from ancestry groups traditionally underrepresented in such research is consistent with equity goals in sensory and nutrition science. Findings from this study will help in the development of a more personalized nutrition approach for diverse populations.

TRIAL REGISTRATION

This protocol has been preregistered with the Center for Open Science (https://doi.org/10.17605/OSF.IO/WPR9E).

Understanding the Determinants of Sweet Liking in the African and East Asian Ancestry Groups in the U.S. - A Study Protocol

Background

The liking for sweet taste is a powerful driver for consuming added sugars, and therefore, understanding how sweet liking is formed is a critical step in devising strategies to lower added sugars consumption. However, current research on the influence of genetic and environmental factors on sweet liking is mostly based on research conducted with individuals of European ancestry. Whether these results can be generalized to people of other ancestry groups warrants investigation.

Methods

We will determine the differences in allele frequencies in sweet-related genetic variants and their effects on sweet liking in 426 adults of either African or East Asian ancestry, who have the highest and lowest average added sugars intake, respectively, among ancestry groups in the U.S. We will collect information on participants' sweet-liking phenotype, added sugars intake (sweetness exposure), anthropometric measures, place-of-birth, and for immigrants, duration of time living in the U.S. and age when immigrated. Ancestry-specific polygenic scores of sweet liking will be computed based on the effect sizes of the sweet-related genetic variants on the sweet-liking phenotype for each ancestry group. The predictive validity of the polygenic scores will be tested using individuals of African and East Asian ancestry from the UK Biobank. We will also compare sweet liking between U.S.-born individuals and immigrants within each ancestry group to test whether differences in environmental sweetness exposure during childhood affect sweet liking in adulthood.

Discussion

Expanding genetic research on taste to individuals from ancestry groups traditionally underrepresented in such research is consistent with equity goals in sensory and nutrition science. Findings from this study will help in the development of a more personalized nutrition approach for diverse populations.

Trial registration

This protocol has been preregistered with the Center for Open Science (https://doi.org/10.17605/OSF.IO/WPR9E) and is approved by the City University of New York Human Research Protection Program (IRB#: 2023-0064-Brooklyn).

The entero-endocrine response following a mixed-meal tolerance test with a non-nutritive pre-load in participants with pre-diabetes and type 2 diabetes: A crossover randomized controlled trial proof of concept study

INTRODUCTION

This crossover randomized controlled trial (RCT) investigated differences in short-term entero-endocrine response to a mixed-meal tolerance test preceded by nutrient sensing between participants with pre-diabetes (pre-T2D) and type 2 diabetes (T2D). Additionally, differences in gut and oral microbiome composition between participants with a high and low entero-endocrine response were investigated.

RESEARCH DESIGN AND METHODS

Ten participants with pre-T2D and ten with T2D underwent three test days with pre-loads consisting of either swallowing water (control), or rinsing with a non-nutritive sweetener solution, or swallowing the sweetener solution before a mixed-meal tolerance test. Blood glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), glucagon, glucose, insulin and peptide YY (PYY) were determined at t = -20, 0, 15, 30, 60, 120 and 240 minutes. The composition of the oral and gut microbiome at baseline were also determined.

RESULTS

The entero-endocrine response differed by pre-loads, e.g. a lower PYY response after swallowing the non-nutritive sweetener (-3585.2pg/mL [95% CI: -6440.6; -729.8]; p = 0.01). But it also differed by T2D status, e.g. a higher glucose, glucagon and PYY response was found in participants with T2D, compared to those with pre-T2D. Evidence for associations between the oral and gut microbiome composition and the entero-endocrine response was limited. Still, the level of entero-endocrine response was associated with several oral microbiome measures. Higher oral anterior α-diversity was associated with a lower PYY response (e.g. Inverse Simpson index -1357pg/mL [95% CI -2378; -336; 1.24]), and higher oral posterior α-diversitywith a higher GIP response (e.g. Inverse Simpson index 6773pg/mL [95% CI 132; 13414]) in models adjusted for sex, age and T2D status.

CONCLUSIONS

Non-nutritive pre-loads influence the entero-endocrine response to a mixed-meal, and this effect varies based on (pre-)T2D status. The entero-endocrine response is likely not associated with the gut microbiome, and there is limited evidence for association with the α-diversity of the oral microbiome composition.

TRIAL REGISTRATION

Trial register: Netherlands Trial Register NTR7212, accessible through International Clinical Trials Registry Platform: ICTRP Search Portal (who.int).

Finding the Sweet Spot: Measurement, Modification, and Application of Sweet Hedonics in Humans

Sweetness is a sensation that contributes to the palatability of foods, which is the primary driver of food choice. Thus, understanding how to measure the appeal (hedonics) of sweetness and how to modify it are key to effecting dietary change for health. Sweet hedonics is multidimensional so can only be captured by multiple approaches including assessment of elements such as liking, preference, and consumption intent. There are both innate and learned components to the appeal of sweet foods and beverages. These are responsive to various behavioral and biological factors, suggesting the opportunity to modify intake. Given the high amount of added sugar intake in the United States and recommendations from many groups to reduce this, further exploration of current hypothesized approaches to moderate sugar intake (e.g., induced hedonic shift, use of low-calorie sweeteners) is warranted.

Pharmacological significance of extra-oral taste receptors

It has recently been shown that taste receptors, in addition to being present in the oral cavity, exist in various extra-oral organs and tissues such as the thyroid, lungs, skin, stomach, intestines, and pancreas. Although their physiological function is not yet fully understood, it appears that they can help regulate the body's homeostasis and provide an additional defense function against pathogens. Since the vast majority of drugs are bitter, the greatest pharmacological interest is in the bitter taste receptors. In this review, we describe how bitter taste 2 receptors (TAS2Rs) induce bronchodilation and mucociliary clearance in the airways, muscle relaxation in various tissues, inhibition of thyroid stimulating hormone (TSH) in thyrocytes, and release of glucagon-like peptide-1 (GLP-1) and ghrelin in the digestive system. In fact, substances such as dextromethorphan, chloroquine, methimazole and probably glimepiride, being agonists of TAS2Rs, lead to these effects. TAS2Rs and taste 1 receptors (TAS1R2/3) are G protein-coupled receptors (GPCR). TAS1R2/3 are responsible for sweet taste perception and may induce GLP-1 release and insulin secretion. Umami taste receptors, belonging to the same superfamily of receptors, perform a similar function with regard to insulin. The sour and salty taste receptors work in a similar way, both being channel receptors sensitive to amiloride. Finally, gene-protein coupled receptor 40 (GPR40) and GPR120 for fatty taste perception are also protein-coupled receptors and may induce GLP-1 secretion and insulin release, similar to those of other receptors belonging to the same superfamily.

Sweet Taste Is Complex: Signaling Cascades and Circuits Involved in Sweet Sensation

Sweetness is the preferred taste of humans and many animals, likely because sugars are a primary source of energy. In many mammals, sweet compounds are sensed in the tongue by the gustatory organ, the taste buds. Here, a group of taste bud cells expresses a canonical sweet taste receptor, whose activation induces Ca²⁺ rise, cell depolarization and ATP release to communicate with afferent gustatory nerves. The discovery of the sweet taste receptor, 20 years ago, was a milestone in the understanding of sweet signal transduction and is described here from a historical perspective. Our review briefly summarizes the major findings of the canonical sweet taste pathway, and then focuses on molecular details, about the related downstream signaling, that are still elusive or have been neglected. In this context, we discuss evidence supporting the existence of an alternative pathway, independent of the sweet taste receptor, to sense sugars and its proposed role in glucose homeostasis. Further, given that sweet taste receptor expression has been reported in many other organs, the physiological role of these extraoral receptors is addressed. Finally, and along these lines, we expand on the multiple direct and indirect effects of sugars on the brain. In summary, the review tries to stimulate a comprehensive understanding of how sweet compounds signal to the brain upon taste bud cells activation, and how this gustatory process is integrated with gastro-intestinal sugar sensing to create a hedonic and metabolic representation of sugars, which finally drives our behavior. Understanding of this is indeed a crucial step in developing new strategies to prevent obesity and associated diseases.

Single nucleotide polymorphisms in sweet, fat, umami, salt, bitter and sour taste receptor genes are associated with gustatory function and taste preferences in young adults

Taste is a fundamental mechanism whereby compounds are detected orally, yet it is highly variable among individuals. The variability in taste that is attributable to genetics is not well-characterized despite its potential role in food selection, and therefore, eating habits that contribute to risk of overweight and obesity. In order to implicate measures of taste function and preference as potentially deterministic factors in adverse eating behaviors that lead to obesity, it must be shown that a relationship exists between genetic variation in taste receptor genes and psychophysical measures of taste in the absence high body mass index. The primary objective of this pilot study was to investigate the relationship between single nucleotide polymorphisms (SNPs) in taste receptor genes and 3 different psychophysical measures of taste in healthy young adults. Sweet, salt, umami, fat, sour, and bitter taste receptor gene SNPs were genotyped in 49 participants (ages 24.6 ± 0.6 years) who completed testing to determine oral detection threshold (DT), suprathreshold sensitivity (ST) and taste preference (PR). A simultaneous association test was conducted between each SNP and the 3 taste outcomes (DT, ST, and PR). Twelve SNPs were associated with at least one of the 3 taste outcomes. Associations were observed between SNPs in taste receptor genes and psychophysical measures of sweet, fat, umami, and salt taste. These results suggest that differences in interindividual psychophysical measures of tastes, namely DT, ST, and PR, may be partially attributed to genetic variation in taste receptor genes. Future studies are warranted to investigate if these findings have consequences for habitual dietary intake of foods that elicit these tastes.

The effects of kefir in mixed meals on appetite and food intake: a randomized cross-over trial

ABSTRACT Objective The natural probiotic kefir is fermented milk, and may have effects on satiety and voluntary energy intake. This randomized crossover trial aimed to determine whether kefir, consumed with low- or high-glycemic index meals, affects appetite and subsequent food intake. Methods Twenty four healthy females aged 21-24 years, were recruited from Erciyes University and the surrounding community. The participants were submitted to three different breakfasts: a low glycemic index accompanied by milk, a low glycemic index with kefir, and a high glycemic index with kefir, with a 1-week washout period between meals. At 0, 15, 30, 60, 90, 120, 150, and 180 minutes after the meal, appetite ratings were measured by the visual analog scale, and then ad libitum lunch was served. Results No differences in appetite scores and voluntary energy intake were detected between the test meals. Furthermore, palatability ratings were similar between test meals, except for the higher score of high glycemic index kefir for overall palatability. Conclusion This study demonstrated that adding kefir to a high glycemic index meal may prevent increases in appetite and food intake, resulting in postprandial responses similar to those of a low glycemic index meal. These findings might enable the development of novel dietary strategies based on appetite regulation to treat or prevent obesity, particularly for Western societies. This trial was registered at ClinicalTrials.gov under the process NCT03636217.

Immune Regulatory Roles of Cells Expressing Taste Signaling Elements in Nongustatory Tissues

G protein-coupled taste receptors and their downstream signaling elements, including Gnat3 (also known as α-gustducin) and TrpM5, were first identified in taste bud cells. Subsequent studies, however, revealed that some cells in nongustatory tissues also express taste receptors and/or their signaling elements. These nongustatory-tissue-expressed taste receptors and signaling elements play important roles in a number of physiological processes, including metabolism and immune responses. Special populations of cells expressing taste signaling elements in nongustatory tissues have been described as solitary chemosensory cells (SCCs) and tuft cells, mainly based on their morphological features and their expression of taste signaling elements as a critical molecular signature. These cells are typically scattered in barrier epithelial tissues, and their functions were largely unknown until recently. Emerging evidence shows that SCCs and tuft cells play important roles in immune responses to microbes and parasites. Additionally, certain immune cells also express taste receptors or taste signaling elements, suggesting a direct link between chemosensation and immune function. In this chapter, we highlight our current understanding of the functional roles of these "taste-like" cells and taste signaling pathways in different tissues, focusing on their activities in immune regulation.

Consuming Gymnema sylvestre Reduces the Desire for High-Sugar Sweet Foods

Background. Gymnemic acids, from the plant Gymnema sylvestre (GS), selectively suppress taste responses to sweet compounds without affecting the perception of other taste elements. The aim of this study was to investigate the effect of consuming a GS-containing mint on the desire to consume high-sugar sweet foods directly thereafter. Methods. This study utilized a single-blind, crossover design comparing the consumption of a mint (dissolving tablet) containing 4 mg of gymnemic acids with an isocaloric placebo in 56 healthy young men and women. Participants were given samples of their favourite chocolate (varied between 14–18 g; energy varied between 292–370 kJ) and were directed to rate on their hunger on 100-mm visual analogue scales 30 s prior to consuming high-sugar sweet food (chocolate). They then consumed the GS mint or placebo mint and rated their perceived pleasantness and desire for more chocolate on separate visual analogue scales immediately following consumption of the high-sugar sweet food before being offered up to five additional servings (and asked to rate hunger, pleasantness and desire to eat more chocolate between each ingestion period). Results. The number of chocolate bars eaten decreased by 0.48 bars (21.3%) within a 15-min period of consumption of the GS mint (p = 0.006). Desire to eat more of the high-sugar sweet food (p = 0.011) and pleasantness of the high-sugar sweet food (p < 0.001) was reduced after GS mint intake. Those who reported having a ‘sweet tooth’ had a greater reduction in the pleasantness of chocolate (p = 0.037) and desire to eat more (p = 0.004) after consuming the GS mint for the first serving of a high-sugar sweet food following the mint. Conclusion. Consuming gymnema-containing mints compared to placebo significantly reduced the quantity of chocolate eaten mainly due to a decrease in the desire and pleasantness of consuming it.

Evaluation of Sweetener Synergy in Humans by Isobole Analyses

The chemical senses and pharmaceuticals fundamentally depend on similar biological processes, but novel molecule discovery has classically been approached from vastly different vantage points. From the perspective of ingredient and flavor companies, there are countless ingredients that act via largely unknown mechanisms, whereas the pharmaceutical industry has numerous mechanisms in search of novel compounds. Mixtures of agonists can result in synergistic (superadditive) responses, which can be quantified via isobole analysis, a well-proven clinical approach in pharmacology. For the food and beverage industries, bulk (caloric) sweeteners like sugars are a key ingredient in sweetened foods and beverages, but consumers also desire products with fewer calories, which has led to the development of sweet enhancers and sweetener blends intended to achieve synergy or superadditivity. Synergistic mixtures are highly attractive targets commercially as they enable lower usage levels and enhanced efficacy. Although the psychophysical literature contains numerous prior reports of sweetener synergy, others have also noted that classical additive models fail to account for nonlinear dose-response functions. To address this shortcoming, here we systematically apply the isobole method from pharmacology to quantify the presence or absence of psychophysical synergy for binary pairs of sweeteners in a series of 15 separate experiments, each with ~100 adult volunteers (total n = 1576). Generally, these data support the hypothesis that structurally similar sweeteners acting as agonists will not synergize, whereas structurally dissimilar sweeteners binding to overlapping or distal sites can act as allosteric agonists or agonist-antagonists, respectively.

Taste Perception and Cerebral Activity in the Human Gustatory Cortex Induced by Glucose, Fructose, and Sucrose Solutions

Glucose, fructose, and sucrose are important carbohydrates in Western diets with particular sweetness intensity and metabolisms. No study has compared their cerebral detection and their taste perception. Gustatory evoked potentials (GEPs), taste detection thresholds, intensity perception, and pleasantness were compared in response to glucose, fructose, and sucrose solutions at similar sweetness intensities and at identical molar concentrations. Twenty-three healthy subjects were randomly stimulated with 3 solutions of similar sweetness intensity (0.75 M of glucose, 0.47 M of fructose and 0.29 M of sucrose - sit. A), and with an identical molar concentration (0.29 M - sit. B). GEPs were recorded at gustatory cortex areas. Intensity perception and hedonic values of each solution were evaluated as were gustatory thresholds of the solutions. No significant difference was observed concerning the GEP characteristics of the solutions according to their sweetness intensities (sit. A) or their molar concentration (sit. B). In sit. A, the 3 solutions were perceived to have similar intensities and induced similar hedonic sensations. In sit. B, the glucose solution was perceived to be less intense and pleasant than the fructose and the sucrose solutions (P < 0.001) and the fructose solution was perceived to be less intense and pleasant than the sucrose (P < 0.001). Since GEP recordings were similar for glucose, fructose, and sucrose solutions whatever the concentrations, activation of same taste receptor induces similar cortical activation, even when the solutions were perceived differently. Sweet taste perception seems to be encoded by a complex chemical cerebral neuronal network.

Changes in Oral Health Behaviors Associated With a Nursing Intervention in Primary Care

Objective. To describe changes in oral health behaviors following implementation of a nursing intervention targeting children at risk for early childhood caries at an urban 2-site primary care practice. Methods. Nurses used a proprietary Nursing Caries Assessment Tool (N-CAT) to identify behaviors associated with early childhood caries risk, then provided brief focused dental education, fluoride varnish applications, and dental referrals to children without a dental home. We used generalized estimating equation logistic regression models, adjusted for age at visit, to analyze changes in oral health behaviors over time including the following: (1) tooth brushing frequency, (2) use of fluoride toothpaste, and (3) adult help with brushing among children younger than 5 years of age who had at least 2 N-CATs documented during well care visits between April 2013 and June 2015. We also evaluated dietary habits including going to bed with a bottle or sippy cup and sugar-sweetened beverage consumption, as secondary study outcomes during the same time frame. Results. A total of 2097 children with a mean age of 15.8 (SD 7.6) months at the initial visit were included in the analysis; 51% were boys; 28% were black, 36% Hispanic/Latino, 5% white, 2% Asian, and 19% other; 75% were publicly insured. During the study period, significant (P < .05) improvements were noted across the 3 oral health behaviors studied among children younger than 18 months. Conclusion. Nursing interventions show promise for promoting preventive dental care in primary care settings and deserve further study.

The top five selling UK energy drinks: implications for dental and general health

Aim Energy drinks are widely consumed worldwide and are recognised for their adverse health effects, usually due to their high caffeine content. However, little is known about their impact on oral and general health. The aim of this investigation was to review the most popular energy drinks sold in the UK, for their possible effect on oral health and contribution to obesity. Materials and methods Five drinks representing 75% of the UK energy drinks market were purposively selected (Lucozade, Red Bull, Monster, Rockstar and Relentless). pH and sugar content were measured and their ingredients reviewed in the context of oral and general health, focusing on dental caries and erosion and obesity. Results All five energy drinks investigated had pH values below the critical value (5.5) associated with dental erosion; the lowest pH was 2.72 (Lucozade) and the highest was 3.37 (Monster). The drinks also contained excessive amounts of free sugars, ranging from 25.5 g (Red Bull) to 69.2 g (Rockstar). Differences in sugar content were mainly explained by portion size. Other ingredients contained within the energy drinks, caffeine and various acids, are also linked to oral and general health. Conclusion Regular consumption of energy drinks could contribute to dental erosion and the development of obesity. Lucozade and Rockstar were found to potentially have the greatest impact on oral health and obesity. Achieving a healthy product by reformulation is highly unlikely due to the very high initial free sugar content. Thus, health professionals need to acknowledge the popularity of these products and help their clients to reduce their use. This is the first study which compares in detail the potential oral and general health consequences of overuse of a selection of energy drinks popular in the UK.

Exploring parenting variables associated with sweetness preferences and sweets intake of children

BACKGROUND/OBJECTIVES

Excessive sugar intake is one of the causes associated with obesity and several chronic diseases prevalent in the modern society. This study was undertaken to investigate the effect of parenting variables based on the theory of planned behavior, on the sweetness preferences and sweets intake of children.

SUBJECTS/METHODS

Parents and their children (n = 103, aged 5–7 years) were enrolled to participate in a survey for this study, after providing the required informed consent. Parents were asked to fill out a self-administered questionnaire at their residence. The sweetness preference test for children was conducted at a kindergarten (or daycare center) by applying the one-on-one interview method.

RESULTS

The children were divided into two clusters categorized by the K-mean cluster analysis: Cluster 1 had higher sweetness preference (0.42 M sugar, 35%; 0.61 M sugar, 65%); Cluster 2 exhibited lower sweetness preference (0.14 M sugar, 9.5%; 0.20 M sugar, 9.5%; 0.29 M sugar, 81%). Cluster 1 had a higher frequency of sweets intake (P < 0.01), and lower sweets restriction (P < 0.05) and nutrition quotient score (P < 0.05). Sweets intake was negatively correlated with the nutritional quotient (r = −0.204, P < 0.05). The behavioral intention of parents was higher in cluster 2 (P < 0.05), while affective attitude, feeding practice, and reward were higher in cluster 1 (P < 0.001, P < 0.05, and P < 0.01, respectively). Furthermore, behavioral intention of parents showed a negative correlation with affective attitude (r = −0.282, P < 0.01) and feeding practice (r = −0.380, P < 0.01), and a positive correlation with subjective norm (r = 0.203, P < 0.05) and parenting attitude (r = 0.433, P < 0.01).

CONCLUSIONS

This study indicates that the sweetness preferences and sweets intake of children is related to the parent's affective attitude, feeding practice and reward. We suggest that to reduce the sugar consumption of children, guidelines for access to sweets and pertinent parenting practices are required.

The Relationship between Single Nucleotide Polymorphisms in Taste Receptor Genes, Taste Function and Dietary Intake in Preschool-Aged Children and Adults in the Guelph Family Health Study

Taste is a fundamental determinant of food selection, and inter-individual variations in taste perception may be important risk factors for poor eating habits and obesity. Characterizing differences in taste perception and their influences on dietary intake may lead to an improved understanding of obesity risk and a potential to develop personalized nutrition recommendations. This study explored associations between 93 single nucleotide polymorphisms (SNPs) in sweet, fat, bitter, salt, sour, and umami taste receptors and psychophysical measures of taste. Forty-four families from the Guelph Family Health Study participated, including 60 children and 65 adults. Saliva was collected for genetic analysis and parents completed a three-day food record for their children. Parents underwent a test for suprathreshold sensitivity (ST) and taste preference (PR) for sweet, fat, salt, umami, and sour as well as a phenylthiocarbamide (PTC) taste status test. Children underwent PR tests and a PTC taste status test. Analysis of SNPs and psychophysical measures of taste yielded 23 significant associations in parents and 11 in children. After adjusting for multiple hypothesis testing, the rs713598 in the TAS2R38 bitter taste receptor gene and rs236514 in the KCNJ2 sour taste-associated gene remained significantly associated with PTC ST and sour PR in parents, respectively. In children, rs173135 in KCNJ2 and rs4790522 in the TRPV1 salt taste-associated gene remained significantly associated with sour and salt taste PRs, respectively. A multiple trait analysis of PR and nutrient composition of diet in the children revealed that rs9701796 in the TAS1R2 sweet taste receptor gene was associated with both sweet PR and percent energy from added sugar in the diet. These findings provide evidence that for bitter, sour, salt, and sweet taste, certain genetic variants are associated with taste function and may be implicated in eating patterns. (Support was provided by the Ontario Ministry of Agriculture, Food, and Rural Affairs).

Stevioside modulates oxidative damage in the liver and kidney of high fat/low streptozocin diabetic rats

This study investigated the potential of stevioside to prevent oxidative DNA damage in the liver and kidney of type 2 diabetes mellitus (T2DM) using high fat-low streptozocin rat model. Rats were treated daily with 12.5, 25 and 50 mg/kg stevioside orally for 21 days. Levels of biomarkers of T2DM, lipid profile and oxidative stress were assayed spectrophotometrically. The DNA ladder assay method was used to assess DNA fragmentation in the liver and kidney while computational analysis was used to predict the mechanisms of antidiabetic properties of stevioside. Stevioside significantly (p < 0.05) decreased the levels of plasma glucose, insulin, dipeptidyl peptidase IV and activities of kidney angiotensin converting enzyme. Stevioside significantly reduced oxidative stress by decreasing the levels of lipid peroxidation and nitric oxide in the liver and kidney; thereby, reducing the extent of DNA fragmentation in the liver and kidney of the diabetic rats. The in silico analysis showed that the ability of stevioside to exert these effects is linked to its inhibition of beta-adrenergic receptor kinase and G-protein-coupled receptor kinase. The results of this study suggest that the prevention of DNA fragmentation may be an additional benefit of the use of stevioside in the management of T2DM.

Single Nucleotide Polymorphisms in Taste Receptor Genes Are Associated with Snacking Patterns of Preschool-Aged Children in the Guelph Family Health Study: A Pilot Study

Snacking is an integral component of eating habits in young children that is often overlooked in nutrition research. While snacking is a substantial source of calories in preschoolers' diets, there is limited knowledge about the factors that drive snacking patterns. The genetics of taste may help to better understand the snacking patterns of children. The rs1761667 single nucleotide polymorphism (SNP) in the CD36 gene has been linked to fat taste sensitivity, the rs35874116 SNP in the TAS1R2 gene has been related to sweet taste preference, and the rs713598 SNP in the TAS2R38 gene has been associated with aversion to bitter, green leafy vegetables. This study seeks to determine the cross-sectional associations between three taste receptor SNPs and snacking patterns among preschoolers in the Guelph Family Health Study. Preschoolers' snack quality, quantity, and frequency were assessed using three-day food records and saliva was collected for SNP genotyping (n = 47). Children with the TT genotype in TAS1R2 consumed snacks with significantly more calories from sugar, and these snacks were consumed mostly in the evening. Total energy density of snacks was highest in the CC and CG genotypes compared to the GG genotype in TAS2R38, and also greater in the AA genotype in CD36 compared to G allele carriers, however this difference was not individually attributable to energy from fat, carbohydrates, sugar, or protein. Genetic variation in taste receptors may influence snacking patterns of preschoolers.

Oral health and the frailty syndrome

The frailty syndrome is an ever-growing area of study among older adults because of its association with an increased risk of falls, hospitalization, institutionalization, dependency and mortality. Frailty is neither a disease nor a disability but is better understood as a medical syndrome of multisystem dysregulation that results in a diminished ability to overcome everyday stressors. The prevalence of frailty in any given population can vary widely, in part because of the way in which it is defined and measured, but in general it is higher among women and in those with advanced age and declining health. Whilst it is largely understood that older adults will differ biologically, psychologically and socially, and that each of these domains can impact oral health, we are only beginning to investigate how the mouth is affected in frailty. Given that both hard and soft structures contribute to oral health and disease status among older adults with varying degrees of impairment and disability, frailty adds yet another dimension to be considered. This paper will discuss how frailty can influence and be influenced by oral disorders, as well as the potential relationship to oral neglect and the resultant consequences among this vulnerable population.

Personal Variation in Preference for Sweetness: Effects of Age and Obesity

BACKGROUND

Use of nonnutritive sweeteners (NNSs), which provide sweet taste with few to no calories, has increased, but data on whether children's hedonic responses to NNSs differ from nutritive sugars or from adults' hedonic responses are limited.

METHODS

Most preferred levels of sucrose and the NNS sucralose were determined via a forced-choice tracking procedure in 48 children, 7-14 years (mean = 10 years), and 34 adults. Each participant also rated the liking of these taste stimuli, as well as varying concentrations of aspartame on 3- and 5-point facial hedonic scales. Anthropometric measures were obtained, and motives for palatable food intake were assessed with the Palatable Eating Motives Scale (PEMS, adults) and Kids PEMS.

RESULTS

While use of the 3-point scale showed no age-related differences in liking of sweeteners, the 5-point scale showed that more children than adults liked higher concentrations of sucrose, sucralose, and aspartame, and the tracking procedure showed that children most preferred higher concentrations of sucrose and sucralose than adults. Regardless of age, sweet preference did not differ between obese and nonobese participants and showed no association with motives for eating palatable foods. Children's body mass index z-scores were positively associated with social and conformity motive scores for eating palatable foods.

CONCLUSION

Research should move beyond measures of variation in sweet taste hedonics to include identifying motives, and the physiological and psychological consequences of eating sweets, to shed light on what children are more vulnerable to develop unfavorable eating habits, increasing risk for obesity, and other diseases.

Sugar addiction: is it real? A narrative review

In animal studies, sugar has been found to produce more symptoms than is required to be considered an addictive substance. Animal data has shown significant overlap between the consumption of added sugars and drug-like effects, including bingeing, craving, tolerance, withdrawal, cross-sensitisation, cross-tolerance, cross-dependence, reward and opioid effects. Sugar addiction seems to be dependence to the natural endogenous opioids that get released upon sugar intake. In both animals and humans, the evidence in the literature shows substantial parallels and overlap between drugs of abuse and sugar, from the standpoint of brain neurochemistry as well as behaviour.

Is Sweet Taste Perception Associated with Sweet Food Liking and Intake?

A range of psychophysical taste measurements are used to characterize an individual’s sweet taste perception and to assess links between taste perception and dietary intake. The aims of this study were to investigate the relationship between four different psychophysical measurements of sweet taste perception, and to explore which measures of sweet taste perception relate to sweet food intake. Forty-four women aged 20–40 years were recruited for the study. Four measures of sweet taste perception (detection and recognition thresholds, and sweet taste intensity and hedonic liking of suprathreshold concentrations) were assessed using glucose as the tastant. Dietary measurements included a four-day weighed food record, a sweet food-food frequency questionnaire and a sweet beverage liking questionnaire. Glucose detection and recognition thresholds showed no correlation with suprathreshold taste measurements or any dietary intake measurement. Importantly, sweet taste intensity correlated negatively with total energy and carbohydrate (starch, total sugar, fructose, glucose) intakes, frequency of sweet food intake and sweet beverage liking. Furthermore, sweet hedonic liking correlated positively with total energy and carbohydrate (total sugar, fructose, glucose) intakes. The present study shows a clear link between sweet taste intensity and hedonic liking with sweet food liking, and total energy, carbohydrate and sugar intake.

The development of sweet taste: From biology to hedonics

From the age of 2 years, an American child is more likely to consume a sugar-sweetened product than a fruit or vegetable on any given day-a troubling statistic, given that food preferences are established early in childhood, as well as the strong association between this dietary pattern and increased risk of developing a number of chronic diseases. Here, we review the ontogeny and biopsychology of sweet taste, highlighting how a biological drive to prefer sweetness at high concentrations during childhood, which would have conferred an advantage in environments of scarcity, now predisposes children to overconsume all that is sweet in a modern food system replete with added sugars. We review the power of sweet taste to blunt expressions of pain and mask bad tastes in foods as well as factors that predispose some to consume high-sugar diets, including experiential learning and taste preferences driven in part by genetics. Understanding children's unique vulnerability to our current food environment, rich in both nutritive and nonnutritive sweeteners, is highlighted as a priority for future research to develop evidence-based strategies to help establish healthy dietary behaviors early in life.

Individual Differences Among Children in Sucrose Detection Thresholds: Relationship With Age, Gender, and Bitter Taste Genotype

BACKGROUND

Little research has focused on whether there are individual differences among children in their sensitivity to sweet taste and, if so, the biological correlates of such differences.

OBJECTIVES

Our goal was to understand how variations in children's sucrose detection thresholds relate to their age and gender, taste genotype, body composition, and dietary intake of added sugars.

METHODS

Sucrose detection thresholds in 7- to 14-year-old children were tested individually using a validated, two-alternative, forced-choice, paired-comparison tracking method. Five genetic variants of taste genes were assayed: TAS1R3 and GNAT3 (sweet genes; one variant each) and the bitter receptor gene TAS2R38 (three variants). All children were measured for body weight and height. A subset of these children were measured for the percentage of body fat and waist circumference and provided added sugar intake by 24-hour dietary recall.

RESULTS

Sucrose thresholds ranged from 0.23 to 153.8 mM with most of the children completing the threshold task (216/235; 92%). Some children were biologically related (i.e., siblings), and for the genetic analysis, one sibling from each family was studied. Variants in the bitter but not the sweet genes were related to sucrose threshold and sugar intake; children with two bitter-sensitive alleles could detect sucrose at lower concentrations (F(2,165) = 4.55, p = .01; rs1726866) and reported eating more added sugar (% kcal; F(2, 62) = 3.64, p = .03) than did children with less sensitive alleles. Age, gender, and indices of obesity also were related to child-to-child differences in sucrose threshold; girls were more sensitive than boys (t(214) = 2.0, p = .05), older children were more sensitive than younger children (r(214) = -.16, p = .02), and fatter (r(84) = -.22, p = .05) or more centrally obese children (r(84) = -.26, p = .02) were more sensitive relative to others.

DISCUSSION

Inborn differences in bitter sensitivity may affect childhood dietary sugar intake with long-term health consequences. There may be a more complex interplay between the developing bitter and sweet taste systems than previously understood.

Genetics of taste receptors

Taste receptors function as one of the interfaces between internal and external milieus. Taste receptors for sweet and umami (T1R [taste receptor, type 1]), bitter (T2R [taste receptor, type 2]), and salty (ENaC [epithelial sodium channel]) have been discovered in the recent years, but transduction mechanisms of sour taste and ENaC-independent salt taste are still poorly understood. In addition to these five main taste qualities, the taste system detects such noncanonical "tastes" as water, fat, and complex carbohydrates, but their reception mechanisms require further research. Variations in taste receptor genes between and within vertebrate species contribute to individual and species differences in taste-related behaviors. These variations are shaped by evolutionary forces and reflect species adaptations to their chemical environments and feeding ecology. Principles of drug discovery can be applied to taste receptors as targets in order to develop novel taste compounds to satisfy demand in better artificial sweeteners, enhancers of sugar and sodium taste, and blockers of bitterness of food ingredients and oral medications.

Does sucrose intake affect antropometric variables, glycemia, lipemia and C-reactive protein in subjects with type 1 diabetes?: a controlled-trial

BACKGROUND

It is unclear if the sugar intake may affect metabolic parameters in individuals with type 1 diabetes. Therefore, the purpose of this study was to evaluate the effects of sucrose intake in glycemic, lipemic, anthropometric variables, as well as in C-reactive protein (CRP) levels in these individuals.

METHODS

Thirty-three subjects with type 1 diabetes were evaluated at baseline and 3-months after intervention. Volunteers were randomized into groups: sucrose-free (diet without sucrose) or sucrose-added (foods containing sucrose in composition). Both groups received the same macronutrient composition and used the carbohydrate counting methods. All underwent an interview and anthropometric evaluation. Blood was drawn for glycated haemoglobin, glucose, total cholesterol, HDL, and CRP measurement, and the medical charts were reviewed in all cases.

RESULTS

At baseline, anthropometric, clinical and laboratory variables did not differ between groups, except for the triglycerides. Although at baseline triglycerides levels were higher in the sucrose-added group (p = 0.01), they did not differ between groups after the intervention (p = 0.92). After 3-months, CRP was higher in the sucrose-added than in the sucrose-free group (p = 0.04), but no further differences were found between the groups, including the insulin requirements, anthropometric variables, body composition, and glycemic control. Both groups showed sugars intake above the recommendations at baseline and after intervention.

CONCLUSIONS

Sucrose intake, along with a disciplined diet, did not affect insulin requirements, anthropometric variables, body composition, lipemic and glycemic control. However, although the sucrose intakes increase CRP levels, the amount of sugar in the diet was not associated with this inflammatory marker.

A preference test for sweet taste that uses edible strips

A novel delivery method is described for the rapid determination of taste preferences for sweet taste in humans. This forced-choice paired comparison approach incorporates the non-caloric sweetener sucralose into a set of one-inch square edible strips for the rapid determination of sweet taste preferences. When compared to aqueous sucrose solutions, significantly lower amounts of sucralose were required to identify the preference for sweet taste. The validity of this approach was determined by comparing sweet taste preferences obtained with five different sucralose-containing edible strips to a set of five intensity-matched sucrose solutions. When compared to the solution test, edible strips required approximately the same number of steps to identify the preferred amount of sweet taste stimulus. Both approaches yielded similar distribution patterns for the preferred amount of sweet taste stimulus. In addition, taste intensity values for the preferred amount of sucralose in strips were similar to that of sucrose in solution. The hedonic values for the preferred amount of sucralose were lower than for sucrose, but the taste quality of the preferred sucralose strip was described as sweet. When taste intensity values between sucralose strips and sucralose solutions containing identical amounts of taste stimulus were compared, sucralose strips produced a greater taste intensity and more positive hedonic response. A preference test that uses edible strips for stimulus delivery should be useful for identifying preferences for sweet taste in young children, and in clinical populations. This test should also be useful for identifying sweet taste preferences outside of the lab or clinic. Finally, edible strips should be useful for developing preference tests for other primary taste stimuli and for taste mixtures.

Beyond the Paleolithic prescription: incorporating diversity and flexibility in the study of human diet evolution

Evolutionary paradigms of human health and nutrition center on the evolutionary discordance or "mismatch" model in which human bodies, reflecting adaptations established in the Paleolithic era, are ill-suited to modern industrialized diets, resulting in rapidly increasing rates of chronic metabolic disease. Though this model remains useful, its utility in explaining the evolution of human dietary tendencies is limited. The assumption that human diets are mismatched to the evolved biology of humans implies that the human diet is instinctual or genetically determined and rooted in the Paleolithic era. This review looks at current research indicating that human eating habits are learned primarily through behavioral, social, and physiological mechanisms that start in utero and extend throughout the life course. Adaptations that appear to be strongly genetic likely reflect Neolithic, rather than Paleolithic, adaptations and are significantly influenced by human niche-constructing behavior. Several examples are used to conclude that incorporating a broader understanding of both the evolved mechanisms by which humans learn and imprint eating habits and the reciprocal effects of those habits on physiology would provide useful tools for structuring more lasting nutrition interventions.

Sweet preference modified by early experience in mice and the related molecular modulations on the peripheral pathway

The sweet taste is of immense interest to scientists and has been intensively studied during the last two decades. However, the sweet preference modification and the related mechanisms are still unclear. In this study, we try to establish a mice model with manipulated sweet taste preference and explore the involved possible molecular mechanisms. The animals were exposed to acesulfame-K via maternal milk during lactation and the sweet preference tests were carried out when they grew to adulthood. Our results showed that the preference thresholds for sweet taste were increased in adults by early acesulfame-K exposure and the preference ratios for sweet tastants at low or preferred concentrations were decreased. Moreover, by means of qRT-PCR and Western blot, we observed the increased expression of leptin receptor Ob-Rb and downregulation of Gα-gustducin protein in the soft palate. Thereby, the sweet taste sensitivity may be modified by early sweetener experience during lactation. Along the peripheral sweet sensory pathway, the sweet regulator receptors Ob-Rb, CB1 and components of sweet transduction signal Gα-gustducin and T1R2 in both the soft palate and tongue may be cooperatively involved in the plastic development of sweet taste.

Taking the bitter with the sweet: relationship of supertasting and sweet preference with metabolic syndrome and dietary intake

Results examining the effects of tasting profile on dietary intake and health outcomes have varied. This study examined the interaction of sweet liker (SL) and supertaster (ST) (bitter taste test through phenylthiocarbamide [PTC]) status with incidence of metabolic syndrome. Participants (n = 196) as part of baseline testing in a behavioral weight loss study completed measures assessing SL and ST status, metabolic syndrome, and dietary intake. SLs were more likely to be African American. More women than men were STs. There was a significant interaction between ST and SL status as associated with metabolic syndrome, after adjustment for demographic characteristics. This interaction was also significantly associated with fiber and caloric beverage intake. Post hoc analyses showed that participants who were only an ST or SL appeared to have a decreased risk of having metabolic syndrome compared with those who have a combination or are neither taster groups (P = 0.047) and that SL + ST consumed less fiber than SL + non-ST (P = 0.04). Assessing genetic differences in taster preferences may be a useful strategy in the development of more tailored approaches to dietary interventions to prevent and treat metabolic syndrome.

PRACTICAL APPLICATION

Tasting profile, such as sweet liking (SL) or supertaster (ST), may be influenced by genetics, and therefore in turn, may influence dietary intake. The present study found an interaction between ST and SL status with incidence of metabolic syndrome and fiber and caloric beverage intake. Testing people for these tasting profiles may assist with tailoring dietary recommendations, particularly around fiber and caloric beverage intake, and provide a way to modify metabolic syndrome risk.

Sweetness and food preference

Human desire for sweet taste spans all ages, races, and cultures. Throughout evolution, sweetness has had a role in human nutrition, helping to orient feeding behavior toward foods providing both energy and essential nutrients. Infants and young children in particular base many of their food choices on familiarity and sweet taste. The low cost and ready availability of energy-containing sweeteners in the food supply has led to concerns that the rising consumption of added sugars is the driving force behind the obesity epidemic. Low-calorie sweeteners are one option for maintaining sweet taste while reducing the energy content of children's diets. However, their use has led to further concerns that dissociating sweetness from energy may disrupt the balance between taste response, appetite, and consumption patterns, especially during development. Further studies, preferably based on longitudinal cohorts, are needed to clarify the developmental trajectory of taste responses to low-calorie sweeteners and their potential impact on the diet quality of children and youth.

The scientific exploration of saliva in the post-proteomic era: from database back to basic function

The proteome of human saliva can be considered as being essentially completed. Diagnostic markers for a number of diseases have been identified among salivary proteins and peptides, taking advantage of saliva as an easy-to-obtain biological fluid. Yet, the majority of disease markers identified so far are serum components and not intrinsic proteins produced by the salivary glands. Furthermore, despite the fact that saliva is essential for protecting the oral integuments and dentition, little progress has been made in finding risk predictors in the salivary proteome for dental caries or periodontal disease. Since salivary proteins, and in particular the attached glycans, play an important role in interactions with the microbial world, the salivary glycoproteome and other post-translational modifications of salivary proteins need to be studied. Risk markers for microbial diseases, including dental caries, are likely to be discovered among the highly glycosylated major protein species in saliva. This review will attempt to raise new ideas and also point to under-researched areas that may hold promise for future applicability in oral diagnostics and prediction of oral disease.

Heritable differences in chemosensory ability among humans

The combined senses of taste, smell and the common chemical sense merge to form what we call ‘flavor.’ People show marked differences in their ability to detect many flavors, and in this paper, we review the role of genetics underlying these differences in perception. Most of the genes identified to date encode receptors responsible for detecting tastes or odorants. We list these genes and describe their characteristics, beginning with the best-studied case, that of differences in phenylthiocarbamide (PTC) detection, encoded by variants of the bitter taste receptor gene TAS2R38. We then outline examples of genes involved in differences in sweet and umami taste, and discuss what is known about other taste qualities, including sour and salty, fat (termed pinguis), calcium, and the ‘burn’ of peppers. Although the repertoire of receptors involved in taste perception is relatively small, with 25 bitter and only a few sweet and umami receptors, the number of odorant receptors is much larger, with about 400 functional receptors and another 600 potential odorant receptors predicted to be non-functional. Despite this, to date, there are only a few cases of odorant receptor variants that encode differences in the perception of odors: receptors for androstenone (musky), isovaleric acid (cheesy), cis-3-hexen-1-ol (grassy), and the urinary metabolites of asparagus. A genome-wide study also implicates genes other than olfactory receptors for some individual differences in perception. Although there are only a small number of examples reported to date, there may be many more genetic variants in odor and taste genes yet to be discovered.

Reliability of a common solution-based taste perception test: implications for validity and a briefer test

The aim of this study was to assess test-retest reliability of a common method for quantifying taste perception and its association with gustatory responses and individual risk for obesity and related health conditions. Forty-six healthy adults rated 20 mixtures comprised of 5 dairy beverages varied in fat content and mixed with sugar concentrations of 0%, 5%, 10%, and 20%, following existing procedures. Individuals rated the sweetness, creaminess, and pleasantness of each mixture during two taste testing sessions occurring 7±2 days apart. Test-retest correlations were of the expected magnitudes (r≥.50) only for the pleasantness ratings of mixtures with higher sugar concentrations. Correlations for sweetness and creaminess taste perception ratings were low, indicating that such ratings may not be reliable over approximately one week, and challenging the validity of such ratings for measuring trait taste perception. A shortened version of the test may be warranted.

Genetics of sweet taste preferences

Sweet taste is a powerful factor influencing food acceptance. There is considerable variation in sweet taste perception and preferences within and among species. Although learning and homeostatic mechanisms contribute to this variation in sweet taste, much of it is genetically determined. Recent studies have shown that variation in the T1R genes contributes to within- and between-species differences in sweet taste. In addition, our ongoing studies using the mouse model demonstrate that a significant portion of variation in sweetener preferences depends on genes that are not involved in peripheral taste processing. These genes are likely involved in central mechanisms of sweet taste processing, reward and/or motivation. Genetic variation in sweet taste not only influences food choice and intake, but is also associated with proclivity to drink alcohol. Both peripheral and central mechanisms of sweet taste underlie correlation between sweet-liking and alcohol consumption in animal models and humans. All these data illustrate complex genetics of sweet taste preferences and its impact on human nutrition and health. Identification of genes responsible for within- and between-species variation in sweet taste can provide tools to better control food acceptance in humans and other animals.

Genetics of taste and smell: poisons and pleasures

Eating is dangerous. While food contains nutrients and calories that animals need to produce heat and energy, it may also contain harmful parasites, bacteria, or chemicals. To guide food selection, the senses of taste and smell have evolved to alert us to the bitter taste of poisons and the sour taste and off-putting smell of spoiled foods. These sensory systems help people and animals to eat defensively, and they provide the brake that helps them avoid ingesting foods that are harmful. But choices about which foods to eat are motivated by more than avoiding the bad; they are also motivated by seeking the good, such as fat and sugar. However, just as not everyone is equally capable of sensing toxins in food, not everyone is equally enthusiastic about consuming high-fat, high-sugar foods. Genetic studies in humans and experimental animals strongly suggest that the liking of sugar and fat is influenced by genotype; likewise, the abilities to detect bitterness and the malodors of rotting food are highly variable among individuals. Understanding the exact genes and genetic differences that affect food intake may provide important clues in obesity treatment by allowing caregivers to tailor dietary recommendations to the chemosensory landscape of each person.

The receptor basis of sweet taste in mammals

The taste of sweeteners is hedonically pleasing, suggests high caloric value in food, and contributes to increased intake. In recent years, many of the molecular mechanisms underlying the detection of sweeteners have been elucidated. Of particular note is the identification of the sweet taste receptor, the heteromeric G-protein-coupled receptor T1R2:T1R3, which responds to a vast array of chemically diverse natural and artificial sweeteners. In this chapter, we discuss some of the mechanisms underlying the detection of sweeteners by mammals, with a particular focus on the function and role of the T1R2:T1R3 receptor in these processes.

Taste receptor genes

In the past several years, tremendous progress has been achieved with the discovery and characterization of vertebrate taste receptors from the T1R and T2R families, which are involved in recognition of bitter, sweet, and umami taste stimuli. Individual differences in taste, at least in some cases, can be attributed to allelic variants of the T1R and T2R genes. Progress with understanding how T1R and T2R receptors interact with taste stimuli and with identifying their patterns of expression in taste cells sheds light on coding of taste information by the nervous system. Candidate mechanisms for detection of salts, acids, fat, complex carbohydrates, and water have also been proposed, but further studies are needed to prove their identity.