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International Journal of Environmental... Sep 2021The notion of food "addiction" often focuses on the overconsumption of sweet tasting foods or so-called sugar "addiction". In the extreme, some have suggested that sugar... (Review)
Review
The notion of food "addiction" often focuses on the overconsumption of sweet tasting foods or so-called sugar "addiction". In the extreme, some have suggested that sugar and sweet tastes elicit neural and behavioral responses analogous to those observed with drugs of abuse. These concepts are complicated by the decades long uncertainty surrounding the validity and reproducibility of functional magnetic resonance imaging (fMRI) methodologies used to characterize neurobiological pathways related to sugar and sweet taste stimuli. There are also questions of whether sweet taste or post-ingestion metabolic consequences of sugar intake would lead to addiction or excessive caloric intake. Here, we present a focused narrative review of literature related to the reward value of sweet taste which suggests that reward value can be confounded with the construct of "addictive potential". Our review seeks to clarify some key distinctions between these constructs and questions the applicability of the addiction construct to human over-eating behaviors. To adequately frame this broad discussion requires the flexibility offered by the narrative review paradigm. We present selected literature on: techniques used to link sugar and sweet tastes to addiction neurobiology and behaviors; sugar and sweet taste "addiction"; the relationship of low calorie sweetener (LCS) intake to addictive behaviors and total calorie intake. Finally, we examined the reward value of sweet tastes and contrasted that with the literature describing addiction. The lack of reproducibility of fMRI data remains problematic for attributing a common neurobiological pathway activation of drugs and foods as conclusive evidence for sugar or sweet taste "addiction". Moreover, the complicated hedonics of sweet taste and reward value are suggested by validated population-level data which demonstrate that the consumption of sweet taste in the absence of calories does not increase total caloric intake. We believe the neurobiologies of reward value and addiction to be distinct and disagree with application of the addiction model to sweet food overconsumption. Most hypotheses of sugar "addiction" attribute the hedonics of sweet foods as the equivalent of "addiction". Further, when addictive behaviors and biology are critically examined in totality, they contrast dramatically from those associated with the desire for sweet taste. Finally, the evidence is strong that responses to the palatability of sweets rather than their metabolic consequences are the salient features for reward value. Thus, given the complexity of the controls of food intake in humans, we question the usefulness of the "addiction" model in dissecting the causes and effects of sweet food over-consumption.
Topics: Behavior, Addictive; Humans; Reproducibility of Results; Reward; Sugars; Sweetening Agents; Taste
PubMed: 34574716
DOI: 10.3390/ijerph18189791 -
Current Pharmaceutical Design 2014Taste 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... (Review)
Review
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.
Topics: Animals; Humans; Receptors, G-Protein-Coupled; Taste; Taste Buds
PubMed: 23886383
DOI: 10.2174/13816128113199990566 -
Pflugers Archiv : European Journal of... Jan 2021The variety of taste sensations, including sweet, umami, bitter, sour, and salty, arises from diverse taste cells, each of which expresses specific taste sensor... (Review)
Review
The variety of taste sensations, including sweet, umami, bitter, sour, and salty, arises from diverse taste cells, each of which expresses specific taste sensor molecules and associated components for downstream signal transduction cascades. Recent years have witnessed major advances in our understanding of the molecular mechanisms underlying transduction of basic tastes in taste buds, including the identification of the bona fide sour sensor H channel OTOP1, and elucidation of transduction of the amiloride-sensitive component of salty taste (the taste of sodium) and the TAS1R-independent component of sweet taste (the taste of sugar). Studies have also discovered an unconventional chemical synapse termed "channel synapse" which employs an action potential-activated CALHM1/3 ion channel instead of exocytosis of synaptic vesicles as the conduit for neurotransmitter release that links taste cells to afferent neurons. New images of the channel synapse and determinations of the structures of CALHM channels have provided structural and functional insights into this unique synapse. In this review, we discuss the current view of taste transduction and neurotransmission with emphasis on recent advances in the field.
Topics: Animals; Humans; Synapses; Synaptic Transmission; Taste; Taste Buds
PubMed: 32936320
DOI: 10.1007/s00424-020-02464-4 -
Handbook of Clinical Neurology 2019The gustatory system contributes to the flavor of foods and beverages and communicates information about nutrients and poisons. This system has evolved to detect and... (Review)
Review
The gustatory system contributes to the flavor of foods and beverages and communicates information about nutrients and poisons. This system has evolved to detect and ultimately respond to hydrophilic molecules dissolved in saliva. Taste receptor cells, located in taste buds and distributed throughout the oral cavity, activate nerve afferents that project to the brainstem. From here, information propagates to thalamic, subcortical, and cortical areas, where it is integrated with information from other sensory systems and with homeostatic, visceral, and affective processes. There is considerable divergence, as well as convergence, of information between multiple regions of the central nervous system that interact with the taste pathways, with reciprocal connections occurring between the involved regions. These widespread interactions among multiple systems are crucial for the perception of food. For example, memory, hunger, satiety, and visceral changes can directly affect and can be affected by the experience of tasting. In this chapter, we review the literature on the central processing of taste with a specific focus on the anatomic and physiologic responses of single neurons. Emphasis is placed on how information is distributed along multiple systems with the goal of better understanding how the rich and complex sensations associated with flavor emerge from large-scale, systems-wide, interactions.
Topics: Afferent Pathways; Animals; Brain; Humans; Nerve Net; Neurons; Taste; Thalamus
PubMed: 31604547
DOI: 10.1016/B978-0-444-63855-7.00012-5 -
Nature Jun 2018The ability of the taste system to identify a tastant (what it tastes like) enables animals to recognize and discriminate between the different basic taste qualities....
The ability of the taste system to identify a tastant (what it tastes like) enables animals to recognize and discriminate between the different basic taste qualities. The valence of a tastant (whether it is appetitive or aversive) specifies its hedonic value and elicits the execution of selective behaviours. Here we examine how sweet and bitter are afforded valence versus identity in mice. We show that neurons in the sweet-responsive and bitter-responsive cortex project to topographically distinct areas of the amygdala, with strong segregation of neural projections conveying appetitive versus aversive taste signals. By manipulating selective taste inputs to the amygdala, we show that it is possible to impose positive or negative valence on a neutral water stimulus, and even to reverse the hedonic value of a sweet or bitter tastant. Remarkably, mice with silenced neurons in the amygdala no longer exhibit behaviour that reflects the valence associated with direct stimulation of the taste cortex, or with delivery of sweet and bitter chemicals. Nonetheless, these mice can still identify and discriminate between tastants, just as wild-type controls do. These results help to explain how the taste system generates stereotypic and predetermined attractive and aversive taste behaviours, and support the existence of distinct neural substrates for the discrimination of taste identity and the assignment of valence.
Topics: Amygdala; Animals; Appetitive Behavior; Avoidance Learning; Clozapine; Discrimination, Psychological; Male; Mice; Mice, Inbred C57BL; Models, Neurological; Neurons; Taste; Water
PubMed: 29849148
DOI: 10.1038/s41586-018-0165-4 -
Proceedings. Biological Sciences Feb 2022The evolutionary history of sour taste has been little studied. Through a combination of literature review and trait mapping on the vertebrate phylogenetic tree, we... (Review)
Review
The evolutionary history of sour taste has been little studied. Through a combination of literature review and trait mapping on the vertebrate phylogenetic tree, we consider the origin of sour taste, potential cases of the loss of sour taste, and those factors that might have favoured changes in the valence of sour taste-from aversive to appealing. We reconstruct sour taste as having evolved in ancient fish. By contrast to other tastes, sour taste does not appear to have been lost in any major vertebrate taxa. For most species, sour taste is aversive. Animals, including humans, that enjoy the sour taste triggered by acidic foods are exceptional. We conclude by considering why sour taste evolved, why it might have persisted as vertebrates made the transition to land and what factors might have favoured the preference for sour-tasting, acidic foods, particularly in hominins, such as humans.
Topics: Animals; Humans; Phylogeny; Taste
PubMed: 35135352
DOI: 10.1098/rspb.2021.1918 -
Biosensors Mar 2023Bitterness is one of the basic tastes, and sensing bitterness plays a significant role in mammals recognizing toxic substances. The bitter taste of food and oral... (Review)
Review
Bitterness is one of the basic tastes, and sensing bitterness plays a significant role in mammals recognizing toxic substances. The bitter taste of food and oral medicines may decrease consumer compliance. As a result, many efforts have been made to mask or decrease the bitterness in food and oral pharmaceutical products. The detection of bitterness is critical to evaluate how successful the taste-masking technology is, and many novel taste-sensing systems have been developed on the basis of various interaction mechanisms. In this review, we summarize the progress of bitterness response mechanisms and the development of novel sensors in detecting bitterness ranging from commercial electronic devices based on modified electrodes to micro-type sensors functionalized with taste cells, polymeric membranes, and other materials in the last two decades. The challenges and potential solutions to improve the taste sensor quality are also discussed.
Topics: Animals; Taste; Electronics; Mammals
PubMed: 37185489
DOI: 10.3390/bios13040414 -
Annual Review of Physiology Feb 2023Salt taste, the taste of sodium chloride (NaCl), is mechanistically one of the most complex and puzzling among basic tastes. Sodium has essential functions in the body... (Review)
Review
Salt taste, the taste of sodium chloride (NaCl), is mechanistically one of the most complex and puzzling among basic tastes. Sodium has essential functions in the body but causes harm in excess. Thus, animals use salt taste to ingest the right amount of salt, which fluctuates by physiological needs: typically, attraction to low salt concentrations and rejection of high salt. This concentration-valence relationship is universally observed in terrestrial animals, and research has revealed complex peripheral codes for NaCl involving multiple taste pathways of opposing valence. Sodium-dependent and -independent pathways mediate attraction and aversion to NaCl, respectively. Gustatory sensors and cells that transduce NaCl have been uncovered, along with downstream signal transduction and neurotransmission mechanisms. However, much remains unknown. This article reviews classical and recent advances in our understanding of the molecular and cellular mechanisms underlying salt taste in mammals and insects and discusses perspectives on human salt taste.
Topics: Animals; Humans; Taste; Sodium Chloride; Taste Buds; Sodium; Signal Transduction; Mammals
PubMed: 36332657
DOI: 10.1146/annurev-physiol-031522-075853 -
International Journal of Molecular... Aug 2022Taste receptors are responsible for detecting their ligands not only in taste receptor cells (TRCs) but also in non-gustatory organs. For several decades, many research... (Review)
Review
Taste receptors are responsible for detecting their ligands not only in taste receptor cells (TRCs) but also in non-gustatory organs. For several decades, many research groups have accumulated evidence for such "ectopic" expression of taste receptors. More recently, some of the physiologic functions (apart from taste) of these ectopic taste receptors have been identified. Here, we summarize our current understanding of these ectopic taste receptors across multiple organs. With a particular focus on the specialized epithelial cells called tuft cells, which are now considered siblings of type II TRCs, we divide the ectopic expression of taste receptors into two categories: taste receptors in TRC-like cells outside taste buds and taste receptors with surprising ectopic expression in completely different cell types.
Topics: Epithelial Cells; Taste; Taste Buds
PubMed: 36077074
DOI: 10.3390/ijms23179677 -
Annals of Oncology : Official Journal... May 2017Malnutrition is highly prevalent in cancer patients and an important predictor of morbidity, mortality, treatment response, and toxicity. Taste and smell changes (TSCs)... (Review)
Review
CONTEXT
Malnutrition is highly prevalent in cancer patients and an important predictor of morbidity, mortality, treatment response, and toxicity. Taste and smell changes (TSCs) are common and may contribute to malnutrition. Research has previously focused on patients receiving chemotherapy (CT) or head and neck radiotherapy (RT). However, TSCs may occur pre-treatment, with other treatment modalities, and in cancer survivors. This review evaluates objective and subjective assessment of taste and smell, discusses the prevalence of TSCs in cancer, and reviews the clinical sequelae of TSCs in cancer patients.
OBJECTIVES
To critically evaluate objective and subjective assessment of TSCs, and the prevalence and clinical sequelae of TSCs in cancer.
METHODS
A literature search was conducted using PubMed, CINAHL and Embase for English-language articles published January 2009-June 2016. Search terms included combinations of the following: chemosensory, taste, smell, cancer, chemotherapy, radiotherapy, hormone therapy, immunotherapy, survivors. Reference lists of articles retrieved were also reviewed.
RESULTS
Variation in objective and subjective assessment methodologies has resulted in difficulties interpreting the literature. TSC prevalence varies depending on stage of disease and treatment regimens, from 16% to 70% and 50% to 70% during CT and RT, respectively. TSCs in patients who are treatment-naïve, receiving hormone or immunotherapy treatment, post-treatment and cancer survivors have not been adequately studied. TSCs are associated with impaired nutritional status. The relationship between cancer-associated symptoms and nutritional status is not clearly defined.
CONCLUSION
There is no gold standard assessment tool for TSCs. Heterogeneity in study methods hinders conclusive identification of the most appropriate way to measure TSCs. Subjective measures may reflect the patient experience and more reliably predict changes in dietary behaviour. Evaluation of TSCs should form part of all nutritional assessments in cancer patients. The true prevalence and severity of TSCs at all stages of cancer could then be established.
Topics: Head and Neck Neoplasms; Humans; Malnutrition; Nutrition Assessment; Nutritional Status; Smell; Survivors; Taste
PubMed: 28327968
DOI: 10.1093/annonc/mdx018