An advance in novel intelligent sensory technologies: From an implicit-tracking perspective of food perception.

Food sensory evaluation mainly includes explicit and implicit measurement methods. Implicit measures of consumer perception are gaining significant attention in food sensory and consumer science as they provide effective, subconscious, objective analysis. A wide range of advanced technologies are now available for analyzing physiological and psychological responses, including facial analysis technology, neuroimaging technology, autonomic nervous system technology, and behavioral pattern measurement. However, researchers in the food field often lack systematic knowledge of these multidisciplinary technologies and struggle with interpreting their results. In order to bridge this gap, this review systematically describes the principles and highlights the applications in food sensory and consumer science of facial analysis technologies such as eye tracking, facial electromyography, and automatic facial expression analysis, as well as neuroimaging technologies like electroencephalography, magnetoencephalography, functional magnetic resonance imaging, and functional near-infrared spectroscopy. Furthermore, we critically compare and discuss these advanced implicit techniques in the context of food sensory research and then accordingly propose prospects. Ultimately, we conclude that implicit measures should be complemented by traditional explicit measures to capture responses beyond preference. Facial analysis technologies offer a more objective reflection of sensory perception and attitudes toward food, whereas neuroimaging techniques provide valuable insight into the implicit physiological responses during food consumption. To enhance the interpretability and generalizability of implicit measurement results, further sensory studies are needed. Looking ahead, the combination of different methodological techniques in real-life situations holds promise for consumer sensory science in the field of food research.

Lingual Taste Nerve Transection Alters Food Selection, Relative Macronutrient Intake, and Meal Patterns in Rats Consuming a Cafeteria Diet without Changing Total Energy Intake.

The control of ingestive behavior is complex and involves input from many different sources, including the gustatory system. Signals transmitted via the taste nerves trigger responses that promote or discourage ingestion. The lingual taste nerves innervate 70% of taste buds, yet their role in the control of food selection and intake remarkably remains relatively underinvestigated. Here we used our custom five-item Food Choice Monitor to compare postsurgical behavioral responses to chow and a five-choice cafeteria diet (CAF) between male rats that had sham surgery (SHAM) or histologically verified transection of the chorda tympani and glossopharyngeal nerves (2NX). Compared with SHAM rats, 2NX rats ate significantly more of the high-fat CAF foods. The altered food choices led to dramatically increased fat intake and substantially reduced carbohydrate intake by 2NX vs SHAM rats. Furthermore, whether offered chow or CAF, 2NX rats ate fewer, larger meals each day. Eating rates implied that, compared with SHAM, 2NX rats were equally motivated to consume CAF but less motivated to eat chow. Even with these differences, energy intake and weight gain trajectories remained similar between SHAM and 2NX rats. Although some rats experienced CAF before surgery, contrary to our expectations, the effects of prior CAF experience on postsurgical eating were minimal. In conclusion, although total energy intake was unaffected, our results clearly indicate that information from one or both lingual taste nerves has a critical role in food selection, regulation of macronutrient intake, and meal termination but not long-term energy balance.

Does vaping affect the taste and smell perception? An exploratory study with New Zealand young adults.

OBJECTIVE: The study aimed to assess potential effects of vaping on individual taste and smell perception in a sample of young adult New Zealanders. DESIGN: This cross-sectional study measured taste and smell perception using intensity and hedonic ratings to two olfactory (i.e., vanillin, methional) and two gustatory stimuli (i.e., sucrose, monosodium glutamate), representing sweet and savoury flavours. Detection sensitivities to sucrose and vanillin were also assessed using a forced choice detection paradigm aligned with the signal detection framework. MANCOVAs were employed to compare sensory perception between groups based on vaping use frequency. Additional regression analyses were conducted to identify potential predictors of intensity and hedonic sensory ratings. SETTING: Participants were recruited from the University of Otago student population and surrounding neighbourhoods of Dunedin, New Zealand in 2023. PARTICIPANTS: The study included 213 university students (98 vapers and 115 non-vapers) RESULTS: We found a significant difference in hedonic ratings for vanillin, indicating a stronger preference among non-vapers. However, no other differences between the two groups were significant. Notably, the use of tobacco and mint flavours were emerged as significant predictors for hedonic responses to the savoury smell and sweet taste stimulus, respectively. No significant differences were observed between groups in the ability to detect weak stimuli. CONCLUSIONS: Our findings suggest that vape use, particularly with specific flavours, may be associated with alterations in hedonic responses to smells. This finding may have potential implications for how vaping affects on food preferences and dietary choices.

Bitter taste function-related genes are implicated in the behavioral association between taste preference and ethanol preference in male mice.

Alcohol use disorder in humans is highly heritable, and as a term is synonymous with alcoholism, alcohol dependence, and alcohol addiction. Defined by the NIAAA as a medical condition characterized by an impaired ability to stop or control alcohol use despite adverse social, occupational, or health consequences, the genetic basis of alcohol dependence is much studied. However, an intriguing component to alcohol acceptance exists outside of genetics or social factors. In fact, mice of identical genetic backgrounds without any prior experience of tasting ethanol display widely varying preferences to it, far beyond those seen for typical taste solutions. Here, we hypothesized that a preference for ethanol, which tastes both bitter and sweet to humans, would be influenced by taste function. Using a mouse model of taste behavior, we tested preferences for bitter and sweet in mice that, without training or previous experience, either preferred or avoided ethanol solutions in consumption trials. Data showed clear sex differences, in which male mice that preferred ethanol also preferred a bitter quinine solution, whereas female mice that preferred ethanol also preferred a sweet sucralose solution. Male mice preferring ethanol also exhibited lower expression levels of mRNA for genes encoding the bitter taste receptors T2R26 and T2R37, and the bitter transducing G-protein subunit GNAT3, suggesting that the higher ethanol preference observed in the male mice may be due to bitter signaling, including that arising from ethanol, being weaker in this group. Results further support links between ethanol consumption and taste response, and may be relevant to substance abuse issues in human populations.

Mapping expectancy-based appetitive placebo effects onto the brain in women.

Suggestions about hunger can generate placebo effects on hunger experiences. But, the underlying neurocognitive mechanisms are unknown. Here, we show in 255 women that hunger expectancies, induced by suggestion-based placebo interventions, determine hunger sensations and economic food choices. Functional magnetic resonance imaging in a subgroup (n = 57/255) provides evidence that the strength of expecting the placebo to decrease hunger moderates medial prefrontal cortex activation at the time of food choice and attenuates ventromedial prefrontal cortex (vmPFC) responses to food value. Dorsolateral prefrontal cortex activation linked to interference resolution formally mediates the suggestion-based placebo effects on hunger. A drift-diffusion model characterizes this effect by showing that the hunger suggestions bias participants' food choices and how much they weigh tastiness against the healthiness of food, which further moderates vmPFC-dlPFC psychophysiological interactions when participants expect decreased hunger. Thus, suggestion-induced beliefs about hunger shape hunger addressing economic choices through cognitive regulation of value computation within the prefrontal cortex.

Nutrigenomics: SNPs correlated to Food Preferences and Susceptibilities.

Background: Nutrigenomics explores the intricate interplay between single nucleotide polymorphisms (SNPs), food preferences, and susceptibilities. Methods: This study delves into the influence of SNPs on food sensitivities, allergies, tyramine intolerance, and taste preferences. Genetic factors intricately shape physiological reactions to dietary elements, with polymorphisms contributing to diverse sensitivities and immune responses. Results: Tyramine intolerance, arising from metabolic inefficiencies, unveils genetic markers exerting influence on enzyme function. SNPs transcend genetic diversity by exerting substantial impact on food sensitivities/allergies, with specific variants correlating to heightened susceptibilities. Genes accountable for digesting food components play pivotal roles. Given the rising prevalence of food sensitivities/allergies, understanding genetic foundations becomes paramount. In the realm of taste and food preferences, SNPs sculpt perception and choice, yielding variances in taste perception and preferences for sweetness, bitterness, and umami. This genetic medley extends its reach to encompass wider health implications. Conclusions: In this review article, we have focused on how polymorphisms wield significant sway over physiological responses, sensitivities, and dietary inclinations. Unraveling these intricate relationships illuminates the path to personalized nutrition, potentially revolutionizing tailored recommendations and interventions.

Obesity-mediated Lipoinflammation Modulates Food Reward Responses.

Accumulation of white adipose tissue (WAT) during obesity is associated with the development of chronic low-grade inflammation, a biological process known as lipoinflammation. Systemic and central lipoinflammation accumulates pro-inflammatory cytokines including IL-6, IL-1ß and TNF-α in plasma and also in brain, disrupting neurometabolism and cognitive behavior. Obesity-mediated lipoinflammation has been reported in brain regions of the mesocorticolimbic reward circuit leading to alterations in the perception and consumption of ultra-processed foods. While still under investigation, lipoinflammation targets two major outcomes of the mesocorticolimbic circuit during food reward: perception and motivation ("Wanting") and the pleasurable feeling of feeding ("Liking"). This review will provide experimental and clinical evidence supporting the contribution of obesity- or overnutrition-related lipoinflammation affecting the mesocorticolimbic reward circuit and enhancing food reward responses. We will also address neuroanatomical targets of inflammatory profiles that modulate food reward responses during obesity and describe potential cellular and molecular mechanisms of overnutrition linked to addiction-like behavior favored by brain lipoinflammation.

Sweet taste preference is associated with greater hypothalamic response to glucose and longitudinal weight gain.

The hypothalamus has an abundant expression of sweet taste receptors that play a role in glucose sensing and energy homeostasis. Evidence suggests that liking "sweets" can be associated with weight gain, but the relationship between sweet taste preference and hypothalamic regulation of appetite is unknown. This study tested the hypothesis that sweet taste preference is associated with increased hypothalamic activation in response to glucose (a purported neural marker for weight gain risk) and greater longitudinal increases in body mass index (BMI). Fifty-four adults aged 18-35 years with a mean (± SD) BMI of 27.99 ± 5.32 kg/m2 completed the study. Height and weight were measured at baseline and 6-12 months later in a subset of 36 participants. Sweet taste preference was assessed via the Monell 2-series, forced-choice tracking procedure. Arterial spin labeling magnetic resonance imaging was performed before and after oral glucose ingestion to determine hypothalamic blood flow response to glucose. Linear models were used to examine relationships between sweet taste preference and the hypothalamic response to glucose and longitudinal changes in BMI, adjusting for age, sex, and baseline BMI. Sweet taste preference was positively associated with glucose-linked hypothalamic blood flow (beta = 0.017, p = 0.043), adjusted for age, sex and BMI. We also observed a positive association between sweet taste preference and longitudinal change in BMI (beta = 0.088, p = 0.015), adjusted for age, sex and baseline BMI. These findings suggest that heightened sweet taste preference is associated with glucose-linked hypothalamic activation and may be linked to increased susceptibility for weight gain.

Development, sensitivity and reliability of a French version of the Leeds food preference questionnaire (LFPQ-fr) for the evaluation of food preferences and reward.

BACKGROUND: There is a growing global interest in the evaluation of food reward, necessitating the adaptation of culturally appropriate instruments for use in empirical studies. This work presents the development and validation of a culturally adapted French version of the Leeds Food Preference Questionnaire (LFPQ-fr). METHODS: The LFPQ-fr was developed and validated in healthy-weight adults using the following systematic approach: i) selection and validation of appropriate food pictures; ii) linguistic translation of liking and wanting constructs in the target population (n = 430; 81% female; 42.2 ± 12.7 years); iii) validation of the sensitivity and reliability of the task performed in a fasted state and in response to a standardized test meal (n = 50; 50% female; 30.0 ± 8.4 years). RESULTS: During the first and second phases, the nutritional and perceptual validation of culturally appropriate food pictures and pertinent reward constructs, respectively, was demonstrated in a healthy-weight French sample. Findings from the third phase indicated that all food reward components were sensitive to the test meal and showed moderate to high agreement in both fasted (Lin's CCC =0.72-0.94) and fed (Lin's CCC = 0.53-0.80) appetitive states between visit 1 (V1) and visit (V2). Except for explicit liking fat bias, all primary outcomes were statistically consistent in fasted and fed states between V1 and V2. Changes in fat and taste biases in response to a standardized meal for all primary outcomes were also consistent between V1 and V2 except for explicit liking fat bias (Lin's CCC = 0.49- 0.72). CONCLUSION: The LFPQ-fr developed and tested in this study is a reproducible and reliable method to assess food reward in both the fasted and fed states in a healthy-weight French population.

Decreased retronasal olfaction and taste perception in obesity are related to saliva biochemical and microbiota composition.

Understanding the individual factors that modulate flavor perception is a central issue for the development of personalized diets strategies to fight obesity. This study aimed to investigate differences in flavor perception between adults with normal weight and those with obesity, as well as some potential biological factors related to these differences. To do that, liking and flavor perception intensity were measured against retronasal olfactory (pineapple, butter, tropical and chocolate) and taste attributes (sweetness, umami and bitter) in 77 individuals grouped as normalweight or obese, according to their body mass index (BMI). Unstimulated saliva was collected from all participants and characterized in terms of salivary flow, total protein content, total antioxidant capacity, total esterase activity and bacterial composition through 16S rDNA amplicon sequencing. The results showed that participants displayed differences in flavor perception according to their BMI group. Thus, the group with obesity showed significant lower liking and intensity scores for low calorie related food aroma (pineapple and tropical), lower taste intensity scores for sweet and umami, and a higher acceptability for umami than the group with normal weight. Significant differences between BMI groups were observed for salivary biochemical variables and specific bacterial taxa, some of which were significantly correlated to flavor intensity. This work suggests for the first time the existence of an oral-brain axis that might contribute to the development or perpetuation of obesity, which opens new and interesting avenues of research.

A value accumulation account of unhealthy food choices: testing the influence of outcome salience under varying time constraints.

People often engage in unhealthy eating despite having an explicit goal to follow a healthy diet, especially under certain conditions such as a lack of time. A promising explanation from the value accumulation account is that food choices are based on the sequential consideration of the values of multiple outcomes, such as health and taste outcomes. Unhealthy choices may result if taste is considered before health. We examined whether making a health outcome more salient could alter this order, thereby leading to more healthy choices even under time pressure. Two studies examined the time-dependent effect of outcome values and salience on food choices. Participants first completed priming trials on which they rated food items on healthiness (health condition), tastiness (taste condition), or both healthiness and tastiness (control condition). They then completed blocks of binary choice trials between healthy and tasty items. The available response time was manipulated continuously in Study 1 (N = 161) and categorically in Study 2 (N = 318). As predicted, results showed that the values of health and taste outcomes influenced choices and that priming led to more choices in line with the primed outcomes even when time was scarce. We did not obtain support for the prediction that the priming effect is time-dependent in the sense that primed outcomes are considered before non-primed outcomes. Together, these findings suggest that increasing the value and salience of a health outcome may be effective ways to increase healthy choices, even under poor conditions such as time pressure.

Dietary experience with glucose and fructose fosters heightened avidity for glucose-containing sugars independent of TRPM5 taste transduction in mice.

OBJECTIVE: Experience with metabolically distinct sugars, glucose and fructose, enhances attraction to the orosensory properties of glucose over fructose. To gain insight into which sensory signals are affected, we investigated how this nutritive learning reshapes behavioral responding to various sugars in brief access taste tests in C57BL6/J (B6) mice and assessed whether sugar-exposed mice lacking the TRPM5 channel involved in G-protein coupled taste transduction could acquire these types of preferences for glucose-containing sugars. METHODS: B6, TRPM5 knockout (KO), and TRPM5 heterozygous (Het) mice were given extensive access to water (sugar naïve) or 0.316, 0.56, and 1.1 M glucose and fructose (sugar-exposed) and then tested, whilst food deprived, for their relative avidities for glucose, fructose, sucrose, maltose, and/or a non-metabolizable glucose analog in a series of taste tests. RESULTS: Sugar-exposed B6 mice licked relatively more for glucose than fructose, driven by an increased avidity for glucose, not an avoidance of fructose, and licked more for maltose, compared to their sugar-naïve counterparts. Sugar-exposed B6 mice did not lick with such avidity for a non-metabolizable glucose analog. TRPM5 KO mice took longer to acquire the sugar discrimination than the Het controls, but both groups ultimately licked significantly more for glucose than fructose. Het mice displayed clear preferential licking for sucrose over fructose, while licking comparably high for glucose, sucrose, and maltose. KO mice licked significantly more for maltose than sucrose. CONCLUSIONS: Collectively, the findings suggest that ingestive experience with glucose and fructose primarily reprograms behavioral responding to a TRPM5-independent orosensory signal generated by glucose-containing sugars.

Recruitment of dlPFC during dietary self-regulation predicts the transience of regulatory effects.

Recent work on the cognitive regulation of dietary decision-making suggests that regulation can alter both the choices that people make in the moment and longer-lasting preferences. However, it is unclear what mechanisms lead to temporary or lingering changes. To address this question, we used fMRI during a task employing the cognitive regulation of food choice and assessed changes in food preference from baseline to post-regulation. We found evidence that regulation may result in a temporary reconfiguration of the neural drivers of choice, de-emphasizing goal-inconsistent value-related computations in the ventromedial prefrontal cortex and resulting in more goal-consistent changes in value-related computations in the dorsolateral prefrontal cortex (dlPFC). Moreover, we find that the extent to which the dlPFC was recruited to represent different regulatory goals during the moment of choice negatively predicted the extent to which those regulatory goals produced lingering changes in preference. Our results suggest that the recruitment of the dlPFC in the service of regulation may have a downside: it is effective at changing behavior in the moment, but its effects on preferences are transient.

Emotional responses to taste and smell stimuli: Self-reports, physiological measures, and a potential role for individual and genetic factors.

Taste and olfaction elicit conscious feelings by direct connection with the neural circuits of emotions that affects physiological responses in the body (e.g., heart rate and skin conductance). While sensory attributes are strong determinants of food liking, other factors such as emotional reactions to foods may be better predictors of consumer choices even for products that are equally-liked. Thus, important insights can be gained for understanding the full spectrum of emotional reactions to foods that inform the activities of product developers and marketers, eating psychologist and nutritionists, and policy makers. Today, self-reported questionnaires and physiological measures are the most common tools applied to study variations in emotional perception. The present review discusses these methodological approaches, underlining their different strengths and weaknesses. We also discuss a small, emerging literature suggesting that individual differences and genetic variations in taste and smell perception, like the genetic ability to perceive the bitter compound PROP, may also play a role in emotional reactions to aromas and foods.

Novel Fat Taste Receptor Agonists Curtail Progressive Weight Gain in Obese Male Mice.

BACKGROUND & AIMS: The spontaneous preference for dietary lipids is principally regulated by 2 lingual fat taste receptors, CD36 and GPR120. Obese animals and most of human subjects exhibit low orosensory perception of dietary fat because of malfunctioning of these taste receptors. Our aim was to target the 2 fat taste receptors by newly synthesized high affinity fatty acid agonists to decrease fat-rich food intake and obesity. METHODS: We synthesized 2 fat taste receptor agonists (FTA), NKS-3 (CD36 agonist) and NKS-5 (CD36 and GPR120 agonist). We determined their molecular dynamic interactions with fat taste receptors and the effect on Ca2+ signaling in mouse and human taste bud cells (TBC). In C57Bl/6 male mice, we assessed their gustatory perception and effects of their lingual application on activation of tongue-gut loop. We elucidated their effects on obesity and its related parameters in male mice fed a high-fat diet. RESULTS: The two FTA, NKS-3 and NKS-5, triggered higher Ca2+ signaling than a dietary long-chain fatty acid in human and mouse TBC. Mice exhibited a gustatory attraction for these compounds. In conscious mice, the application of FTA onto the tongue papillae induced activation of tongue-gut loop, marked by the release of pancreato-bile juice into collecting duct and cholecystokinin and peptide YY into blood stream. Daily intake of NKS-3 or NKS-5 via feeding bottles decreased food intake and progressive weight gain in obese mice but not in control mice. CONCLUSIONS: Our results show that targeting fat sensors in the tongue by novel chemical fat taste agonists might represent a new strategy to reduce obesity.

Imagined eating - An investigation of priming and sensory-specific satiety.

While obesity remains a pressing issue, the wider population continues to be exposed to more digital food content than ever before. Much research has demonstrated the priming effect of visual food content, i.e., exposure to food cues increasing appetite and food intake. In contrast, some recent research points out that repeated imagined consumption can facilitate satiate and decrease food intake. Such findings have been suggested as potential remedies to excessive food cue exposure. However, the practically limitless variety of digital food content available today may undermine satiation attempts. The present work aims to replicate and extend prior findings by introducing a within-subjects baseline comparison, disentangling general and (sensory-) specific eating desires, as well as considering the moderating influence of visual and flavour stimulus variety. Three online studies (n = 1149 total) manipulated food colour and flavour variety and reproducibly revealed a non-linear dose-response pattern of imagined eating: 3 repetitions primed, while 30 repetitions satiated. Priming appeared to be specific to the taste of the exposed stimulus, and satiation, contrary to prior literature, appeared to be more general. Neither colour nor flavour variety reliably moderated any of the responses. Therefore, the results suggest that a more pronounced variety may be required to alter imagery-induced satiation.

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.

Taste perception and food preferences in patients with diabetic foot ulcers before and after hyperbaric oxygen therapy.

OBJECTIVE: The aim of the study was to evaluate the effect of hyperbaric oxygen therapy (HBOT) on taste perception and food preferences in patients with diabetic foot ulcers. METHODS: The study involved 75 healthy people (Group C) and 23 patients with diabetic foot ulcers before HBOT (Group Db) and after 25-30 HBOT treatments (Group Da) (2.5 ATA, 87 min). The sip and spit method was used to examine the taste perception for 5 basic flavours. Food preferences were studied using photographs of dishes. RESULTS: The recognition thresholds in Group C were lower than in Group Db for 5 basic flavours. The taste intensity in Group C was higher than in Group Db for: 0.1% and 1.0% monosodium glutamate, 0.02% citric acid, and 0.002% quinine hydrochloride. The hedonic response in Group C was more negative than in Group Db for: 0.18% sodium chloride, 0.3% monosodium glutamate and 0.1% citric acid. The pleasure derived from eating in Group C was lower than in Group Db for sour and salty products. The recognition thresholds in Group Db were higher than in Group Da for umami and sour. The taste intensity in Group Db was lower than in Group Da for: 0.1%, 0.3% and 1.0% monosodium glutamate. The pleasure derived from eating in Group Db was higher than in Group Da for chocolate and crisps. CONCLUSIONS: In people with diabetic foot ulcers, an impaired all 5 basic tastes occurred with different food preferences compared to healthy people. HBOT causes beneficial changes resulting in increased sensitivity to umami and sour taste as well as a decrease in the pleasure derived from eating chocolate and crisps.

A Systematic Review of Salt Taste Function and Perception Impairments in Adults with Chronic Kidney Disease.

Individuals with chronic kidney disease (CKD) experience physiological changes that likely impair salt taste function and perception. Sodium restriction is a cornerstone of CKD management but dietary sodium plays an important role in food enjoyment and may interfere with compliance to this intervention. Therefore, confirming that taste deficits are present in CKD will improve our understanding of how taste deficits can affect intake, and inform dietary counselling in the future. A systematic review was conducted. Studies that included adults with CKD and healthy controls, and assessed salt taste sensitivity, perceived intensity, and/or hedonic ratings were included. Study quality was assessed using the Academy of Nutrition and Dietetics Evidence Analysis Library Quality Criteria Checklist: Primary Research. Of the 16 studies, the majority reported decreased salt taste sensitivity, but no consistent differences in intensity or hedonic ratings were observed. Higher recognition thresholds in CKD patients were associated with higher sodium intake, but results should be interpreted with caution as the measures used were subject to error in this population. In conclusion, salt taste sensitivity is decreased in CKD, but intensity and hedonic evaluations appear to be more robust. Given that hedonic assessments are better predictors of intake, and that salt taste preferences can be changed over time, dietary counselling for low-sodium intake is likely to be effective for this population.

Gut-brain circuits for fat preference.

The perception of fat evokes strong appetitive and consummatory responses1. Here we show that fat stimuli can induce behavioural attraction even in the absence of a functional taste system2,3. We demonstrate that fat acts after ingestion via the gut-brain axis to drive preference for fat. Using single-cell data, we identified the vagal neurons responding to intestinal delivery of fat, and showed that genetic silencing of this gut-to-brain circuit abolished the development of fat preference. Next, we compared the gut-to-brain pathways driving preference for fat versus sugar4, and uncovered two parallel systems, one functioning as a general sensor of essential nutrients, responding to intestinal stimulation with sugar, fat and amino acids, whereas the other is activated only by fat stimuli. Finally, we engineered mice lacking candidate receptors to detect the presence of intestinal fat, and validated their role as the mediators of gut-to-brain fat-evoked responses. Together, these findings reveal distinct cells and receptors that use the gut-brain axis as a fundamental conduit for the development of fat preference.