Intraduodenal infusion of a combination of tastants decreases food intake in humans

Differential effects of nutritive and non-nutritive sweet mouth rinsing on appetite in adults with obesity

BACKGROUND

Excessive added sugar intake has been associated with obesity; however, the effect of dietary sweetness on energy intake (EI) and appetite in adults with and without obesity has not yet been determined.

OBJECTIVE

To assess the effect of mouth rinses with and without energy and sweetness on measures of appetite, and to compare responses between subjects with body mass index (BMI) between 18.5 and 24.9 kg/m2 or ≥30 kg/m2.

METHODS

In this randomized, double-blind crossover study, 39 subjects (age 23±5y; 17 male, 22 female; BMI 18.5-24.9 kg/m2: n = 21; ≥30 kg/m2: n = 18) performed modified sham-feeding (MSF) with a mouth rinse containing either sucrose, sucralose, maltodextrin, or water for 2min before expectorating the solution. Blood sampling and subjective appetite assessments occurred at baseline (-5) and 15, 30, 60, and 90min post-MSF. After, EI was assessed at a buffet meal and post-meal appetite ratings were assessed hourly for 3h.

RESULTS

Post-MSF ghrelin increased for water vs. maltodextrin (water: p = 0.03). Post-MSF cholecystokinin increased following maltodextrin-MSF (p = 0.03) and sucralose-MSF (p = 0.005) vs. sucrose for those with BMI:18.5-24.9 kg/m2 only. There was greater post-MSF desire to eat in response to water vs. sucrose (p = 0.03) and reduced fullness with sucralose for those with BMI≥30 vs. 18.5-24.9 kg/m2 (p < 0.001). There was no difference in EI at the buffet meal by mouth rinse (p = 0.98) or by BMI (p = 0.12). However, there was greater post-meal fullness following sucralose-MSF vs. water (p = 0.03) and sucrose (p = 0.004) for those with BMI≥30 vs. 18.5-24.9 kg/m2.

CONCLUSION

Sucralose rinsing led to greater cephalic phase CCK release in adults with a BMI:18.5-24.9 kg/m2 only; however, ghrelin responses to unsweetened rinses were energy-specific for all adults. As subsequent EI was unaffected, further investigation of cephalic phase appetite is warranted.

Milk protein digestion and the gut microbiome influence gastrointestinal discomfort after cow milk consumption in healthy subjects

Many healthy people suffer from milk-related gastrointestinal discomfort (GID) despite not being lactose intolerant; the mechanisms underpinning such condition are unknown. This study aimed to explore milk protein digestion and related physiological responses (primary outcome), gut microbiome and gut permeability in 19 lactose-tolerant healthy nonhabitual milk consumers [NHMCs] reporting GID after consuming cow milk compared to 20 habitual milk consumers [HMCs] without GID. NHMCs and HMCs participated in a milk-load (250 mL) test, underwent blood sample collection at 6 time points over 6 h after milk consumption and collected urine samples and GID self-reports over 24 h. We measured the concentrations of 31 milk-derived bioactive peptides (BAPs), 20 amino acids, 4 hormones, 5 endocannabinoid system mediators, glucose and the dipeptidyl peptidase-IV (DPPIV) activity in blood and indoxyl sulfate in urine samples. Subjects also participated in a gut permeability test and delivered feces sample for gut microbiome analysis. Results showed that, compared to HMCs, milk consumption in NHMCs, along with GID, elicited a slower and lower increase in circulating BAPs, lower responses of ghrelin, insulin, and anandamide, a higher glucose response and serum DPPIV activity. The gut permeability of the two groups was similar, while the habitual diet, which was lower in dairy products and higher in the dietary-fibre-to-protein ratio in NHMCs, possibly shaped the gut microbiome; NHMCs exhibited lower abundance of Bifidobacteria, higher abundance of Prevotella and lower abundance of protease-coding genes, which may have reduced protein digestion, as evidenced by lower urinary excretion of indoxyl sulfate. In conclusion, the findings showed that a less efficient digestion of milk proteins, supported by a lower proteolytic capability of the gut microbiome, may explain GID in healthy people after milk consumption.

Effects of intraduodenal or intragastric administration of a bitter hop extract (Humulus lupulus L.), on upper gut motility, gut hormone secretion and energy intake in healthy-weight men

Gastrointestinal functions, particularly pyloric motility and the gut hormones, cholecystokinin and peptide YY, contribute to the regulation of acute energy intake. Bitter tastants modulate these functions, but may, in higher doses, induce GI symptoms. The aim of this study was to evaluate the effects of both dose and delivery location of a bitter hop extract (BHE) on antropyloroduodenal pressures, plasma cholecystokinin and peptide YY, appetite perceptions, gastrointestinal symptoms and energy intake in healthy-weight men. The study consisted of two consecutive parts, with part A including n = 15, and part B n = 11, healthy, lean men (BMI 22.6 ± 1.1 kg/m², aged 25 ± 3 years). In randomised, double-blind fashion, participants received in part A, BHE in doses of either 100 mg ("ID-BHE-100") or 250 mg ("ID-BHE-250"), or vehicle (canola oil; "ID-control") intraduodenally, or in part B, 250 mg BHE ("IG-BHE-250") or vehicle ("IG-control") intragastrically. Antropyloroduodenal pressures, hormones, appetite and symptoms were measured for 180 min, energy intake from a standardised buffet-meal was quantified subsequently. ID-BHE-250, but not ID-BHE-100, had modest, and transient, effects to stimulate pyloric pressures during the first 90 min (P < 0.05), and peptide YY from t = 60 min (P < 0.05), but did not affect antral or duodenal pressures, cholecystokinin, appetite, gastrointestinal symptoms or energy intake. IG-BHE-250 had no detectable effects. In conclusion, BHE, when administered intraduodenally, in the selected higher dose, modestly affected some appetite-related gastrointestinal functions, but had no detectable effects when given in the lower dose or intragastrically. Thus, BHE, at none of the doses or routes of administration tested, has appetite- or energy intake-suppressant effects.

The effect of gastrointestinal bitter sensing on appetite regulation and energy intake: A systematic review

Taste receptors are located on the epithelial surface throughout the alimentary canal to identify nutrients and potential toxins. In the oral cavity, the role of taste is to encourage or discourage ingestion, while in the gastrointestinal (GI) tract, the taste receptors help the body prepare for an appropriate response to the ingested foods. The GI sensing of bitter compounds may alter the secretion of appetite-related hormones thereby reducing food intake, which may have potential use for managing health outcomes. This systematic literature review investigated the acute effects of administering different bitter tasting compounds on circulating levels of selected GI hormones, subjective appetite, and energy intake in humans. A literature search was conducted using Medline, CINAHL and Web of Science databases. Of 290 articles identified, 16 met the inclusion criteria. Twelve studies assessed food intake; four of these found bitter administration decreased food intake and eight did not. Fourteen studies assessed subjective appetite; seven found bitter administration affected at least one measure of appetite and seven detected no significant changes. Nine studies included measures of GI hormones; no significant effects were found for changes in GLP-1, CCK or PYY. Four studies measured motilin and ghrelin and found mostly consistent changes in either food intake or subjective appetite. Overall, the data on food intake and subjective appetite were inconsistent, with only motilin and ghrelin responsive to post-oral bitter administration. There is limited consistent conclusive evidence that bitter compounds influence food intake, appetite or hormones with the reasons for this discussed within. SYSTEMATIC REVIEW REGISTRATION: CRD42021226102.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

An extract of hops (Humulus lupulus L.) modulates gut peptide hormone secretion and reduces energy intake in healthy-weight men: a randomized, crossover clinical trial

BACKGROUND

Gastrointestinal enteroendocrine cells express chemosensory bitter taste receptors that may play an important role in regulating energy intake (EI) and gut function.

OBJECTIVES

To determine the effect of a bitter hop extract (Humulus lupulus L.) on acute EI, appetite, and hormonal responses.

METHODS

Nineteen healthy-weight men completed a randomized 3-treatment, double-blind, crossover study with a 1-wk washout between treatments. Treatments comprised either placebo or 500 mg of hop extract administered in delayed-release capsules (duodenal) at 11:00 h or quick-release capsules (gastric) at 11:30 h. Ad libitum EI was recorded at the lunch (12:00 h) and afternoon snack (14:00 h), with blood samples taken and subjective ratings of appetite, gastrointestinal (GI) discomfort, vitality, meal palatability, and mood assessed throughout the day.

RESULTS

Total ad libitum EI was reduced following both the gastric (4473 kJ; 95% CI: 3811, 5134; P = 0.006) and duodenal (4439 kJ; 95% CI: 3777, 5102; P = 0.004) hop treatments compared with the placebo (5383 kJ; 95% CI: 4722, 6045). Gastric and duodenal treatments stimulated prelunch ghrelin secretion and postprandial cholecystokinin, glucagon-like peptide 1, and peptide YY responses compared with placebo. In contrast, postprandial insulin, glucose-dependent insulinotropic peptide, and pancreatic polypeptide responses were reduced in gastric and duodenal treatments without affecting glycemia. In addition, gastric and duodenal treatments produced small but significant increases in subjective measures of GI discomfort (e.g., nausea, bloating, abdominal discomfort) with mild to severe adverse GI symptoms reported in the gastric treatment only. However, no significant treatment effects were observed for any subjective measures of appetite or meal palatability.

CONCLUSIONS

Both gastric and duodenal delivery of a hop extract modulates the release of hormones involved in appetite and glycemic regulation, providing a potential "bitter brake" on EI in healthy-weight men.

Sensation of dietary nutrients by gut taste receptors and its mechanisms

Nutrients sensing is crucial for fundamental metabolism and physiological functions, and it is also an essential component for maintaining body homeostasis. Traditionally, basic taste receptors exist in oral cavity to sense sour, sweet, bitter, umami, salty and et al. Recent studies indicate that gut can sense the composition of nutrients by activating relevant taste receptors, thereby exerting specific direct or indirect effects. Gut taste receptors, also named as intestinal nutrition receptors, including at least bitter, sweet and umami receptors, have been considered to be activated by certain nutrients and participate in important intestinal physiological activities such as eating behavior, intestinal motility, nutrient absorption and metabolism. Additionally, gut taste receptors can regulate appetite and body weight, as well as maintain homeostasis via targeting hormone secretion or regulating the gut microbiota. On the other hand, malfunction of gut taste receptors may lead to digestive disorders, and then result in obesity, type 2 diabetes and gastrointestinal diseases. At present, researchers have confirmed that the brain-gut axis may play indispensable roles in these diseases via the secretion of brain-gut peptides, but the mechanism is still not clear. In this review, we summarize the current observation of knowledge in gut taste systems in order to shed light on revealing their important nutritional functions and promoting clinical implications.

The endocrine effects of bitter tastant administration in the gastrointestinal system: intragastric versus intraduodenal administration

Bitter tastants are recently introduced as potential hunger-suppressive compounds, the so-called "Bitter pill." However, the literature about bitter administration lacks consistency in methods and findings. We want to test whether hunger ratings and hormone plasma levels are affected by: 1) the site of administration: intragastrically (IG) or intraduodenally (ID), 2) the bitter tastant itself, quinine hydrochloride (QHCl) or denatonium benzoate (DB), and 3) the timing of infusion. Therefore, 14 healthy, female volunteers participated in a randomized, placebo-controlled six-visit crossover study. After an overnight fast, DB (1 µmol/kg), QHCl (10 µmol/kg), or placebo were given IG or ID via a nasogastric feeding tube. Blood samples were taken 10 min before administration and every 10 min after administration for a period of 2 h. Hunger was rated at the same time points on a visual analogue scale. ID bitter administration did not affect hunger sensations, motilin, or acyl-ghrelin release compared with its placebo infusion. IG QHCl infusion tended to suppress hunger increase, especially between 50 and 70 min after infusion, simultaneously with reduced motilin values. Here, acyl-ghrelin was not affected. IG DB did not affect hunger or motilin, however acyl-ghrelin levels were reduced 50-70 minutes after infusion. Plasma values of glucagon-like peptide 1 and cholecystokinin were too low to be properly detected or to have any physiological relevance. In conclusion, bitter tastants should be infused into the stomach to reduce hunger sensations and orexigenic gut peptides. QHCl has the best potential to reduce hunger sensations, and it should be infused 60 min before food intake.NEW & NOTEWORTHY Bitter tastants are a potential new weight-loss treatment. This is a noninvasive, easy approach, which should be received with considerable enthusiasm by the public. However, literature about bitter administration lacks consistency in methods and findings. We summarize how the compound should be given based on: the site of administration, the best bitter compound to use, and at what timing in respect to the meal. This paper is therefore a fundamental step to continue research toward the further development of the "bitter pill."

Comparative Effects of Intragastric and Intraduodenal Administration of Quinine on the Plasma Glucose Response to a Mixed-Nutrient Drink in Healthy Men: Relations with Glucoregulatory Hormones and Gastric Emptying

BACKGROUND

In preclinical studies, bitter compounds, including quinine, stimulate secretion of glucoregulatory hormones [e.g., glucagon-like peptide-1 (GLP-1)] and slow gastric emptying, both key determinants of postprandial glycemia. A greater density of bitter-taste receptors has been reported in the duodenum than the stomach. Thus, intraduodenal (ID) delivery may be more effective in stimulating GI functions to lower postprandial glucose.

OBJECTIVE

We compared effects of intragastric (IG) and ID quinine [as quinine hydrochloride (QHCl)] administration on the plasma glucose response to a mixed-nutrient drink and relations with gastric emptying, plasma C-peptide (reflecting insulin secretion), and GLP-1.

METHODS

Fourteen healthy men [mean ± SD age: 25 ± 3 y; BMI (in kg/m2): 22.5 ± 0.5] received, on 4 separate occasions, in double-blind, randomly assigned order, 600 mg QHCl or control, IG or ID, 60 min (IG conditions) or 30 min (IG conditions) before a mixed-nutrient drink. Plasma glucose (primary outcome) and hormones were measured before, and for 2 h following, the drink. Gastric emptying of the drink was measured using a 13C-acetate breath test. Data were analyzed using repeated-measures 2-way ANOVAs (factors: treatment and route of administration) to evaluate effects of QHCl alone and 3-way ANOVAs (factors: treatment, route-of-administration, and time) for responses to the drink.

RESULTS

After QHCl alone, there were effects of treatment, but not route of administration, on C-peptide, GLP-1, and glucose (P < 0.05); QHCl stimulated C-peptide and GLP-1 and lowered glucose concentrations (IG control: 4.5 ± 0.1; IG-QHCl: 3.9 ± 0.1; ID-control: 4.6 ± 0.1; ID-QHCl: 4.2 ± 0.1 mmol/L) compared with control. Postdrink, there were treatment × time interactions for glucose, C-peptide, and gastric emptying, and a treatment effect for GLP-1 (all P < 0.05), but no route-of-administration effects. QHCl stimulated C-peptide and GLP-1, slowed gastric emptying, and reduced glucose (IG control: 7.2 ± 0.3; IG-QHCl: 6.2 ± 0.3; ID-control: 7.2 ± 0.3; ID-QHCl: 6.4 ± 0.4 mmol/L)  compared with control.

CONCLUSIONS

In healthy men, IG and ID quinine administration similarly lowered plasma glucose, increased plasma insulin and GLP-1, and slowed gastric emptying. These findings have potential implications for lowering blood glucose in type 2 diabetes. This study was registered as a clinical trial with the Australian New Zealand Clinical Trials at www.anzctr.org.au as ACTRN12619001269123.

Review on the Regional Effects of Gastrointestinal Luminal Stimulation on Appetite and Energy Intake: (Pre)clinical Observations

Macronutrients in the gastrointestinal (GI) lumen are able to activate “intestinal brakes”, feedback mechanisms on proximal GI motility and secretion including appetite and energy intake. In this review, we provide a detailed overview of the current evidence with respect to four questions: (1) are regional differences (duodenum, jejunum, ileum) present in the intestinal luminal nutrient modulation of appetite and energy intake? (2) is this “intestinal brake” effect macronutrient specific? (3) is this “intestinal brake” effect maintained during repetitive activation? (4) can the “intestinal brake” effect be activated via non-caloric tastants? Recent evidence indicates that: (1) regional differences exist in the intestinal modulation of appetite and energy intake with a proximal to distal gradient for inhibition of energy intake: ileum and jejunum > duodenum at low but not at high caloric infusion rates. (2) the “intestinal brake” effect on appetite and energy appears not to be macronutrient specific. At equi-caloric amounts, the inhibition on energy intake and appetite is in the same range for fat, protein and carbohydrate. (3) data on repetitive ileal brake activation are scarce because of the need for prolonged intestinal intubation. During repetitive activation of the ileal brake for up to 4 days, no adaptation was observed but overall the inhibitory effect on energy intake was small. (4) the concept of influencing energy intake by intra-intestinal delivery of non-caloric tastants is intriguing. Among tastants, the bitter compounds appear to be more effective in influencing energy intake. Energy intake decreases modestly after post-oral delivery of bitter tastants or a combination of tastants (bitter, sweet and umami). Intestinal brake activation provides an interesting concept for preventive and therapeutic approaches in weight management strategies.

Effects of Bitter Substances on GI Function, Energy Intake and Glycaemia-Do Preclinical Findings Translate to Outcomes in Humans?

Bitter substances are contained in many plants, are often toxic and can be present in spoiled food. Thus, the capacity to detect bitter taste has classically been viewed to have evolved primarily to signal the presence of toxins and thereby avoid their consumption. The recognition, based on preclinical studies (i.e., studies in cell cultures or experimental animals), that bitter substances may have potent effects to stimulate the secretion of gastrointestinal (GI) hormones and modulate gut motility, via activation of bitter taste receptors located in the GI tract, reduce food intake and lower postprandial blood glucose, has sparked considerable interest in their potential use in the management or prevention of obesity and/or type 2 diabetes. However, it remains to be established whether findings from preclinical studies can be translated to health outcomes, including weight loss and improved long-term glycaemic control. This review examines information relating to the effects of bitter substances on the secretion of key gut hormones, gastric motility, food intake and blood glucose in preclinical studies, as well as the evidence from clinical studies, as to whether findings from animal studies translate to humans. Finally, the evidence that bitter substances have the capacity to reduce body weight and/or improve glycaemic control in obesity and/or type 2 diabetes, and potentially represent a novel strategy for the management, or prevention, of obesity and type 2 diabetes, is explored.

The critical role of CCK in the regulation of food intake and diet-induced obesity

In 1973, Gibbs, Young, and Smith showed that exogenous cholecystokinin (CCK) administration reduces food intake in rats. This initial report has led to thousands of studies investigating the physiological role of CCK in regulating feeding behavior. CCK is released from enteroendocrine I cells present along the gastrointestinal (GI) tract. CCK binding to its receptor CCK1R leads to vagal afferent activation providing post-ingestive feedback to the hindbrain. Vagal afferent neurons' (VAN) sensitivity to CCK is modulated by energy status while CCK signaling regulates gene expression of other feeding related signals and receptors expressed by VAN. In addition to its satiation effects, CCK acts all along the GI tract to optimize digestion and nutrient absorption. Diet-induced obesity (DIO) is characterized by reduced sensitivity to CCK and every part of the CCK system is negatively affected by chronic intake of energy-dense foods. EEC have recently been shown to adapt to diet, CCK1R is affected by dietary fats consumption, and the VAN phenotypic flexibility is lost in DIO. Altered endocannabinoid tone, changes in gut microbiota composition, and chronic inflammation are currently being explored as potential mechanisms for diet driven loss in CCK signaling. This review discusses our current understanding of how CCK controls food intake in conditions of leanness and how control is lost in chronic energy excess and obesity, potentially perpetuating excessive intake.

Effects of gastrointestinal delivery of non-caloric tastants on energy intake: a systematic review and meta-analysis

Purpose

Taste receptors are expressed throughout the gastrointestinal tract. The activation of post-oral taste receptors using tastants could provide a non-invasive treatment option in combating the obesity epidemic. The aim of this review was to examine the effect of post-oral delivery of non-caloric tastants on eating behavior reflected by primary outcome energy intake and secondary outcomes GI symptoms and perceptions and potential underlying mechanisms. This review was conducted according to the PRISMA guidelines for systematic reviews.

Methods

A systematic literature search of the Cochrane, PubMed, Embase, and Medline databases was performed. This systematic review and meta-analysis was registered in the PROSPERO database on 26 February 2020 (ID: CRD42020171182). Two researchers independently screened 11,912 articles and extracted information from 19 articles. If at least two studies investigated the effect of the same taste compound on primary outcome energy intake, a meta-analysis was performed to determine pooled effect sizes.

Results

Nineteen papers including healthy volunteers were included. In the 19 papers analyzed, effects of various tastants were investigated in healthy volunteers. Most extensively investigated were bitter tastants. The meta-analysis of effects of bitter tastants showed a significant reduction in energy intake of 54.62 kcal (95% CI − 78.54 to − 30.69, p = 0.0014).

Conclusions

Bitter stimuli are most potent to influence eating behavior. Energy intake decreased after post-oral delivery of bitter tastants. This highlights the potential of a preventive role of bitter tastants in battling the obesity epidemic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02485-4.

Effect of oral or intragastric delivery of the bitter tastant quinine on food intake and appetite sensations: a randomised crossover trial

Stimulation of gastrointestinal taste receptors affects eating behaviour. Intraduodenal infusion of tastants leads to increased satiation and reduced food intake, whereas intraileal infusion of tastants does not affect eating behaviour. Currently, it is unknown whether oral- or intragastric administration of tastants induces a larger effect on eating behaviour. This study investigated the effects of oral- and/or intragastric administration of quinine on food intake, appetite sensations and heart rate variability (HRV). In a blinded randomised crossover trial, thirty-two healthy volunteers participated in four interventions with a 1-week washout: oral placebo and intragastric placebo (OPGP), oral quinine and intragastric placebo (OQGP), oral placebo and intragastric quinine (OPGQ) and oral quinine and intragastric quinine (OQGQ). On test days, 150 min after a standardised breakfast, subjects ingested a capsule containing quinine or placebo and were sham-fed a mixture of quinine or placebo orally. At 50 min after intervention, subjects received an ad libitum meal to measure food intake. Visual analogue scales for appetite sensations were collected, and HRV measurements were performed at regular intervals. Oral and/or intragastric delivery of the bitter tastant quinine did not affect food intake (OPGP: 3273·6 (sem 131·8) kJ, OQGP: 3072·7 (sem 132·2) kJ, OPGQ: 3289·0 (sem 132·6) kJ and OQGQ: 3204·1 (sem 133·1) kJ, P = 0·069). Desire to eat and hunger decreased after OQGP and OPGQ compared with OPGP (P < 0·001 and P < 0·05, respectively), whereas satiation, fullness and HRV did not differ between interventions. In conclusion, sole oral sham feeding with and sole intragastric delivery of quinine decreased desire to eat and hunger, without affecting food intake, satiation, fullness or HRV.

Progress in research of gastrointestinal motility regulation

Gastrointestinal motility is an important part of the physiological function of the digestive tract, and its dysfunction is one of the key factors that cause different gastrointestinal motility disorders. These diseases seriously affect patients' normal life. With the development of scientific research and technology, well-designed research studies have been conducted on the regulatory mechanisms of gastrointestinal motility, which mainly include the regulation of gastrointestinal hormones, intestinal microflora, neurotransmitters, brain-gut peptides, interstitial cells of Cajal, and gastrointestinal electrical activities. In addition, current studies have proved that bitter taste receptors have certain regulatory effects on gastrointestinal motility. This paper primarily discusses the relevant pathways controlling gastrointestinal motility.

Effects of the Daily Consumption of Stevia on Glucose Homeostasis, Body Weight, and Energy Intake: A Randomised Open-Label 12-Week Trial in Healthy Adults

Stevia is a non-nutritive sweetener, providing sweet taste with no calories. This randomised, controlled, open-label 2-parallel arm trial examined the effects of daily stevia consumption on glycaemia in healthy adults. Secondary endpoints included body weight (BW) and energy intake (EI). Healthy participants (n = 28; aged 25 ± 5y, body mass index 21.2 ± 1.7 kg/m²) were randomised into either the stevia group (n = 14)—required to consume a stevia extract daily—or to the control group (n = 14). At weeks 0 and 12, the glucose and insulin responses to an oral glucose tolerance test were measured; BW and EI were assessed at weeks 0, 6, and 12. There was no significant difference in the glucose or insulin responses. There was a significant main effect of group on BW change (F(1,26) = 5.56, p = 0.026), as the stevia group maintained their weight as opposed to the control group (mean weight change at week 12: −0.22 kg, 95%CI [−0.96, 0.51] stevia group, +0.89 kg, 95%CI [0.16, 1.63] control group). The energy intake was significantly decreased between week 0 and 12 in the stevia group (p = 0.003), however no change was found in the control group (p = 0.973). Although not placebo-controlled, these results suggest that daily stevia consumption does not affect glycaemia in healthy individuals, but could aid in weight maintenance and the moderation of EI.

Effect of bolus enteral tube feeding on body weight in ambulatory adults with obesity and type 2 diabetes: a feasibility pilot randomized trial

Background/objectives

To ascertain the effect on body weight of 14 days of bolus enteral feeding with mixed meal (MM) and electrolyte solution (ES) in ambulatory adults with type 2 diabetes and obesity, and also the safety and feasibility of using a modified, intraorally anchored enteral feeding tube for this purpose.

Subjects/methods

We conducted a randomized, crossover pilot trial with 16 participants. A 140 cm, 8-French feeding tube was placed in the jejunum under electromagnetic guidance and anchored intraorally. Participants were randomized to self-administer 120 mL 523 kJ (125 kcal) MM, or 50 kJ (12 kcal) ES four times/day for 14 days. After ≥14 days without the tube, participants crossed over to the other treatment. The primary outcome compared weight change between treatments. Thereafter, participants could elect to undergo additional MM cycles. Participants were encouraged to continue with all usual activities including eating ad lib throughout the study.

Results

Ten participants withdrew prior to completing two randomized 14-day cycles (4 social, 3 intolerant of anchor, and 3 intolerant of tube). Six participants were assessed for the primary outcome and showed no significant difference in weight loss between MM and ES (p = 0.082). For the secondary outcome of within-group weight loss, average weight loss from baseline was significant for MM but not for ES: −2.40 kg (95% CI: −3.78, −1.02; p = 0.008) vs. −0.64 kg (95% CI: −2.01, 0.74; p = 0.27). A total of 23 2-week cycles were completed (12 paired, 2 unpaired, and 9 additional), with no significant adverse events for 334 days of tube use.

Conclusions

Repeated bolus nutrient administration via enteral feeding tube is associated with weight loss in adults with obesity and type 2 diabetes, with no significant difference seen between MM and ES feeds. The prototype device was safe, but requires development for further investigation into the effect of bolus jejunal feeding on weight and to improve acceptability.

Stevia Beverage Consumption prior to Lunch Reduces Appetite and Total Energy Intake without Affecting Glycemia or Attentional Bias to Food Cues: A Double-Blind Randomized Controlled Trial in Healthy Adults

BACKGROUND

Stevia is a zero-calorie alternative to caloric sugars. Substituting caloric sweeteners with noncaloric sweeteners reduces available energy, but their effects on appetite, subsequent food intake, and neurocognitive responses are still unclear.

OBJECTIVE

The aim was to examine whether sweetness with or without calories influences food intake, appetite, blood glucose concentrations, and attentional bias (AB) to food cues.

METHODS

This was a randomized, controlled, double-blind crossover study. Healthy participants [n = 20; aged 27 ± 5 y,  55% female; BMI (kg/m2): 21.8 ± 1.5] completed 5 visits, consuming 5 study beverages: 330 mL water (control, no sweet taste, no calories) and either 330 mL water containing 40 g glucose or sucrose (sweet taste; calories, both 160 kcal), maltodextrin (no sweet taste; calories, 160 kcal), or 240 ppm stevia (sweet taste, no calories). Glucose and stevia beverages were matched for sweetness. Subjective appetite ratings and blood glucose were measured at baseline and at 15, 30, and 60 min postprandially. At 15 min participants performed a visual-dot probe task to assess AB to food cues; at 30 min, participants were offered an ad libitum lunch; food intake was measured.

RESULTS

Subjective appetite ratings showed that preload sweetness and calorie content both affected appetite. The total AUC for glycemia was significantly higher after the caloric beverages (mean ± SD: maltodextrin, 441 ± 57.6;  glucose, 462 ± 68.1;  sucrose, 425 ± 53.6 mmol × min × L-1 ) compared with both stevia (320 ± 34.2 mmol × min × L-1) and water (304 ± 32.0 mmol × min × L-1) (all P < 0.001). Total energy intake (beverage and meal) was significantly lower after the stevia beverage (727 ± 239 kcal) compared with water (832 ± 198 kcal,  P = 0.013), with no significant difference between the water and caloric beverages (P = 1.00 for water vs. maltodextrin, glucose, and sucrose). However, food-related AB did not differ across conditions (P = 0.140).

CONCLUSIONS

This study found a beneficial and specific effect of a stevia beverage consumed prior to a meal on appetite and energy intake in healthy adults. This trial is registered at clinicaltrials.gov as NCT03711084.

Intragastric administration of the bitter tastant quinine lowers the glycemic response to a nutrient drink without slowing gastric emptying in healthy men

The rate of gastric emptying and the release of gastrointestinal (GI) hormones are major determinants of postprandial blood-glucose concentrations and energy intake. Preclinical studies suggest that activation of GI bitter-taste receptors potently stimulates GI hormones, including glucagon-like peptide-1 (GLP-1), and thus may reduce postprandial glucose and energy intake. We evaluated the effects of intragastric quinine on the glycemic response to, and the gastric emptying of, a mixed-nutrient drink and the effects on subsequent energy intake in healthy men. The study consisted of 2 parts: part A included 15 lean men, and part B included 12 lean men (aged 26 ± 2 yr). In each part, participants received, on 3 separate occasions, in double-blind, randomized fashion, intragastric quinine (275 or 600 mg) or control, 30 min before a mixed-nutrient drink (part A) or before a buffet meal (part B). In part A, plasma glucose, insulin, glucagon, and GLP-1 concentrations were measured at baseline, after quinine alone, and for 2 h following the drink. Gastric emptying of the drink was also measured. In part B, energy intake at the buffet meal was quantified. Quinine in 600 mg (Q600) and 275 mg (Q275) doses alone stimulated insulin modestly (P < 0.05). After the drink, Q600 and Q275 reduced plasma glucose and stimulated insulin (P < 0.05), Q275 stimulated GLP-1 (P < 0.05), and Q600 tended to stimulate GLP-1 (P = 0.066) and glucagon (P = 0.073) compared with control. Quinine did not affect gastric emptying of the drink or energy intake. In conclusion, in healthy men, intragastric quinine reduces postprandial blood glucose and stimulates insulin and GLP-1 but does not slow gastric emptying or reduce energy intake under our experimental conditions.

Development of a delayed-release nutrient for appetite control in adults with obesity and type 2 diabetes and initial clinical testing in a single dose randomized controlled trial

Background and objectives

Delivery of nutrients directly to the small intestine, either via enteral feeding tube or by gastric bypass surgery, is associated with increased levels of appetite-suppressing and glucoregulatory hormones, including GLP-1, and reduced appetite. Achieving these changes non-invasively using formulated foods may be of therapeutic benefit in individuals with obesity and related comorbidities. The aim of this pilot study was to determine the effect of a single dose of a novel delayed-release nutrient (DRN) on glucose, GLP-1, c-peptide, insulin, and appetite in adults with obesity and type 2 diabetes.

Subjects and methods

We formulated an all-natural, generally recognized as safe (‘GRAS”) DRN and conducted a randomized prospective crossover trial. Nineteen adults with obesity and type 2 diabetes underwent paired 3-h meal tolerance tests (MTT) in randomized order 1–4 weeks apart. Subjects ingested a single dose of DRN and the same nutrients as unformulated powders (UN).

Results

For DRN compared with UN, the maximal concentration (Cmax) was significantly lower for glucose, c-peptide, and insulin, and the time of maximal concentration (Tmax) was significantly delayed. While Tmax for GLP-1 was also significantly delayed following DRN compared with UN (45 min later; p = 0.26), Cmax did not differ significantly. GLP-1 rose significantly during the last 90 min of the 3-h MTT (β₁ = 0.16 pg/mL/min, p = 0.025), while following UN it decreased (β₁ = −0.21 pg/mL/min, p = 0.0026) (p difference = 0.0003). There were minimal differences in seven measures of appetite and adverse symptoms between DRN and UN.

Conclusions

We conclude that nutrient can be formulated using all-natural ingredients to induce a delayed rise in GLP-1. Further testing is needed to determine the amount and site of nutrient release, when maximum GLP-1 levels occur, and if modification of the formulation specifications and dose are associated with appetite and glucose control.

Effects of Intraduodenal Infusion of the Bitter Tastant, Quinine, on Antropyloroduodenal Motility, Plasma Cholecystokinin, and Energy Intake in Healthy Men

BACKGROUND/AIMS

Nutrient-induced gut hormone release (eg, cholecystokinin [CCK]) and the modulation of gut motility (particularly pyloric stimulation) contribute to the regulation of acute energy intake. Non-caloric bitter compounds, including quinine, have recently been shown in cell-line and animal studies to stimulate the release of gastrointestinal hormones by activating bitter taste receptors expressed throughout the gastrointestinal tract, and thus, may potentially suppress energy intake without providing additional calories. This study aims to evaluate the effects of intraduodenally administered quinine on antropyloroduodenal pressures, plasma CCK and energy intake.

METHODS

Fourteen healthy, lean men (25 ± 5 years; BMI: 22.5 ± 2.0 kg/m2) received on 4 separate occasions, in randomized, double-blind fashion, 60-minute intraduodenal infusions of quinine hydrochloride at doses totaling 37.5 mg ("Q37.5"), 75 mg ("Q75") or 225 mg ("Q225"), or control (all 300 mOsmol). Antropyloroduodenal pressures (high-resolution manometry), plasma CCK (radioimmunoassay), and appetite perceptions/gastrointestinal symptoms (visual analog questionnaires) were measured. Ad libitum energy intake (buffet-meal) was quantified immediately post-infusion. Oral quinine taste-thresholds were assessed on a separate occasion using 3-alternative forced-choice procedure.

RESULTS

All participants detected quinine orally (detection-threshold: 0.19 ± 0.07 mmol/L). Intraduodenal quinine did not affect antral, pyloric or duodenal pressures, plasma CCK (pmol/L [peak]; control: 3.6 ± 0.4, Q37.5: 3.6 ± 0.4, Q75: 3.7 ± 0.3, Q225: 3.9 ± 0.4), appetite perceptions, gastrointestinal symptoms or energy intake (kcal; control: 1088 ± 90, Q37.5: 1057 ± 69, Q75: 1029 ±7 0, Q225: 1077 ± 88).

CONCLUSIONS

Quinine, administered intraduodenally over 60 minutes, even at moderately high doses, but low infusion rates, does not modulate appetite-related gastrointestinal functions or energy intake.

Role of Bitter Taste Receptors in Regulating Gastric Accommodation in Guinea Pigs

Taste stimulants play important roles in triggering digestion and absorption of nutrients and in toxin detection, under the control of the gut-brain axis. Bitter compounds regulate gut hormone secretion and gastrointestinal motility through bitter taste receptors (TAS2Rs) located in the taste buds on the tongue and in the enteroendocrine cells. Gastric accommodation (GA) is an important physiologic function. However, the role of TAS2R agonists in regulating GA remains unclear. To clarify whether GA is influenced by bitter stimulants, we examined the effect of TAS2R agonist denatonium benzoate (DB), administered intraorally and intragastrically, by measuring the consequent intrabag pressure in the proximal stomach of guinea pigs. Effects of the Kampo medicine rikkunshito (RKT) and its bitter components liquiritigenin and naringenin on GA were also examined. Intraoral DB (0.2 nmol/ml) administration enhanced GA. Intragastric DB administration (0.1 and 1 nmol/kg) promoted GA, whereas higher DB doses (30 μmol/kg) inhibited it. Similar changes in GA were observed with intragastric (1000 mg/kg) and intraoral (200 mg/ml) RKT administration. Liquiritigenin and naringenin also promoted GA. These findings suggest that GA is affected by the stimulation of TAS2Rs in the oral cavity or gut in guinea pigs.

Intraintestinal Delivery of Tastants Using a Naso-Duodenal-Ileal Catheter Does Not Influence Food Intake or Satiety

Intraduodenal activity of taste receptors reduces food intake. Taste receptors are expressed throughout the entire gastrointestinal tract. Currently, there are no data available on the effects of distal taste receptor activation. In this study, we investigate the effect of intraduodenal and/or intraileal activation of taste receptors on food intake and satiety. In a single-blind randomized crossover trial, fourteen participants were intubated with a naso-duodenal-ileal catheter and received four infusion regimens: duodenal placebo and ileal placebo (DPIP), duodenal tastants and ileal placebo (DTIP), duodenal placebo and ileal tastants (DPIT), duodenal tastants and ileal tastants (DTIT). Fifteen minutes after cessation of infusion, subjects received an ad libitum meal to measure food intake. Visual analog scale scores for satiety feelings were collected at regular intervals. No differences in food intake were observed between the various interventions (DPIP: 786.6 ± 79.2 Kcal, DTIP: 803.3 ± 69.0 Kcal, DPIT: 814.7 ± 77.3 Kcal, DTIT: 834.8 ± 59.2 Kcal, p = 0.59). No differences in satiety feelings were observed. Intestinal infusion of tastants using a naso-duodenal-ileal catheter did not influence food intake or satiety feelings. Possibly, the burden of the four-day naso-duodenal-ileal intubation masked a small effect that tastants might have on food intake and satiety.

Umami as an 'Alimentary' Taste. A New Perspective on Taste Classification

Applied taste research is increasingly focusing on the relationship with diet and health, and understanding the role the sense of taste plays in encouraging or discouraging consumption. The concept of basic tastes dates as far back 3000 years, where perception dominated classification with sweet, sour, salty, and bitter consistently featuring on basic taste lists throughout history. Advances in molecular biology and the recent discovery of taste receptors and ligands has increased the basic taste list to include umami and fat taste. There is potential for a plethora of other new basic tastes pending the discovery of taste receptors and ligands. Due to the possibility for an ever-growing list of basic tastes it is pertinent to critically evaluate whether new tastes, including umami, are suitably positioned with the four classic basic tastes (sweet, sour, salty, and bitter). The review critically examines the evidence that umami, and by inference other new tastes, fulfils the criteria for a basic taste, and proposes a subclass named ‘alimentary’ for tastes not meeting basic criteria.

Olfactory, Taste, and Photo Sensory Receptors in Non-sensory Organs: It Just Makes Sense

Sensory receptors that detect and respond to light, taste, and smell primarily belong to the G-protein-coupled receptor (GPCR) superfamily. In addition to their established roles in the nose, tongue, and eyes, these sensory GPCRs have been found in many ‘non-sensory' organs where they respond to different physicochemical stimuli, initiating signaling cascades in these extrasensory systems. For example, taste receptors in the airway, and photoreceptors in vascular smooth muscle cells, both cause smooth muscle relaxation when activated. In addition, olfactory receptors are present within the vascular system, where they play roles in angiogenesis as well as in modulating vascular tone. By better understanding the physiological and pathophysiological roles of sensory receptors in non-sensory organs, novel therapeutic agents can be developed targeting these receptors, ultimately leading to treatments for pathological conditions and potential cures for various disease states.

The sweet taste signalling pathways in the oral cavity and the gastrointestinal tract affect human appetite and food intake: a review

Sweet taste is associated with food reward and energy source in the form of carbohydrate. Excessive sweet consumption is blamed for the prevalence of obesity. However, evidence for the potential of sweet taste to influence food intake and bodyweight regulation in humans remains unclear. The purpose of this review was to examine the physiological responses relevant to sweet taste mechanisms and the impact on appetite control. The literature was examined for studies that assessed the effects of non-nutritive sweeteners and natural sugars on hormonal secretions and neural activations via oral and gastrointestinal pathways. The findings indicated that a network of sweet taste signalling pathways in the oral cavity and the gut seem to mediate hormonal responses and some metabolism differences in neural circus that orchestrating the hunger-satiety cycle. Individual variations of sweet taste perception which is modulated by hormonal and genetic factors have been associated with dietary nutrient and sugar consumption.

Intragastric quinine administration decreases hedonic eating in healthy women through peptide-mediated gut-brain signaling mechanisms

Objectives: Intragastric bitter tastants may decrease appetite and food intake. We aimed to investigate the gut-brain signaling and brain mechanisms underlying these effects.Methods: Brain responses to intragastric quinine-hydrochloride (QHCl, 10 µmol/kg) or placebo infusion were recorded using functional magnetic resonance imaging in 15 healthy women. Appetite-related sensations, plasma levels of gastrointestinal hormones and hedonic food intake (ad libitum drink test) were assessed.Results: Lower octanoylated ghrelin (P<0.04), total ghrelin (P<0.01), and motilin (P<0.01) plasma levels were found after QHCl administration, along with lower prospective food consumption ratings (P<0.02) and hedonic food intake (P<0.05). QHCl increased neural activity in the hypothalamus and hedonic (anterior insula, putamen, caudate, pallidum, amygdala, anterior cingulate cortex, orbitofrontal cortex, midbrain) regions, but decreased activity in the homeostatic medulla (all pFWE-corrected<0.05). Differential brain responses to QHCl versus placebo covaried with subjective and hormonal responses and predicted differences in hedonic food intake.Discussion: Intragastric QHCl decreases prospective and actual food intake in healthy women by interfering with homeostatic and hedonic brain circuits in a ghrelin- and motilin-mediated fashion. These findings suggest a potential of bitter tastants to reduce appetite and food intake, through the gut-brain axis.

Targeted intestinal delivery of incretin secretagogues-towards new diabetes and obesity therapies

A new strategy under development for the treatment of type 2 diabetes and obesity is to mimic some of the effects of bariatric surgery by delivering food-related stimuli to the distal gastrointestinal tract where they should enhance the release of gut hormones such as glucagon-like peptide-1 (GLP-1) and peptideYY (PYY). Methods include inhibition of food digestion and absorption in the upper GI tract, or oral delivery of stimuli in capsules or pelleted form to protect them against gastric degradation. A variety of agents have been tested in humans using capsules, microcapsules or pellets, delivering nutrients, bile acids, fatty acids and bitter compounds. This review examines the outcomes of these different approaches and supporting evidence from intestinal perfusion studies.

Intragastric infusion of the bitter tastant quinine suppresses hormone release and antral motility during the fasting state in healthy female volunteers

BACKGROUND

Intragastric administration of the bitter tastant denatonium benzoate inhibits the increase of motilin plasma levels and antral contractility. While these findings suggest that gastrointestinal bitter taste receptors could be new targets to modulate gastrointestinal motility and hormone release, they need confirmation with other bitter receptor agonists. The primary aim was to evaluate the effect of intragastric administration of the bitter tastant quinine-hydrochloride (QHCl) on motilin and ghrelin plasma levels. Secondly, we studied the effect on interdigestive motility.

METHODS

Ten healthy female volunteers were recruited (33±4 y; 22±0.5 kg/m²). Placebo or QHCl (10 μmol/kg) was administered intragastrically through a nasogastric feeding tube after an overnight fast in a single-blind randomized fashion. Administration started 20 min after the first phase III of the migrating motor complex. The measurement continued for another 2 h after the administration. Blood samples were collected every 10 min with the baseline sample taken 10 min prior to administration.

KEY RESULTS

The increase in plasma levels of motilin (administration; P=.04) and total ghrelin (administration; P=.02) was significantly lower after QHCl. The fluctuation of octanoylated ghrelin was reduced after QHCl (time by administration; P=.03). Duodenal motility did not differ. The fluctuation of antral activity differed over time between placebo and QHCl (time by administration; P=.03).

CONCLUSIONS AND INFERENCES

QHCl suppresses the increase of both motilin and ghrelin plasma levels. Moreover, QHCl reduced the fluctuation of antral motility. These findings confirm the potential of bitter taste receptors as targets for modifying interdigestive motility in man.

Intragastric infusion of denatonium benzoate attenuates interdigestive gastric motility and hunger scores in healthy female volunteers

Background: Denatonium benzoate (DB) has been shown to influence ongoing ingestive behavior and gut peptide secretion.Objective: We studied how the intragastric administration of DB affects interdigestive motility, motilin and ghrelin plasma concentrations, hunger and satiety ratings, and food intake in healthy volunteers.Design: Lingual bitter taste sensitivity was tested with the use of 6 concentrations of DB in 65 subjects. A placebo or 1 μmol DB/kg was given intragastrically to assess its effect on fasting gastrointestinal motility and hunger ratings, motilin and ghrelin plasma concentrations, satiety, and caloric intake.Results: Women (n = 39) were more sensitive toward a lingual bitter stimulus (P = 0.005) than men (n = 26). In women (n = 10), intragastric DB switched the origin of phase III contractions from the stomach to the duodenum (P = 0.001) and decreased hunger ratings (P = 0.04). These effects were not observed in men (n = 10). In women (n = 12), motilin (P = 0.04) plasma concentrations decreased after intragastric DB administration, whereas total and octanoylated ghrelin were not affected. The intragastric administration of DB decreased hunger (P = 0.008) and increased satiety ratings (P = 0.01) after a meal (500 kcal) in 13 women without affecting gastric emptying in 6 women. Caloric intake tended to decrease after DB administration compared with the placebo (mean ± SEM: 720 ± 58 compared with 796 ± 45 kcal; P = 0.08) in 20 women.Conclusions: Intragastric DB administration decreases both antral motility and hunger ratings during the fasting state, possibly because of a decrease in motilin release. Moreover, DB decreases hunger and increases satiety ratings after a meal and shows potential for decreasing caloric intake. This trial was registered at clinicaltrials.gov as NCT02759926.

Flavor Preferences Conditioned by Dietary Glutamate

Our understanding of the molecular basis of umami taste and its appetitive qualities has been greatly aided by studies in laboratory rodents. This review describes methods for testing responses to the prototypical umami substance monosodium glutamate (MSG) in rodents. Two techniques, forced exposure to MSG and 2-bottle choice tests with ascending concentrations, were used to evaluate the responses to the taste of umami itself, and 2 other methods used oral or postoral MSG to modify the responses to other flavors. Intake and preference for MSG are enhanced in mice by experience with MSG and with other nutrients with positive postoral effects. In addition, flavor preferences are enhanced in mice and rats by gastric or intestinal MSG infusions via an associative learning process. Even mice with an impaired or absent ability to taste MSG can learn to prefer a flavor added to an MSG solution, supporting the notion that glutamate acts postorally. The more complex flavor of dashi seasoning, which includes umami substances (inosinate, glutamate), is attractive to rodents, but dashi does not condition flavor preferences. Details of the postoral glutamate detection process and the nature of the signal involved in learned preferences are still uncertain but probably involve gastric or intestinal sensors or both and vagal transmission. Some findings suggest that postoral glutamate effects may enhance food preferences in humans, but this requires further study.

Olfactory Receptors in Non-Chemosensory Organs: The Nervous System in Health and Disease

Olfactory receptors (ORs) and down-stream functional signaling molecules adenylyl cyclase 3 (AC3), olfactory G protein α subunit (Gαolf), OR transporters receptor transporter proteins 1 and 2 (RTP1 and RTP2), receptor expression enhancing protein 1 (REEP1), and UDP-glucuronosyltransferases (UGTs) are expressed in neurons of the human and murine central nervous system (CNS). In vitro studies have shown that these receptors react to external stimuli and therefore are equipped to be functional. However, ORs are not directly related to the detection of odors. Several molecules delivered from the blood, cerebrospinal fluid, neighboring local neurons and glial cells, distant cells through the extracellular space, and the cells’ own self-regulating internal homeostasis can be postulated as possible ligands. Moreover, a single neuron outside the olfactory epithelium expresses more than one receptor, and the mechanism of transcriptional regulation may be different in olfactory epithelia and brain neurons. OR gene expression is altered in several neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), progressive supranuclear palsy (PSP) and sporadic Creutzfeldt-Jakob disease (sCJD) subtypes MM1 and VV2 with disease-, region- and subtype-specific patterns. Altered gene expression is also observed in the prefrontal cortex in schizophrenia with a major but not total influence of chlorpromazine treatment. Preliminary parallel observations have also shown the presence of taste receptors (TASRs), mainly of the bitter taste family, in the mammalian brain, whose function is not related to taste. TASRs in brain are also abnormally regulated in neurodegenerative diseases. These seminal observations point to the need for further studies on ORs and TASRs chemoreceptors in the mammalian brain.

Food structure is critical for optimal health

Much nutrition policy is nutrient-based, supported by nutrient science, food nutrient composition tables and dietary nutrient recommendations, but not by reference to food structure.