Effect of viscosity on learned satiation

Oral Somatosensory Sensitivity in Patients With Taste Disturbance

OBJECTIVE

The significance of the human sense of taste is typically underestimated until it is altered or even lost. Hypogeusia, a diminished capacity to taste, has an adverse influence on a patient's quality of life. Similar to interactions between the oral senses and between olfaction and intranasal trigeminal sensitivity, taste disturbance may also affect the mechanosensitivity of the tongue. In this study, we investigated the lingual tactile sensitivity of patients with subjective taste disturbance and people with normogeusia.

STUDY DESIGN

Prospective case-control study.

METHODS

Forty-six patients with subjective taste disturbance (mean age 60 years) and 43 participants with normogeusia (mean age 55 years) were enrolled and underwent a stereognostic test of edge and point sensitivity based on 3D-printed letters sized from 2 to 8 mm. Gustatory function and salivary production were also tested.

RESULTS

Patients with dysgeusia needed significantly bigger letters to recognize them compared with controls (P = .01). Apart from this, patients with dysgeusia had no significant association between gustatory function and salivary production. Duration of dysgeusia and age were not associated with the presently obtained measures of gustatory or oral mechanosensory function.

CONCLUSIONS

The results of this study indicate that taste dysfunction has a negative impact on oral mechanosensitivity and hence possibly on oral texture perception.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:2572-2577, 2021.

Sensory and physical characteristics of foods that impact food intake without affecting acceptability: Systematic review and meta-analyses

This systematic review with meta-analyses aimed to identify the sensory and physical characteristics of foods/beverages which increase satiation and/or decrease/delay subsequent consumption without affecting acceptability. Systematic searches were first undertaken to identify review articles investigating the effects of any sensory and physical food characteristic on food intake. These articles provided some evidence that various textural parameters (aeration, hardness, homogeneity, viscosity, physical form, added water) can impact food intake. Individual studies investigating these effects while also investigating acceptability were then assessed. Thirty-seven individual studies investigated a textural manipulation and provided results on food intake and acceptability, 13 studies (27 comparisons, 898 participants) investigated effects on satiation, and 29 studies (54 comparisons, 916 participants) investigated effects on subsequent intake. Meta-analyses of within-subjects comparisons (random-effects models) demonstrated greater satiation (less weight consumed) from food products that were harder, chunkier, more viscous, voluminous, and/or solid, while demonstrating no effects on acceptability. Textural parameters had limited effects on subsequent consumption. Between-subjects studies and sensitivity analyses confirmed these results. These findings provide some evidence that textural parameters can increase satiation without affecting acceptability. The development of harder, chunkier, more viscous, voluminous, and/or solid food/beverage products may be of value in reducing overconsumption.

Effects of Oro-Sensory Exposure on Satiation and Underlying Neurophysiological Mechanisms-What Do We Know So Far?

The mouth is the first part of the gastrointestinal tract. During mastication sensory signals from the mouth, so-called oro-sensory exposure, elicit physiological signals that affect satiation and food intake. It has been established that a longer duration of oro-sensory exposure leads to earlier satiation. In addition, foods with more intense sweet or salty taste induce earlier satiation compared to foods that are equally palatable, but with lower taste intensity. Oro-sensory exposure to food affects satiation by direct signaling via the brainstem to higher cortical regions involved in taste and reward, including the nucleus accumbens and the insula. There is little evidence that oro-sensory exposure affects satiation indirectly through either hormone responses or gastric signals. Critical brain areas for satiation, such as the brainstem, should be studied more intensively to better understand the neurophysiological mechanisms underlying the process of satiation. Furthermore, it is essential to increase the understanding of how of highly automated eating behaviors, such as oral processing and eating rate, are formed during early childhood. A better understanding of the aforementioned mechanisms provides fundamental insight in relation to strategies to prevent overconsumption and the development of obesity in future generations.

Are the nutrient and textural properties of Australian commercial infant and toddler foods consistent with infant feeding advice?

Infant feeding guidelines worldwide recommend first foods to be Fe rich with no added sugars and that nutrient-poor discretionary foods are to be avoided. Feeding guidelines also recommend exposing infants to a variety of foods and flavours with increasingly complex textures. Here, we compare nutritional and textural properties of commercial infant and toddler foods available in Australia with established infant feeding guidelines. Nutrition information and ingredient lists were obtained from food labels, manufacturer and/or retailer websites. In total, 414 foods were identified, comprising mostly mixed main dishes, fruit and vegetable first foods and snacks. Most products were poor sources of Fe, and 80 % of first foods were fruit-based. Half of all products were purées in squeeze pouches, and one-third of all products were discretionary foods. The nutritional content of many products was inconsistent with guidelines, being low in Fe, sweet, smooth in consistency or classified as discretionary. Reformulation of products is warranted to improve Fe content, particularly in mixed main dishes, expand the range of vegetable-only foods and textural variety. Greater regulatory oversight may be needed to better inform parents and caregivers. Frequent consumption of commercial baby foods low in Fe may increase the risk of Fe deficiency. Excessive consumption of purées via squeeze pouches may also have implications for overweight and obesity risk.

No evidence of flavour-nutrient learning in a two-week 'home exposure' study in humans

Flavour-nutrient learning is robust in animals but remains elusive in humans. Recent evidence suggests flavour-nutrient learning may be more likely to occur with beverages that contain relatively few calories (compared to no calories), while others show that learned associations can influence satiation, without an effect on preference. The objective of this research was to determine whether acquired liking for a caloric drink could be observed in a 'home learning' context over 2 weeks, and whether it is impacted by viscosity. In combination, we also explored changes in learning relating to fullness and expected satiety. In a double-blind study, participants (N = 83; BMI = 23.3 kg/m²) were randomly allocated to one of four groups differing in either calories (0 kcal vs. 112.5 kcal) or viscosity (low vs. high) and consumed a novel-flavoured drink over 15 days. Measures of flavour (10 ml sample) and beverage liking, grip force (a measure of beverage reward value), fullness, and expected satiety were taken at the start and the end of the study. While the high-viscous beverages were less liked (M = 40.3 mm, SD = 24.7) than the low viscous beverages (M = 64.4 mm, SD = 15.3; p = .022), there was no evidence that repeated exposure to a calorie-containing beverage impacted subsequent liking for the flavour (p = .115) or for the beverage (p = .448), grip force (ps > .26), fullness, and expected satiety (ps > .12). Accordingly, we conclude that we found no evidence of flavour-nutrient learning and flavour-satiety learning. This null finding accords with previous observations indicating that humans do not acquire flavour-nutrient associations as readily as some non-human animals.

Textural Effects on Perceived Satiation and Ad Libitum Intake of Potato Chips in Males and Females

Food texture plays a critical role in influencing an individual’s perceived satiation and ad libitum intake. It remains unclear, however, whether such textural changes can also affect snack consumption. This study aimed to address this question by testing for changes in perceived satiation and ad libitum intake of two types of potato chips with varying hardness. In addition, the observed effect was compared across gender groups. With a crossover design, 74 participants (31 females and 43 males) performed a food consumption task for two types of chips produced from potatoes that were either untreated or treated with pulsed electric fields (PEF) technology. Sensory analyses indicated that these two types of chips had comparable hedonic value, despite a clear textural difference. Across sexes, the results revealed a significant difference in perceived satiation for the two types of chips (p = 0.009), but not in intake. By contrast, analyses of males alone revealed that male participants rated PEF-treated chips to be more satiating than the control chips and correspondingly consumed less (p < 0.05). Overall, findings from the study suggest that modifications of food texture can be a helpful tool in reducing energy intake from snack consumption. The contrasting results from different gender groups highlight the importance of considering gender effects in studies of eating behaviour.

Effect of Macronutrient Type and Gastrointestinal Release Site on PYY Response in Normal Healthy Subjects

BACKGROUND AND AIMS

Enteroendocrine L cells release satiety inducing hormones in response to stimulation by luminal macronutrients. We sought to profile the differential effect of macronutrient type and site of release on circulating concentrations of the L cell-derived enteroendocrine hormone peptide tyrosine tyrosine (amino acids 1 to 36) (PYY).

MATERIALS AND METHODS

Eight healthy volunteers were recruited to a randomized, double-blinded, six-way crossover study. At each visit, the participants consumed a 500-kcal drink containing carbohydrate, protein, or fat in either gastric or small intestinal release formulations. Plasma PYY concentrations and hunger ratings were assessed for 3 hours after consumption of the test drink. The food intake was recorded thereafter at an ad libitum lunch.

RESULTS

Microcapsular formulations targeting the distal small intestinal delivery of fat, but not carbohydrate or protein, markedly enhance PYY release relative to macronutrient delivery in gastric release formulations. Food intake at an ad libitum meal was lowest after consumption of the formulation releasing fat at the distal small intestine.

CONCLUSION

Targeting of fat to the distal small intestine in delayed release microcapsules enhanced PYY release and was associated with reductions in food intake.

Food portion size influences accompanying beverage selection in adults

When trying to reduce food portion size, it is important that meal satisfaction is, as far as possible, preserved. Otherwise, individuals may select accompaniments to the meal (e.g., snacks, beverages) to achieve satisfaction and, in doing so, negate any benefit of the original portion size reduction. This study investigated whether varying portion sizes of food would influence choice of accompanying beverages. That is, when presented with a food portion size that is smaller or larger than their ideal, an individual may compensate by choosing a beverage based on its satiating and/or orosensory properties to balance the expected satiation and satisfaction of a meal. Data from an online interactive study (n = 93) was analysed using multilevel ordinal logistic regression models. Food portion size (100, 300, 500, 700, or 900 kcal) predicted beverage choice (water, low-energy sweetened beverage, high-energy sweetened beverage). For example, the sweetened beverages were more likely to be selected with small food portion sizes (p < .001). Participant ideal food portion size did not interact with this relationship. Participants appear to have recognised that sweetened beverages provide flavour and/or energy, and used them to compensate for a smaller meal. While switching to a low-energy beverage with an increased food portion size is advantageous for energy balance, choosing a high-energy beverage with a decreased food portion size is likely to be detrimental for those attempting to reduce energy intake and body weight.

Smoothies: Exploring the Attitudes, Beliefs and Behaviours of Consumers and Non-Consumers

Smoothies are popular dietary products. An online survey of Australian adults (n=833; 79% female) was used to explore patterns of smoothie consumption and individual motives for consuming these beverages. Participants commonly reported consuming fruit (98%), yoghurt (66%), milk (58%), honey (52%), fruit juice (46%), and nutritional supplements (46%) in smoothies. Compared to Infrequent Smoothie-Consumers (I-SC, < 1•week-1; n=514), Frequent Smoothie-Consumers (F-SC, >= 1•week-1; n=269) were more likely to consume core-foods (e.g. vegetables, p < 0.001) and less likely to consume discretionary items (e.g. honey or ice-cream, p’s < 0.020) in smoothies. It followed that F-SC typically cited “health-related reasons” for consuming these beverages (i.e. to increase fruit/vegetable [57%] or nutrient [50%] intake, and/or to be “healthy” [56%]) and perceived these products as “nutritious” (84%); whilst I-SC often perceived them as “indulgent” (62%). Smoothies may play a positive role in the diet. However, beverages incorporating discretionary choices may increase energy, saturated fat and/or sugar intakes, offsetting the benefits of fruit/vegetable consumption.

Somatosensory innervation of the oral mucosa of adult and aging mice

Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner’s corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.

Somatosensory innervation of the oral mucosa of adult and aging mice

Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner's corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.

Comparison of oro-sensory exposure duration and intensity manipulations on satiation

Oro-sensory exposure (OSE) is an important factor in the regulation of food intake with increasing OSE leading to lower food intake. Oral processing time and taste intensity both play an important role in OSE but their individual contribution to satiation is unknown. We aimed to determine the independent and combined effects of oral processing time and taste intensity on satiation. Fifty eight participants (23±9y, BMI 22±2kg/m²) participated in a 2×2 factorial randomized crossover study in which they consumed one of four gel-based model foods until satiation during four sessions. Model foods were offered ad libitum and differed in texture (soft or hard texture, yielding shorter and longer oral processing time) and sweetness (low or high intensity). Model foods were isocaloric and were matched for flavor and palatability. Outcome measures were intake of the model food and the microstructure of eating behavior, such as number of chews and eating rate. There was an overall significant effect of texture (p<0.001) but not sweetness (p=0.33) on intake with a 29.2% higher intake of the soft model foods compared to the hard model foods. After correction for palatability the difference in intake between the soft and hard model foods was 21.5% (p<0.001). The number of chews was significantly lower for the soft (10.1±6.2) than for the hard (26.9±6.2) model foods (p<0.001), which resulted in a significantly lower eating rate (soft, 26.3±10.2 and hard, 15.3±7.1g/min, p<0.001). These results show that increasing texture hardness of gel model foods decreases food intake independent of sweet taste intensity. The higher number of chews and faster eating rate may cause this effect. In conclusion, oro-sensory exposure duration rather than taste intensity appears to be the main determinant of food intake.

Sensory influences on food intake control: moving beyond palatability

The sensory experience of eating is an important determinant of food intake control, often attributed to the positive hedonic response associated with certain sensory cues. However, palatability is just one aspect of the sensory experience. Sensory cues based on a food's sight, smell, taste and texture are operational before, during and after an eating event. The focus of this review is to look beyond palatability and highlight recent advances in our understanding of how certain sensory characteristics can be used to promote better energy intake control. We consider the role of visual and odour cues in identifying food in the near environment, guiding food choice and memory for eating, and highlight the ways in which tastes and textures influence meal size and the development of satiety after consumption. Considering sensory characteristics as a functional feature of the foods and beverages we consume provides the opportunity for research to identify how sensory enhancements might be combined with energy reduction in otherwise palatable foods to optimize short-term energy intake regulation in the current food environment. Moving forward, the challenge for sensory nutritional science will be to assess the longer-term impact of these principles on weight management.

Energy density, energy intake, and body weight regulation in adults

The role of dietary energy density (ED) in the regulation of energy intake (EI) is controversial. Methodologically, there is also debate about whether beverages should be included in dietary ED calculations. To address these issues, studies examining the effects of ED on EI or body weight in nonelderly adults were reviewed. Different approaches to calculating dietary ED do not appear to alter the direction of reported relations between ED and body weight. Evidence that lowering dietary ED reduces EI in short-term studies is convincing, but there are currently insufficient data to determine long-term effectiveness for weight loss. The review also identified key barriers to progress in understanding the role of ED in energy regulation, in particular the absence of a standard definition of ED, and the lack of data from multiple long-term clinical trials examining the effectiveness of low-ED diet recommendations for preventing both primary weight gain and weight regain in nonobese individuals. Long-term clinical trials designed to examine the impact of dietary ED on energy regulation, and including multiple ED calculation methods within the same study, are still needed to determine the importance of ED in the regulation of EI and body weight.

Effects of learning and food form on energy intake and appetitive responses

Energy-yielding beverages reportedly contribute to positive energy balance uniquely. They are highly consumed and evoke weaker satiety signaling and dietary energy compensation than solid foods of the same energy content. This study measured the contribution of learning to appetitive sensations and adjustments of energy intake for preloads varying in energy content and food form in lean and obese adults. One-hundred seven participants received four preload trials before and after a dietary intervention in this randomized cross-over trial with the stipulation that lean and obese individuals were evenly assigned to each intervention. The study entailed monitoring appetitive sensations and daily energy intake after consumption of low and high energy beverage and solid food loads on weekly visit days. Preload testing was conducted at baseline, followed by daily ingestion of one load for 14 days and then retesting responses to the four treatments. Lean individuals compensated precisely for the high energy beverage and solid loads from the onset of the study, whereas the obese did not alter eating patterns after consuming the higher energy beverage load. The learning intervention did not have an effect on the responses to the preloads, as responses in both lean and obese participants did not differ from baseline values. Responses to personality and eating behavior questionnaires revealed differences between the lean and obese groups and weakly, but significantly, predicted challenge meal and total daily energy intake. These data suggest that lean and obese individuals respond to energy in beverage form differently, and this is not altered by purposeful daily exposure to loads varying in physical form and energy content for two weeks.

Effects of repeated consumption on sensory-enhanced satiety

Previous research has suggested that sensory characteristics of a drink modify the acute satiating effects of its nutrients, with enhanced satiety being evident when a high-energy drink was thicker and tasted creamier. The present study tested whether this modulation of satiety by sensory context was altered by repeated consumption. Participants (n 48) consumed one of four drinks mid-morning on seven non-consecutive days, with satiety responses being measured pre-exposure (day 1), post-exposure (day 6) and at a 1-month follow-up. The drinks combined two levels of energy (lower energy (LE), 326 kJ and higher energy, 1163 kJ) with two levels of satiety-predictive sensory characteristics (low sensory (LS) or enhanced sensory). Test lunch intake 90 min after drink consumption depended on both the energy content and sensory characteristics of the drink before exposure, but on the energy content alone after exposure and at the follow-up. The largest change was an increase in test meal intake over time in the LE/LS condition. The effects on intake were reflected in appetite ratings, with rated hunger and expected filling affected by sensory characteristics and energy content pre-exposure, but were largely determined by energy content post-exposure and at the follow-up. In contrast, a measure of expected satiety reflected sensory characteristics regardless of energy content on all the three test days. Overall, these data suggest that some aspects of the sensory modulation of satiety are changed by repeated consumption, with covert energy becoming more effective in suppressing appetite over time, but also suggest that these behavioural changes are not readily translated into expectations of satiety.

Texture and satiation: the role of oro-sensory exposure time

One of the characteristics of the current obesogenic food supply is the large availability of foods that can be ingested quickly. Controlled nutrition intervention studies have shown that the ingestion of simple energy containing beverages, which are consumed very quickly, do not lead to a lower compensatory intake of other foods. One of the theories behind this observation is that calories that are ingested quickly are not well sensed by the sense of taste, and do not lead to an adequate satiety response. This idea is confirmed by the results of a series of studies, where we have shown that the low satiation/satiety response of beverages can be largely attributed to their short oral residence time. Prolonging the oro-sensory exposure time to foods leads to earlier meal termination and/or a higher satiety response. The low satiation/satiety response to simple energy containing beverages is congruent with the observation from studies on the cephalic phase response to foods, i.e. the physiological response to sensory signals. Energy containing beverages do not lead to an adequate cephalic phase response. Various recent studies showed that slower eating leads to higher levels of satiety hormones. These results are in line with the idea that the sense of taste is a nutrient sensor which informs the brain and the gut about the inflow of nutrients. The sense of taste has an important contribution to the satiating effect of foods. One of the challenges in future research is to see whether or not these proofs of principles can be applied in longer term studies with regular commercial foods. This may make our obesogenic food supply more satiating, and may lead to a lower energy intake.

Successful development of satiety enhancing food products: towards a multidisciplinary agenda of research challenges

In the context of increasing prevalence of overweight and obesity in societies worldwide, enhancing the satiating capacity of foods may help people control their energy intake and weight. This requires an integrated approach between various food-related disciplines. By structuring this approach around the new product development process, this paper aims to present the contours of such an integrative approach by going through the current state of the art around satiety enhancing foods. It portrays actual food choice as the end result of a complex interaction between internal satiety signals, other food benefits, and environmental cues. Three interrelated routes to satiating enhancement are to change the food composition to develop stronger physiological satiation and satiety signals, anticipate and build on smart external stimuli at the moment of purchase and consumption, and improve palatability and acceptance of satiety enhanced foods. Key research challenges in achieving these routes in the field of nutrition, food technology, consumer, marketing, and communication are outlined.