Novel flavours paired with glutamate condition increased intake in older adults in the absence of changes in liking

The effect of high-polyphenol sumac (Rhus coriaria) on food intake using sensory and appetite analysis in younger and older adults: A randomized controlled trial

Aging is accompanied by a decline in appetite and food intake with associated deficiencies in both macronutrients and micronutrients. The aim of this study was to investigate the impact of adding Iranian brown sumac (Rhus coriaria) (CIBS) into butternut squash soup on sensory evaluation and food intake among older adults (n = 20; >65 years old) and younger adults (n = 20; 18-35 years old). To evaluate the polyphenol content and antioxidant activity of the sumac samples, a Folin-Ciocalteu assay (FCR) and ferric ion reducing antioxidant power (FRAP) assay were used, respectively. L-glutamic acid was assessed using a Megazyme L-glutamic acid assay. Compusense software was used to assess the sensory evaluation attributes of free-living older adults and younger adults receiving different doses of sumac in butternut squash soup. Nutritics software was used to assess food intake following the addition of 0.37 g of sumac to soup. CIBS was selected based on a preliminary assessment in vitro for L-glutamic acid, antioxidant, and polyphenol content of six varieties of sumac. Sensory evaluation results revealed that the difference in perceived intensity of brown color between the soup samples with different doses of CIBS was greater in the younger adults' group (p = .001) than in older adults (p = .037). In addition, the food intake study found that during the ad libitum lunch, older adults consumed more energy (kcal; p = .014), protein (g; p = .025), carbohydrate (g; p = .013), and fat (g; p = .002) after soup with sumac compared to control soup. The overall findings of this study suggest that the addition of sumac to food may have a potential benefit in enhancing ad libitum lunch intake in older adults leading to effective management of malnutrition. This may promote healthy aging and minimize the burden and the consequences of anorexia of aging as main public health concerns.

Dysgeusia: A review in the context of COVID-19

Background

Taste disorders in general, and dysgeusia in particular, are relatively common disorders that may be a sign of a more complex acute or chronic medical condition. During the COVID-19 pandemic, taste disorders have found their way into the realm of general as well as specialty dentistry, with significance in screening for patients who potentially may have the virus.

Types of Studies Reviewed

The authors searched electronic databases (PubMed, Embase, Web of Science, Google Scholar) for studies focused on dysgeusia, ageusia, and other taste disorders and their relationship to local and systemic causes.

Results

The authors found pertinent literature explaining the normal physiology of taste sensation, proposals for suggested new tastes, presence of gustatory receptors in remote tissues of the body, and etiology and pathophysiology of taste disorders, in addition to the valuable knowledge gained about gustatory disorders in the context of COVID-19. Along with olfactory disorders, taste disorders are one of the earliest suggestive symptoms of COVID-19 infection.

Conclusions

Gustatory disorders are the result of local or systemic etiology or both. Newer taste sensations, such as calcium and fat tastes, have been discovered, as well as taste receptors that are remote from the oropharyngeal area. Literature published during the COVID-19 pandemic to date reinforces the significance of early detection of potential patients with COVID-19 by means of screening for recent-onset taste disorders.

Practical Implications

Timely screening and identification of potential gustatory disorders are paramount for the dental care practitioner to aid in the early diagnosis of COVID-19 and other serious systemic disorders.

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.

Aging and the (Chemical) Senses: Implications for Food Behaviour Amongst Elderly Consumers

The growing aging population are increasingly suffering from the negative health consequences of the age-related decline in their senses, especially their chemical senses. Unfortunately, however, unlike for the higher senses of vision and hearing, there is currently nothing that can be done to bring back the chemical senses once they are lost (or have started their inevitable decline). The evidence suggests that such chemosensory changes can result in a range of maladaptive food behaviours, including the addition of more salt and sugar to food and drink in order to experience the same taste intensity while, at the same time, reducing their overall consumption because food has lost its savour. Here, though, it is also important to stress the importance of the more social aspects of eating and drinking, given the evidence suggesting that a growing number of older individuals are consuming more of their meals alone than ever before. Various solutions have been put forward in order to try to enhance the food experience amongst the elderly, including everything from optimising the product-intrinsic food inputs provided to the remaining functional senses through to a variety of digital interventions. Ultimately, however, the aim has to be to encourage healthier patterns of food consumption amongst this rapidly-growing section of the population by optimising the sensory, nutritional, social, and emotional aspects of eating and drinking. An experimental dinner with the residents of one such home where nostalgic-flavoured healthy ice-creams were served is described.

Breaking the vicious circle of diet, malnutrition and oral health for the independent elderly

Aging impairs senses, mastication, oral status and function, causing nutritional needs and diet insufficiencies. The present needs of independent older adults suggest that health research and oral health care should shift from reductionist disease management to integral and personal treatment plans, including lifestyle, psychological, nutritional and oral health coaching approaches. Dentists and other medical professionals that work in the field of gerodontology should be educated on the macro and micronutrient needs of the elderly and incorporate certain nutritional plans early in the life of their patients with their approval and cooperation, in order to postpone tooth loss and masticatory impairment. Old recipes such as the Mediterranean diet should be kept as a base for all the elderly and be enriched in a customized interpersonal way from the dentist as well as the medical professional according to the specific needs of one's oral and general health status. In this nonsystematic review paper, the basic aspects of the vicious cycle of nutrition and oral health status are discussed and suggestions of major nutrients' influence and needs for independent elders are reported. Based on the scientific data collected, suggestions are made for the food industry for better quality and dosage of foods for this category of individuals. Such strategies can be a whole new area of interest for the food industry in order to obtain better quality of food packaging for the independent OA with accepted texture, odor, colors, macronutrients and micronutrients' consistency and in specific portions.

Quercetin mitigates monosodium glutamate-induced excitotoxicity of the spinal cord motoneurons in aged rats via p38 MAPK inhibition

Various studies reported the possibility of deterioration of blood-brain barrier (BBB) integrity owing to the aging process. The current work was performed to investigate the ability of Monosodium glutamate (MSG) to cross BBB in aged rats, the damage affecting the anterior horn cells of the spinal cord due to excitotoxicity, and the mechanisms by which quercetin (Que) administration might suppress such damage. Forty male rats aged 18 months were assigned equally to 4 groups: control group, Que group (received Que, 20 mg/kg/d intraperitonealy for 10 days), MSG group (received MSG, 4.0 g/kg/d subcutaneously for 10 days), MSG + Que group (received both Que and MSG as done in the Que and MSG groups respectively). Cervical spinal cord specimens were obtained and prepared for routine histological study, immunohistochemical staining by caspase-3 and glial fibrillary acidic protein (GFAP), assessment of oxidative stress, measurement of cytokines, assessment of caspase-3 activity and GFAP levels as well as for western blotting of phosphorylated activating transcription factor 2 (ATF2^pp) as an indicator for the activity of p38 mitogen-activated protein kinase (MAPK). The MSG group revealed variable degenerative and apoptotic changes in the motoneurons and neuroglia, a marked rise in the cytoplasmic caspase-3 expression in motoneurons and a significant reduction (p < 0.001) in the astrocyte surface area percentage. In addition, the spinal cord tissue exhibited a significant elevation (p < 0.001) in the levels of malondialdehyde (MDA), IL-1, IL-6, TNFα, INFɣ, caspase-3 activity and ATF2 ^pp expression as well as a significant reduction (p < 0.001) in SOD, IL-10 and GFAP levels compared with the control group. On combining Que with MSG, most of the degenerative changes were reversed and all the impaired parameters were nearly normalized except for IL-6 and GFAP levels which were still significantly (p < 0.05) different from those of the control group. Our study suggests that MSG can break through the BBB of the aged rats and induce excitotoxicity dependent changes in spinal cord motoneurons. Most of these changes were reversed by Que probably via targeting the p38 MAPK-ATF2 pathway, antagonizing oxidative stress, anti-inflammatory effect, and promoting GFAP expression.

Potential effects of umami ingredients on human health: Pros and cons

Umami taste is the most recent confirmed basic taste in addition to sour, sweet, bitter, and salty. It has been controversial because of its effects on human nutritional benefit. Based on the available literatures, this review categorized 13 positive and negative effects of umami taste on human health. On the positive side, umami taste can improve food flavor and consumption, improve nutrition intake of the elderly and patients, protect against duodenal cancer, reduce ingestion of sodium chloride, decrease consumption of fat, and improve oral functions. On the other hand, umami taste can also induce hepatotoxicity, cause asthma, induce migraine headaches, damage the nervous system, and promote obesity. Due to its novelty, there are many functions and effects of umami taste waiting to be discovered. With further investigation, more information regarding the effects of umami taste on human health will be discerned.

Considerations for the Development of Innovative Foods to Improve Nutrition in Older Adults

The population of older adults is growing globally. This increase has led to an accumulation of chronic illnesses, so-called age-related diseases. Diet and nutrition are considered the main drivers of the global burden of diseases, and this situation applies especially to this population segment. It relates directly to the development of coronary heart disease, hypertension, some types of cancer, and type 2 diabetes, among other diseases, while age-associated changes in body composition (bone and muscle mass, fat, sarcopenia) constitute risk factors for functional limitations affecting health status and the quality of life. Older adults present eating and swallowing problems, dry mouth, taste loss, and anorexia among other problems causing “anorexia of aging” that affects their nutritional status. The strategies to overcome these situations are described in this study. The impact of oral food processing on nutrition is discussed, as well as approaches to improve food acceptance through the design of innovative foods. These foods should supply a growing demand as this group represents an increasing segment of the consumer market globally, whose needs must be fulfilled.

Influence of Monosodium Glutamate and Its Substitutes on Sensory Characteristics and Consumer Perceptions of Chicken Soup

Soup manufacturers are removing monosodium glutamate (MSG) to meet consumer demand for natural ingredients. This research investigated the influence of MSG and its substitutes (yeast extract: YE; mushroom concentrate: MC; tomato concentrate: TC) on clear chicken soup with 0.4% sodium chloride (salt) by comparing sensory attributes and consumer acceptability among each other, and to a chicken soup sample containing 0.5% salt (Salt 0.5%). The soup with 0.4% salt without enhancers was designated as the control. Corresponding list of ingredients was also presented to consumers to study the effects on consumer expectations about chicken soup products. Our results showed that MSG and its substitutes significantly (P < 0.05) enhanced the sensory properties of chicken soup. These flavor enhancers also achieved statistically same or stronger improvement in overall flavor, meaty flavor, chicken flavor and umami taste when compared to Salt 0.5% sample. Consumers significantly preferred MSG 0.1%, YE 0.025%, and Salt 0.5% samples than others. Compared to MC and TC samples, less consumers perceived MSG and YE samples as “free of artificial” and “natural” with lower consumption interest. Claims about artificial/natural ingredients were attractive selling points for chicken soups, but good sensory appealing was the most important attribute linearly affecting consumer satisfactions.

Optimizing nutrition in older people

Older adults are at increased risk of malnutrition, for a variety of physiological and psychological reasons. This has implications for health, quality of life, independence and economic circumstances. Improvements in nutrition are known to bring tangible benefits to older people and many age-related diseases and conditions can be prevented, modulated or ameliorated by good nutrition. However, practical and realistic approaches are required to optimize diet and food intake in older adults. One area where improvements can be made relates to appetite. Encouraging older adults to prepare meals can increase appetite and food intake, and providing opportunities for older adults to eat a wide variety of foods, in company, is a simple strategy to increase food intake. The protein requirement of older adults is subject to controversy and although considered the most satiating macronutrient, it appears that protein does not elicit as great a satiating effect in older adults as it does in younger individuals. This indicates that there is potential to increase protein intake without impacting on overall energy intake. Other areas where simple practical improvements can be made include both packaging of foods that are easy to prepare and the education of older adults on the safe storage and preparation of food. Research into improving the diets and nutritional status of older adults has indicated that many of the strategies can be easily and cost-effectively undertaken.

Explicit wanting and liking for palatable snacks are differentially affected by change in physiological state, and differentially related to salivation and hunger

Incentive salience theory (IST) suggests that 'wanting' and liking are dissociable processes. We argue that explicit measures of wanting in humans can reflect the impact of implicit 'wanting' as envisaged by IST, suggesting that dissociations should also be evident for explicit judgments of wanting and liking. To test this, participants were asked to make ratings of these variables for 8 palatable snack foods - and in a related test salivation rate was also assessed. Participants viewed and sniffed each snack food and rated wanting, and then sampled it and rated liking and whether they wanted more of it. Following a lunch eaten to satiety, and composed in part of half of the palatable snack foods, participants repeated their evaluations of the snack foods (and salivation rate). Liking changed less across lunch than wanting and want more ratings, the last-mentioned changing the most. Change in liking was associated with change in salivation rate, independent of wanting, and change in wanting was associated with change in hunger independent of liking. We argue these dissociations are consistent with 'wanting' influencing explicit wanting, and that want more ratings may represent a 'purer' measure of IST 'wanting'.

Can We Selectively Reduce Appetite for Energy-Dense Foods? An Overview of Pharmacological Strategies for Modification of Food Preference Behavior

Excessive intake of food, especially palatable and energy-dense carbohydrates and fats, is largely responsible for the growing incidence of obesity worldwide. Although there are a number of candidate antiobesity drugs, only a few of them have been proven able to inhibit appetite for palatable foods without the concurrent reduction in regular food consumption. In this review, we discuss the interrelationships between homeostatic and hedonic food intake control mechanisms in promoting overeating with palatable foods and assess the potential usefulness of systemically administered pharmaceuticals that impinge on the endogenous cannabinoid, opioid, aminergic, cholinergic, and peptidergic systems in the modification of food preference behavior. Also, certain dietary supplements with the potency to reduce specifically palatable food intake are presented. Based on human and animal studies, we indicate the most promising therapies and agents that influence the effectiveness of appetite-modifying drugs. It should be stressed, however, that most of the data included in our review come from preclinical studies; therefore, further investigations aimed at confirming the effectiveness and safety of the aforementioned medications in the treatment of obese humans are necessary.

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.

Effects of chronic dietary exposure to monosodium glutamate on feeding behavior, adiposity, gastrointestinal motility, and cardiovascular function in healthy adult rats

BACKGROUND

Monosodium glutamate (MSG) is a flavor-enhancer widely used as a food additive. However, its safe dietary concentration and its toxicity, including its possible implication in the recent metabolic syndrome pandemia, is still a controversial issue. Therefore, a deep knowledge of its effects upon regular dietary use is needed. Our aim was to evaluate the effects of chronic exposure to MSG on feeding behavior, abdominal fat, gastrointestinal motility, and cardiovascular function in rats.

METHODS

Two groups of adult male Wistar rats were used: control and treated with MSG (4 g/L in drinking water) for 6 weeks. Different functional parameters were determined and the histological structure was analyzed in tissues of interest.

KEY RESULTS

Compared to control animals, chronic MSG increased water intake but did not modify food ingestion or body weight gain. Neither the abdominal fat volume nor the fat fraction, measured by magnetic resonance imaging, was modified by MSG. Monosodium glutamate did not alter general gastrointestinal motility, but significantly increased the colonic response to mechanical stimulation. It slightly reduced endothelium-dependent relaxation in aorta, without significantly modifying any other cardiovascular parameters. No significant histological alterations were detected in salivary glands, intestinal wall, aorta, heart, and kidney.

CONCLUSIONS & INFERENCES

Chronic treatment with MSG in the adult rat increased water intake. This supports its potential to improve acceptance of low-fat regimens and to increase hydration in the elderly and sportspeople, often at risk of dehydration. Changes in colonic contractility and cardiovascular function could have some long-term repercussions warranting further research.