More Than Just a Pretty Face. The Relationship Between Infant’s Temperament, Food Acceptance, and Mothers’ Perceptions of Their Enjoyment of Food

The goal of the present study was to determine whether mothers’ assessment of their infants’ temperament is associated with objective measures of the infant’s acceptance patterns and their judgments of the infants’ liking of a green vegetable. To this end, infants (N = 92) were video-recorded as their mothers fed them green beans. From these videos, we determined the frequency of facial distaste expressions made during the first 2 min of the feeding. Other measures included intake, maternal ratings of infants’ enjoyment of this vegetable, and temperament. Infants who scored high on the approach dimension of the temperament questionnaire were less likely to express facial expressions of distaste, consumed more food, and were perceived by their mothers as enjoying the food more. Mediation analyses revealed that ratings of enjoyment were not directly related to the child’s approach temperament, but rather the relationship between mothers’ ratings and temperament was mediated by the amount of time infants spent eating the vegetable. Regression analyses suggested that in addition to the length of time children ate, mothers’ ratings of their infants’ enjoyment was predicted by the number of squints that the infant expressed during the meal. These findings suggest that although certain aspects of children’s temperament are related to their food acceptance, mothers attend to facial expressions and time spent eating independently of these temperamental characteristics when judging their infant’s enjoyment of a food. Understanding how mothers use this information to decide which foods to feed their infants is an important area for future research

The Relationship Between Infant Facial Expressions and Food Acceptance

Purpose of Review To highlight the range of methodological approaches used to objectively measure hedonic responses to taste stimuli during the first year of life and how these behavioral responses change with experience. Challenges inherent to this type of research are discussed. Recent Findings Although newborns display characteristic orofacial reactivity to four of the five basic tastes, the facial expressions made and the amount of food consumed can be modified by experience: children learn to like what they are fed. In some cases, changes in facial responses are concordant with infant consumption, whereas in other cases facial reactivity follows changes in intake. Summary Together with ingestive measurements, precise and objective measurements of orofacial reactivity provide an understanding of how early experiences shift the hedonic tone of the taste of foods, the foundation of dietary preferences

Innate and learned preferences for sweet taste during childhood

Purpose of review: In nature, carbohydrates are a source of energy often equated with sweetness, the detection of which is associated with powerful hedonic appeal. Intakes of processed carbohydrates in the form of added sugars and sugar-sweetened beverages have risen consistently among all age groups over the last two decades. In this review, we describe the biological underpinnings that drive the consumption of sweet-tasting foods among pediatric populations. Recent findings: Scientific literature suggests that children\u27s liking for all that is sweet is not solely a product of modern-day technology and advertising but reflects their basic biology. In fact, heightened preference for sweet-tasting foods and beverages during childhood is universal and evident among infants and children around the world. The liking for sweet tastes during development may have ensured the acceptance of sweet-tasting foods, such as mother\u27s milk and fruits. Moreover, recent research suggests that liking for sweets may be further promoted by the pain-reducing properties of sugars

An experimental approach to study individual differences in infants\u27 intake and satiation behaviors during bottle-feeding

Background: As a group, bottle-fed infants are at higher risk for rapid weight gain compared with breast-fed infants. However, little is known about individual differences in feeding behaviors of bottle-feeding infants, as well as maternal and infant characteristics associated with bottle-feeding outcomes. Methods: We conducted a 2-day, within-subject study of 21 formula-feeding dyads; the within-subject factor was feeding condition: mother-led (ML; mothers were given the instruction to feed their infants as they typically would) vs. infant-led (IL; the experimenter ensured feeding began when infants signaled hunger and ended when they rejected the bottle on three consecutive occasions). Intake was determined by bottle weight; feedings were video-recorded and later analyzed to determine feeding duration and types of satiation behaviors displayed. Percent difference scores were calculated for each outcome as [((ML – IL)/IL) × 100] to standardize differences among dyads. Mothers completed questionnaires of feeding styles and infant temperament. Results: On average, infants consumed ∼42% more formula during the ML- than IL-condition (p = 0.03). However, notable variation existed in difference scores for intake (range = −52.8% to 268.9%; higher scores reflect greater intake during ML than IL). Stepwise regression illustrated that greater intakes during the ML-condition were predicted by the combination of: (1) higher infant age; (2) lower levels of infant rhythmicity and adaptability; (3) higher levels of infant positive mood; and (4) lower levels of maternal restrictive and responsive feeding styles. Conclusions: This objective, experimental approach illustrated that variation in bottle-feeding outcomes is associated with characteristics of both members of the dyad

Free amino acid content in infant formulas

Purpose – Infant formula is the sole nutrition and food source for many infants. Information on the free amino acid (FAA) content of formulas, particularly those that are protein hydrolysate based, is limited, despite emerging evidence for the role of FAAs in regulating eating behaviour. The purpose of this paper is to measure levels of essential, semi‐essential, and nonessential FAAs in commercially available infant formulas to provide a foundation for future research examining the influence of FAAs on infant development. Design/methodology/approach – Using an automatic amino acid analyzer, we measured the concentrations of FAAs in four types of formula: two cow milk (CMF); three soy protein (SPF); and three protein hydrolysate (PHF), one of which was a partial hydrolysate (pPHF) and two of which were extensive hydrolysate (ePHF). Findings – It was found that the amount and number of FAAs varied significantly across formula types: for CMF, total FAAs ranged from 523‐864 μmol/L, with taurine being the most prominent; SPF, 1933‐2450, methionine; pPHF, 2329, taurine; and ePHF, 80375‐85445, leucine. ePHF had the highest levels and the most diversified profiles of FAAs. Research limitations/implications – Striking discrepancies exist for FAA profiles of infant formulas. Comparison of these data to published psychophysical data on the taste qualities of individual FAAs provides insights into the unique flavor profiles of infant formulas. Overall, the data from this study provide a necessary foundation for future research examining the influence of FAAs in formulas on infant growth and development. Originality/value – Published data on the FAA content of PHF is limited, despite their increased availability and use. This research is the first to report the FAA content of partial and extensive PHF, and to compare these values to CMF and SPF

Acute alcohol consumption disrupts the hormonal milieu of lactating

Abstract Despite the lack of scientific evidence to support the claim that alcohol is a galactagogue, lactating women have been advised to drink alcohol as an aid to lactation for centuries. To test the hypothesis that alcohol consumption affects the hormonal response in lactating women, we conducted a withinsubjects design study in which 17 women consumed a 0.4 g/kg dose of alcohol in orange juice during one test session and an equal volume of orange juice during the other. Changes in plasma prolactin, oxytocin, and cortisol levels during and after breast stimulation, lactational performance, and mood states were compared under the two experimental conditions. Oxytocin levels significantly decreased, whereas prolactin levels and measures of sedation, dysphoria, and drunkenness significantly increased, during the immediate hours after alcohol consumption. Changes in oxytocin were related to measures of lactational performance such as milk yield and ejection latencies, whereas changes in prolactin were related to self-reported measures of drunkenness. Although alcohol consumption resulted in significantly higher cortisol when compared with the control condition, cortisol levels were not significantly correlated with any of the indices of lactational performance or self-reported drug effects. Moreover, cortisol levels steadily decreased on the control day, indicating that the procedures were not stressful to the subjects. In conclusion, recommending alcohol as an aid to lactation may be counterproductive. In the short term, mothers may be more relaxed, but the Correspondence to: Julie A. Mennella. Address all correspondence and requests for reprints to: Julie A. Mennella, Ph.D., 3500 Market Street, Philadelphia, Pennsylvania 19104-3308. E-mail: [email protected] hormonal milieu underlying lactational performance is disrupted, and, in turn, the infant's milk supply is diminished. THE TRADITIONAL WISDOM of many cultures relates that women can optimize the quality and quantity of their milk to meet the needs of their infants through diet and psychological well-being. Each culture claims some milk-producing (galactogenic) substances, and many cultures claim alcohol to be such a substance (1). Such beliefs were so ingrained in American tradition that, in 1895, Anheuser-Busch Company, a major U.S. brewery, produced MaltNutrine, a low-alcoholic beer that was sold exclusively in drugstores and prescribed by physicians as a tonic for pregnant and lactating women (2). Even in more modern times, a popular book for nursing mothers hailed the virtues of alcohol as a galactagogue, claiming ". . . this is one time in life when the therapeutic qualities of alcohol are a blessing " (3). Such claims have not gone unchallenged. In 1987, the Journal of the American Medical Association published a letter from a physician asking whether there was any scientific basis for prescribing a daily beer to lactating women (4). The scientific basis, it was declared (5), can be found in the finding that the consumption of beer, unlike other alcoholic beverages, increases serum prolactin (5,6). There are several problems with this conclusion, however. First, the subjects in these research studies were men and nonlactating women. No study to date had examined the effects of alcohol consumption on the hormonal milieu of lactating women, additionally highlighting the lack of evidence-based practice related to recommendations regarding alcohol consumption during lactation. There has been considerable research in animal models (for review, see Ref. 7), however. Although the vast majority of these studies reported that ethanol administration decreased suckling-induced prolactin, the most recent study, which extended the observation period Second, the rise in prolactin levels after alcohol consumption was observed after the consumption of different types of alcoholic beverages (9,10) and was not specific to beer consumption, as the folklore suggested (2,4,5). Moreover, if alcohol does indeed increase prolactin levels in maternal circulation, it is not apparent whether such increases affect lactational performance. Although prolactin appears to be essential for the initiation of lactation and its maintenance in the long term (11), no clear temporal correlation exists between plasma prolactin levels and milk yield of a particular breastfeed in humans (12). Third, it is perplexing that one would argue that alcohol enhances lactational performance when this same drug, at similar or slightly higher doses, was used in the not-so-distant past to treat premature labor Fourth, research conducted during the past decade refutes the lore that alcohol is a galactagogue. Rather, lactating mothers produced less milk without changes in the caloric content of their milk (16), and, in turn, infants consumed less breast milk and less calories during the immediate hours after maternal consumption of beer as well as other types of alcoholic beverages NIH-PA Author Manuscript The present study tested the hypothesis that the alcohol-induced depression in milk production in lactating women was due to disruptions in the hormonal milieu. Oxytocin and prolactin responses were evaluated when lactating women consumed a moderate dose of alcohol, one that was equivalent to one to two drinks and represents the average amount of alcohol lactating women reported consuming during a drinking occasion (20). Subjects and Methods Subjects Seventeen nonsmoking, healthy lactating women (six primiparous and 11 multiparous), who were exclusively nursing infants between the ages of 2 and 4 months, were recruited from ads in local newspapers and newsletters. One additional woman began testing but was excluded because of procedural difficulties. During initial screening, women were excluded if they were lifetime alcohol abstainers, on any medication including oral contraceptives, or had resumed menstruation, because there is some suggestion that both basal and peak prolactin levels are lower in such women (21). All procedures were approved by the Office of Regulatory Affairs at the University of Pennsylvania, and each subject gave informed written consent before testing. The women (10 Caucasian, five African American, one Asian, and one from another ethnic group) were, on average, 31.9 ± 1.2 yr of age, with a mean body mass index of 26.4 ± 1.1 kg/ m 2 . They reported that alcohol intake was low during pregnancy (mean = 0.2 ± 0.1 standard drinks per month) but significantly increased to, on average, 1.5 ± 0.6 drinks per month during lactation [paired t-test (16df) = -2.14; P = 0.048]. These numbers likely underestimate alcohol usage (22). Procedures A within-subjects design study that controlled for time of day was employed because milk composition and hormonal responses vary throughout the day. Using methodologies developed for the study of neurally mediated hormonal responses in humans (23), women were tested at the General Clinical Research Center (GCRC) at the University of Pennsylvania on 2 d separated by 1 wk (±2 d). After abstaining from alcohol for at least 3 d, all subjects arrived at the GCRC at 0800 h (±30 min) after an overnight fast and remained fasted during the entire testing procedures, because prolactin levels can be potentiated by certain gastrointestinal hormones and high blood glucose levels (24). Mothers were not allowed to watch television, sleep, or talk, as well as read about food or infants throughout the entire testing session because these behaviors may affect the hormones under study. Instead, they were able to read magazines or novels or to converse on other topics. Moreover, infants were not present because the mere sound, sight, or smell of the baby often stimulates milk let-down or leaking (25). Breast stimulation was provided by an electric breast pump because prior work revealed that infants ′ sucking intensity changes when their mothers′ milk contains alcohol (20). Approximately 30 min after arrival, an iv line was inserted into the antecubital vein of an arm. Because prolactin is very stress labile and rises during the first half-hour after a needle prick (26), subjects acclimated in a private testing room for 45 min. After acclimatization, blood samples were obtained at fixed intervals (-40, -25, and -10 min) before drinking a 0.4 g/kg dose of alcohol in orange juice (15% vol/vol) on one testing day (alcohol condition) and an equal volume of orange juice on the other day (control condition). During both conditions, 3 ml of alcohol were pipetted onto the surface of the cup to serve as a smell and flavor mask (27). The order of testing was randomized between subjects. The beverage was aliquoted into two equal volumes, and each aliquot was consumed within consecutive 5-min periods. As shown in Blood alcohol concentrations (BAC; g/liter) were estimated by having subjects breathe into an Alco-Sensor III (Intoximeters, Inc., St. Louis, MO) throughout the test sessions ( Hormone assays Plasma samples were measured in duplicate by double-antibody RIAs for oxytocin and cortisol and by immunoradiometric assay for prolactin. Standards were run with each assay. All samples from a given subject from both days (alcohol and control) of testing were run within the same assay to reduce interassay variability. Cortisol levels were monitored on the control day to ensure that alterations in hormonal responses were not related to the stress of the procedures (10). Intraassay variation was 2.8, 3.0, and 1.3%, and interassay variation was 1.9, 8.9, and 10.2% for oxytocin, prolactin, and cortisol, respectively. All assays were performed by the Diabetes Research Center of the University of Pennsylvania. Oxytocin was assayed without extraction by using a competitive RIA, with materials supplied by Phoenix Pharmaceuticals, Inc. (Belmont, CA). The antiserum cross-reactivity with arginine vasopressin, GH, α-atrial natriuretic peptide (1-28), methionine-enkephalin, GH-releasing factor, somastatin, TRH, vasoactive intestinal peptide, and pituitary adenylate cyclaseactivating polypeptide 27-NH 2 is 0%. The minimal detectable concentration was 10 pg/ml (8 pmol/liter). Prolactin was assayed by a direct, two-site immunoradiometric assay without extraction, using materials supplied by ICN Diagnostics (Costa Mesa, CA). The antiserum cross-reactivity is less than 0.01% for human chorionic gonadotropin, TSH, LH, and FSH. The minimal detectable concentration was 2.5 ng/ml (108.8 pmol/liter). Cortisol was measured without extraction by a competitive double-antibody RIA kit from ICN Diagnostics. The antiserum cross-reacts 12.3% with 11-deoxycortisol, 5.5% with corticosterone, and less than 2.7% with all other steroids tested. Data analyses Separate repeated measures mixed ANOVA were conducted to determine whether there were significant differences in prolactin, oxytocin, cortisol, and BAC levels, as well as various measures of self-reported drug effects with experimental condition (alcohol and control) and time as the within-subjects factors. When significant, post hoc Fisher least significant difference analyses were conducted. Because there were no significant differences in the basal values for oxytocin [F(2,32df) = 2.17; P = 0.13] and prolactin [F(2,32df) = 0.50; P = 0.61], we calculated changes in prolactin and oxytocin from respective baseline value (mean of three baseline samples) for each subject. There was a significant effect of time on cortisol baseline samples [F(2,32df) = 60.77; P < 0.0001]. Therefore, the last sample (t =-10 min) was used as the baseline value. We then determined the peak value for each hormone when compared with baseline and calculated the area under the curve (AUC) values by using a point-to-point method (OriginLab Corporation, Northampton, MA) from baseline to the end of the test session (t = 140 min). The areas for each hormone and for each subject were calculated independently. Paired t-tests were used to compare the peak value of each hormone and the AUC between experimental conditions, respectively. The critical value for significance was P < 0.05, and all P values represent two-tailed tests. Results Hormonal responses and lactational performance Oxytocin. There was a significant interaction between condition and time on oxytocin levels [F(15,240df) = 1.83; P = 0.03]. As shown in Although there were no significant correlations with oxytocin AUC during breast stimulation and milk ejection latency Twelve of the 17 women produced less oxytocin during breast stimulation on the alcohol day when compared with the control day (P < 0.05). These women also had lower milk yields during the 16 min of pumping when compared with the remaining women [F(1,15df) = 9.35; P = 0.008]. They produced, on average, 13 ± 7% less milk during these 16 min of pumping (control vs. alcohol, 131 ± 10 vs. 113 ± 11 ml). There were no significant relationships between the oxytocin AUCs or oxytocin levels on either the control or alcohol day and any of the selfreported measured indices of drug effects (all P values >0.10). Prolactin. There was a significant interaction between condition and time on prolactin plasma levels [F(15,240df) = 3.31; P < 0.001]. As shown in NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript = 3.52; P = 0.003]. This enhanced response was observed in 76% of the women tested (P = 0.02). Although there were no significant relationships on the control day between prolactin levels and milk ejection latency or amount of milk expressed (all P values > 0.10), prolactin AUCs during breast stimulation were significantly correlated with milk ejection latencies on the day women consumed alcohol ( Cortisol. Although the repeated measure mixed ANOVA analysis revealed only a tendency for an interaction effect between condition and time for cortisol levels [F(15,240df) = 1.63; P = 0.07], there were significant effects of condition [F(1,16df) = 5.91; P = 0.03] and time [F (15,240df) = 4.39; P < 0.001] on cortisol levels. As shown in Ethanol pharmacokinetics and self-reported drug effects BAC peaked approximately 43-51 min after alcohol consumption and decreased thereafter. As shown in Discussion Moderate alcohol consumption disrupted the two key hormones underlying lactational performance. During the immediate hours after alcohol consumption, oxytocin levels significantly decreased, whereas prolactin levels significantly increased both during and after breast stimulation. The magnitude and persistence of the hormonal response in lactating women is more robust when compared with men and nonlactating women (5,6,9,10), further highlighting the dynamics of the system under study. The diminished oxytocin response was significantly related to decreases in milk yield and milk ejection. These latter findings suggest that such changes in hormonal responses mediate the diminished milk production by lactating women (16) and disruption in their infants′ suckling behaviors and milk intake observed in prior research In contrast to the response observed for oxytocin, prolactin levels significantly increased after alcohol consumption both during and after periods of breast stimulation. The alcohol-induced increases in prolactin were related to self-reported perceptions of drunkenness. Women also reported increased feelings of sedation and dysphoria during the immediate hours after alcohol consumption. Because sleep deprivation increases feelings of sedation and dysphoria (32), we hypothesize that sleep deprivation, which is common among mothers of young infants, contributed to the increased feelings of sedation and dysphoria observed on the day lactating women consumed alcohol, as discussed herein. Although prolactin levels during breast stimulation were related to milk ejection latency on the day women consumed alcohol, it should be emphasized that no relationships were observed between prolactin levels or AUCs and the amount of milk produced on either test day. This is consistent with prior research revealing that although prolactin appears to be essential for the initiation of lactation and its maintenance in the long term (11), no clear temporal correlation exists between plasma prolactin levels and milk yield of a particular breastfeed in humans (12). It remains to be determined whether the relationship between alcohol-induced changes in prolactin and milk ejection latency was a spurious correlation and secondary to the effect of alcohol on other mediating factors underlying ejection. Cortisol levels were also increased during the test session in which women consumed the alcoholic beverage, a finding that is consistent with research from animal models (33) and some human studies (34). However, such changes in cortisol were not related to changes in oxytocin or prolactin, measures of lactational performance, or mood states. The production, secretion, and ejection of milk are the result of highly synchronized endocrine and neuroendocrine processes, which are governed, in part, by the frequency and intensity of the infants′ sucking. Breast stimulation resulted in transient release of both oxytocin and prolactin to levels previously observed by other researchers (35). Although these two key hormones usually behave in tandem under normal conditions, alcohol consumption resulted in differential and divergent responses. We hypothesize that alcohol acts at the central nervous system level through a general depression or by inhibiting synaptic transmission of afferent impulses to the hypothalamus. Such depression or inhibition would decrease oxytocin levels (36), but, because projections from the hypothalamus exert an inhibitory control of prolactin, prolactin levels would increase (37). Whether the enhanced prolactin response is also due to alcohol′s simulation of extrapituitary tissues such as the mammary glands (38), which are capable of producing prolactin, is not yet known. Animal studies suggest that alcohol, directly or indirectly via estrogens, may elevate prolactin by stimulating activity of lactotropes in the adenohypophysis (38). Recent studies indicate that one fourth of the women surveyed reported that they were encouraged by health professionals to drink once they began lactating (1,39). Advice ranged from the recommendation that drinking alcohol shortly before nursing will facilitate let-down and milk production to the belief that by drinking such milk, the infant will relax, become less "colicky," and obtain warmth. Some health professionals promote moderate drinking (1,39), whereas others caution that extremely high doses (≥1.0 g/kg) inhibit the milk ejection reflex (40). The present findings, which employed more sensitive measures and controls than research conducted in the 1960-1970s (15), revealed that lower doses of alcohol have similar effects on hormonal milieu and lactational performance. Several explanations, not mutually exclusive, may shed light on why the folklore that alcohol consumption enhances lactational performance has persisted for centuries. First, because difficulties with lactational performance are often attributed to stress, alcohol is then prescribed as an aid to lactation because of its anxiolytic and sedative properties. The present study revealed that relatively low BACs produce slight, but significant, alterations in feelings of drunkenness, dysphoria, and sedation. However, paralleling these mood changes are disruptions in the hormonal milieu that may impair lactational performance. Second, the lactating mother does not have an immediate means of assessing milk yield or intake. Although breast-fed infants consumed, on average, 20% less milk after mothers′ consumption of the Mennella et al

Children\u27s Hedonic Responses to the Odors of Alcoholic Beverages: A Window to Emotions

The present study of 145 children and their mothers aimed to determine whether children\u27s responses to the odors of alcoholic beverages were related to their mothers\u27 reasons for drinking. Mothers completed a series of questionnaires to describe the emotional context in which they drink and whether they use alcohol to “escape” by changing their state of mind and reducing feelings of dysphoria. Children participated in two age-appropriate tasks that focused on the most salient psychological attribute of an odor, its perceived hedonic valence. To this aim, we determined children\u27s liking, reaction times, and identification of individual odors including beer and whiskey in Task 1, and their preference for beer relative to odors that differed in hedonic valence in Task 2. The type of task and behavioral measure revealed different aspects of children\u27s responses, to alcohol odors. In Task 1, verbally identifying an odor was a more difficult task than deciding whether they liked the odor. Although there were few group differences in liking for individual odors, children of Escape drinkers took significantly longer to determine whether they liked the odors. In Task 2, children of Escape drinkers preferred beer less often, particularly when it was compared with less pleasant odors. They preferred coffee to beer odors and, if their mothers did not smoke cigarettes, preferred the odors of cigarette smoke and pyridine to beer. These children experienced the odor of alcohol more frequently and in the context of mood disturbed mothers who felt guilty and worried about their drinking. Whether children who associate the odor of alcohol with such emotional contexts display a trajectory toward or against using alcohol to escape remains unknown

Exposure to a slightly sweet lipid-based nutrient supplement during early life does not increase the level of sweet taste most preferred among 4- to 6-year-old Ghanaian children: follow-up of a randomized controlled trial

Background: The impact of feeding a slightly sweet nutrient supplement early in life on later sweet taste preference is unknown. Objective: We tested the hypothesis that the level of sucrose most preferred by 4–6-y-old children exposed to a slightly sweet lipid-based nutrient supplement (LNS) early in life would not be higher than that of children never exposed to LNS. Design: We followed up children born to women (n = 1,320) who participated in a randomized trial in Ghana. In one group, LNS was provided to women on a daily basis during pregnancy and the first 6 mo postpartum and to their infants from age 6 to 18 mo (LNS group). The control groups received daily iron and folic acid or multiple micronutrients during pregnancy and the first 6 mo postpartum, with no infant supplementation (non-LNS group). At age 4–6 y, we randomly selected a subsample of children (n = 775) to assess the concentration of sucrose most preferred using the Monell 2-series, forced-choice, paired-comparison tracking procedure. We compared LNS with non-LNS group differences using a noninferiority margin of 5% weight/volume (wt/vol). Results: Of the 624 children tested, most (61%) provided reliable responses. Among all children, the mean ± SD sucrose solution most preferred (% wt/vol) was 14.6 ± 8.6 (LNS group 14.9 ± 8.7; non-LNS group 14.2 ± 8.4). However, among children with reliable responses, it was 17.0 ± 10.2 (LNS group 17.5 ± 10.4; non-LNS group 16.5 ± 10.0). The upper level of the 95% CI of the difference between groups did not exceed the noninferiority margin in either the full sample or those with reliable responses, indicating that the LNS group did not have a higher sweet preference than the non-LNS group. Conclusion: Exposure to a slightly sweet nutrient supplement early in life did not increase the level of sweet taste most preferred during childhood. This trial was registered at clinicaltrials.gov as NCT00970866

Protein Hydrolysates Are Avoided by Herbivores but Not by Omnivores in Two-Choice Preference Tests

Background: The negative sensory properties of casein hydrolysates (HC) often limit their usage in products intended for human consumption, despite HC being nutritious and having many functional benefits. Recent, but taxonomically limited, evidence suggests that other animals also avoid consuming HC when alternatives exist. Methodology/Principal Findings: We evaluated ingestive responses of five herbivorous species (guinea pig, mountain beaver, gopher, vole, and rabbit) and five omnivorous species (rat, coyote, house mouse, white-footed mouse, and deer mouse; N = 16–18/species) using solid foods containing 20% HC in a series of two-choice preference tests that used a nonprotein, cellulose-based alternative. Individuals were also tested with collagen hydrolysate (gelatin; GE) to determine whether it would induce similar ingestive responses to those induced by HC. Despite HC and GE having very different nutritional and sensory qualities, both hydrolysates produced similar preference score patterns. We found that the herbivores generally avoided the hydrolysates while the omnivores consumed them at similar levels to the cellulose diet or, more rarely, preferred them (HC by the white-footed mouse; GE by the rat). Follow-up preference tests pairing HC and the nutritionally equivalent intact casein (C) were performed on the three mouse species and the guinea pigs. For the mice, mean HC preference scores were lower in the HC v C compared to the HC v Cel tests, indicating that HC’s sensory qualities negatively affected its consumption. However, responses were species-specific. For the guinea pigs, repeated exposure to HC or C (4.7-h sessions; N = 10) were found to increase subsequent HC preference scores in an HC v C preference test, which was interpreted in the light of conservative foraging strategies thought to typify herbivores. Conclusions/Significance: This is the first empirical study of dietary niche-related taxonomic differences in ingestive responses to protein hydrolysates using multiple species under comparable conditions. Our results provide a basis for future work in sensory, physiological, and behavioral mechanisms of hydrolysate avoidance and on the potential use of hydrolysates for pest management

The Flavor World of Childhood

Many of the chronic illnesses that plague modern society, such as obesity, diabetes, and hypertension, derive in large part from poor food choices, dictated in part by flavor preferences. Against the advice and recommendations of health authorities worldwide, people eat too much salt, fat, and simple sugars and too few fruits and vegetables, even and especially among children. How can we account for patterns of food choice that are antithetical to health, and why is it so difficult to develop good food habits and to change bad food habits? Two factors conspire to predispose some children to consume obesogenic diets: (a) inborn, evolutionarily driven flavor preferences and (b) detrimental consequences of not being exposed to flavors of healthful foods early in life (reviewed in [1]). Children live in different “flavor” worlds than adults. They have sensory systems that detect and prefer the once rare calorie- and mineral-rich foods that taste sweet or salty, while rejecting the potentially toxic ones that taste bitter. Such age-related changes in taste perception and preference, documented by experimental research during the past century, indicate that the rewarding properties of sweet and salt and the aversive properties of bitter are more pronounced during childhood [2]. In the case of sugars, its taste is not just liked by children, tasting something sweet can also blunt expressions of pain. The more they like sweets, the better its analgesic properties. But the senses that underlie flavor perception are “plastic” and can be modified by early experience. Adding sugar to beverages and to solid foods increases both liking and acceptance by young children, especially in the context in which the taste is experienced. Further, now that our food supply includes several low- or no-calorie sweeteners that provide sweetness with fewer calories, we know little of their impact on the learning of these senses in children. For example, what are the long-term consequences of children learning to associate sweet taste with certain foods that typically are not sweet but, because of the addition of low-calorie sweeteners, have been processed to taste sweet? How can they be ‘retaught’ to like a particular food in its natural, unsweetened form? Like experiences with sweet, preferences for salt taste are shaped by experiences with foods during the first year of life. A recent Institute of Medicine report stressed the importance of understanding salt taste and salt taste preference in children and how early experiences modulate these sensory responses. Salt in the food environment of infants and children—and any changes in lowering the overall amounts—may “have the most profound effects” [3]. And the same may be true for sugar. In other words, basic biology does not predispose children to favor the recommended low-sugar, low-sodium, vegetable-rich diets and makes them especially vulnerable to our current food environment of foods high in salt and refined sugars. Thus, the struggle parents have in modifying their children’s diets to reduce added sugars and salt appears to have a strong biological basis, emphasizing the need for new, research-based strategies to approach children’s diets. If this is the bad news, the good news is that a variety of early flavor experiences, beginning even before the child has their first ‘taste’ of food, can shape preferences. Longitudinal studies have revealed that food habits established during infancy track into childhood and adolescence for both nutrient-dense and nutrient-poor foods [4-6]. Such dietary patterns, which begin to be identified during childhood, are significant determinants of the quality of the adult diet. In a wide variety of species, the young first learn about their mothers’ dietary choices through transmitted flavor cues in amniotic fluid and then mother’s milk; such early flavor experiences cause neurological and physiological changes that influence later behaviors. During the past two decades, we have systematically shown that similar processes operate in humans: several dietary flavor volatiles from the mother’s diet are transferred to amniotic fluid and human breast milk. Infants’ experience with these flavors and tastes modifies their acceptance in milk and in solid foods. This continuity in flavor helps the baby transition to solid foods. Breastfeeding confers greater acceptance of healthy foods such as fruits and vegetables, but only if these foods and flavors are part of the maternal diet. Since mothers typically feed children foods that are part of their own diet and culture, the breast-fed infant continues to learn the flavors of the foods they will be offered. Sensory experiences with food flavors in mother’s milk in children whose mothers eat a varied diet may explain why children who were breast-fed tend to be less picky and more willing to try new foods during childhood. Learning about foods and flavors continues during and after weaning since experience with repeated exposure and variety can modify liking of fruits and vegetables [1]. Through basic research we have discovered that regardless if the infant is breast or formula fed or both, they learn through repeated (8-10) exposure to a particular food or exposure to foods that vary in both flavor and texture. This, in turn, promotes willingness to eat not only the introduced foods but also other, novel foods. Exposing infants to multiple sensory contrasts (between- and within-meal flavor variety) also provides more opportunities to develop flavor preferences based on post-ingestive reinforcing effects of nutritious foods. Early experiences with nutritious foods and flavor variety may maximize the likelihood that, as children grow, they choose a healthier diet because they like the tastes and variety of the foods it contain. These foods need to be part of the family’s diet so that once the preference develops, the infant continues to be exposed to the food to maintain the preference, learning to like more complicated flavors and textures. Ultimately, the goal is to gradually accustom children to a varied diet that meets nutritional needs for growth and development and provides them with opportunities to learn to like and prefer a variety of healthy foods. Although some may view food choice as a cultural trait, not directly related to our biology, overwhelming evidence suggests that children’s biology makes them especially vulnerable to the current food environment of processed foods high in salt and refined sugars. Emerging research in humans and animal models suggests that, beginning very early in life, sensory experiences shape and modify flavor and food preferences and have far-reaching effects on behavior. Such early life experiences with healthy levels of salt and sweet tastes and repeated exposure to healthy food flavors may go a long way toward promoting healthy eating and growth, which could have a significant impact in addressing the many chronic illnesses associated with poor food choice. Yet because of the lack of research, many feeding practices are based on idiosyncratic parental behavior, family traditions, or medical lore, rather than research. One of the keys to continued advances and applications on how to develop good food habits comes from studying the fundamental principles underlying flavor learning, which provides an understanding and appreciation of essential aspect of cultural food practices and habits