Catherine A. Forestell

Early milk feeding influences taste acceptance and liking during infancy

BACKGROUND We identified a model system that exploits the inherent taste variation in early feedings to investigate food preference development. OBJECTIVE The objective was to determine whether exposure to differing concentrations of taste compounds in milk and formulas modifies acceptance of exemplars of the 5 basic taste qualities in a familiar food matrix. Specifically, we examined the effects of consuming hydrolyzed casein formulas (HCFs), which have pronounced bitter, sour, and savory tastes compared with breast milk (BM) and bovine milk-based formulas (MFs), in which these taste qualities are weaker. DESIGN Subgroups of BM-, MF- and HCF-fed infants, some of whom were fed table foods, were studied on 6 occasions to measure acceptance of sweet, salty, bitter, savory, sour, and plain cereals. RESULTS In infants not yet eating table foods, the HCF group ate significantly more savory-, bitter-, and sour-tasting and plain cereals than did the BM or MF groups. HCF infants displayed fewer facial expressions of distaste while eating the bitter and savory cereals, and they and BM infants were more likely to smile while they were eating the savory cereal. In formula-fed infants eating table foods, preferences for the basic tastes reflected the types of foods they were being fed. In general, those infants who ate more food displayed fewer faces of distaste. CONCLUSIONS The type of formula fed to infants has an effect on their response to taste compounds in cereal before solid food introduction. This model system of research investigation sheds light on sources of individual differences in taste and perhaps cultural food preferences.

Illness-induced anorexia and its possible function in the caterpillar, Manduca sexta

Although many animals exhibit illness-induced anorexia when immune-challenged, the adaptive significance of this behavior remains unclear. Injecting Manduca sexta larvae (caterpillars) with live bacteria (Serratia marcescens), heat-killed bacteria or bacterial lipopolysaccharides resulted in a decline in feeding, demonstrating illness-induced anorexia in this species. We used M. sexta to test four commonly suggested adaptive functions for illness-induced anorexia. (1) Food deprivation did not reduce the iron content of the hemolymph. (2) Immune-challenged M. sexta were not more likely to move to a different part of the plant. Therefore, the decline in feeding is unlikely to be an adaptive response allowing the animal to move away from a patch of contaminated food. (3) M. sexta force-fed S. marcescens bacteria were not more susceptible to a S. marcescens systemic infection than were M. sexta force-fed nutrient broth. (4) Force-feeding infected M. sexta during illness-induced anorexia did not increase mortality and short-term food deprivation did not enhance survival. However, force-feeding M. sexta with a high lipid diet (linseed oil and water) resulted in an increase in mortality when challenged with S. marcescens. Force-feeding sucrose or water did not reduce resistance. Force-feeding a high lipid diet into healthy animals did not reduce weight gain, suggesting that it was not toxic. We hypothesize that there is a conflict between lipid metabolism and immune function, although whether this conflict has played a role in the evolution of illness-induced anorexia remains unknown. The adaptive function of illness-induced anorexia requires further study in both vertebrates and invertebrates.

Increasing children's consumption of fruit and vegetables: Does the type of exposure matter?

This study sought to determine how eight days of home exposure to information about healthful foods and eating behaviors in the form of childrens books and a variety of fruit and vegetables interacted to affect 4- to 8-year-old childrens (N=59) consumption of fruit and vegetables. Before and after the home exposure, children participated in a task in which their consumption of a variety of fruit and vegetables that ranged in familiarity was measured. Results indicated that exposure to food and books were both effective at increasing consumption of fruit, but not vegetables. Additionally, children who were exposed to books consumed more of an infrequently consumed fruit presented during the post-test, but only if they had not been exposed to food during the home exposure. Overall, childrens fruit consumption increased more if their mothers did not pressure them to eat, and those who were less neophobic were more likely to try a novel fruit or vegetable during the post-test. These findings suggest that information and food variety both can be effective for increasing acceptance of fruit, and highlight the need for more research that investigates the efficacy of intervention strategies that promote vegetable consumption in young children.

Assessing the effect of food exposure on children's identification and acceptance of fruit and vegetables

Currently, fewer than 15% of children between the ages of 4-8 years consume the recommended levels of fruit and vegetables. In order to address this serious public health issue, a variety of nutrition programs have been implemented across the United States which have varied in their success. The present research analyzed the effectiveness of providing fruit and vegetable exposure as part of a school nutrition program. Kindergarten students at two schools (N=59) were exposed to interactive activities about healthy eating and physical activity. In addition, those at one school (n=29) were exposed to a variety of fruits and vegetables as part of this program. Assessment of childrens ability to identify and their willingness to try fruit and vegetables before and after the program indicated that while all children were better able to identify a range of fruit, only those who received exposure to healthful foods were more willing to try fruit after the program. There were no changes in their identification or willingness to eat vegetables. These results suggest that schools should provide exposure to a variety of healthy foods as part of their nutrition programs. Such programs should focus specifically on exposing children to vegetables because increasing childrens willingness to try foods that are typically considered unpalatable may be especially challenging.

Palatability shifts in taste and flavour preference conditioning

Changes in palatability of tastes and flavours as a result of flavour preference conditioning were examined. In Experiment 1, when tastes were paired with glucose in a reverse-order differential conditioning paradigm, rats acquired conditioned preferences for CS + and displayed more hedonic responses to CS + than to CS − in a postconditioning taste reactivity test. In Experiment 2, rats that received oral infusions of flavours as CSs during a reverse-order conditioning procedure expressed both palatability shifts and conditioned preferences for CS +. Rats that received a forward conditioning procedure acquired a preference for CS +, but the palatability of CS + was unchanged. In Experiment 3, hungry rats drank mixtures of a flavour CS and a calorific or sweet tasting reinforcer in a long-exposure conditioning paradigm. When tested hungry, rats preferred CS + whether they had acquired flavour-calorie or flavour-taste associations. However, CS + became more palatable only for rats that acquired flavour-calorie associations. These results suggest that acquisition of flavour preferences, as measured by 2-bottle tests, may not always be accompanied by enhanced palatability.

Effect of food restriction on acquisition and expression of a conditioned odor discrimination in mice.

Level of food restriction was manipulated in mice to assess its importance for the acquisition and expression of a conditioned odor discrimination. In training, animals were exposed to odors (either rose or lemon) presented on a piece of filter paper in a pot covered in bedding. For half of the conditioning trials, group paired received one odor (CS+) with sucrose, the unconditioned stimulus (us), under the bedding. For the remaining trials, they received the other odor (CS-) alone. Group CS-alone was also exposed to both odors, but neither odor was paired with sugar on any of the conditioning trials. During training, Group Paired mice that were food-restricted tended to dig more readily and longer in the odors, especially in the CS+ odor, than animals that were not restricted. Both restricted and nonrestricted PAIRED GROUPS dug more in the CS+ than in the CS- by the end of training, but the CS-alone mice dug very little in either. Following training, mice were exposed to both odors simultaneously in a discrimination test. Half the mice in each training food restriction condition were tested under food restriction, and half were not. Only PAIRED animals that were food-restricted in the test expressed an odor discrimination, digging only in the CS+. This occurred regardless of their previous restriction state in training. These data suggest that both food-restricted and nonrestricted mice can acquire an odor discrimination; however, expression of this odor discrimination depends on food restriction.

Fermented foods, neuroticism, and social anxiety: An interaction model

Animal models and clinical trials in humans suggest that probiotics can have an anxiolytic effect. However, no studies have examined the relationship between probiotics and social anxiety. Here we employ a cross-sectional approach to determine whether consumption of fermented foods likely to contain probiotics interacts with neuroticism to predict social anxiety symptoms. A sample of young adults (N=710, 445 female) completed self-report measures of fermented food consumption, neuroticism, and social anxiety. An interaction model, controlling for demographics, general consumption of healthful foods, and exercise frequency, showed that exercise frequency, neuroticism, and fermented food consumption significantly and independently predicted social anxiety. Moreover, fermented food consumption also interacted with neuroticism in predicting social anxiety. Specifically, for those high in neuroticism, higher frequency of fermented food consumption was associated with fewer symptoms of social anxiety. Taken together with previous studies, the results suggest that fermented foods that contain probiotics may have a protective effect against social anxiety symptoms for those at higher genetic risk, as indexed by trait neuroticism. While additional research is necessary to determine the direction of causality, these results suggest that consumption of fermented foods that contain probiotics may serve as a low-risk intervention for reducing social anxiety.

Relationship between alcohol dependence, escape drinking, and early neural attention to alcohol-related cues

RationalePrevious work has indicated that implicit attentional biases to alcohol-related cues are indicative of susceptibility to alcohol dependence and escape drinking, or drinking to avoid dysphoric mood or emotions.ObjectiveThe goal of the current study was to examine whether alcohol dependence and escape drinking were associated with early neural attentional biases to alcohol cues.MethodsElectroencephalography data were recorded from 54 college students who reported that they regularly drank alcohol, while they viewed alcohol and control pictures that contained human content (active) or no human content (inactive).ResultsThose who were alcohol dependent showed more neural attentional bias to the active alcohol-related stimuli than to the matched control stimuli early in processing, as indicated by N1 amplitude. Escape drinkers showed greater neural attention to the active alcohol cues than non-escape drinkers, as measured by larger N2 amplitudes.ConclusionsWhile alcohol dependence is associated with enhanced automatic attentional biases early in processing, escape drinking is associated with more controlled attentional biases to active alcohol cues during a relatively later stage in processing. These findings reveal important information about the time-course of attentional processing in problem drinkers and have important implications for addiction models and treatment.

A comparison of daily and occasional smokers' implicit affective responses to smoking cues.

Previous research has not compared implicit affective responses to smoking-related stimuli in occasional (i.e., those who smoke less than one cigarette per day) and daily smokers (i.e., those who smoke at least once per day). In addition to assessing their motivations for smoking, implicit affective responses were measured using the Affect Misattribution Procedure (AMP) in occasional (n=19) and daily smokers (n=34) to smoking-related and neutral cues. Half of the cues depicted a human interacting with an object (i.e., active), whereas the remaining cues depicted objects alone (i.e., inactive). Results indicated that for the active cues, daily smokers responded more positively to smoking-related than to neutral cues, whereas occasional smokers showed no difference in their implicit responses. In addition to smoking frequency, relative differences in implicit responses to active cues were related to cognitive enhancement motivation. For inactive cues, implicit responses were related to cognitive enhancement as well as reinforcement. Because daily smokers have more positive implicit responses to active smoking-related cues than occasional smokers, these cues may play an important role in maintaining smoking behavior in daily smokers.

Food, Folklore, and Flavor Preference Development

Food choices during pregnancy and lactation are influenced by a variety of factors. While internal factors, such as cravings and aversions, play an important role especially during the first trimester of pregnancy, environmental factors such as cultural food practices and beliefs often dictate the types of foods eaten throughout pregnancy and lactation. Such traditional food practices serve to predispose infants to flavors that are characteristic of their mother’s culture and geographical region. As discussed herein, amniotic fluid and human milk are composed of flavors that directly reflect the foods, spices, and beverages eaten by or inhaled by (e.g., tobacco) the mother. Because the olfactory and taste systems are functioning by the last two trimesters, these flavors are detected early in life, and early experience can bias behavioral response to these flavors later in life. Although more research is needed to understand the mechanisms involved in early flavor learning, these pre- and early-postnatal flavor exposures likely serve to facilitate the transition from fetal life through the breastfeeding period to the initiation of a varied solid food diet. Such learning is the first, but not the only, way in which children learn to appreciate and prefer the flavors of the foods cherished by their culture.