Early Nutrition: Impact on Short- and Long-Term Health

H. van Goudoever, S. Guandalini, R. E. Kleinman

• Editore: S. Karger
• Anno: 2011
• ISBN:
  9783805597463
• Argomento: Medizin
• Categoria: Perinatologie & Neonatologie

In this book, a selected group of international experts review nutritional practices and feeding behaviors in infancy and early childhood. They present the latest knowledge on feeding practices during the period considered and their effect on growth, development, and immediate and long-term health. One of the main topics discussed involves feeding practices in the newborn critical care unit, concentrating on the use of human donor milk and probiotics in the diet of premature and ill newborns. Another point of focus is the causes and the effect of an insufficient intake of selected micronutrients, such as iron and zinc, which is highly prevalent particularly in the developing world. Besides, this publication contains information on the influence of early feeding habits on the later development of a number of health-related issues such as food allergies, later food preferences and eating habits, obesity, bone development, the risk of developing celiac disease in genetically predisposed children.This volume provides essential reading for pediatricians, clinical investigators and health workers interested in the effects of early nutrition on health.

van Goudoever H, Guandalini S, Kleinman RE (eds): Early Nutrition: Impact on Short- and Long-Term Health.
Nestlé Nutr Inst Workshop Ser Pediatr Program, vol 68, pp 153-168,
Nestec Ltd., Vevey/S. Karger AG, Basel, © 2011

Early Feeding: Setting the Stage for Healthy Eating Habits

Julie A. Mennella, Alison K. Ventura

Monell Chemical Senses Center, Philadelphia, PA, USA

Abstract

Food habits, an integral part of all cultures, have their beginnings during early life. This chapter reviews the development of the senses of taste and smell, which provide information on the flavor of foods, and discusses how children's innate predispositions interact with early-life feeding experiences to form dietary preferences and habits. Young children show heightened preferences for foods that taste sweet and salty and rejection of that which tastes bitter. These innate responses are salient during development since they likely evolved to encourage children to ingest that which is beneficial, containing needed calories or minerals, and to reject that which is harmful. Early childhood is also characterized by plasticity, partially evidenced by a sensitive period during early life when infants exhibit heightened acceptance of the flavors experienced in amniotic fluid and breast milk. While learning also occurs with flavors found in formulae, it is likely that this sensitive period formed to facilitate acceptance of and attraction to the flavors of foods eaten by the mother. A basic understanding of the development and functioning of the chemical senses during early childhood may assist in forming evidence-based strategies to improve children's diets.

Copyright © 2011 Nestec Ltd., Vevey/S. Karger AG, Basel

Introduction

The unhealthy eating habits that plague adults - too many calories and salty, sweet, and fatty foods, too few fruits and vegetables - are also rampant in the youngest members of society. Infants and toddlers consume an estimated 10-31% more energy than recommended [1], but not by overconsumption of fruits, vegetables, whole grains, or lean proteins - French fries are the ‘vegetable’ they most commonly consume [2, 3]. Eighteen to 33% of infants and toddlers consume no servings of vegetables on a given day, and 23-33% consume no servings of fruits [2]. Additionally, almost half of infants and toddlers consume desserts, sweets, or sweetened beverages daily [2, 3].

The negative impact of these dietary patterns manifests in increasing obesity among children, a worldwide public health crisis [4-8]. Health professionals recommend that children reduce intakes of added sugars, sodium, and saturated fats and increase intakes of whole grains, fruits, and vegetables (especially dark green leafy vegetables) [9-11]. However, this advice is difficult for adults to comply with, let alone young children whose intake patterns are largely driven by taste preferences, not health considerations [12].

Two major factors conspire to predispose children to consume diets high in sugar, fat, and salt that may lead to obesity. First, humans have an evolutionarily drive toward heightened preferences for sweet and salty foods and rejection of bitter tastes. Second, children must be repeatedly exposed to the flavors of healthy foods beginning early in life to promote their acceptance of these foods.

Flavor Biology in Children

Biological Substrates of Flavor Learning

The perceptions arising from the senses of taste and smell combine in the oral cavity to determine flavor. These perceptions are often confused and misappropriated with olfactory sensations such as vanilla, fishy, and strawberry being erroneously attributed to the taste system per se when, in fact, much of the sensory input is due to retronasal olfaction. Because these senses are the major determinants of whether young children will accept a food (i.e. children eat only what they like), they take on even greater significance in understanding the bases for food choices in children than they do for adults.

We now know that flavor perception develops and functions in utero, and the senses of taste and smell continue to develop postnatally [13, 14]. The fetus begins to swallow and inhale large amounts of amniotic fluid around the 12th week of gestation [15, 16], and by the last trimester the receptors underlying taste and odor perception begin to communicate with the central nervous system in response to a variety of taste and odor stimuli [for a review, see 14]. Amniotic fluid, the first food of infants, contains a wide range of nutrients, such as glucose, fructose, lactic acid, fatty acids, and amino acids [17], as well as flavors (for which the odors are perceived retronasally) of the foods consumed by the mother [18, 19]. The fetus can detect these tastants and flavors, as infants prefer flavors previously experienced in amniotic fluid [18, 20-22].

Fetal swallowing frequency increases in response to the introduction of sweet solutions into the amniotic fluid and decreases in response to the introduction of bitter solutions [17, 23], which may be one of the first indications that our basic biology favors consumption of sweet tastes and avoidance of bitter tastes. A similar response pattern is seen shortly after birth. Within hours and days of being born, young infants react as would be expected to pleasurable and aversive taste stimuli [24-33]: provision of sweet or umami solutions to neonates elicits rhythmic tongue protrusions, lip smacks, lip and finger sucking, and elevation of the corners of the mouth, all of which have been interpreted as a positive or hedonic response [27, 31]. In contrast, neonates gape, wrinkle their noses, shake their heads, flail their arms, and frown in response to a bitter solution [27, 29]. Concentrated sour solutions elicit lip pursing and, to a certain extent, gaping, nose wrinkling, and arm flailing as well as tongue protrusions and lip smacking [27, 29, 34]. Unlike the other basic tastes, neonates respond neutrally to salt taste - the taste for salt does not emerge until later in infancy and then remains throughout childhood and adolescence [35].

These specific affective reactions to differing taste stimuli are strikingly similar across cultures [25, 34, 36] and species [27, 37-40], also suggesting a basic biological underpinning for the flavors and foods youngsters prefer and avoid. Thus, when we examine children's dietary patterns from the perspective of the ontogeny of taste development, the foods children naturally prefer are not surprising and reflect their basic biology.

Heightened Sensitivity to Bitter and Preferences for Sweets and Salt in Young Children

Like infants, children live in different sensory worlds than do adults. Children have higher preferences for sweet [41-43], salt [44], and sour [45] tastes and are more rejecting of some bitter tastes [42] than adults. A vast amount of learning occurs during infancy and childhood, and a significant portion of that learning is about what and how to eat. Thus, reactions to taste qualities likely evolved to detect and reject that which is harmful and to seek out and ingest that which is beneficial [46]. Sweetness is associated with readily available calories from carbohydrate sources such as mother's milk or fruits [47], and saltiness is associated with needed minerals [48], whereas bitterness signals toxins and poisons [49]. Hence, from an evolutionary perspective, it makes sense that preferences for sweet and salty foods are inborn while preferences for bitter-tasting foods (e.g. coffee, dark green vegetables) are learned. It also makes sense that it would be protective for young children, who are trying to learn about what and how to eat, to be more sensitive to the cues proffered by foods; this heightened sensitivity would allow them to quickly protect them from that which causes harm and to encourage them to eat that which is beneficial for growth.

Only very recently in human history are foods omnipresent in many parts of the world and readily available for consumption. Rather, our taste preferences evolved in times of ‘feast or famine’. Under such circumstances, preferences for sweet and salt and aversion to bitter were essential for ensuring that energy- and nutrient-dense foods were consumed and harmful substances were avoided. Now, in many parts of the world, a mismatch exists between children's physiology and the current food environment: many children live in an environment that provides food everywhere - it is inexpensive, good tasting, and served in large portions. Further, the increased levels of sugar, fat, and salt in processed foods cater to children's natural taste predispositions.

Flavor Learning in Children

Sensory and biological considerations shed light on why children are predisposed not to favor low-sugar, low-sodium, and vegetable-rich diets and why it is difficult for children to eat nutritious foods when they are unfamiliar and do not taste good to them. However, while we cannot easily change children's basic biology, we can modulate children's flavor preferences by providing early exposure, starting in utero, to a wide variety of healthy flavors available within the culture.

Flavor Learning in Amniotic Fluid

Learning from mother is a fundamental feature of all mammals [50, 51]. In part, young mammals learn about things like body control, fine and gross motor movements, and social behaviors from what is modeled or transmitted by their parents [52]. Learning about flavors and foods is no different: young mammals first learn about what and how to eat through information transmitted by mot...