The Flavor World of Childhood
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Monell Chemical Senses Center, United States
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.
Acknowledgements
NIH grants R01HD37119 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development and R01DC01128 from the National Institute of Deafness and Other Communication Disorders.
References
1. Mennella JA (2014) Am J Clin Nutr 99:704S-11S.
2. Forestell CA, Mennella JA (2014). In: Doty RL, ed. Handbook of Olfaction and Gustation, 3rd edition. 3rd ed. Wilmington, DE: Wiley, John & Sons, Incorporated, 2014.
3. Henney JE, Taylor CE, Boon CS (2010) Strategies to Reduce Sodium Intake in the United States. Washington, D.C.: Committee on Strategies to Reduce Sodium Intake; Institute of Medicine.
4. Northstone K, Emmett PM (2008) Br J Nutr 100:1069-76.
5. Lioret S, McNaughton SA, Spence AC, Crawford D, Campbell KJ (2013) Eur J Clin Nutr 67:275-81.
6. Mikkila V, Rasanen L, Raitakari OT, Marniemi J, Pietinen P, Ronnemaa T, Viikari J (2007) Br J Nutr 98:218-25.
Keywords:
breastfeeding,
childhood,
flavor,
Food experience,
food choice,
Sweeteners,
Sodium intake
Conference:
Science of Human Flavor Perception, New York, United States, 9 May - 9 May, 2014.
Presentation Type:
Abstract
Topic:
Science of Human Flavor Perception
Citation:
Mennella
JA
(2015). The Flavor World of Childhood.
Front. Integr. Neurosci.
Conference Abstract:
Science of Human Flavor Perception.
doi: 10.3389/conf.fnint.2015.03.00007
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Received:
28 Jul 2014;
Published Online:
30 Jan 2015.
*
Correspondence:
Dr. Julie A Mennella, Monell Chemical Senses Center, Philadelphia, PA, United States, mennella@monell.org