“And yet your fair discourse hath been as sugar, Making the hard way sweet and delectable.”1
The Birth to 24 (B-24) Months and Pregnancy Project was initiated by the US Department of Agriculture and the US Department of Health and Human Services in 2012 to develop evidence-based dietary recommendations for the B–24 month age group and for women who are pregnant.2 The first step in this process was provided by the deliberations of 4 expert work groups (WGs) (WG 1, infancy period of sole nutrient source feeding [0–6 months]; WG 2, infancy period of complementary feeding [6–12 months]; WG 3, period of transitional feeding [12–24 months]; WG 4, caregivers [mothers, other], factors influencing nutrient needs, infant feeding choice, dietary quality, and food habits) that developed priority topics for systematic reviews and a research agenda to address critical research gaps. These work groups recognized several research gaps—not the least of which were those voiced by WG 3, period of transitional feeding (12–24 months)—including food sources of nutrients and energy that were either overconsumed or underconsumed and the “microenvironmental” effects on the transition to the adult diet. Specifically, WG 3 raised the question, “How do inborn responses to basic tastes, learning and experience with food and eating, and exposure to caregiver practices influence the transition to the adult diet during this critical time frame?”2 This supplement follows up on this previous work, pulling together a deeper, targeted examination of the influences that may impact a young child's sweet taste perception and dietary intake of sugar in the context of the interaction of the child, the caregiver, and the food for improving nutrient intakes and, furthermore, the potential impact on lifelong dietary patterns.
WHY THE INTEREST IN SWEET TASTE PERCEPTION NOW?
A large data gap exists for randomized controlled trials (RCTs) related to infant and toddler feeding.3 Despite the limited evidence to support specific guidance,2 infant feeding guidelines exist in most developed countries but do not yet exist in the United States.3 That condition is about to change in the 2020 Dietary Guidelines for Americans (DGA), and presumably, sugar consumption will be addressed.
A HISTORIC LOOK AT DIETARY GUIDANCE AND SUGAR
The infant diet is not the same as the toddler diet.4 Kleinman and Coletta5 provide an overview of the history of child feeding recommendations and practices with a particular focus on the American Academy of Pediatrics Committee on Nutrition guidelines across the 20th century. They also point out the importance of developmentally appropriate feeding practices and the drop in vegetable consumption between 12 and 24 months.
During B–24 months, the brain is growing rapidly—doubling in size by the first year and tripling in size by the third year.4 In addition, major developmental transitions are occurring simultaneously in growth, fine and gross motor activity, coordination, cognition, feeding behaviors, and the establishment of food preferences and dietary patterns.6
Warnings about sugar in child feeding recommendations appeared routinely in earlier dietary guidance. Previous versions of the DGA made the following recommendations relative to sugar2:
* “You should not add salt or sugar to the baby's foods. Infants do not need these inducements if they are really hungry. The foods are nourishing and extra flavoring with salt and sugar is not necessary.”7
* “Salt and sugar should not be added to an infant's food; they are not needed as inducements to eat.”8
* “To help prevent tooth decay in newly growing teeth, infants should not use as pacifiers, nursing, or bottles containing any beverage other than water, such as milk, juice, or formula at bedtime.”8
Later, the DGA did not address this age group. However, 1 consistent concern has been the role that sugar plays in dental caries. Palmer9 points out that it is not the amount of sugar (or any fermentable carbohydrate) that is problematic so much as the frequency of consumption. In addition, cariogenic foods and beverages consumed between meals are more harmful than when they are consumed with meals.
For those 2 years and older, the 2015–2020 DGA recommends that added sugar consumption be limited to less than 10% of total energy intake.10 Actual consumption patterns are very different. The data concerning sugar intake in toddlerhood vary. Added sugar intake among toddlers is approximately 8% to 10% of total energy.11,12 This level of added sugar intake is greater than the World Health Organization limit of 5% of total energy that is specific to dental caries13 and at the upper limit of 10% of total energy for the 2015–2020 DGA.10
SO WHY NOW?
The vilification of sugar is hardly new. Sugar has been described as “unnatural,”14,15 with some even going so far as to describe it as an evil,16,17 an agent of social injustice and exploitation of the poor,18 or a lever to promote poverty and social injustice.19
What is new is the increasingly rancorous tenor of debate in scientific circles, which quickly circulates in Internet media and impacts local policy decisions. In the fall 2016 elections, San Francisco, Oakland, and Albany, California, as well as Boulder, Colorado, all passed taxes on sodas and other sugary drinks.20 Other cities and other countries have done the same. A recent article in JAMA received considerable public attention as well, claiming that the integrity of some of our best known nutrition scientists was compromised because they downplayed sugar's harmful role in coronary heart disease during the 1960s.21 This was purportedly done to create the belief that our major health ills were due to fat intake.21,22 Others rebut the article as providing only circumstantial evidence or argue that any 1 article was only a sliver of information in a much larger and broad-based scientific debate at that time.23–25 Indeed, even the authors of the JAMA article recognized that the basis for their arguments was circumstantial evidence, regardless of how it played out in the media.
Some note the misplaced blame on a single commodity,26 whereas others question all nutrition research funded by the corporate food industry.27–29 In contrast, Myers30 reacted with a careful consideration of how we might as a field act to protect our work against the risk of bias. Importantly, Myers30 underscores a general public distrust of research and government more broadly.
Regardless of distrust, rigorous, unbiased scientific research about sugar and its relationship to health must continue to move forward.
Regardless of the backdrop of distrust, rigorous, unbiased scientific research about sugar and its relationship to health and healthful dietary patterns must continue to move forward. The real issues are whether sugar at levels currently consumed by toddlers impacts health11,12 and the role of sweet taste preference in supporting healthy eating habits. The liking for sugar is universal.31 It increases the palatability of most foods, and this preference is apparently independent of experience and is ubiquitous among all mammals.31 At the same time, personal experience and social norms may drive an individual to desire and consume more sugar than might be predicted by instinct alone.31 In other words, biological, environmental, and cultural norms must be taken into account to explain or predict sugar consumption.
The articles in this supplement give little attention to cultural considerations. Different people eat different foods in different ways and in accordance with food availability and ethnic or cultural practices. Centrone Stefani and Humphries32 point out that beliefs, ideas, norms of behavior, expectations, identities, unspoken rules of the group, and other symbolic elements are important on the international nutrition stage, but many others seemingly fail to recognize that these elements are equally as important on the domestic front.
Regardless of the era or the culture, sugar carries an emotional and social load and has a significant affective effect. Some have suggested that sugar is addictive,33,34 but it is far too early to make any conclusions in that regard. Sugar immediately reinforces mother-child bonding in the early stages of infant feeding. More broadly, as Johnson and Hayes6 noted, nearly all major contemporary occasions in this country are marked by sugary foods (wedding cakes, birthday cakes, Valentine chocolates, retirement parties, etc). Sugar is also associated with love, romance, and terms of affection (eg, honey pie, sweetie, and sugar plum). Sugar symbolizes and is generally equated to one of the “good things in life.”
The feeding relationship between mother and child or caregiver and child is of central importance because of its impact on socioemotional development and the formation of interpersonal bonding.6 Murray4 notes the close physical-emotional bonding that occurs during breastfeeding, but close bonds extend in the feeding relationship as the child transitions to solid food and finally to family table food. As the mother or caregiver feeds the young child, meanings about and preferences for food—good or bad—are created and reinforced on a daily basis. People tend to act toward things (objects, ideas, processes) in accordance with the meanings they have for those things.35 Meaning also impacts attitudinal belief sets and future learning such that simply providing conceptual knowledge to fill in perceived gaps or correct misconceptions will unlikely overcome previous affective or attitudinal belief sets.35 Anthropologists have long observed that the meanings we associate with foods tend to sort people by culture, age, class, gender, and even occupation.36 Indeed, a recent study by Yuan et al37 illustrated that boys and girls are exposed to differing amounts of sweetness and fat depending on their gender and also whether their mothers worked. Therefore, we have reason to believe (if not evidence) that what a child learns to eat and/or reject on his/her mother's lap may have long-lasting effects on dietary choices later on.
Johnson and Hayes6 raised the issue of using small amounts of added sugar to disguise bitter flavors in vegetables to increase a child's liking and intake of these foods. How much is enough? We simply do not know. How much is too much? We simply do not know. It needs to be investigated. Johnson and Hayes6 also raised the interesting issue that mothers may not adopt the classical advice by Birch et al38 of offering a new food 8 to 10 times because the mothers say that they have more pressing needs to attend to, including a concern for wasting food and time. Sugar may or may not be the gateway to obesity, but if the mother perceives it to be, she may not want it in her child's food. On the other hand, if it makes feeding her child easier, then she may be receptive to the practice. We need more research to determine which predisposition is dominant and how this varies by caregivers' characteristics.
WHAT IS NEXT?
…There are many notable gaps, especially pertaining to the behavioral and environmental aspects of infant and toddler feeding.
This collection of articles amply illustrates that there are many different kinds of data collected by different methods for different aims, but there are many notable gaps, especially those pertaining to the behavioral and environmental aspects of infant and toddler feeding. Gaps include a lack of pediatric data, lack of suitable review criteria, lack of unifying theory/multidisciplinary integration, and exclusion of the social sciences, as well as process concerns and missing content topics.
Lack of Pediatric Data
The lack of pediatric data has been underscored several times. Industry holds proprietary data, but we have no means of knowing how much exists, on which topics, of what quality, or from which country/culture they were collected. This is by no means a criticism of industry. The overriding issue is that there has been very little public funding available for pediatric and/or behavioral nutrition research.
The National Institutes of Health and the US Department of Agriculture have funded some. Studies tend to be internationally focused and funded either by industry or the US Agency for International Development.39,40 This phenomenon is especially perplexing given recent recognition of the importance of the first 1000 days of life relative to brain development, cognition, and behavior. Nutrition was recognized as an important factor in brain development and learning in the 1970s.41,42 Why then is pediatric nutrition left out of brain science and other major funding initiatives now?
Lack of Suitable Review Criteria
We must be careful of the review criteria we establish. Many nutrition scientists argue that dietary guidelines should be based solely on evidence derived from RCTs. Others note the value of evidence that lies “in the spectrum between purely association and definitively causal.”43 It is important to note that an overzealous evidence-based approach may result in more nonsense than good. For instance, a case was made that no one should use parachutes because of a lack of RCTs to test parachute interventions as a means to prevent death or injury severity.44 Similarly, there are no RCTs or double-blind, placebo-controlled crossover trials to establish that giving infants soda pop in their nightly bottle feedings causes any harm. Yet, it is widely accepted that this practice does cause harm.9 Randomized controlled trials for addressing infant and toddler feeding questions are particularly problematic. Ethical responsibilities abound in this fragile age group because these children are constantly and rapidly developing, making valid crossover designs impossible. Allison et al43 presented an excellent summary of the common errors noted in the published literature. However, the authors do not go far enough with problem identification. Absence of evidence does not indicate evidence of absence. Researchers and policy makers must be open to a variety of designs and approaches, and simultaneously, good judgment must not be sacrificed for the sake of dogmatic prejudice.
Absence of evidence does not indicate evidence of absence.
Lack of Unifying Theory/Multidisciplinary Integration and Exclusion of the Social Sciences
There has been little progress on the lack of theory, and the hard conceptual work that is required has yet to happen.45 The social sciences must be given their due. Nutrition has always been interdisciplinary—a biological science to be sure, but also a social science. It is perplexing that the nutrition field seems to have lost so many of the disciplines it once embraced (ie, the sociocultural, behavioral, developmental, and cultural aspects of food and nutrition). As Beauman et al46 observed, the purpose of nutrition is the preservation, maintenance, development, and sustenance of life on Earth, a science that integrates the facts about food with metabolism and feeding the individual, the family, and the nation. Oddly enough, it is probably more difficult to do that today in most nutrition programs than it was 30 years ago. Psychology, sociology, human development, anthropology, and community nutrition along with biochemistry, medicine, and public health all have their important and rightful places in the study of food, nutrition, food choice, dietary intake, food patterns, and health outcomes.
At a minimum, a conceptual framework is needed to synthesize data, not only from a cross-disciplinary or multidisciplinary perspective, but also from an interdisciplinary and transdisciplinary perspective.47 Consider a set of sciences, such as sensory science, information science, anthropology, human development, nutrition, and genomics. Presumably, a combination of these sciences would more likely resolve complex, knotty problems than would any one of these sciences alone. More specifically, a synthesis of concepts, methods, results, understanding, and the richness thereof increases as the communication across disciplines increases. A cross-disciplinary/multidisciplinary perspective would yield several scientists tackling the same research question, each working independently from the other and then collecting that work together (as in this supplement).43,47–49 An interdisciplinary approach would involve these same scientists working in tandem as a team to answer the same research question with a conceptual framework that explicitly described how the findings from each of the scientists connected or intersected. A transdisciplinary approach derives from a single scientist who is trained in all the relevant scientific fields tackling the research question and drawing on all the applicable sciences simultaneously. Ideally, teams of transdisciplinary scientists would work together in the future. Pediatric nutrition provides a perfect platform to begin such an effort because the problem sets, such as transitioning to table food and the effect of transitioning behaviors on health, can be highly focused and can simultaneously yield to different perspectives or approaches of study.
Attention needs to be given to the processes used to collect and evaluate the research literature and evidence used to generate dietary recommendations for infants and toddlers. Child hedonics are easier to collect than dietary intake, but the data most needed come from a “real-life” context rather than a laboratory setting. According to Raiten et al,2 the B-24 Project represents the first time the Nutrition Evidence Library used a topic nomination and refinement process involving the input from technical work groups. This is a “best practice” approach that should be both commended and repeated in the 2020 Dietary Guidelines Advisory Committee (DGAC) process. In fact, that process needs to capture all the relevant types of data, exploit existing data sources, and identify what new types of data are not currently available.2
Perhaps the larger process question pertains to the composition of the 2020 DGAC. Certainly, the collection of research articles being analyzed underscores the breadth of expertise needed to develop a comprehensive set of guidelines for infants and toddlers. No single person “owns” this expertise. If the 2020 DGAC is not expanded to increase the number and breadth of experts, it will inevitably be inadequate to meet the new required change to address the B–24 month age group. Undoubtedly, workload will be prodigious.
Missing Content Topics
Of course, attention also needs to be given to a host of content questions. A strong theory would help in this respect, but Kleinman et al50 did an outstanding job outlining a series of research questions and priorities that address the caregiver-child feeding experience, vegetable acceptance, nutrient density, and development of healthy lifelong eating patterns. One of their more interesting questions was whether there are critical windows when children learn that certain foods should be sweet or nonsweet.
An important issue missing from Kleinman et al50 was that future research should explore the factors that influence portion size, dietary variety (eating many different foods), and moderation (not overconsuming any 1 type of food). Which interventions positively impact these intake behaviors? Which do not work? What is required to effectively change versus develop these patterns? The meaning of “healthy” also needs to be reexamined. Is a child with attention deficit hyperactivity disorder or a child who uses a hearing aid or wheelchair fundamentally different than a picky eater, an overweight child, or a child exhibiting food refusals? Where does one draw the line in describing whether an individual is healthy? Will the 2020 DGA, which is designed to address a healthy population, be pertinent to all of them?
Furthermore, if sugar is of any concern, it is of greater concern in low-income and minority populations. In general, low-income and food-insecure populations in the United States tend to purchase high-fat, high-sugar, low-cost foods that provide more energy per dollar spent than other kinds of foods.51 Non-Hispanic black toddlers consumed the highest percentage of added sugar, and conversely, toddlers in high-income households consumed the lowest percentage of added sugar. Given that added sugar, total carbohydrate, and total sugar intake are correlated11 and that concern for health equity in our marginalized populations is a major public health issue, we need to take a closer look at these patterns.
Another content area missing from the articles in this supplement is sugar metabolism during B–24 months. One needs only to consider lactose to acknowledge that children of this age group do not metabolize ingested foods the same way that older children and adults do. All we can do currently, however, is extrapolate from observational studies on children older than 2 years. Is there a direct linear relationship between increased health risk (eg, heart disease and type 2 diabetes) and increased levels of added sugar consumption in children younger than 2 years? In writing for the American Heart Association, Vos et al52 speculate that “added sugars during infancy appear to be particularly harmful and should be avoided.” However, the validity of the various recommended limits on added sugar intake (ie, from “avoid” to 5% or 10% of total energy) has been recently questioned.29,53 Given the unique nutritional needs due to rapid growth and brain development during the B–24 months period, the appropriate recommendation for sugar intake—both intrinsic and added—for infants and toddlers remains an open question. There is a lack of evidence to support any given value. This is a critical research gap.
The use of low-calorie or nonnutritive sweeteners (NNS) also needs to be explored. The American Academy of Pediatrics has no official recommendation regarding the use of sugar substitutes due to the limited number of studies in children.54,55 Nonnutritive sweeteners include aspartame, acesulfame K, neotame, saccharin, and sucralose, all of which are generally recognized as safe by the US Food and Drug Administration (FDA). The FDA has not made a ruling yet on stevia.56 Research is again sparse relative to the long-term health implications of the consumption of NNS, especially in pediatric populations.52 A recent review identified 2 RCTs and 6 prospective cohort studies that identified longer-term outcomes (≥6 months) of consumption of NNS in children aged 2 to 11 years.57 Half of these studies (1 RCT and 3 cohort studies) showed an association between the consumption of NNS and body mass index, whereas half did not. Most of the existing literature for all age groups focused on replacement/displacement of regular soft drinks,56 which may have little bearing on the B–24 month group. Nonnutritive sweeteners are typically used as an alternative to sugar to counter excessive energy consumption and nutrient displacement. Their role in early childhood may or may not be of interest to consumers. However, the number of food products containing NNS continues to rise, and if young children are exposed to and consume NNS in their transition to table food, the topic is worth further investigation relative to taste preference, food acceptance and consumption, metabolism, safety, and longer-term individual and public health implications.
Many research gaps remain that must be filled.
None of the articles in this collection mention microbiota, although it is an active topic of research with thousands of articles published in the last 5 years. Multiple reviews indicate that the gut microbiota evolve into a relatively stable composition during the first 3 years of life.58–61 The composition varies according to gestational age, cesarean versus vaginal birth, duration of breast feeding, use of antibiotics, introduction and timing of different complementary foods, use of supplements, prebiotic and/or probiotic formula/foods, and the mother's body mass index and intrauterine environment. For example, breast milk from obese mothers tends to contain a different and less diverse microbiota than breast milk from normal-weight mothers.58
If 70% of the immune system is located in the gastrointestinal tract,43 then studying microbiota development across dietary patterns, cultures, and geographies from infancy to adolescence is essential. Fecal microbiota transplants have already been approved by the FDA as therapy for unresponsive Clostridium difficile infections and pseudomembranous enterocolitis even among children.62 Fecal microbiota transplants are also drawing an increasing interest as a potential treatment of obesity.63 Most recently, a clinical trial was reported that helped children with Crohn's disease and ulcerative colitis reach remission with dietary treatment alone (presumably by affecting the gut microbiota).64 As Luoto et al58 conclude, the gut microflora may be the “missing link” in the fight against the obesity epidemic, and early infancy may be the most critical time for intervention to prevent or reduce the risk of overweight in future generations. Clearly, the role of diet and the impact of sugar consumption—if any—on the establishment of gut microflora are important and deserving of more research.
There are important gaps in the knowledge about sugar consumption and its impact in the B–24 month period. The taste for sweetness is inherent, and sugar may provide significant energy to the diet, either expanding or restricting dietary variety and balance. Sugar also has many associations, both good and bad. Given the widespread concerns about and interest in sugar among consumers, as well as the specific concerns about childhood obesity, diet quality, and long-term chronic disease prevention, it is evident that sugar should be examined in the B-24 month population in preparation for the 2020 DGA. Simultaneously, intrinsic versus added sugar intake should be considered from a holistic dietary perspective, such as in the context of a whole foods versus a single nutrient approach and from a refined carbohydrate, total carbohydrate, and total macronutrient perspective versus a single energy source.
Coupling the secular changes in sugar consumption to questions about the impact these changes might have on short- or long-term health status leads us to ask the question not on whether sugar matters but how much does it matter?
The question is not whether sugar matters but how much does it matter?
Many people may react negatively to added sugar in a baby's diet on moral, medical, economic, political, or social grounds. On the basis of the evidence here, however, there is little scientific justification for its prohibition in small amounts. In fact, a case can be made to consider the role of a small amount of sugar in vegetables to cultivate a taste or preference for vegetables in young children. Overall, the guidelines for sugar intake need to be made more rigorous, more transparent, and evidence based.
Finally, pediatric nutrition research needs to be expanded. Kleinman et al50 asked the important question of what is needed to encourage a larger funding stream. Ideally, research should be funded and conducted from a comprehensive, transdisciplinary, holistic, and systems perspective that integrates translational research, clinical investigations,65 and the social sciences with a biomedical, molecular, or metabolomics approach. Evidence gaps should continue to be identified, and the studies that are of the greatest importance should be prioritized. Requests for proposals can then be issued to fund studies, while also preserving best practices and working with available resources as wisely as possible. There will also be the need to revise and update guidelines frequently to reflect new and emerging science/evidence.
Obviously, there is a great deal of work to do. The articles in this supplement provide an excellent platform from which to work.
2. Raiten DJ, Raghavan R, Porter A, Obbagy JE, Spahn JM. Executive summary: evaluating the evidence base to support the inclusion of infants and children from birth to 24 mo of age in the Dietary Guidelines for Americans—“the B-24 Project”. Am J Clin Nutr
3. Perreault M, Mikail S, Atkinson SA. New Health Canada nutrition recommendations for infants birth to 24 months address the importance of early nutrition. Nutr Today
4. Murray RD. Influences on the initial dietary pattern among children from birth to 24 months. Nutr Today
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5. Kleinman RE, Coletta FA. Historical overview of transitional feeding recommendations and vegetable feeding practices for infants and young children. Nutr Today
6. Johnson SL, Hayes JE. Developmental readiness, caregiver and child feeding behaviors, and sensory science as a framework for feeding young children. Nutr Today
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9. Palmer CA. Oral and dental health considerations in feeding toddlers. Nutr Today
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11. Welsh JA, Figueroa J. Intake of added sugars during the early toddler period. Nutr Today
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12. Moshfegh AJ, Rhodes DG, Goldman JD, Clemens JC. Characterizing the dietary landscape of children, 12 to 35 months old. Nutr Today
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21. Kearns CE, Schmidt LA, Glantz SA. Sugar industry and coronary heart disease research: a historical analysis of internal industry documents. JAMA Intern Med
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29. Schillinger D, Kearns C. Guidelines to limit added sugar intake: junk science or junk food? Ann Intern Med
30. Myers EF. Nutrition research integrity: to believe or not to believe? That is the question! Nutr Today
31. Hayes JE, Johnson SL. Sensory aspects of bitter and sweet tastes during early childhood. Nutr Today
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32. Centrone Stefani M, Humphries DL. Boundary development in the field of international nutrition science. Adv Nutr
33. Gearhardt AN, Davis C, Kuschner R, Brownell KD. The addiction potential of hyperpalatable foods. Curr Drug Abuse Rev
34. Ahmed SH, Guillem K, Vandaele Y. Sugar addiction: pushing the drug-sugar analogy to the limit. Curr Opin Clin Nutr Metab Care
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39. Grantham-McGregor S, Baker-Henningham H. Review of the evidence linking protein and energy to mental development. Public Health Nutr
40. Walker SP, Chang SM, Powell CA, Grantham-McGregor SM. Effects of early childhood psychosocial stimulation and nutritional supplementation on cognition and education in growth-stunted Jamaican children: prospective cohort study. Lancet
41. Brockman LM, Ricciuti HN. Severe protein-calorie malnutrition and cognitive development in infancy and early childhood. Dev Psychol
42. Levitsky DA, Strupp BJ. Malnutrition and the brain: changing concepts, changing concerns. J Nutr
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43. Allison DB, Bassaganya-Riera J, Burlingame B, et al. Goals in nutrition science 2015–2020. Front Nutr
44. Smith GC, Pell JP. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomized controlled trials. Int J Prosthodont
45. Achterberg CL, Novak JD, Gillespie AH. Theory-driven research as a means to improve nutrition education. J Nutr Educ
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47. Fardet A, Rock E. Toward a new philosophy of preventive nutrition: from a reductionist to a holistic paradigm to improve nutritional recommendations. Adv Nutr
48. Corda KW, Quick V, Schefske S, DeCandia J, Byrd-Bredbenner C. Toward a polytheoretical framework for health behavior change. Am J Health Stud
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51. Murimi MW, Kanyi MG, Mupfudze T, Mbogori TN, Amin MR. Prevalence of food insecurity in low-income neighborhoods in West Texas. J Nutr Educ Behav
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