Nutrition in Health


According to the American Academy of Pediatrics, the goal of pediatrics is “to attain optimal physical, mental, and social health and well-being for all infants, children, adolescents, and young adults.” It is self-evident that maintaining good nutrition is a prerequisite to attaining this goal. Appropriate nutrition supplies the “building blocks” for healthy physical growth. Optimal mental health and mental capacity rely on adequate nutrition, from conception to old age. D.J.P. Barker theorized that fetal nutrition is associated with a number of chronic conditions of later life. The Barker hypothesis, in its expanded form, proposes that infant nutrition, as well as fetal nutrition, has long-term health effects reaching into adulthood and old age. Some of the parameters that may be affected by nutrition in infancy include cardiovascular health, blood pressure, bone mineralization, low-density lipoprotein cholesterol, split proinsulin, and cognitive development. While these observations are tantalizing, they are observational. A causal relationship has not been established. The Barker hypothesis continues to be debated, but to the extent that it proves true, early nutrition gains tremendous importance.

Much of the early work on establishing nutritional requirements focused on preventing diseases and deficiencies. It was assumed that if a child were given adequate amounts and varieties of foods, good nutrition would automatically follow. The present obesity epidemic that has affected all age groups in our society has proven this assumption incorrect. It has become clear that we need to monitor the nutritional health of our youth and encourage good nutrition for all. In order to accomplish this, we must know the nutritional requirements for optimal growth and to avoid future nutrition-related complications, not merely to avoid deficiency states.

Nutritional Needs and Requirements


Recommended Dietary Allowances (RDAs) were first established in 1941 and first published in 1943. The RDAs were based on scientific evidence and intended to serve as goals for good nutrition. Over the years the RDAs have changed according to the needs of the country. When first devised, the country was struggling with war-time shortages and the RDAs were used to guide priorities and to avoid widespread deficiencies in groups of people. Over time, the emphasis changed to goals for individuals. The eighth edition of the RDAs published in 1974 included the following definition of RDA: “the levels of essential nutrients that, on the basis of scientific knowledge, are judged by the Food and Nutrition Board to be adequate to meet the known nutrient needs of practically all healthy persons.” The exception to the “practically all healthy persons” rule is the RDA for energy. Since it would not be reasonable to recommend the high end of the distribution curve for energy, in this case the RDA was set at approximately the average. Planning for the present Dietary Reference Intakes (DRIs), that have superseded the RDAs, began in 1993 with the realization that RDAs need to be “continuously” updated rather than periodically reviewed and updated and that values beyond RDAs were necessary. Among other things, Upper Limits (UL) needed to be established. The DRIs are now the accepted reference standard for most nutrient requirements for all age groups. There is now a standing committee of the Institute of Medicine (IOM) that sets DRIs as directed by the Food and Nutrition Board (FNB). The IOM has published these references in a series of eight volumes that cover more than 40 nutrient substances.1 These books can be purchased or are available free online at Table 8–1 lists and defines the reference values included in the DRIs. As with earlier versions, the DRIs list energy requirements (Table 8–2) at approximately the average, rather than two standard deviations above the average. The DRIs take into consideration both gender and age in establishing requirements. This discussion will adhere to the age groups used in the DRIs. They are: 0–6 months, 7–12 months, 1–3 years, 4–8 years, 9–13 years, and 14–18 years. Table 8–2 lists the DRIs for a number of nutrients. Table 8–3 shows how to calculate energy requirements and Table 8–4 lists approximate energy requirements from infancy to adolescence.

Table 8–1. Dietary Reference Intakes

Table 8–2. Dietary Reference Intakes

Table 8–3. Calculated Energy Requirements from Infancy to Adolescence

Table 8–4. Estimated Energy Requirements in Infants to Adolescents

Infant Requirements (0–6 and 7–12 Months)

In establishing values for infants, the IOM relied heavily on clinical trials including dose–response, balance, depletion/repletion, prospective observational, case–control studies, and clinical observations in humans. Greater emphasis was placed on studies that measured actual dietary and supplement intake than those that depended on self-reported food and supplement intake. All studies were published in peer-reviewed journals. For some nutrients, the available data did not provide a basis for proposing different requirements for various life stages or genders, most notably infants less than 6 months of age. For infants 0–6 months, only Adequate Intakes (AI) (Table 8–1) exist. For infants, the AI is based on the reported intake of human milk (780 mL/day) determined by test weighing of full-term infants and by the reported average human milk concentration of a specified nutrient after 1 month of lactation. While this is an intuitively logical approach, it provides information only for breastfed infants. Human milk is a matrix of interacting factors and each factor may be more or less biologically available in this matrix compared to the biological availability of the factor when not in the human milk matrix. This means that there are no reference values applicable to non-breastfed infants (Tables 8–2 and 8–3). The AIs, based solely on estimates of nutrients in human milk, may result in frank deficiency for some nutrients if those nutrients are fed to non-breastfed infants at the level of AI. Further, this approach assumes that the mother has no nutrient deficiency, that all events surrounding the birth were optimal (cord clamping, etc.), and that the mother’s milk has at least the average amount of nutrients. If any of these assumptions are not correct and the infant is not supplemented, nutrient deficiency can occur. Nevertheless, the DRIs are the best estimates of infant nutrition needs available.

Toddler Requirements (1–3 Years)

There is no widely accepted definition of “toddler.” The term is taken from the wide-based gait seen in children who are just learning to walk. While it is generally agreed that “toddlerhood” begins at 12 months of age, the upper boundary of this age bracket is poorly defined. In this discussion, it will be assumed that toddlerhood ends at 36 months. Thus, a child less than 12 months is an infant and after 36 months a toddler becomes a “pre-schooler.” Growth and therefore nutritional requirements peak during the first year of life. Growth rate during the second 12 months of life continues to be high. The second year of life is one of transition from an infant diet to a modified adult diet. There is a paucity of studies and guidelines on toddlers’ nutrition, although there are a number of studies that describe what toddlers eat. These have included studies documenting a change in eating patterns of toddlers over time, and there have been reports on the psychological and behavioral aspects of toddler nutrition. There are, however, few studies to determine actual nutritional requirements for children of this age group. There are also few published guidelines, but those that are available often use data extrapolated from other age groups.

School Age Requirements (4–8 Years)

This age group is characterized by very much slower rate of growth than in the infant and toddler age groups. Children at this age are typically in a formal education system and are often making some nutritional choices independently. School age children are often viewed as “picky eaters.” This may be merely a perception as, because of their slower growth rate, the rate of increase in the consumption slackens.

Pre-Teen Requirements (9–13 Years)

The genders in this age group grow at different rates, as many girls will have completed their growth spurt by age 13 years, while many boys have not entered this rapid growth phase. This means that requirements for boys and girls may be substantially different. Because there is a wide range of normal progression of puberty and because nutritional requirements, in part, depend on pubertal status, making fixed recommendations in this age group is difficult.

Teenager Requirements (14–18 Years)

Nutritional requirements vary by gender in this age category as well. During teenage years, nutritional requirements can vary with requirements for growth and with physical activity. Teenagers have a keen sense of their body image. This can result in either healthy eating habits or unhealthy ones. Nutritional syndromes such as anorexia and obesity become very important.

Nutritional Assessment


The four elements of nutritional assessment are: (1) history, including social history and medications, (2) physical examination and anthropometrics, (3) laboratory tests, and (4) observation including general behavior, feeding behavior, and familial interactions.


A nutritional history focuses on the potential reasons for undernutrition or for overnutrition. Causes of undernutrition at any age fall into the same categories: decreased intake, increased losses, malabsorption, increased requirements, and decreased synthetic function, such as might accompany inborn errors of metabolism. Similarly, causes of overnutrition at all ages are increased intake and decreased energy expenditure. Recent literature has highlighted genetic predisposition to obesity and overweight. These genetic differences have existed for many generations and therefore do not explain the recent “epidemic of obesity.” Another recent finding is that obese individuals have an identifiably different microbiome. Their GI flora are said to consist of “obesogenic bacteria.” There remains a debate as to which come first, diets predisposing to weight gain, the weight gain itself, or the altered bacterial flora.

Physical Examination

For the most part, physical findings other than changes in growth parameters are late findings in malnutrition. Physical evidence of single-nutrient deficiencies are not commonly encountered in the developed world. These are listed in Table 8–5.

Table 8–5. Physical Findings in Nutrient Deficiencies
Jan 21, 2019 | Posted by in GASTROENTEROLOGY | Comments Off on Nutrition
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