Nutritional Requirements

Chapter 41 Nutritional Requirements




Nutritional intakes for infants, children, and adolescents should provide for maintenance of current weight and support normal growth and development. The infancy growth period is rapid, is critical for neurocognitive development, and bears higher metabolic rate and nutrient requirements, relative to body size, than other periods of growth. It is followed by the childhood period of growth, during which 60% of total growth occurs, and then by the puberty phase. Nutrition and growth during the first 3 yr of life predict adult stature and some health outcomes. The major risk period for growth stunting (impaired linear growth) is between 4 mo and 2 yr of age, and it may be followed by a delay in the childhood phase of growth. It is critical to identify nutrient deficiencies promptly and to address them aggressively early in life, because they can impart lasting effects on growth and development.


Failure to meet the substantial dietary needs in childhood can result in energy and nutrient deficiencies that adversely affect the growth and development process. Deficiency in any one nutrient can be growth limiting. In parallel to the risk for nutrient and energy deficiencies, issues relating to excesses pose important challenges because of their negative health effects, such as obesity or cardiovascular disease risk factors. The nutrition transition under way in the developing world from traditional diets to the Western diet has been associated with increases in noncommunicable diseases, often coexisting with undernutrition and malnutrition, observed sometimes in the same communities or even the same families.


In addition to providing calories to meet energy requirements, dietary intake also provides macronutrients and micronutrients essential for sustaining the functioning of multiple vital processes. Therefore, in addition to nutrient deficiencies potentially limiting growth, impairments in immune functioning and increased morbidity and mortality can occur. Zinc is a micronutrient that supports multiple metabolic functions in the body, is essential for normal immune functioning, and is required to support linear growth; zinc deficiency is associated with impaired immune functioning and poor linear growth. The significant global burden of malnutrition and undernutrition is the leading worldwide cause of acquired immunodeficiency and the major underlying factor for morbidity and mortality globally for children <5 yr of age.


It is important to view the impact of nutrition on health with various perspectives: to prevent deficiency, to promote adequacy, and to prevent noncommunicable diseases associated with excess intakes. As illustrated by the examples of intake of vitamin D and polyunsaturated fatty acids (PUFAs), our understanding of nutritional needs is evolving beyond deficiency and adequacy states to intakes and status associated with optimal health.



Dietary Reference Intakes


The dietary reference intake (DRI) has been established for most nutrients by the Food and Nutrition Board of the Institute of Medicine using a rigorous process of scientific evidence evaluation (Tables 41-1 to 41-8). The DRI provides guidance as to nutrient needs for individuals and groups across different life stages and by sex. The DRI replaces the former recommended dietary allowances (RDA).




Table 41-2 EQUATIONS TO ESTIMATE ENERGY REQUIREMENT



































INFANTS AND YOUNG CHILDREN: EER (kcal/day) = TEE + ED
0-3 mo EER = (89 × weight [kg] − 100) + 175
4-6 mo EER = (89 × weight [kg] − 100) + 56
7-12 ms EER = (89 × weight [kg] − 100) + 22
13-35 mo EER = (89 × weight [kg] − 100) + 20
CHILDREN AND ADOLESCENTS 3-18 yr: EER (kcal/day) = TEE + ED
Boys
3-8 yr EER = 88.5 − (61.9 × age [yr] + PA × [(26.7 × weight [kg] + (903 × height [m])] +20
9-18 yr EER = 88.5 − (61.9 × age [yr] + PA × [(26.7 × weight [kg] + (903 × height [m])] +25
Girls
3-8 yr EER = 135.3 − (30.8 × age [yr] + PA [(10 × weight [kg] + (934 × height [m])] + 20
9-18 yr EER = 135.3 − (30.8 × age [yr] + PA [(10 × weight [kg] + (934 × height [m])] + 25

ED, energy deposition; EER, estimated energy requirement; PA, physical activity quotient; TEE, total energy expenditure.








Key DRI concepts include the estimated average requirement (EAR), the recommended dietary allowance (RDA), and the tolerable upper limit of intake (UL) (Fig. 41-1). The EAR is the average daily nutrient intake level estimated to meet the requirements for 50% of the population, assuming normal distribution; the RDA is an estimate of the daily average nutrient intake to meet the nutritional needs of >97% of the individuals in a population, and it can be used as a guideline for individuals to avoid deficiency in the population. When an EAR cannot be derived, an RDA cannot be calculated; therefore, an adequate intake (AI) is developed as a guideline for individuals based on the best available data and scientific consensus. The UL denotes the highest average daily intake at which no adverse health effects are associated for almost all individuals in a particular group. The relationships among EAR, RDA, and UL are characterized in Figure 41-2.






Energy


Energy is thought of in terms of both intake and expenditure. Deficits and excesses of energy intake yield undesirable health consequences. Inadequate energy intake can lead to catabolism of body tissues and inability to provide energy substrate, whereas excess energy intakes can increase the risk for obesity. Adequacy of energy intake in adults is associated with maintenance of a healthy weight. The 3 components of energy expenditure in adults are the basal metabolic rate, the thermal effect of food (energy required for digestion and absorption), and energy for physical activity. Additional energy intake and expenditure are required to support growth and development for children.


The estimated energy requirement (EER) is the average dietary energy intake predicted to maintain energy balance in a healthy individual of a defined group. The EER accounts for age, gender, weight, stature, and physical activity level (PAL) (see Tables 41-2 and 41-3). The Dietary Guidelines for Americans and the DRI recommend 60 min of moderately intense daily activity for children >2 yr of age to maintain a healthy weight and to prevent or delay progression of chronic noncommunicable diseases such as obesity and cardiovascular disease. The EER was determined based on empirical research in healthy persons at different physical activity levels, including levels different from the recommended levels. They do not necessarily apply to children with acute or chronic diseases. EER is estimated by equations that account for total energy expenditure as well as energy deposition for healthy growth. Note that the EER for infants, relative to body weight, are approximately twice those for adults, due to the increased metabolic rate and requirements for weight maintenance and tissue accretion affecting growth.


The nutrients that provide energy intake in the child’s diet are fats (∼ 9 kcal/g), carbohydrates (∼ 4 kcal/g), and proteins (∼ 4 kcal/g). They are referred to as macronutrients. Alcohol intake can also contribute to energy intake (∼ 7 kcal/g). The EER does not specify the relative energy contributions of carbohydrates, fats, or proteins. Once the minimal intakes of each of the respective macronutrients are attained to meet physiologic requirements and to achieve adequacy (sufficient protein intake to meet specific amino acid requirements), the remainder of the intake is used to meet energy requirements with some degrees of freedom and interchangeability among fats, carbohydrates, and proteins. This forms the basis for the acceptable macronutrient distribution ranges (AMDR) (see Table 41-4), expressed as a function of total energy intake. In the following sections, each macronutrient is reviewed.


Jun 18, 2016 | Posted by in PEDIATRICS | Comments Off on Nutritional Requirements

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