CHAPTER 28

Nutritional Needs

Sara T. Stewart, MD, MPH, FAAP

Good nutrition is essential for typical growth and development. The physician plays an important role not only in assessing the growth of children but also in counseling parents about the nutritional needs of maturing children. The primary care physician should be knowledgeable about key nutritional concepts for children, including typical growth patterns and assessment of the child’s nutritional status, changing nutritional requirements and feeding patterns from infancy through adolescence, and common feeding and nutritional disorders.

Growth Patterns and Nutritional Requirements of Typical Children

Monitoring the growth and nutritional status of infants and children is an integral component of well-child care. The average expected increases in weight, height, and head circumference for the first several years after birth are listed in Table 28.1.

The energy and nutritional requirements of children vary with age. Postnatal growth is most rapid during the first 6 to 12 months after birth; hence, caloric and protein needs are very high at this time. The average daily energy and protein needs of children from birth to 18 years of age are presented in Table 28.2.

On average, newborns weigh 3.5 kg (7.7 lb), are about 50 cm (20 in) long, and have a head circumference of 35 cm (14 in). They lose about 5% to 10% of their birth weight during the first several postnatal days and usually regain this weight by the age of 10 to 14 days. During the first several months after birth, weight gain serves as an important indicator of infants’ general well-being. Failure to gain weight during this time may be a clue to a wide variety of problems, ranging from underfeeding to malabsorption. Newborns and infants gain about 30 g/day (1.1 oz/day; roughly 1% of their birth weight per day) for the first 3 postnatal months and about 10 to 20 g/day (0.4–0.7 oz/day) for the rest of the first year. Infants double their birth weight by 6 months of age and triple their birth weight by 12 months of age. Children aged 2 years to puberty gain approximately 5 to 10 g/day (0.2–0.4 oz/day). On average, children weigh about 10 kg (22 lb) at 1 year of age, 20 kg (44 lb) at 5 years of age, and 30 kg (66 lb) at 10 years of age. A rough rule that can be used to estimate the expected weight of a child based on age is 2 × age (years) + 10 = weight (kg). A prepubertal child who does not gain at least 1 kg/year should be monitored for nutritional deficits.

Infants and young children grow about 25 cm (9.8 in) during the first postnatal year, 12.5 cm (4.9 in) during the second year, and 6.25 cm (2.5 in) per year after that until puberty. This is followed by the prepubertal-pubertal growth spurt. Girls grow 3 to 4 cm (1.2–1.6 in) every 6 months and boys grow 5 to 6 cm (2.0–2.4 in) every 6 months during this period.

Feeding Patterns of Infants and Children

Liquid Foods

Human milk is generally recommended as the exclusive nutrient for newborns and infants during the first 6 months after birth and then could be continued along with complementary foods through 12 months of age. However, there are situations in which breastfeeding is not possible for the mother or is contraindicated because of a disease or medication. Therefore, although breastfeeding is the most advantageous for mother and baby and should be encouraged, mothers should never be made to feel inadequate or guilty if they are unable to breastfeed. Human milk or an iron-fortified infant formula provides complete nutrition for infants during the first 4 to 6 months after birth. During the first postnatal month or 2, newborns and infants take about 2 to 3 oz of formula (approximately 10 minutes on each breast) every 2 to 3 hours.

Because human milk is more easily digested than formula, it passes out of the stomach in 90 minutes; formula may take up to 4 hours. Therefore, during the first 4 to 6 postnatal weeks, breastfed newborns and infants want to feed more frequently (8–12 times in 24 hours) than formula-fed newborns and infants (6–8 times in 24 hours), with an increased number of nighttime feedings as well. By about 3 to 5 months of age, breastfed and bottle-fed infants do not differ in the number of nighttime feedings, although some breastfed infants continue to wake out of habit.

Most infants 6 months or younger consume about 4 to 5 oz per feeding every 4 to 5 hours. Under routine circumstances, human milk is preferred to infant formulas because it has emotional, nutritional, and immunologic advantages. Breastfeeding allows infants and mothers to develop a unique relationship that can be emotionally satisfying (see Chapter 29).

The composition of human milk varies over time. Colostrum, the first milk produced after delivery, is high in protein, immunoglobulin (Ig), and secretory IgA. Colostrum gradually changes to mature milk 7 to 10 days after delivery. The nutrient content of human milk of mothers who deliver preterm compared with those who deliver at term may vary considerably. Individual assessment may be necessary to determine the appropriateness of human milk for preterm newborns.

Nutritionally, human milk is uniquely tailored to meet the specific needs of babies. Human milk provides approximately 20 kcal/oz, the same as routine infant formulas. Table 28.3 compares the composition of human milk and several infant formulas. Human milk has relatively low amounts of protein compared with cow’s milk (1% vs 3%), yet the levels are sufficient to provide for satisfactory growth of babies. Protein content is highest at birth at 2.3 g/dL, then declines over the first month to 1.8 g/dL, yet it ensures adequate protein status throughout the first postnatal year.

Qualitative differences also make human milk more desirable. Casein to whey ratio in human milk is about 30:70, making it easier to digest than most infant formulas, which tend to have higher casein to whey ratios at 82:18. Whey is more easily digested and associated with faster gastric emptying compared with casein. Newborns and infants who breastfeed tend to digest their milk more easily, have softer stools, and be less satiated overnight, requiring more feeds, than those fed formula. Other whey proteins, such as IgA, lysozyme, and lactoferrin, all contribute and help host defenses.

Lactose is the major carbohydrate of human and cow’s milk, but it is present in higher concentrations in human milk. Lactose in human milk also contributes to softer stool consistency with nonpathological fecal flora and improved absorption of minerals. Oligosaccharides in human milk found in the carbohydrate polymers and glycoproteins have been structurally shown to mimic bacterial antigen receptors and may have a role in host defense. Fat is the primary source (50%) of calories in human milk. The fat in cow’s milk, which contains primarily saturated fatty acids, is not as well digested by newborns and infants as human milk fat, which is predominantly composed of polyunsaturated fats. Within the last decade, the long-chain polyunsaturated fatty acids docosahexaenoic acid (DHA) and arachidonic acid (ARA) have been added to most infant formulas to simulate the higher levels found in human milk. Research continues to be inconclusive, however, as to whether DHA and ARA supplementation may enhance vision and improve growth and cognitive development in formula-fed infants.

Human milk from well-nourished women should provide adequate amounts of all vitamins and other micronutrients. However, vitamin K, vitamin D, iron, and fluoride are not present in sufficient quantities to satisfy all nutritional needs over a prolonged period, and supplementation should be considered. The American Academy of Pediatrics (AAP) recommends that all newborns receive a prophylactic dose of 0.5 to 1 mg of parenteral vitamin K in the immediate newborn period to help prevent bleeding disorders. Even though the vitamin D content of human milk is low compared with cow’s milk, newborns and infants of healthy mothers have generally not been observed to develop rickets if there is sufficient exposure to sunlight. Newborns require about 1 minute of exposure to sunlight on the face to produce enough vitamin D. However, adequate sun exposure is difficult to assess, and there are increasing concerns about the harmful effects of sunlight. Compared with the previous recommendation of an average intake of 200 IU of vitamin D per day, the 2010 Institute of Medicine, now known as the Health and Medicine Division of the National Academies, recommendation calls for an average intake of 400 IU of vitamin D per day to meet the needs of most infants younger than 12 months. Although human milk contains less iron than iron-fortified formulas (fortified to about 12 mg/L of iron), the bioavailability of the iron in human milk is greater. Breastfed infants do not need iron supplementation until 6 months of age. For children 6 months and older who live in communities with suboptimally fluoridated water, the AAP recommends systemic (dietary) supplementation. Such supplementation can be provided through the use of a fluoridated toothpaste twice a day (see Chapter 31).

Abbreviations: ARA, arachidonic acid; DHA, docosahexaenoic acid; MCT, medium-chain triglycerides.

Human milk has several immunologic advantages, which are allergy and infection protective, over standard cow’s milk–based formulas. Its allergy-protective characteristics are attributed, in part, to the decreased intestinal permeability associated with human milk compared with standard formulas. The host defense factors present in human milk include Ig, complement, and cellular components (eg, macrophages, neutrophils, lymphocytes). Studies have shown that the incidences of viral and bacterial illnesses are lower in exclusively breastfed infants compared with their formula-fed peers.

The AAP recommends exclusive breastfeeding for about 6 months, followed by continued breastfeeding as complementary foods are introduced, with continuation of breastfeeding for 1 year or longer as mutually desired by mother and infant. Rarely, breastfeeding is contraindicated (see Chapter 29).

Solid Foods

Supplemental foods may be added to infants’ diets between the ages of 4 and 6 months. Solid foods should be introduced as soon as infants require the additional calories and are developmentally mature (ie, infant can sit and support his or her head and has lost tongue thrust). Introduction of solid foods prior to 4 months of age can interfere with an infant’s ability to take sufficient amounts of human milk or formula to meet nutritional needs. Waiting beyond 6 months of age to introduce solid foods may increase an infant’s risk of having inadequate iron or zinc intake.

Infants should first be given cereal grains, fruits, and vegetables, although 2 to 3 days should separate the introduction of new foods. Once several of these foods have been tolerated, the early introduction of subsequent, more allergenic, foods, such as milk, eggs, soy, wheat, nuts, and seafood, between 4 and 6 months of age may decrease the risk of the infant developing food allergies. Factors that indicate infants may be ready for solid foods include current weight twice that of birth weight, or about 6 to 7 kg (13.2–15.4 lb); consumption of more than 32 oz of formula per day (if on a formula-only diet); frequent feeding (regularly more than 8–10 times per day or more often than every 3 hours); and perceived persistent hunger after nursing.

Iron-fortified infant cereal, most commonly rice cereal because it does not contain gluten, is usually the first solid food offered to infants. Other single-grain cereals, such as barley cereal or oatmeal, are also appropriate early supplemental foods. Precooked infant cereals can be mixed with a variety of liquids, including human milk, formula, water, or infant fruit juices. The vitamin C in juice increases the bioavailability of the iron in the cereal, hence the recommendation to add it to dry cereal. Initially, the cereal should be mixed to a thinner consistency (eg, about 1 tablespoon of cereal to 2 oz of liquid). It is not unusual for infants to reject their first several spoonfuls of cereal because the tastes and textures are new. If they refuse the feeding, it should be stopped and reintroduction of the food delayed for 1 week. Once infants have accepted the new taste and texture, the mixture should gradually be worked to a thicker consistency. By about 7 to 8 months of age, infants should be taking 4 to 6 tablespoons of cereal mixed with enough liquid to give the mixture the consistency of mustard. Mixed cereal grains may be given to older infants.

Fruits and vegetables may be introduced within a few weeks of the introduction of cereal. The order is not as important as the need to add only 1 new food at a time and no more than 1 to 2 new foods per week. Meats may be introduced after 6 months of age.

A wide variety of commercially prepared baby foods designed to be developmentally appropriate and labeled by stage (ie, first, second, third) are available. The jars of different stages contain the amount of food that an infant at a given age should be able to eat at 1 sitting. This is not always the case, however, and opened jars of baby food may safely be stored in the refrigerator for 2 to 3 days. Infants should not be fed directly from the jar because saliva on the spoon mixes with the remaining food and digests it, causing it to liq-uefy. Vegetables and meats may be offered at room temperature but should be warmed slightly for greater palatability. Fruits and desserts may be at room or refrigerator temperature. Home-cooked fruits and vegetables should be thoroughly washed, pureed, and strained before giving to infants. Home-prepared foods tend to have a shorter shelf life than commercially bought baby foods because of lack of preservatives, but some may find that they are more palatable to the infant.

First-stage foods, for infants 4 to 6 months of age, include strained infant juices, single-grain cereals, and pureed strained fruits and vegetables such as bananas, carrots, and peas. These foods contain no egg, milk, wheat, or citrus, to which some infants may be sensitive. Second-stage foods, for infants about 6 to 9 months of age, are smooth, mixed-ingredient foods, such as mixed vegetables, or meat dinners, such as chicken noodle. Third-stage foods, or junior foods, are for infants about 9 to 10 months of age who can sit well without support, have some teeth, and have begun self-feeding. These more coarsely textured foods, such as vegetable and meat dinner combinations, contain a wider variety of nutrients. Finger foods, such as crackers, cheese wedges, or cookies, can also be introduced by 9 to 10 months of age, once infants have developed a pincer grasp. Most infants are eating the same meals as the rest of the family (table foods) by about 1 year of age. Foods that can easily be aspirated, such as raw carrots, nuts, and hard candies, should be avoided until children are older than 4 years.

Baby foods can be prepared at home as long as they are finely pureed or strained and contain enough liquid to make them easy for infants to swallow. One danger of preparing foods at home is that sugar, salt, or spices can be easily added to make foods palatable to adults. These ingredients are not necessary for infants. In addition, homegrown, home-prepared vegetables may be contaminated with high levels of nitrates (eg, because of contaminated well water) and nitrites (eg, in vegetables such as carrots, beets, and spinach). Nitrates and nitrites have been implicated in the development of methemoglobinemia, especially in infants younger than 6 months. Methemoglobinemia decreases the oxygen-carrying capacity of the blood, leading to anoxic injury and death. This is more of a concern in rural areas that primarily use well water.

Weaning from the breast or bottle to a cup usually occurs by 12 months of age but may be delayed up to 18 months of age in some children. Homogenized, vitamin D–fortified cow’s milk may be given at 12 months of age. Fat-free (skim) and low-fat (1%) milk should not be given before 2 years of age.

Diet of Children and Adolescents

The caloric and protein needs of children decrease in the second year after birth, paralleling the decrease in growth rate during this time. Milk intake also decreases and may drop to 16 oz/day by 24 to 36 months of age. Except for increased caloric requirements, the diet of school-age children and adolescents should be similar to that of normal adults. Evidence that foods eaten during childhood may have long-lasting effects on adult health is increasing, and it is important that children develop healthy eating habits early in life. Atherosclerosis, osteoporosis, and obesity are some of the diseases that may have their beginnings during childhood.

The US departments of Agriculture (USDA) and Health and Human Services (HHS) have replaced the food pyramid with a new visual aid—a circular plate on a square mat. Half of the plate consists entirely of vegetables and fruits, whereas the other half of the plate is divided into one-quarter protein and one-quarter grains, with a small side of dairy. It’s a much more visually descriptive tool that guides how to divide daily meals. The website www.choosemyplate.gov provides individual dietary guidance according to a child’s age, sex, and activity level based on the USDA/HHS dietary guideline for Americans older than 2 years.

To promote lifelong heart healthy habits, the American Heart Association (AHA) released a statement of dietary recommendations for children and adolescents (Box 28.1). It recognizes that children are often offered nutrient-poor foods that are high in fat and sugar and overly processed. The AHA recommendations support USDA guidelines and include eating fruits and vegetables daily while limiting fruit juice intake, using vegetable oils, using butter instead of soft margarines, eating whole grain rather than refined grain breads and cereals, using nonfat or low-fat milk and dairy products, eating more fish, and reducing salt intake.

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