Infant Feeding Robert T. Hall, MD,* and Robin E. Carroll, MS, RD

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1 ARTICLE Robert T. Hall, MD,* and Robin E. Carroll, MS, RD OBJECTIVES After completing this article, readers should be able to: 1. Delineate the optimum nutrition for infants through the first year of life. 2. Describe the formulas that can be used as adequate substitutes for term infants whose mothers cannot or choose not to breastfeed through the first year of life. 3. Explain the place of low-iron-containing formulas in infant feeding. 4. Explain the differences and implications of growth velocity in formula-fed and breastfed infants. 5. Explain the implications of adding solid foods to the diets of breastfed and formula-fed infants. Breastfeeding The American Academy of Pediatrics (AAP) has recommended exclusive breastfeeding during the first 6 months of life and continuation of breastfeeding for the second 6 months as optimum nutrition in infancy. 1 There are multiple reasons for this recommendation. First, human milk is the optimum nutrient for term and near-term infants with respect to protein, fat, and carbohydrate composition. Second, the antiinfective properties of human milk reduce the incidence of acute illnesses such as infectious diarrhea, pathogenic bacterial fecal flora, necrotizing enterocolitis, otitis media, lower respiratory tract infections, and urinary tract infections in infants. Third, it has been suggested that the incidence of immunemediated diseases such as diabetes mellitus, Crohn disease, eczema, asthma, and allergic gastroenteritis is lower among breastfed infants. Fourth, psychological and long-term cognitive advantages have been observed in breastfed infants compared with formula-fed infants. It is believed that mother-infant bonding is enhanced during breastfeeding, *Professor of Pediatrics; Chief, Division of Human Development. AssistantProfessorofPediatrics,University of Missouri Kansas City School of Medicine, Children s Mercy Hospital, Kansas City, MO. DrHallandMsCarrollreceivegrant support from Wyeth, Ross Nutritionals, and Mead-Johnson Companies. and there are consistently improved scores on tests of cognitive development directly correlated with the duration of breastfeeding. However, it is clear that other factors associated with breastfeeding enhance infant development, including maternal socioeconomic status, the Home Inventory (a measure of the adequacy of the home environment), maternal educational level, and maternal intelligence quotient (IQ). 2 COMPOSITION OF HUMAN MILK The protein content of human milk is approximately 70% and 30% casein, which differs from that of bovine milk (18%, 82% casein). The proteins are resistant to acid precipitation and are digested more easily, which promotes gastric emptying. The protein fraction provides lower concentrations of phenylalanine, tyrosine, and methionine and higher concentrations of taurine than does casein. The major component of protein is alpha-lactalbumin. Lactoferrin, lysozyme, and secretory immunoglobulin A are specific proteins involved in host defense. Oligosaccharides, nucleotides, growth factors, and cellular components of human milk also enhance the infant s immune system. The mother may produce specific antibodies that are excreted in her milk as secretory immunoglobulin A (IgA) (intramammary-immune system) when exposed to foreign antigens. Therefore, specific passive immunity is enhanced in this system. Lipids provide approximately 50% of the caloric content of human milk. Lipids are contained in milk fat globules, and absorption is enhanced by bile salt-stimulated lipase. The fatty acid content of human milk is high in palmitic, oleic, linoleic, and alpha-linolenic acids. Arachidonic acid (AA) and docosahexaenoic acid (DHA), derivatives of linoleic and alpha-linolenic acids, respectively, are found in human but not in bovine milk. They are related specifically to the composition of neural and retinal tissue, and deficiencies of these very longchain polyunsaturated fatty acids have been shown to be associated with decreased neural, developmental, and visual function in experimental animal models. 3 These very long-chain polyunsaturated fatty acids have not been determined to be essential in term infants because of formation from their precursors, but the question remains unanswered for preterm and very low-birthweight (VLBW) infants. Lactose is the major carbohydrate in human milk. It is hydrolyzed in the small intestine into glucose and galactose by lactase. This enzyme appears somewhat late in the developing fetal intestine, and some lactose, even in term infants, enters the distal small bowel where it ferments, permitting proliferation of predominantly acidophilic bacterial flora (lactobacilli). These bacteria produce an acid medium that suppresses growth of more pathogenic organ- ABBREVIATIONS AA: arachidonic acid AAP: American Academy of Pediatrics DHA: docosahexaenoic acid ELBW: extremely low-birthweight Ig: immunoglobulin LCPUFAs: long-chain polyunsaturated fatty acids NCHS: National Center for Health Statistics VLBW: very low-birthweight Pediatrics in Review Vol. 21 No. 6 June

2 isms and promotes absorption of calcium and phosphorus. Human milk also contains minerals, vitamins, and micronutrients in concentrations sufficient to achieve optimum growth in the term and near-term infant. No supplementation is required until 4 to 6 months of age when iron (approximately 1 mg/kg per day) should be added to the diet, preferably in the form of iron-fortified cereal. Vitamin D supplementation also may be necessary in term infants at approximately 4 to 6 months of age if they are darkskinned or exposed to low levels of sunlight. Vitamin D supplementation of 400 IU/d is recommended for these breastfed infants and may be provided in the form of multiple vitamin preparations for infants who are exclusively breastfed. Fluoride supplementation is recommended from 6 months to 3 years of age in breastfed and formula-fed infants if the water supply contains less than 0.3 ppm fluoride. 4 Other minerals and micronutrients contained in human milk are adequate for normal growth and nutrition, although rates of growth in breastfed infants are lower than in formula-fed infants in the second 6 months of life. Solid foods commonly are introduced beginning at 4 to 6 months of age, but such additions do not change the growth velocity of breastfed infants. SUCCESSFUL BREASTFEEDING Successful breastfeeding of the newborn infant is a complex process and frequently requires support and encouragement. Recommendations of the AAP, the United Nations Children s Fund, and the World Health Organization have been designed to promote breastfeeding. Important among these recommendations are discussion of feeding plans with the mother prior to delivery and education about the details of breastfeeding during prenatal classes. Instruction and discussion should continue during hospitalization and thereafter. Breasts should be examined prenatally to identify problems such as inverted nipples. Breastfeeding should begin as soon as possible after delivery, preferably in the first hour. Infants should room-in with their mothers and be encouraged to breastfeed at least 8 to 12 times per day. If the breastfeeding is incomplete or ineffective, the mother should initiate a regimen of expressing her milk. Supplementary feedings of water, glucose water, or formula generally are not necessary for healthy infants and may be counterproductive. CONSEQUENCES OF LACTATION FAILURE Early hospital discharge ( 48 h) and prematurity constitute risk factors for lactation failure that can Lactoseisthemajorcarbohydrateinhumanmilk... somelactose...entersthedistalsmallbowelwhereit ferments, permitting proliferation of... bacterial flora...thatproduceanacidmedium...thatpromotes absorption of calcium and phosphorus. result in excessive jaundice and dehydration. Infants should be examined within 2 days of hospital discharge to assess breastfeeding and initiate appropriate intervention strategies as necessary. Mothers and caregivers should understand that excessive jaundice is the result of inadequate human milk intake during the first week of life, necessitating increased frequency of breastfeeding. This may be provided best by employing a feeding tube attached to the breast, gastric tube, or supplemental bottle feedings with human milk or formula. Jaundice due to human milk is uncommon. It usually begins and peaks after the first week of life, whereas breastfeeding jaundice that is associated with decreased intake and increased enteropathic circulation occurs predominantly during the first week of life. Bilirubin levels in breastfed infants may peak normally at 306 to 340 mcmol/l (18 to 20 mg/dl). Such levels do not require phototherapy or discontinuation of breastfeeding unless there are other associated conditions (eg, hemolysis, inborn errors of metabolism, infection). STORAGE OF HUMAN MILK Expressed human milk that will be fed within 48 hours of collection can be refrigerated; that which is not to be fed within 48 hours should be frozen. Milk expressions should be packaged and frozen separately and preferably labeled with the name and date if the infant is to be cared for in a child care center. Frozen milk should be thawed in warm water. Microwave warming should be avoided. Formula Feeding for Term and Near-term Infants Cow milk formulas and soy milk formulas are adequate substitutes for term and near-term infants who are not breastfeeding during the first 12 months of life. 5 All of the infant s nutritional needs may be met with iron-fortified formulas fed during the first 4 to 6 months, and these formulas provide a major source of nutrition for the second 6 months of life. Indications for the use of infant formulas are: 1) as substitute or supplement feedings for mothers who do not or cannot provide human milk for their infants; 2) infants who have certain inborn errors of metabolism or other conditions causing intolerance to human milk (eg, galactosemia and tyrosinemia); 3) infants whose mothers have certain infections caused by organisms known to be transmitted in human milk (eg, human immunodeficiency virus and, under rare circumstances, cytomegalovirus, herpes simplex virus, and bacteria); 4) infants whose mothers are undergoing cancer chemotherapy or are receiving certain other drugs, foods, medications, or environmental agents that are excreted into human milk. 6 Formula supplementation also should be considered if the infant fails to gain weight following optimal encouragement and therapy for breastfeeding. FORMULA COMPOSITION Cow milk infant formulas vary in composition but generally have been altered to optimize nutrient intake. 192 Pediatrics in Review Vol. 21 No. 6 June 2000

3 Protein in cow milk formula varies in concentration from approximately 1.4 to 1.6 g/dl, which is approximately 40% greater than that in human milk (Table 1). Although the composition varies in ratios of to casein, the bovine -dominant formulas produce amino acid patterns that differ from those seen with human milk protein. The predominant protein in cow milk is beta-lactoglobulin. Infants fed bovine -predominant formula have increased serum levels of threonine, phenylamine, valine, and methionine compared with breastfed infants. There are no known adverse effects of these differing amino acid patterns in otherwise normal infants. The fat content of cow milk formulas constitutes approximately 50% of their energy. The butterfat of cow milk formula is replaced largely with vegetable oils that enhance digestibility and absorption. Fat blends vary among formulas, but generally they provide a mixture of highly digestible short-chain fatty acids (coconut NUTRITION oil), long-chain polyunsaturated fatty acids (LCPUFAs) (palm oil), and polyunsaturated fatty acids (soy, corn, and safflower oils). The essential fatty acids, linoleic and alpha-linolenic acids, are added in concentrations sufficient to provide adequate substrate for their longchain polyunsaturated derivatives, AA and DHA, respectively. However, there is debate over whether the very long-chain polyunsaturated fatty acids, AA, and DHA that are present in human milk TABLE 1. Human Milk and Commerical Formulas for Term Infants RDA 0 TO 12 MO Energy (kcal) 98 to 108 kcal/kg HUMAN MILK NUTRIENT COMPOSITION PER LITER ENFAMIL WITH IRON SIMILAC WITH IRON Protein (g) 13 to Source Whey (% total) Casein (% total) CARNATION GOOD START Fat (g) Source Polyunsaturated (%) Monounsaturated (%) Saturated (%) Predominant oil Human milk fat Palm olein, soy, coconut, sunflower Soy, coconut, safflower Carbohydrate (g) Source Lactose Minerals Calcium (mg) 400 to Phosphorus (mg) 300 to Magnesium (mg) 40 to Iron (mg) 6 to Zinc (mg) Copper (mcg) 400 to Iodine (mcg) 40 to Sodium (meq) 5 to Potassium (meq) 13 to Chloride (meq) 5 to Renal solute load (mosm) Osmolality (mosm/kg H 2 O) Fat-soluble Vitamins A (IU) 1,240 2,230 2,027 2,027 2,027 D (IU) 300 to E (IU) 3 to K (mcg) 5 to Palm olein, soy, coconut, safflower Pediatrics in Review Vol. 21 No. 6 June

4 should be added to term infant formulas. Lactose is the major carbohydrate in standard cow milk-based formulas, although some formulas contain starch or other complex carbohydrates. Lactose intolerance appears to be uncommon in the first year of life, but there is a growing market for nonlactosecontaining formulas for infants who have nonspecific symptoms of bloating, gaseous distention, vomiting, spitup, and nonspecific diarrhea. With the exception of galactosemia and secondary lactase deficiency following small intestinal injury (usually following gastroenteritis), there are very few indications for a lactose-free formula in infancy. Iron is an important component of cow milk formulas and is present in a concentration of 12 mg/l. Lowiron-containing formulas continue to be marketed because of a perception that iron causes constipation and other feeding problems. Data are inadequate to support this perception, and the AAP has recommended that all cow milk formula-fed infants receive iron-fortified formula. 7 Mineral and vitamin content of standard cow and soy milk formulas is adequate to meet the nutritional needs of infants in the first year of life except for fluoride, which should be added after 6 months of age if the fluoride concentration in the water supply is less than 0.3 ppm. 4 Formula intake should beadlibidum and adequate to support weight gains of approximately 25 to 30 g/d for the first 3 months, 15 to 20 g/d for the second 3 months, and 10 to 15 g/d between 6 and 12 months of age. Formula intake generally ranges from 5 to 7 oz/kg per day in the first 3 months and remains at 26 to 32 oz/d thereafter through the first year of life. Solid feedings provide additional caloric intake for formula-fed infants after 4 to 6 months of age and result in greater weight gains than in breastfed infants, perhaps because breastfed infants decrease their intake of human milk when introduced to solid foods. Formula-fed infants generally continue to consume the same volume of milk in spite of additional caloric intake from solids and have accentuated weight gain velocity. Soy formulas and lactose-free cow milk formulas support the growth of normal term infants through the first year of life. They may be used in lieu of cow milk formula. Use of these formulas reportedly comprises nearly 25% of the formula market, although this far exceeds the estimated incidence of cow milk protein and lactose intolerance for which they are employed. Phytate in soy formula in addition to the absence of lactose diminishes calcium absorption, although adequate bone mineralization has been demonstrated in term infants Mineral and vitamin content of standard cow and soy milk formulas is adequate to meet the nutritional needs ofinfantsinthefirstyearoflifeexceptforfluoride... receiving these formulas. Because premature and enriched formulas are available for preterm infants, there is no indication for the use of soy or lactose-free formulas in preterm infants who have no demonstrated intolerance. FORMULA MIXING Boiling Water Most municipal water supplies are safe, and boiling water infrequently is recommended to prepare infant formulas. However, families using well water or pond water or who live in areas where flooding is a problem should boil the water used to prepare formula. Lead Exposure Lead exposure is still a common problem in the United States that affects all ethnic and socioeconomic groups. Infants can be exposed to lead if contaminated tap water is used to prepare their formula. Older homes may contain lead pipes, and some newer homes are at risk because the pipes may have been soldered with lead. To reduce the possibility of lead contamination in tap water, mothers should be instructed to use only cold water, run the water for 2 minutes before using it, and avoid boiling water excessively, which can increase the concentration of lead. Fluid Requirements Infants are particularly vulnerable to fluid imbalances. Compared with adults, infants have a larger surface area-to-body weight ratio and a higher percentage of body water and are unable to communicate thirst. In general, infants who weigh 0.5 to 3 kg require 120 ml/kg per day of fluid, and those who weigh 3 to 10 kg require 100 ml/kg per day. Infants weighing 10 to 20 kg require 1,000 ml plus 50 ml/kg per day for each kilogram above 10 kg. Inappropriate mixing of infant formulas may lead to dehydration, overhydration, and weight loss. Nutritional Needs of Preterm Infants The preterm infant who is born at 34 weeks gestation and weighs less than 2,000 g and perhaps is as large as 2,500 g and as old as 36 weeks gestation has special nutritional needs. Specific data on the 34- to 36-week-gestation infant are sparse. Special nutritional supplementation of these infants may shorten the time of recovery from deficiencies of abbreviated intrauterine accretion and those accrued from inadequate nutritional intake during early neonatal life. Clearly, the VLBW infant ( 1,500 g birthweight and 32 weeks gestation) has extraordinary nutritional needs and special requirements for intake that can be met only with fortified human milk and preterm infant formulas. The energy intake required for growth of the VLBW infant is approximately 100 to 120 kcal/kg per day or greater to achieve a weight gain of 15 g/kg per day. Protein intakes necessary to achieve this growth are 3.5 to 4 g/kg per day. Preterm infant formulas are -predominant (albeit bovine ), which produces plasma amino acid levels close to those of breastfed infants (Table 2). Fat should constitute approximately 50% of the energy intake. The fat content of human milk is fairly constant from early lactation 194 Pediatrics in Review Vol. 21 No. 6 June 2000

5 TABLE 2. Fortified Human Milk and Formulas for Preterm Infants HUMAN MILK POWDERED FORTIFIER 1 PKG/ 25 ML HUMAN MILK LIQUID FORTIFIER 50/50 PREMATURE INFANT FORMULA SIMILAC 24 SPECIAL CARE NUTRIENT ENRICHED FORMULA ENFAMIL 24 PREMATURE NEOSURE Energy (kcal) ENFACARE Protein (g) Source Human milk, protein, casein Human milk, nonfat milk, protein Nonfat milk, protein Nonfat milk, protein Nonfat milk, protein Nonfat milk, protein Fat (g) Source Human milk Human milk, MCT, soy, coconut MCT, soy, coconut MCT, soy, coconut Soy, safflower, coconut, MCT Sunflower, soy, coconut, MCT Carbohydrate (g) Source Lactose, corn syrup solids Lactose, corn syrup solids Lactose, corn syrup solids Lactose, corn syrup solids Lactose, corn syrup solids Lactose, corn syrup solids Minerals Calcium (mg) 1, ,452 1, Phosphorus (mg) Magnesium (mg) Iron (mg) (3)* 14.5 (2)* *Low-iron Zinc (mg) Copper (mcg) 1,229 1,330 2,016 1, Iodine (mcg) Sodium (meq) Potassium (meq) Chloride (meq) Renal solute (mosm) Osmolality (mosm/ kg/h 2 O) Fat-soluble vitamins A (IU) 13,015 6,990 10,081 10,081 3,433 3,381 D (IU) 2, ,210 2, E (IU) K (mcg) MCT medium-chaintriglycerides to mature milk, and it is well absorbed. Preterm infant formulas contain a mixture of medium-chain triglycerides and vegetable oils containing polyunsaturated long-chain triglycerides that also are well absorbed. However, preterm infant formulas do not contain very longchain polyunsaturated fatty acids (AA and DHA). Although these very long-chain polyunsaturated fatty acids are important constituents of the brain and retina, data are not yet conclusive to determine whether adequate levels are produced from their precursors linoleic and alpha-linolenic acids in preterm infants. This is an area of intense investigation. Carbohydrate requirements for the VLBW infant are estimated to be 40% to 50% of calories or approximately 10 to 14 g/kg per day. Human milk has fairly constant levels of lactose from early to late gestation, which may result in undigested lactose in the distal bowel because of inadequate lactase activ- Pediatrics in Review Vol. 21 No. 6 June

6 ity. Although this may cause a fermentative diarrhea, human milk is well tolerated in most clinical settings. However, preterm infant formulas frequently contain 50% carbohydrate with glucose polymers to avoid problems of osmotic diarrhea and lactose intolerance. These special formulas generally have been well tolerated because of high glucosidase activity in the small intestinal mucosa of the preterm infant. Mineral absorption with these formulas has not been impaired. Mineral requirements of the VLBW infant are higher than for larger preterm infants. Sodium and potassium requirements are estimated to be 2.5 to 3.5 meq/kg per day and even higher in extremely low-birthweight (ELBW) infants ( 1,000 g birthweight). Calcium, phosphorus, and magnesium requirements are related inversely to gestational age in the VLBW infant on a per-kilogram basis. This is due in large part to the extremely high accretion rates generally achieved in the last trimester of pregnancy. Mature human milk is clearly inadequate to meet these needs, and preterm infant formulas contain 100 to 180 mg/100 kcal of calcium and 50 to 70 mg/100 kcal of phosphorus in an attempt to achieve intrauterine accretion rates. Fortification of human milk to these levels has been demonstrated to be adequate to achieve bone mineralization and intrauterine accretion within the normal range for term infants. Human milk fortifiers are available in powdered and liquid form in the United States. When added to human milk (1 pack per 25 ml), the powdered fortifier is sufficient to achieve an energy content of 24 kcal/oz and is similar in composition to a 24 kcal/oz preterm infant formula. However, fat absorption is less when employing the currently available powdered fortifier compared with premature formula, necessitating intakes of approximately 180 ml/kg per day of fortified human milk compared with intakes of approximately 150 ml/kg per day of premature formula to achieve similar weight gain. New powdered fortifiers are being evaluated, which appear to overcome problems of fat malabsorption while maintaining adequate absorption of calcium, phosphorus, and magnesium. Although fat absorption is better (90%) with the commercially Iron intake represents a special nutritional need for the VLBW infant. Human milk contains very low quantities of iron, and formulas for preterm infants are available withorwithoutironsupplementation... ironinthe formofferroussulfateshouldbeprovided... tothe formula-fed growing preterm infant. available liquid fortifier, dilution of the liquid fortifier with human milk diminishes the content of human milk fat. The result of using liquid fortifiers is dilution of both human milk and the fortifier in concentrations proportionate to the mixture. Iron intake represents a special nutritional need of the VLBW infant. Human milk contains very low quantities of iron, and formulas for preterm infants are available with or without iron supplementation. It is clear that iron in the form of ferrous sulfate should be provided in quantities of 2 to 4 mg/kg per day to the formula-fed growing preterm infant. Infants receiving erythropoietin may require iron supplementation of 6 mg/kg per day or greater. Enriched formulas (Similac Neo- Sure and Enfamil Enfacare ) have been designed for the growing preterm infant who has achieved a weight of at least 1,800 g (approximately 34 weeks postconceptual age). These formulas generally provide 22 kcal/oz and are midway in composition between fortified human milk or preterm infant formula and mature human milk or cow milk formula (Table 2). The enhanced protein and caloric density of these formulas has been shown to achieve increased growth in weight, length, and even head circumference in the VLBW infant. Unfortunately, data are not available to recommend precisely either the time of initiation or discontinuation of enriched formula. However, data to date suggest that initiation at 1,800 g weight or 34 weeks postconceptual age and continuation to a postconceptual age of 52 to 56 weeks (3 to 4 mo) is associated with enhanced growth compared with infants receiving cow milk formula or human milk. Bone mineralization also is enhanced in infants receiving enriched formula. Clinical studies are underway to evaluate the optimum duration for continuation of enriched formula in VLBW infants. Meeting the nutritional needs of VLBW infants who are breastfeeding following hospital discharge has been evaluated incompletely. Data suggest that growth and bone mineralization are significantly lower in these infants than those fed standard cow milk formula or enriched formula. Therefore, supplementation with 8 oz/d of enriched formula or fortified human milk may be prudent. Assessment of nutritional adequacy by obtaining serum calcium, phosphorus, alkaline phosphatase, urea nitrogen, and transthyretin (prealbumin) levels at 4 to 6 weeks postdischarge is recommended. Phosphorus levels less than 1.49 mmol/l (4.5 mg/dl) suggest the need for additional supplementation of calcium and phosphorus. Urea nitrogen less than 1.79 mmol/l (5 mg/dl) or transthyretin less than 10 mg/dl indicates the need for additional protein. Special Infant Formulas (Table 3) Soy protein formulas are lactose-free and may be used for infants who have lactase deficiency or galactosemia. Short-term use may be indicated for infants who have postdiarrheal lactose intolerance, although infants generally should be rechallenged with lactose in these circumstances because lactase deficiency is transient. Soy formulas also have been employed in infants who are perceived to have intolerance to cow milk formula for a variety of reasons. Infants who have IgE-mediated cow milk protein intolerance may benefit from soy 196 Pediatrics in Review Vol. 21 No. 6 June 2000

7 TABLE 3. Commonly Employed Special Formulas NUTRIENT COMPOSITION PER LITER SOY FORMULAS LACTOSE-FREE PROTEIN HYDROLYSATE ISOMIL PROSOBEE ALSOY SIMILAC LACTOSE FREE LACTOFREE ALIMENTUM NUTRAMIGEN PREGESTIMIL Energy (kcal) Protein (g) Source Soy protein and methionine Soy protein and methionine Soy protein and methionine Milk protein isolate Milk protein isolate Casein hydrolysate Casein hydrolysate Casein hydrolysate Fat (g) Source Safflower, coconut, and soy Palm olein, soy, coconut, and sunflower Palm olein, soy, coconut, and safflower Soy and coconut Palm olein, soy, coconut, and sunflower Safflower, MCT, and soy Palm olein, soy, coconut, and sunflower MCT, soy, corn, and safflower Carbohydrate (g) Source Corn syrup solids, sucrose Corn syrup solids Corn, maltodextrin, sucrose Corn syrup solids, sucrose Corn syrup solids Sucrose and modified tapioca starch Corn syrup solids and modified cornstarch Corn syrup solids, dextrose, modified cornstarch Minerals Calcium (mg) Phosphorus (mg) Magnesium (mg) Iron (mg) Zinc (mg) Copper (mcg) Iodine (mcg) Sodium (meq) Potassium (meq) Chloride (meq) Renal solute (mosm) Osmolality (mosm/kg/h 2 O) Fat-soluble vitamins A (IU) 2,027 2,027 2,095 2,027 2,027 2,027 2,027 2,568 D (IU) E (IU) K (mg) MCT medium-chaintriglycerides Pediatrics in Review Vol. 21 No. 6 June

8 formula, although many of these infants also may have soy milk intolerance for nonspecific reasons that frequently is manifested by loose stools, spitting up, vomiting, and irritability. Lactose-free cow milk formulas are enjoying an increased market for infants who are perceived to have lactose intolerance characterized by bloating, gaseousness, vomiting, colic, and diarrhea. It is not clear that this market exuberance is justified by true lactose intolerance. Rechallenging affected infants with cow milk formula may avoid the false impression of lactose or cow milk protein intolerance that frequently is perceived by the parents, thereby creating a pattern of avoiding milk products. Protein hydrolysate formulas are more appropriate for the infant who is intolerant to intact milk protein. The protein in these formulas is extensively hydrolyzed, resulting in peptides that do not elicit an immunologic response in most infants. In addition, the fat content of some of the protein hydrolysate formulas contains medium-chain triglycerides to facilitate the absorption of fat. Therefore, these formulas are suitable for conditions of chronic malabsorption (eg, cystic fibrosis, short gut syndrome, biliary atresia, and other forms of cholestasis). Most protein hydrolysate formulas also are free of lactose, and carbohydrate is provided in varying forms of corn syrup solids, modified corn starch, sucrose, or dextrose. This may facilitate the efficacy of these formulas in patients who have chronic malabsorption syndromes. Beyond hydrolysates, there is a place for the use of L-amino acid formulas for infants who have protein-induced intestinal disease. A wide variety of other special infant formulas have specific but uncommon medical indications, including a low-solute formula (Similac PM 60/40 ) used for infants who have renal or cardiovascular dysfunction. The sodium, potassium, chloride, calcium, phosphorus, and iron concentrations of these formulas are low, necessitating very careful use and evaluation. These formulas are not suitable for use in the growing healthy infant who has no specific indications. A variety of amino acid-based formulas specifically designed for infants who have inborn errors of metabolism also are available. Follow-up or toddler formulas also are commercially available (Pedia- Sure and EleCare ). In general, these formulas have higher protein concentrations than cow milk formula and are more consistent with protein levels in cow milk. The fat and carbohydrate concentrations are also higher, resulting in a caloric The ability to digest and absorb proteins, fats, and carbohydrates is sufficiently mature by 4 to 6 months of age to tolerate cereal, pureed fruits, vegetables, and meats. density of 1,000 kcal/l. These formulas are designed as a nutritional supplement or total feeding for young children who have failure to thrive from a variety of underlying etiologies, such as chronic cardiopulmonary or neurologic disorders. They are not suitable for infants younger than 1 year of age or for the otherwise growing healthy older infant. Introducing Solid Feedings Timing of the introduction of solid feeding depends on neurologic and gastrointestinal maturation of the infant. The infant should be able to sit and to coordinate masticating and swallowing nonliquid foods. The ability to digest and absorb proteins, fats, and carbohydrates is sufficiently mature by 4 to 6 months of age to tolerate cereal, puréed fruits, vegetables, and meats. Renal maturation generally is sufficient to tolerate increased renal solute. There is considerable variation among infants in achieving these neuromaturational requirements. Generally, the extrusion reflex has resolved between 4 and 6 months of age, and the ability to swallow nonliquid foods is established. Infants typically begin to indicate readiness for oral feedings by opening their mouths and leaning forward in the sitting position. Similarly, they can indicate satiety or lack of readiness by turning away. Mothers should be instructed to follow these cues to avoid overfeeding or creating conflict over oral feeding. Introducing solids prior to 4 to 6 months of age may be inappropriate. There is no scientific evidence to support the claim that solids (cereal in the bottle) will help an infant sleep longer at night. Families may need assistance in setting realistic goals for introducing solids. The decision to introduce solid foods into the diet of any infant should be individualized and based on the infant s developmental ability. Feedings prior to this developmental stage may represent a type of forced feeding and can be dangerous. Infants may aspirate food if they do not have the necessary oralmotor skills. It is important to continue breastfeeding or formula feeding through the first year of life. Although it formerly was believed that caloric intake would increase significantly with the onset of solid feedings, evidence suggests that consumption of human milk will decrease, and the addition of solid foods is not associated with increased weight gain in breastfed infants. 8 Single-ingredient foods generally should be introduced first, with no more than one started at weekly intervals to permit identification of any intolerance. Infant cereals are a good first choice, with dry cereal diluted 1:6 by weight with human milk or infant formula. This provides a caloric density of 108 kcal/dl. The introduction of puréed fruits, vegetables, and meats may be guided by individual taste and preference. Juices may be introduced when the infant can drink from a cup, but they should not replace milk or formula. These products are high in carbohydrates and may decrease consumption of proteincontaining liquids if given excessively. Quantities greater than 8 oz/d may result in diarrhea and have the potential for producing caries if 198 Pediatrics in Review Vol. 21 No. 6 June 2000

9 infants are exposed to them for sustained periods throughout the day from a bottle. Extra water generally need not be consumed except in instances of excessive losses, such as diarrhea or excessive perspiration. The caloric density of commercially prepared baby foods varies considerably and is a factor in caloric intake. For example, 100 g strained fruit contains 40 to 50 kcal, strained vegetables contain 30 to 65 kcal, meat contains 95 to 100 kcal, egg yolk contains 195 kcal, and desserts contain 70 to 90 kcal. Although breastfeeding infants will decrease their intake of human milk when solid foods are added to the diet, formula-fed infants may be encouraged by parents to continue the same volume of intake, which can result in greater caloric consumption and the potential for excessive weight gains. Finely chopped foods may be introduced at 10 to 12 months of age, but parents must be watchful for potential aspiration of food particles. Peanuts, raw fruit, popcorn, and hotdogs should not be fed to children younger than 2 years of age. Salt intake varies considerably from product to product and manufacturer to manufacturer. Some caution should be exercised to avoid both deficient and excessive intake, although earlier concerns about salt avoidance to prevent hypertension have not been borne out by longterm studies. Assessment of Growth and Nutritional Status Assessment of growth and nutrition of the infant is fundamental to nutritional care. Although simple in its fundamentals, such assessment is complex in discerning disorders from norms, particularly because there are widely divergent normal values for different populations and nutrient intakes. Growth is assessed primarily by comparing values for weight, length, weight-to-length ratios, and head circumference against National Center for Health Statistics (NCHS) growth standards for boys and girls. However, several shortcomings are evident from these measurements alone. Growth velocity is a more sensitive index than weight or length obtained at a specific time. It is a measure of changes in the parameter over time and should be employed when assessing the nutritional status of infants. For example, weight gain should approximate 10 to 15 g/kg per day in the first month of life, 7 to 10 g/kg per day from 2 to 3 months of age, and 5 to 7 g/kg per day from 3 to 6 months of age. Height velocity and weight-to-length ratios or ponderal index (weight [g] length [cm 3 ] x 100) are excellent measures of stature. Body mass index (weight [g] height [m 2 ]) is useful after 2 years of age. Recumbent length should be employed in infants younger than 2 years of age, having the infant lie supine on a flat surface and using a length board fitted against the soles of the feet and the crown of the head. A second potential shortcoming of using NCHS growth curves is misinterpretation of growth in breastfed infants. Comparison of weight by using this reference standard suggests that breastfed infants are falling below normal growth standards at 4 to 6 months of age and beyond, when their growth velocity tapers compared with that of formula-fed infants. 9 In fact, the growth velocity of formula-fed infants may be accelerated in the second 6 months, raising concern about overweight and subsequent obesity. Weight-to-length ratios should be observed carefully during this time. However, data to date indicate neither that the larger weight and possibly length of formula-fed infants nor the lower weight and possibly length of breastfed infants persists beyond the second year of life. Separate growth charts for formula-fed and breastfed infants are being developed and should be available for use within 3 years. It is important in the interval not to discourage breastfeeding after 4 to 6 months of age because such infants are demonstrating decreased weight and length velocity compared with formula-fed infants. The Z score is another useful marker of infant nutrition. This is a calculation of the variance of the parameter measured with normal NUTRITION values. It is calculated as a function of observed value - median value median value. A 3% or 97% deviation is 1.88 standard deviations from the median. Failure to achieve normal growth rates or growth velocity suggests the need to assess nutritional intake, which traditionally is performed by 24-hour intake recall assessment. A 3-day prospective nutrient intake may be indicated after 6 months of age, when intake may vary from day to day. Reference standards for nutrient composition of infant foods are readily available. Breastfeeding cannot be assessed accurately from historical information, and it may require accurate weights before and after breastfeeding to determine the quantity of intake. There is no evidence that quality of milk is significantly altered by maternal nutritional status, although nutrient content varies considerably throughout the day, and hind milk is known to provide greater fat (energy) intake than that present in early lactation. REFERENCES 1. American Academy of Pediatrics Work Group on Breastfeeding. Breastfeeding and the use of human milk. Pediatrics. 1997;100: Jacobson SW, Chiodo LM, Jacobson JL. Breastfeeding effects on intelligence in 4- and 11-year old children. Pediatrics. 1999;103:e71. cgi/content/full/103/5/e71 3. Neuringer M, Connor WE. n-3 Fatty acids in the brain and retina. Evidence for their essentiality. Nutr Rev. 1986;44: American Academy of Pediatrics Committee on Nutrition. Fluoride supplementation for children: interim policy recommendations. Pediatrics. 1995;95: American Academy of Pediatrics Committee on Nutrition. Soy protein-based formulas: recommendations for use in infant feeding. Pediatrics. 1998;101: American Academy of Pediatrics Committee on Drugs. The transfer of drugs and chemicals into human milk. Pediatrics. 1994;93: American Academy of Pediatrics Committee on Nutrition. Iron-fortified infant formulas. Pediatrics. 1989;84: Dewey KG. Growth characteristics of breast-fed compared to formula fed infants. Biol Neonate. 1998;74: Dewey KG, Peerson JM, Brown KH, et al. Growth of breast-fed infants deviates from current reference data: a pooled analysis of United States, Canadian, and European data sets. Pediatrics. 1995;96: Pediatrics in Review Vol. 21 No. 6 June

10 PIR QUIZ Quiz also available online at 5. The protein content of human milk is closest to: A. 10%. B. 30%. C. 50%. D. 70%. E. 90%. 6. Which of the following statements about supplementing the diets of term breastfed infants exposed to adequate sunlight is most accurate? A. Iron and vitamin D should be added at 2 to 3 months after birth. B. Iron and vitamin D should be added at 4 to 6 months after birth. C. Iron should be added at 2 to 3 months after birth. D. Iron should be added at 4 to 6 months after birth. E. No supplementation is required as long as breastfeeding proceeds. 7. Which of the following statements concerning the introduction of solid feedings in breastfed and formula-fed infants is most accurate? A. Introduction can begin at 3 months in breastfed infants and at 4 to 6 months in formula-fed infants. B. Introduction can begin at 3 months in formula-fed infants and at 4 to 6 months in breastfed infants. C. Introduction can begin at 4 to 6 months in formula-fed infants and 6 to 8 months in breastfed infants. D. Introduction can begin at 3 months, with breastfeeding or formula feeding continuing through the first year. E. Introduction can begin when the infant is sitting erect and demonstrating interest, with breastfeeding or formula feeding continuing throughout the first year. 8. According to available weight and length data, which of the following statements about the growth velocity of infants is most accurate? A. No difference in growth velocity is discernable between breastfed and formula-fed infants either after 4 to 6 months of age or after 2 years of age. B. The growth velocity of breastfed infants appears to be less than that of formula-fed infants at 4 to 6 months of age, and the differences persist beyond age 2 years. C. The growth velocity of breastfed infants appears to be less than that of formula-fed infants at 4 to 6 months of age, but differences do not persist beyond age 2 years. D. The growth velocity of formula-fed infants appears to be less than that of breastfed infants at 4 to 6 months of age, and the differences persist beyond age 2 years. E. The growth velocity of formulafed infants appears to be less than that of breastfed infants at 4 to 6 months of age, but differences do not persist beyond age 2 years. 200 Pediatrics in Review Vol. 21 No. 6 June 2000