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Weaning


Key Points

  • Simply stated, weaning is the transition of the infant from dependence on mother’s milk to reliance on other sources of nourishment for nutrition, health and growth, and development.

  • Current recommendations are for 6 months of exclusive breastfeeding and initiation of complementary foods at 4

    to 7 months of age with continued breastfeeding through 12 months and beyond.

  • The “how to” for transition to complementary feeding is best outlined in the guiding principles of complementary feeding for the breastfed infant published by Pan American Health Organization (see Box 9.1 ).

    Box 9.1
    Guiding Principles for Complementary Feeding of the Breastfed Child
    From Dewey KG; Pan American Health Organization. Guiding Principles for Complementary Feeding of the Breastfed Child . Washington, DC: Pan American Health Organization; 2002.)

    • 1.

      Duration of Exclusive Breastfeeding and Age of Introduction of Complementary Foods . Practice exclusive breastfeeding from birth to 6 months of age, and introduce complementary foods at 6 months of age (180 days) while continuing to breastfeed.

    • 2.

      Maintenance of Breastfeeding . Continue frequent, on-demand breastfeeding until 2 years of age or beyond.

    • 3.

      Responsive Feeding . Practice responsive feeding, applying the principles of psychosocial care. Specifically: (1) Feed infants directly and assist older children when they feed themselves, being sensitive to their hunger and satiety cues; (2) feed slowly and patiently, and encourage children to eat, but do not force them; (3) if children refuse many foods, experiment with different food combinations, tastes, textures, and methods of encouragement; (4) minimize distractions during meals if the child loses interest easily; (5) remember that feeding times are periods of learning and love—talk to children during feeding, with eye to eye contact.

    • 4.

      Safe Preparation and Storage of Complementary Foods . Practice good hygiene and proper food handling by (1) washing caregivers’ and children’s hands before food preparation and eating, (2) storing foods safely and serving foods immediately after preparation, (3) using clean utensils to prepare and serve food, (4) using clean cups and bowls when feeding children, and (5) avoiding the use of feeding bottles, which are difficult to keep clean.

    • 5.

      Amount of Complementary Food Needed . Start at 6 months of age with small amounts of food and increase the quantity as the child gets older, while maintaining frequent breastfeeding. The energy needs from complementary foods for infants with “average” breast milk intake in developing countries are approximately 200 kcal per day at 6 to 8 months of age, 300 kcal per day at 9 to 11 months of age, and 550 kcal per day at 12 to 23 months of age. In industrialized countries these estimates differ somewhat (130, 310, and 580 kcal/day at 6 to 8, 9 to 11, and 12 to 23 months, respectively) because of differences in average breast milk intake.

    • 6.

      Food Consistency . Gradually increase food consistency and variety as the infant gets older, adapting to the infant’s requirements and abilities. Infants can eat pureed, mashed, and semi-solid foods beginning at 6 months. By 8 months most infants can also eat “finger foods” (snacks that can be eaten by children alone). By 12 months, most children can eat the same types of foods as consumed by the rest of the family (keeping in mind the need for nutrient-dense foods, as explained in no. 8). Avoid foods that may cause choking (i.e., items that have a shape and/or consistency that may cause them to become lodged in the trachea, such as nuts, grapes, raw carrots).

    • 7.

      Meal Frequency and Energy Density . Increase the number of times that the child is fed complementary foods as he or she gets older. The appropriate number of feedings depends on the energy density of the local foods and the usual amounts consumed at each feeding. For the average healthy breastfed infant, meals of complementary foods should be provided two or three times per day at 6 to 8 months of age and three or four times per day at 9 to 11 and 12 to 24 months of age, with additional nutritious snacks (such as a piece of fruit or bread or chapatti with nut paste) offered one or two times per day, as desired. Snacks are defined as foods eaten between meals—usually self-fed, convenient, and easy to prepare. If energy density or amount of food per meal is low, or the child is no longer breastfed, more frequent meals may be required.

    • 8.

      Nutrient Content of Complementary Foods . Feed a variety of foods to ensure that nutrient needs are met. Meat, poultry, fish, or eggs should be eaten daily, or as often as possible. Vegetarian diets cannot meet nutrient needs at this age unless nutrient supplements or fortified products are used (see no. 9). Vitamin A–rich fruits and vegetables should be eaten daily. Provide diets with adequate fat content. Avoid giving drinks with low nutrient value, such as tea, coffee, and sugary drinks such as soda. Limit the amount of juice offered so as to avoid displacing more nutrient-rich foods.

    • 9.

      Use of Vitamin-Mineral Supplements or Fortified Products for Infant and Mother . Use fortified complementary foods or vitamin-mineral supplements for the infant, as needed. In some populations, breastfeeding mothers may also need vitamin mineral supplements or fortified products, both for their own health and to ensure normal concentrations of certain nutrients (particularly vitamins) in their breast milk. (Such products also may be beneficial for prepregnant and pregnant women.)

    • 10.

      Feeding During and After Illness . Increase fluid intake during illness, including more frequent breastfeeding, and encourage the child to eat soft, varied, appetizing, favorite foods. After illness, give food more often than usual and encourage the child to eat more.

What does weaning mean? Textbooks on pediatrics and mothers’ manuals imply that it is the process by which one changes from one method of feeding to another. Raphael 1 states that the first introduction of solid foods is the true beginning of weaning. The term weaning is derived from the Anglo-Saxon wenian , which means “to become accustomed to something different.” It does not mean the total cessation of breastfeeding but the addition of other things. If one consults the dictionary, however, one learns that to wean is to transfer the young of any animal from dependence on its mother’s milk to another form of nourishment. A weanling is a child or animal who is newly weaned. The World Health Organization (WHO) in some of its publications uses “weaning” in a narrow sense as the complete stopping of breastfeeding. Complementary foods are nutrient-containing solids or liquids that are introduced during the transition period of weaning. During weaning, the infant transitions from complete dependence on breast milk for all its nutritional needs to ingesting solid and liquid forms of nutrition commonly used, acceptable, and readily available within an infant’s household, family, community, and culture.

Weaning from a physiologic point of view is a complex process involving nutritional, microbiologic, immunologic, biochemical, and psychologic adjustments. This should be a safe process, maintaining optimal nutrition, growth, and development. Conceptually, early nutritional exposures are associated with both the infant’s immediate health and later health through a process of “programming” the gastrointestinal tract, metabolism, and endocrinologic balance of the infant for later functioning in life. The practice of weaning within a family or community also depends on traditions, ethnical origins, and scientific beliefs consistent with perceptions of this stage of life. 2 A qualitative review of the literature on maternal infant feeding practices in the process of weaning revealed three predominant themes: (1) infant physical and behavioral cues suggesting readiness to wean; (2) mother’s knowledge, skills, and coping strategies to demonstrate “good mothering”; and (3) community pressure and inconsistent advice led to generational feeding and adoption of already established cultural feeding practices. The mothers made choices regarding feeding and weaning based on their perceptions of healthy infant feeding and successful parenting. Additional investigation of these factors will be essential to effectively supporting mothers and families in their infant feeding practices, including weaning. 3

Infant’s Need

When discussing the process of weaning a human infant, one might say it is the transition of the infant from dependence on mother’s milk to other sources of nourishment. If one were to determine the appropriate time for this to take place, it would be based on nutritional needs and developmental goals. Observations among other mammals suggest that achievement of a degree of maturity that allows a pup to forage for food is a trigger for initiating weaning by the mother.

The search for the appropriate weaning time for human infants has produced a number of extremes, from the regimen of J.R. Sackett in 1953 of introducing solids on the second day of life to withholding all solid foods until the infant had sufficient teeth to chew thoroughly, a method described by Bartholomäus Mettinger, a German physician, in 1473. 4 The birth of the infant food industry began with German chemist Justis von Leitbig in 1867. He marketed “the perfect infant food” to the public at the turn of the twentieth century, a mixture of wheat flour, malt flour, and cow milk. Abraham Jacobi, called the father of American pediatrics, advised no solids for a year and no vegetables before 2 years of age. Even early on the recommendations concerning weaning varied by culture, ethnic group, medical intervention, and financial considerations.

Acknowledging that humans are primates, Dettwyler recognized that lactation and weaning occur according to certain regular patterns in nonhuman primates. 2 She searched for a natural age of weaning for human infants uninfluenced by culture and trends. Evaluating various “rules of thumb” for determining weaning age by biologic references, she found them inappropriate. Breastfeeding from an anthropologic point of view is both a biologic process and a culturalized activity. In primitive cultures, the age of weaning from the breast was between 2 and 5 years, averaging 3 to 4 years.

If the definition of weaning is used to mean the cessation of all feedings at the breast, the age at weaning in nonhuman primates and other mammals is a function of genetics and instinct. Primates have a longer gestation, greater infant dependency, longer life spans, and larger brains per unit of body size than other mammals. Dettwyler 2 suggests that a possible formula for weaning is the ratio of present weight to birth weight as 4:1; that is, the offspring weans when four times the birth weight is achieved, usually between 2 and 3 years for well-fed healthy human infants.

In using weaning according to attainment of one-third the adult weight as the rule of thumb, Dettwyler notes the variations in size of human adults by ethnic and cultural groups. The average weight of an adult woman is 54 kg (119 lb); one-third is 18 kg (39½ lb), a weight achieved between 4 and 7 years for girls. The average weight of an adult man is 59 kg (130 lb); one-third is 19.3 kg (42½ lb). This would mean boys would be nursed longer. The present tendency for obesity in the developed world would accentuate these calculations.

When length of gestation is used as the determinant for weaning time, the weaning-to-gestation ratio can be determined. The ratio across primate species varies from 0.41 in the Galago demidovii , a small-bodied primate, to 6.40 in the Pan troglodytes (chimpanzee). The former primates nurse less than half the length of pregnancy (11/45 days); chimpanzees nurse 1460 days (228-day gestation). Gorillas nurse for 1583 days (256-day gestation). Because the human is closest to the chimpanzee and gorilla, six times the gestation period might be a more physiologic norm: 54 months, or 4½ years. 2

When the eruption of the first permanent molar is used as the indicator for complete weaning, it estimates weaning at 5½ to 6 years in humans. Tooth eruption is genetically controlled and comparatively unaffected by diet or disease. Six years is also identified as the time of achieving an adult level of immunocompetence in humans.

The range of calculated ages for weaning derived from these formula ranges from 2.3 years to 6 or 7 years. Before the widespread availability of foods suitable for infants and of artificial formulas, infants were traditionally breastfed for 3 to 4 years ( Fig. 9.1 ).

Fig. 9.1, Natural age at weaning according to technique used.

Other species gradually introduce other foods and teach their offspring how to obtain them on their own. Usually the mothers in most species make the determination for final termination and no longer permit the young to nurse. There seems to be a close correlation between age of weaning and age of reproductive maturity measured either as first ovulation (menarche) or average age of first breeding. Dettwyler 5 notes that these markers are also related to body size, with larger bodied species breastfeeding longer.

Cultural Patterns of Weaning

Among humans, many cultural influences mandate weaning time and process. 6 Public and social pressures have influenced weaning for some families in industrialized society. Few traditional societies wean before 1 year of age, and some do not begin until 2 years of age ( Fig. 9.2 ). In ancient Hebrew tradition (c. 536 bc ), breastfeeding duration according to the Talmud was at least 3 years. Aristotle suggested that women should breastfeed while no menstruation was occurring, failing to recognize that one influences the other (lactation suppresses menstruation). The Romans recommended breastfeeding at least to the age of 3 years. In the Muslim world, especially Africa and the Sudan, however, weaning of children is by the Islamic teaching of the Koran, which advises breastfeeding until at least 2 years of age, with many breastfeeding to age 4 or 5. Before 1979, the average time of complete cessation worldwide was 4.2 years. Hervada and Newman 7 provide a historic review of weaning that also presents recent concerns about iron deficiency and other problems more common to formula-fed infants.

Fig. 9.2, Comparison of age at weaning in United States and 64 traditional societies.

Breastfeeding benefits for an older infant also have been evaluated. In the developing world, breastfeeding continues for at least 1 to 2 years after introduction of solid foods. Major benefits include not only the nutrients but also protective, digestive, and trophic agents that extend the period of infertility in the mother and reduce the incidence and severity of infectious diseases for the infant. A review of middle-class breastfed infants between the ages of 16 and 30 months in the United States revealed a decrease in the number of infections and improved overall health compared with those children no longer breastfed. 6

Nutritionally, it is appropriate to begin iron-containing foods at 6 months, the time the stores from birth are diminishing. The requirement at this age exceeds that supplied by human milk. An additional source of protein becomes necessary toward the end of the first year of life because the grams of protein needed per kilogram of body weight can no longer be supplied by milk alone as the infant grows heavier. The content of protein in the milk begins to drop slightly after 9 months of lactation. A human infant also needs bulk, or roughage, in the diet. The exact time this need becomes apparent is not known, but it may well be by the end of the first year.

Developmentally, an infant is ready to learn to chew solids instead of suckle liquids at approximately 6 months. It has been suggested that there is a “critical period of development” during which infants can and must learn to chew. 8 Chewing is an entirely different motion of the tongue and mouth from sucking. The sucking fat pads in the cheeks begin to disappear at the end of the first year. The rooting reflex has been lost. Even though all the teeth are not in, the development of good dentition requires chewing exercise.

Various health organizations have made recommendations for the duration of breastfeeding based on evidence-based literature regarding breastfeeding, exclusive breastfeeding, and transition to complementary foods and infant nutrition, growth and development, health benefits, and risks and morbidity and mortality ( Table 9.1 ). Despite all the investigation, literature, and debate, the question remains whether such “broad” recommendations regarding the optimal duration of exclusive breastfeeding as a definitive time of 6 months should be applicable to the diverse populations across the world. Probably the most convincing data for such broad recommendations comes from the research for the WHO Child Growth Standards and the WHO study of nutrient adequacy of exclusive breastfeeding. 9 , 10 , 11 Using the data collected for growth of breastfeeding infants within 6 countries with sufficient socioeconomic status to ensure adequate nutrition through 36 months of life, growth patterns were analyzed. The growth patterns from the different countries in this study (Brazil, Ghana, India, Norway, Oman, and the United States) were so similar they were “superimposable” and individual country data could be excluded without significantly changing the composite curves (length/height, weight for age) the study generated. The implication is that the genetic potential for growth of children from diverse backgrounds is similar as long as the infants were exclusively breastfed for 4 to 6 months with continued breastfeeding through 12 months simultaneously with the introduction of complementary feeds and received nutritionally adequate intake for continued growth. Exclusive/predominantly breastfeeding occurred in 74.7% of the children for the first 4 months, 99.5% of children began complementary foods by 6 months of age and 68.3% of the children were partially breastfed until 12 months of age.

Table 9.1
Recommendations on Duration of Breastfeeding
Modified from Dettwyler KA. A time to wean: the hominid blueprint for the natural age of weaning in modern human populations. In: Stuart-MacAdam P, Dettwyler KA, eds. Breastfeeding: Biocultural Perspectives . New York: Aldine de Gruyter; 1995.
WHO Exclusive for 6 months Continue 2 years and beyond
AAP Exclusive for 6 months Continue 1 year and as long as mother/infant wish
AAFP Approximately 6 months exclusive Continue 1 year/mutually desired
ACOG Approximately 6 months exclusive As long as possible
Healthy People 2010 75% at birth 25% at 6 months
Healthy People 2020 Exclusive for 6 months Continue for 1 year
AAFP , American Academy of Family Practice; AAP , American Academy of Pediatrics; ACOG , American College of Obstetrics and Gynecology; WHO , World Health Organization.

Role of Development In Initiation of Weaning

Although the developmental milestones of infant behavior are noted to influence the introduction of weaning foods, the development of the gastrointestinal tract plays an equal role. Even the taste buds, which can be identified at the seventh week of fetal life as collections of elongated cells on the dorsal surface of the tongue, are fully innervated over the next weeks. The fetus is known to suck and swallow in utero; sucking is discussed in Chapter 3, Chapter 7 .

When taste becomes a factor in feeding is not known, although a lack of discrimination has been noted in the first weeks of life: infants have consumed formula with high salt or absence of chloride with morbid results. Because of the variation in the composition of mother’s milk over a feeding, over a day, and from time to time according to maternal dietary intake, a breastfed infant has a richer range of experience in tasting than a formula-fed infant. Breastfed infants are, therefore, more accustomed to new taste experiences. 12 Similarly, chronic feeding problems in infants are rare in breastfed infants. 13 , 14 , 15 Conversely, formula-fed infants monotonously receive the same tastes, flavors, and consistencies for weeks, months, and years.

Both sucking and chewing are complex movements, having reflexive as well as learned components. The development of the chew-swallow reflex is necessary for the successful introduction of solids. This skill develops sequentially with neuronal development and then is a learned behavior conditioned by oral stimulation. 16 Before this point, when a spoon is introduced, the infant purses the lips and pushes the tongue against the spoon. By 4 to 6 months, the tongue is depressed in response to the spoon and the food accepted, and by 7 to 9 months, rhythmic biting movements occur regardless of the presence of teeth. Biting and masticatory strength and efficiency progress throughout infancy. If a stimulus is not applied when the neural development is taking place, the chewing reflex will not develop and the infant will always be a poor chewer. For a human infant, nursing also plays a role as a comfort and emotional support, a mechanism often referred to as comfort nursing . Inadequate nipple contact may lead to thumb sucking or the substitute use of a pacifier.

In summary, an infant is ready to explore new feeding experiences at approximately 6 months. Feeding is an important social as well as nutritional encounter. Eating solids and learning to drink from a cup are important behavioral and social achievements as well. This readiness does not mean the infant is taken from the breast, but that the diet is expanded and now includes solid foods, other liquids, and breast milk. Although a range of qualitative, quantitative, and temporal practices for weaning are known, the optimal approach matches the needs and requirements of a given child with the functions and capacities of his or her developing body.

Introduction of Solids

The WHO, the Canadian Pediatric Society, the Paediatric Society of New Zealand, and similar groups in England and Scotland 11 , 13 , 14 , 17 emphasize that weaning is not the termination of breastfeeding but the addition of other liquids and solids while continuing breastfeeding. The key recommendation on length of exclusive breastfeeding from the WHO 17 reads as follows:

To strengthen activities and develop new approaches to protect, promote and support exclusive breastfeeding for six months as a global public health recommendation, taking into account the findings of the WHO expert consultation on optimal duration of exclusive breastfeeding, and to provide safe and appropriate complementary foods, with continued breastfeeding for up to two years of age or beyond, emphasizing channels of social dissemination of these concepts in order to lead communities to adhere to these practices.

The intake of complementary foods may add nutrients in a less bioavailable form, and it decreases the bioavailability of nutrients in human milk and the intake of other important factors in human milk. Investigators have shown that when solid foods are introduced in the diet of breastfed infants, energy intake per kilogram of body weight does not increase. 18 Solid foods displaced energy intake from human milk in 6-month-old infants even though they were breastfed on demand. 19

When to Wean

Recommendations for the optimal time to introduce complementary foods to the breastfed infant remain controversial. The Section on Breastfeeding of the American Academy of Pediatrics (AAP) supports the introduction of solids at 6 months in concert with the WHO and United Nations International Education Fund (UNICEF). 20 This recommendation was in response to a systematic review of published reports in developed and underdeveloped countries conducted by Kramer and Kakuma 21 that included controlled clinical trials and observational studies in many languages. From 2668 reports, only 23 citations met criteria of an internal comparison group. Rigorous assessment of health outcomes included growth, iron and zinc status, infectious morbidity, atopic disease, neuromotor development, rate of maternal weight loss, and duration of lactational amenorrhea. 21

This discussion of the weanling’s dilemma (i.e., the choice between the known protective effects of exclusive breastfeeding against infectious morbidity, reducing atopy, and the theoretical insufficiency of breast milk alone as nutrition) continues. This is because there are numerous other variables that influence breastfeeding duration such as demographic factors of race, age, marital status, education, and socioeconomics and biologic variables, including issues of sufficient or insufficient milk supply, infant health problems, maternal obesity, and the physical challenges of breastfeeding, maternal smoking, parity, and method of delivery. Social variables, including paid work, family support, and professional support, play a role in duration of breastfeeding decisions, accomplishment, and psychological variables of maternal intention, paternal and family interest and support, and confidence in breastfeeding success. These variables were highlighted in a systematic review in 2009 reinforcing the need for further study regarding optimizing duration of breastfeeding for each individual woman and placing emphasis on support of the mother and family in achieving their breastfeeding goals. 22

In summary, exclusive breastfeeding for 6 months supported appropriate gain in weight and length and adequate iron and zinc status when the mother is well nourished, reduced infection rates, provided some reduction in atopy, and had a significant advantage in achieving some developmental milestones. WHO-UNICEF, the AAP, and many other organizations have reached the same conclusion and recommend exclusive breastfeeding for 6 months (see Table 9.1 ).

Nutritional Needs During Weaning

Fewtrell et al. 23 recommend that nutrient intake during introduction of complementary feeds in a healthy full-term infant should be calculated as “the difference between nutrients provided by breast milk and the estimated total needs.” Various organizations offer recommendations on nutrient needs during weaning and complementary feeding. 11 , 24 , 25 , 26

Protein

In information collected by Dewey et al. 27 in 1994 on well-nourished breastfed infants, no “faltering” in growth pattern could be identified. In a review of protein and energy during weaning, Axelsson and Räihä 28 conclude that 1.65 g/kg per day from 5 to 9 months and 1.48 g/kg per day from 9 to 12 months are appropriate. The growth of exclusively breastfed infants, from 4 to 6 months of age, matched or exceeded that of randomly selected breastfed infants given 20% added protein. The exclusively breastfed group received 0.98 g/kg per day, whereas the supplemented group received 1.18 g/kg per day. Thus protein intake is not a limiting factor with respect to growth that would mandate weaning from the breast. On review of protein requirements for infants and children established by the WHO, they were higher than necessary for breastfed infants. Formula-fed infants require more protein because of comparatively poor utilization. 29

Iron and Zinc

The challenge of meeting nutrient needs of infants and young children when complementary foods are added is great. It is a period of high nutrient density requirement, especially iron and zinc. In countries where cereal-based porridges with low nutrient density are the weaning foods, deficiencies are common. Iron and zinc need to be accounted for ( Table 9.2 ).

Table 9.2
Nutrient Density (mg/100 kcal) of Milk During Weaning
WEEK PTM * R †
0 2 4 6 8 10 12
Protein 1.5 1.2 1.3 1.0 1.3 1.2 1.9 1.8 2.7
Na 24.0 17.0 20.0 13.0 24.0 25.0 46.0 25.0 53.0
Ca 38.0 30.0 33.0 21.0 30.0 26.0 38.0 34.5 140.0
Zn 0.21 0.17 0.19 0.09 0.10 0.10 0.11 3.8 0.5

* Nutrient densities of milk from women who deliver premature infants.

† Nutrient densities calculated to achieve intrauterine growth rates assuming that the caloric requirement of low-birth-weight infants is 130 kcal/kg. PTM , Preterm milk; R , rate. From Garza C, Johnson CA, Smith E, et al. Changes in the nutrient composition of human milk during gradual weaning. Am J Clin Nutr . 1983;37:61.

The duration for which the iron endowment at birth remains adequate varies based on maternal iron status in pregnancy and other factors causing lower iron stores in the infant (infants of diabetic mothers, low-birth-weight infants). Some exclusively breastfed infants will benefit from additional iron (1 mg/kg per day) at 4 to 6 months. 30 , 31 Partially breastfed infants who consume over half of their daily milk intake as formula and are not on iron-fortified complementary foods should receive iron supplements until they have an adequate source from complementary foods.

When iron was added to the diet at 4 months by giving iron-rich solids to infants who did not have iron-deficiency anemia, the length growth was less than in unsupplemented control infants. Head growth was also slower in iron-supplemented infants. No improvement in weight gain was observed, and the treated infants had more occurrences of diarrhea if their hemoglobin levels were normal. More boys than girls had iron deficiency anemia at 9 months according to Dewey et al. 30

The data on zinc are meager. The concentrations of zinc in milk decline after the first few months of lactation and are independent of maternal zinc intake. 32 Hepatic stores will sustain levels in the infant early on, but exogenous zinc in the diet will be required after 6 months of age (recommended dietary allowance [RDA] 3 mg/day between 7 to 36 months of age). 33

Energy Requirements During Weaning

Breastfed infants self-regulate their total energy intake when other foods are introduced. No advantage to introducing complementary foods before 6 months has been seen relative to caloric need, growth, or activity. A review by Foote and Marriott 34 expresses the concern that some infants might need additional nutrients. They point out that the energy density of the food should exceed that of breast milk (4.2 kJ/g or 0.55 to 0.80 kcal/g). They also warn that foods with high phytate levels can interfere with mineral absorption and recommend the avoidance of juices and other drinks. Giving infants solids by 4 months is associated with less positive health outcomes such as increased body fat, higher body mass index, and a greater incidence of wheezing and respiratory illness in childhood, according to Fewtrell et al. 35 Other authors report no effect of age at weaning and infant growth. 36

Feeding Infants and Toddlers Study

In the study of nutrient intakes and food choices of 3000 infants and toddlers participating in the Feeding Infants and Toddlers Study (FITS), there were 450 participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) nutrition program. 37 It was observed that infants in the WIC program were less likely to have ever been breastfed and were more likely to be taking formula. 38 The mean usual intake of nutrients exceeded adequate intakes. Mean energy intake was excessive, with little consumption of fruits and vegetables. In the entire study of 3000 infants, 76% were fully or partially breastfed at birth, dropping to 30% at 6 months and to 16% at 1 year. Average duration of breastfeeding was 5.5 months. From 4 to 6 months, more than 65% had been given solids, not all of which were nutrient dense. Sweetened juices, French fries, hot dogs, potato chips, popcorn, pizza, and candy were reported in up to 9% of infants aged 7 to 8 months old.

Other Variables

Exposure to Taste

An infant’s first flavor experiences probably occur in utero. When garlic was ingested by mothers before amniocentesis or delivery, the amniotic fluid smelled of garlic. 39 The normal fetus ingests amniotic fluid in utero and thus experiences those flavors. When breastfed, the infant continues to experience those flavors as a bridging experience to solid foods. 12

Not surprisingly, breastfed infants consume cereal prepared with their mother’s milk more eagerly and in greater volume than when it is prepared with water. In a carefully controlled experiment, infants were fed the cereals by their mothers, who wore facial masks but no perfume to avoid affecting the infant’s interest in the food. 39 The infant’s interest was reflected in opening of the mouth sooner, fewer negative facial expressions, and greater intake. Mennella and Beauchamp 39 suggest that from the perspective of flavors, weaning means “to accustom,” which actually describes what occurs with breastfeeding: the flavors in the milk accustom the infant to new flavors in the transition to solid foods. Putting mother’s milk in the bland cereal is part of the bridging. Infants whose mothers have a more varied diet during pregnancy and lactation tend to adapt to solid foods more readily, according to these investigations. 40

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