The Human
Weaning
Process
R. G. Whitehead,
PhD, FiBioI
From the MRC Dunn Nutrition Unit, Cambridge, United Kingdom, and Keneba, The Gambia
ABSTRACT. The weaning process in relation to the
nu-tritional adequacy of human lactation is reviewed. Cur-rent trends in breast-feeding, both in industrialized coun-tries and the developing world, are considered, as well as associated changes in weaning practices. Consideration is also given to infant growth patterns in the Western world and how these are being influenced by current
dietary practices. The nutritional requirements of babies during the first year of life are discussed, and recent concepts indicating that current estimates might be in excess of physiologic needs are introduced. These theories are of fundamental practical importance in terms of defining the length of time that exclusive breast-feeding remains adequate and determining when the introduction of complementary foods becomes necessary on nutri-tional grounds. It is emphasized that the weaning process is naturally a lengthy one, lasting many months rather than a few weeks, and that the provision of additional foods need not inhibit a mother’s capacity for lactation as long as these feeds are administered in the correct fashion. Pediatrics 1985;75(suppl):189-193; weaning, nu-trition, breast-feeding.
adverse response.
For these reasons, pediatricians and nutritionists have recognized the need to reevaluate a number of key biologic issues rebated to infant nutrition. On nutritional grounds, for how long is it desirable for a mother to breast-feed her baby? As a baby grows older and banger, what proportion of his on her dietary energy and nutrient needs can be expected to be satisfied by breast milk alone? When should weaning foods be introduced? What should their composition be, and how should they be adminis-tered? How can one assess whether the nutritional requirements of an infant are being met during the weaning period? I will be examining current views on some of these subjects with the object of defin-ing, from a scientific point of view, what we can reasonably claim to know and where new knowledge is critically required.
DURATION OF LACTATION
Weaning represents one of the most crucial die-tary events in an infant’s life. Due to conditions in many developing countries, weaning frequently
gives rise to a life or death situation, partly because of the lack of nutritionally suitable weaning foods, but mainly because of diet-related diamrheal dis-ease.1 Such problems are, of course, not a major consideration in the more affluent countries of Eu-mope and North America. In these countries, any worries are more likely to be related to the immu-nobogic response to “foreign” food proteins.2 In both cases, however, the olden and more physiologically mature a baby is when other foods are introduced, the more likely he or she will be abbe to combat any
Read before the Workshop on Current Issues in Feeding the Normal Infant, Palm Springs, CA, April 8-11, 1984.
Reprint requests to (R.G.W.) MRC Dunn Nutrition Laboratory, Cambridge, United Kingdom.
PEDIATRICS (ISSN 0031 4005). Copyright © 1985 by the American Academy of Pediatrics.
It is not possible to identify a single point in time and state categorically that this terminates the natural period of lactation. We can, however, ex-amine what occurs in parts of the world where breast-feeding is taken for granted. In rural areas of Africa, breast-feeding until 2 years is common,3 and this practice fits in with the advice given in the Muhammadan holy book, the Koran, “The Mother shall give suck to her baby for two years” (Al-Baqanah, chapter 2, part 2). Whether a 2-year pe-nod of lactation was ever commonly practiced among Western people is not known, but the evi-dence indicates that even in the early part of this century, when breast-feeding was still very much the rule, few mothers continued beyond 12 months. Hirscham and Butler,4 for example, in a review of
nationally representative American data, reported that between 1911 and 1915 only 3% of mothers were still breast-feeding their babies by 13 months.
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Age (months) In Western communities, most mothers would
pen-haps not wish their life-styles to be so dominated, an attitude observed particularly among women with only basic standards of education. In 1979, for example, in Cambridge, United Kingdom, although 62% of women from social grade 5 (wives of un-skilled workers) had been breast-feeding while in the hospital, only 5% were breast-feeding 3 months later. In social grade 1 (professional), on the other hand, the corresponding figures were 87% breast-feeding while in the hospital and at 3 months as many s 75% of mothers were still doing so.
The ready availability of high-quality infant milk products and other weaning foods in the Western world makes the decision to stop breast-feeding a relatively easy one, but in the developing world such products are not readily available and thus breast milk assumes a particular importance. Even marginally nourished mothers have been shown to be able to produce an average of 400 to 500 mL of milk at 18 months,3 and because there is rarely another nutritionally well-balanced source of food available to the infant, it is clear that bong-term breast-feeding is highly desirable, even if it covers only a fraction ofthe infant’s total nutritional needs in the second year of life.
WEANING
Although it can be argued tht breast-feeding for at least 1 year is the “biologically normal” thing to do, it would be positively harmful to suggest that breast milk can provide total nutrition for the av-erage child for the duration of this period. When encouraging mothers to breast-feed for extended periods, pediatricians and nutritionists also need to emphasize that after an initial period of exclusive breast-feeding, mixed feeding then becomes the
1000
equably natural way of feeding a baby. We can learn a lot from mothers in the developing world about this transition. In our village of Keneba in The Gambia, women routinely introduce some comple-mentary feeding from 3 to 5 months, but at the same time they continue to breast-feed for up to 2 years,’ even mothers who produce only small amounts of milk.
In this context, it should be recognized that an overzealous approach to breast-feeding promotion in an industrialized society that has lost its folk-wisdom about human lactation may actually have a detrimental effect on the confidence of many mothers. There are health workers who teach that the introduction of even small amounts of weaning foods inevitably beads to a rapid inhibition of breast milk production. It is not difficult to suggest how this misapprehension might have arisen. In general, mothers in Europe and North America only breast-feed five to six times a day and not the 12 to 20 times a day encountered among babies fed on de-mand in the Third World. When a Western mother decides hen baby needs more food than she can readily provide from her breasts at each meal, hen frequent response is to substitute completely for one of these meals by introduction of supplementary feeding. As might be expected, hen milk output immediately drops by about 150 mL/d, the average size of a single feeding. Considering the populari-zation of more extreme views, it is not surprising that mothers then regard their need to introduce additional feeding as some sort of a failing and this feeling of inadequacy results in a cascade response with an ever-increasing number of the breast-feed-ing meals being substituted for with artificial (sup-plementary) feeding. This effect is seen, even among well-educated and highly motivated women in Cambridge, United Kingdom6 (Fig 1).
Fig 1. Comparison of effects on milk intake of supplementary feeding in the United
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The quite different response in milk intake en-countered in Gambian babies6 is also shown in Fig 1. No corresponding inflection in the milk intake curve accompanies the introduction of complemen-tary feeding. In The Gambia, weaning food can more easily be given as a true complement because it is superimposed on a high frequency of breast-feeding. Whether such a practice would be compat-ible with a way of life desirable to a woman brought up in an industrialized society, providing a widen mange of social opportunities, is open to debate but at least the Western woman should know that mixed feeding is natural and if weaning is intro-duced in a complementary rather than a supple-mentany fashion her milk output need not
drasti-cabby suffer.
TIMING THE ONSET OF WEANING
When weaning should start tends to be a subject that generates considerable debate, and controversy flourishes in a desert of hard facts. Health author-ities needing to define policies usually want to give a single age for the onset of weaning, but this is clearly illogical. We know that the regular daily milk output of different mothers spans at least a twofold range at all stages during infancy, and it has been our experience6 that babies with the smaller milk intakes during the period of exclusive breast-feeding tend to be those fed additional foods the soonest. This effect can be inferred from the data in Fig 1, particularly values for Cambridge. Additionally, male infants who are, on average, larger than female infants, are given extra foods approximately 4 weeks earlier,7 presumably because they outstrip their mothers’ lactational capacity more quickly. Clearly, the onset of weaning must vary from infant to infant, depending partly on the milk production capacity of the mother and partly on the specific nutritional needs of hem baby. It should also be borne in mind that these two van-ables-the capacity of the mother and the needs of the baby-might functionally be interrelated. A seemingly inadequate milk yield from one mother might still be adequate for hem particular baby if the baby’s dietary requirements are similarly low.
QUANTIFYING LACTATIONAL ADEQUACY
A number of investigative approaches have been adopted in an attempt to define with more exacti-tude the time when exclusive breast-feeding be-comes inadequate. One simple method involves ex-amining serial changes in milk output patterns as the baby gets olden to determine when milk produc-tion starts to level off. When this occurs, it might reasonably be concluded that the needs of the
even-growing baby are beginning not to be met. A sample of longitudinal data on breast milk production from both industrialized and developing countries8 is shown in Fig 2. Although values from the latter areas tend to be bower, all follow the same general qualitative pattern: major increases in milk output only occur at the onset of infancy; after 1 to 2 months any increase is minimal. However, this elementary approach is open to criticism. Some investigators would argue, perhaps justifiably, that most of these data have been misleadingly affected by the introduction of weaning foods as already
discussed.
Other, and somewhat more involved approaches, have attempted to quantify the nutritional effec-tiveness of breast milk at successive ages by relating its total energy or nutrient contribution to recom-mended daily dietary allowances. Although protein has been used as the basis for such calculations, most investigators have used dietary energy.”3
With World Health Organization/Food and Ag-ricubture Organization (WHO/FAO) 1973 mecom-mended energy allowances,” theoretical breast milk requirements rapidly outstrip measured intakes, a finding even more marked with protein as the base line. Current estimates of dietary energy needs range from an average of 120 kcab/kg ofbody weight at 0 to 3 months decreasing gradually to 110 kcal/ kg at 6 to 8 months. Using these factors and assum-ing that breast milk contains 69 kcal/100 mL, it can be calculated that a male child growing along the National Center for Health Statistics (NCHS)
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Age (months)
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Fig 3. Energy intake in Cambridge infants (solid circles)
compared with 1973 World Health Organization/Food and Agriculture Organization (WHO/FAO) recom-mended dietary allowances (short dashes) and a more recent assessment of needs (long dashes).
50th percentile would need about 900 mL at 2 months, 1,100 mL at 4 months, and 1,250 mL at 6 months. Such levels of milk output have, however, only been observed in a minority of women with a high lactationab capacity. This would suggest that the majority of exclusively breast-fed babies would need supplementation well within the first 3 months of life.
Such a conclusion is obviously incompatible with the widely taught view that breast-feeding should be able to satisfy the average baby until at least age 4 months, and this has bed a number of scientists to propose that current estimates of energy require-ments in babies might be unrealistically high. A statistical analysis of the measured energy intakes of both breast-fed and artificially fed babies from a number of European and North American countries has suggested that instead of decreasing slowly from 120 kcab/kg at birth down to 105 kcal/kg at age 1 year, energy requirements actually drop much more quickly, reaching 90 kcal/kg or even lower at age 6 to 8 months. After this age, there could be an upward trend again, once the infant has started to become more mobile.’2”3 These two sets of esti-mates for energy requirements are presented in Fig 3.
The practical consequences of these revised ideas on dietary energy requirements during early infancy are twofold. First, it can be concluded that volumes of breast milk smaller than those calculated above should be able to satisfy the needs of the baby. Using the new estimates shown in Fig 3, the average male infant growing along the National Center for Health Statistics 50th percentile would only need about 800, 930, and 1,020 mL, respectively at 2, 4, and 6 months of age. The values for younger babies
become much closer to observed lactational penfor-mances, at beast in Western countries. Second, it can also be calculated that the introduction of weaning foods is not necessary until some 4 weeks later: furthermore, the amounts initially required are less.
A definite trend among mothers toward the later administration of solid foods both for breast-fed and bottle-fed babies has been demonstrated in two nationwide surveys carried out by the British De-partment of Health and Social Security in 1975 and i980.’’ Understandably, this change beads to a bower total energy intake. Recent data for the period from birth to 15 months for a cohort of British babies who had been exclusively breast-fed up to 4 months of age are presented in Fig 3. The steeper decline in energy intake in the first 6 months is demonstrated as is the effect of the reluctance of mothers to introduce supplementary feeding until they thought it really was necessary. The main difference between the measured intakes and the revised estimates is the virtual absence of the pre-dicted increase in energy intake after 8 months. We cannot explain this lower intake at 1 year of age except to suggest that it could be linked with the generalized concern on the part of the mothers, to minimize the risk of obesity: the fact that this does bead to markedly lower skinfold thickness measure-ments at this age has been demonstrated.9”#{176}”6
GROWTH STANDARDS AND ASSESSMENT OF
WEANING PRACTICES
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106
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98
94
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Age (months)
Fig 4. Relative growth performance of two groups: left, breast-fed and then not
exclu-sively breast-fed infants in Cambridge, United Kingdom;7 right, exclusively breast-fed infants, USA.’8 Weight for age is expressed as percentage of National Center for Health Statistics 50th percentile.
resulting from the use of a growth standard map-propniate to the breast-fed infant and infants not exclusively breast-fed.
It needs to be borne in mind that all current major growth standards are based on data collected prior to 1965; thus the cohorts must have been dominated by infants who were fed formula, and presumably solid foods were also introduced sooner than current recommendations.’6 Thus it could be argued that the standards are for babies we would now consider overfed. It is essential that the corn-pilation of more up-to-date growth standards, spe-cificabby directed at the early infancy period, be initiated as a matter of urgency. Care should be taken to ensure that the babies in such an anthro-pometnic survey are being fed along lines compati-ble with modern concepts in pediatrics and nutni-tion.
CONCLUSION
Obtaining a more adequate scientific perspective on the dietary needs of infants, understanding how the gradual transition from exclusive breast-feeding to the consumption of solid foods can best be ef-fected, and the compilation of better growth and other functional parameters for evaluating infant feeding practices, are cleanly necessary before we can be truly confident about our dietary guidelines for infancy.
REFERENCES
1. Whitehead RG: Infant feeding practices and the develop-ment of malnutrition in rural Gambia. United Nations
Uni-versity Food Nutr Bulb 1979;1:36-41
2. Taitz LS: Soy feeding in infancy. Arch Dis Child
1982;57:814-815
3. Prentice AM: Variations in maternal dietary intake, birth-weight and breast-milk output in The Gambia, in Aebi H, Whitehead RG (eds): Maternal Nutrition During Pregnancy and Lactation. Berne, Hans Huber, 1980, pp 167-183 4. Hirscham C, Butler M: Trends and differentials in
breast-feeding: An update. Demography 1981;18:39-54
5. Whichelow MJ, King BE: Breast-feeding and smoking. Arch Dis Child 1979;54:240-241
6. Whitehead RG, Paul AA, Rowland MGM: Lactation in Cambridge and in The Gambia, in Wharton BA (ed): Topics in Paediatrics: Nutrition in Childhood. Tunbridge Wells, England, Pitman Medical, 1980, vol 2, pp 22-33
7. Whitehead RG, Paul AA: Infant growth and human milk requirements: A fresh approach. Lancet 1981;2:161-163 8. Whitehead RG: Maternal diet, breast feeding capacity and
lactationa! infertility. United Nations University Food Nutr BuhI 1983;5(Suppl 6):1-107
9. Boulton J: Nutrition in childhood and its relationship to early growth, body fat, blood pressure and physical fitness.
Acta Paediatr Scand 1981;284:1-85
10. Ferris AG, Beal VA, Laus MJ, et al: The effect of feeding on fat deposition in early infancy. Pediatrics 1979;64:397-401
11. WHO/FAO: Energy and protein requirements. World Health Organization Technical Report Series No. 522, Food and Agriculture Organization Nutritition Meetings Report Series No. 52. Geneva (WHO) and Rome (FAO), 1973
12. Whitehead RG: Breast feeding and growth. Bull
mt
PediatrAssoc 1983;5:114-129
13. Whitehead RG, Paul AA, Cole TJ: How much breast milk do babies need? Acta Paediatr Scand 1982;299:43-50
14. Martin J: in Infant Feeding 1975: Attitudes and Practices in England and Wales. London, Her Majesty’s Stationery Of-fice, 1978
15. Martin J, Monk J: in Infant feeding 1980. London, Office of Population Censuses and Surveys, 1982
16. Whitehead RG, Paul AA: Growth charts and the assessment of infant feeding practices in the Western world and in developing countries. Early Hum Dev 1984;9:187-207
17. Whitehead RG, Paul AA: Growth standards for early in-fancy. Lancet 1981;2:419-420
