nutrient adequacy of exclusive breastfeeding for the - libdoc.who.int

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NUTRIENT ADEQUACY
OF EXCLUSIVE
BREASTFEEDING
FOR THE TERM INFANT
DURING THE FIRST
SIX MONTHS OF LIFE
DEPARTMENT OF NUTRITION FOR HEALTH AND DEVELOPMENT
DEPARTMENT OF CHILD AND ADOLESCENT HEALTH AND DEVELOPMENT
WORLD HEALTH ORGANIZATION
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NUTRIENT ADEQUACY OF
EXCLUSIVE BREASTFEEDING FOR
THE TERM INFANT DURING THE
FIRST SIX MONTHS OF LIFE
NANCY F. BUTTE, PHD
USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics,
Baylor College of Medicine, Houston, TX, USA
MARDIA G. LOPEZ-ALARCON, MD, PHD
Nutrition Investigation Unit, Pediatric Hospital, CMN, Mexico City, Mexico
CUTBERTO GARZA, MD, PHD
Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
GENEVA
WORLD HEALTH ORGANIZATION
2002
WHO Library Cataloguing-in-Publication Data
Butte, Nancy F.
Nutrient adequacy of exclusive breastfeeding for the term infant during the first six months of life / Nancy F. Butte, Mardia
G. Lopez-Alarcon, Cutberto Garza.
1.Breastfeeding2.Milk, Human – chemistry3.Nutritive value4.Nutritional requirements5.InfantI.Lopez-Alarcon,
Mardia G. II.Garza, CutbertoIII.Expert Consultation on the Optimal Duration of Exclusive Breastfeeding (2001:Geneva,
Switzerland) IV.Title.
ISBN 92 4 156211 0 (NLM Classification: WS 125)
© World Health Organization 2002
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Designed by minimum graphics
Printed in France
REFERENCES
Contents
Abbreviations & acronyms v
Foreword vii
Executive summary 1
1. Conceptual framework 3
1.1 Introduction 3
1.2 Using ad libitum intakes to assess adequate nutrient levels 3
1.3 Factorial approaches 4
1.4 Balance methods 5
1.5 Other issues 6
1.5.1 Morbidity patterns 6
1.5.2 Non-continuous growth 6
1.5.3 Estimating the proportion of a group at risk for specific nutrient deficiencies 6
1.5.4 Summary 7
2. Human-milk intake during exclusive breastfeeding in the first year of life 8
2.1 Human-milk intakes 8
2.2 Nutrient intakes of exclusively breastfed infants 8
2.3 Duration of exclusive breastfeeding 8
2.4 Summary 14
3. Energy and specific nutrients 15
3.1 Energy 15
3.1.1 Energy content of human milk 15
3.1.2 Estimates of energy requirements 15
3.1.3 Summary 15
3.2 Proteins 16
3.2.1 Dietary proteins 16
3.2.2 Protein composition of human milk 16
3.2.3 Total nitrogen content of human milk 17
3.2.4 Approaches used to estimate protein requirements 17
3.2.5 Protein intake and growth 20
3.2.6 Plasma amino acids 21
3.2.7 Immune function 21
3.2.8 Infant behaviour 22
3.2.9 Summary 22
iii
NUTRIENT ADEQUACY OF EXCLUSIVE BREASTFEEDING FOR THE TERM INFANT DURING THE FIRST SIX MONTHS OF LIFE
3.3 Vitamin A 22
3.3.1 Introduction 22
3.3.2 Vitamin A in human milk 22
3.3.3 Estimates of vitamin A requirements 23
3.3.4 Plasma retinol 23
3.3.5 Functional end-points 24
3.3.6 Summary 26
3.4 Vitamin D 26
3.4.1 Introduction 26
3.4.2 Factors influencing the vitamin D content of human milk 26
3.4.3 Estimates of vitamin D requirements 27
3.4.4 Vitamin D status and rickets 29
3.4.5 Vitamin D and growth in young infants 29
3.4.6 Vitamin D and growth in older infants 30
3.4.7 Summary 30
3.5 Vitamin B6 30
3.5.1 Introduction 30
3.5.2 Vitamin B6 content in human milk 30
3.5.3 Approaches used to estimate vitamin B6 requirements 31
3.5.4 Estimates of requirements 31
3.5.5 Vitamin B6 status of breastfed infants and lactating women 31
3.5.6 Growth of breastfed infants in relation to vitamin B6 status 32
3.5.7 Summary 32
3.6 Calcium 32
3.6.1 Human milk composition 32
3.6.2 Estimates of calcium requirements 32
3.6.3 Summary 33
3.7 Iron 34
3.7.1 Human milk composition 34
3.7.2 Estimates of iron requirements 34
3.7.3 Summary 35
3.8 Zinc 35
3.8.1 Human milk composition 35
3.8.2 Estimates of zinc requirements 35
3.8.3 Summary 37
References 38
iv
REFERENCES
Abbreviations & acronyms
AI Adequate intake
BMD Bone mineral density
BMC Bone mineral content
CDC Centers for Disease Control and Prevention (USA)
DPT Triple vaccine against diphtheria, pertussis and tetanus
DXA Dual-energy X-ray absorptiometry
EAR Estimated average requirement
EAST Erythrocyte aspartate transaminase
EPLP Erythrocyte pyridoxal phosphate
ESPGAN European Society of Paediatric Gastroenterology
FAO Food and Agriculture Organization of the United Nations
IDECG International Dietary Energy Consultative Group
IU International units
NCHS National Center for Health Statistics (USA)
NPN Non-protein nitrogen
PLP Pyridoxal phosphate
PMP Pyridoxamine phosphate
PNP Pyridoxine phosphate
PTH Parathyroid hormone
RE Retinol equivalents
SD Standard deviation
SDS Standard deviation score
UNICEF United Nations Children’s Fund
UNU United Nations University
WHO World Health Organization
v
REFERENCES
Foreword
This review, which was prepared as part of the back- adequacy is most commonly evaluated in terms of
ground documentation for a WHO expert consultation,1 growth, but other functional outcomes, e.g. immune
evaluates the nutrient adequacy of exclusive breast- response and neurodevelopment, are also considered to
feeding for term infants during the first 6 months of the extent that available data permit.
life. Nutrient intakes provided by human milk are
This review is limited to the nutrient needs of infants.
compared with infant nutrient requirements. To avoid
It does not evaluate functional outcomes that depend
circular arguments, biochemical and physiological
on other bioactive factors in human milk, or behaviours
methods, independent of human milk, are used to define
and practices that are inseparable from breastfeeding,
these requirements.
nor does it consider consequences for mothers. In
The review focuses on human-milk nutrients, which determining the optimal duration of exclusive breast-
may become growth limiting, and on nutrients for which feeding in specific contexts, it is important that func-
there is a high prevalence of maternal dietary deficiency tional outcomes, e.g. infant morbidity and mortality,
in some parts of the world; it assesses the adequacy of also are taken into consideration.
energy, protein, calcium, iron, zinc, and vitamins A,
The authors would like to thank the World Health
B6, and D. This task is confounded by the fact that the
Organization for the opportunity to participate in
physiological needs for vitamins A and D, iron, zinc –
the expert consultation;1 and Nancy Krebs, Kim
and possibly other nutrients – are met by the combined
Michaelson, Sean Lynch, Donald McCormick, Paul
availability of nutrients in human milk and endogenous
Pencharz, Mary Frances Picciano, Ann Prentice, Bonny
nutrient stores.
Specker and Barbara Underwood for reviewing the draft
In evaluating the nutrient adequacy of exclusive breast- manuscript. They also express special appreciation for
feeding, infant nutrient requirements are assessed in the financial support provided by the United Nations
terms of relevant functional outcomes. Nutrient University.
1 Expert consultation on the optimal duration of exclusive
breastfeeding, Geneva, World Health Organization, 28–30 March
2001.
vii
EXECUTIVE SUMMARY
Executive summary
In this review nutrient adequacy of exclusive The dual dependency on exogenous dietary sources and
breastfeeding is most commonly evaluated in terms of endogenous stores to meet requirements needs to be
growth. Other functional outcomes, e.g. immune borne in mind particularly when assessing the adequacy
response and neurodevelopment, are considered when of iron and zinc in human milk. Human milk, which is a
data are available. The dual dependency on exogenous poor source of iron and zinc, cannot be altered by
dietary sources and endogenous stores for meeting maternal supplementation with these two nutrients. It
requirements is also considered in evaluating human is clear that the estimated iron requirements of infants
milk’s nutrient adequacy. When evaluating the nutrient cannot be met by human milk alone at any stage of
adequacy of human milk, it is essential to recognize the infancy. The iron endowment at birth meets the iron
incomplete knowledge of infant nutrient requirements needs of the breastfed infant in the first half of infancy,
in terms of relevant functional outcomes. Particularly i.e. 0 to 6 months. If an exogenous source of iron is not
evident is the inadequacy of crucial data for evaluating provided, exclusively breastfed infants are at risk of
the nutrient adequacy of exclusive breastfeeding for the becoming iron deficient during the second half of
first 4 to 6 months. infancy. Net zinc absorption from human milk falls short
of zinc needs, which appear to be subsidized by prenatal
Mean intakes of human milk provide sufficient energy
stores.
and protein to meet mean requirements during the first
6 months of infancy. Since infant growth potential In the absence of studies specifically designed to evaluate
drives milk production, the distribution of intakes likely the time at which prenatal stores become depleted,
matches the distribution of energy and protein circumstantial evidence has to be used. Available
requirements. evidence suggests that the older the exclusively breastfed
infant the greater the risk of specific nutrient
The adequacy of vitamin A and vitamin B6 in human
deficiencies.
milk is highly dependent upon maternal diet and
nutritional status. In well-nourished populations the The inability to estimate the proportion of exclusively
amounts of vitamins A and B6 in human milk are breastfed infants at risk of specific deficiencies is a major
adequate to meet the requirements for infants during drawback in terms of developing appropriate public
the first 6 months of life. In populations deficient in health policies. Conventional methodologies require
vitamins A and B6, the amount of these vitamins in that a nutrient’s average dietary requirement and its
human milk will be sub-optimal and corrective measures distribution are known along with the mean and
are called for, either through maternal and/or infant distribution of intakes and endogenous stores.
supplementation, or complementary feeding for infants.
Moreover, exclusive breastfeeding at 6 months is not a
The vitamin D content of human milk is insufficient to common practice in developed countries, and it is rarer
meet infant requirements. Infants depend on sunlight still in developing countries. There is a serious lack of
exposure or exogenous intakes of vitamin D; if these measurement, which impedes evaluation, of the human-
are inadequate, the risk of vitamin D deficiency rises milk intakes of 6-month-old exclusively breastfed
with age as stores become depleted in the exclusively infants from developing countries. The marked attrition
breastfed infant. rates in exclusive breastfeeding through 6 months
postpartum, even among women who are both well
The calcium content of human milk is fairly constant
nourished and highly motivated, is a major gap in our
throughout lactation and is not influenced by maternal
understanding of the biological, cultural and social
diet. Based on the estimated calcium intakes of
determinants of the duration of exclusive breastfeeding.
exclusively breastfed infants and an estimated
A limitation to promoting exclusive breastfeeding for
absorption efficiency of > 70%, human milk meets the
the first 6 months of life is our lack of understanding of
calcium requirements of infants during the first
the reasons for the attrition rates. Improved
6months of life.
understanding of the biological, socioeconomic and
1
NUTRIENT ADEQUACY OF EXCLUSIVE BREASTFEEDING FOR THE TERM INFANT DURING THE FIRST SIX MONTHS OF LIFE
cultural factors influencing the timing of supplemen- for mothers been considered. It is important that
tation of the breastfed infant’s diet is an important part functional outcomes, e.g. infant morbidity and mortality,
of advocating a globally uniform infant-feeding policy be taken carefully into account in determining the
that accurately weighs both this policy’s benefits and optimal duration of exclusive breastfeeding in specific
possible negative outcomes. environments.
It is important to recognize that this review is limited This review was prepared parallel to, but separate from,
to the nutrient needs of infants. No attempt has been a systematic review of the scientific literature on the
made to evaluate functional outcomes that depend on optimal duration of exclusive breastfeeding.1 These
other bioactive factors in human milk, or behaviours assessments served as the basis for discussion during an
and practices that are inseparable from breastfeeding. expert consultation (Geneva, 28–30 March 2001),
Neither have the consequences, positive or negative, whose report is found elsewhere.2
1 Kramer MS, Kakuma R. The optimal duration of exclusive
breastfeeding: a systematic review. Geneva, World Health
Organization, document WHO/NHD/01.08–WHO/FCH/CAH/
01.23, 2001.
2 The optimal duration of exclusive breastfeeding: report of an expert
consultation. Geneva, World Health Organization, document
WHO/NHD/01.09–WHO/FCH/CAH/01.24, 2001.
2