Breast milk: An evolving nutritional solution
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Breast milk: An evolving nutritional solution
Breast milk: An evolving nutritional soluti on
Current guidelines from international health experts recommend exclusive
breast-feeding of infants during the first 6 months of life (IOM 2011, WHO
2013, ESPGHAN 2009). Breast milk is recognized as the ideal form of nutrition
for infants because it is best adapted to their needs and is well-known as
having unique advantages:
• Supports healthy growth and development
• Provides the infant with effective protection against infection and disease
• Contributes to mother-infant bonding
Nevertheless, there still remains so much to learn from this fascinating source
of nutrition. Research in recent years has revealed just how dynamic breast
milk is as a substance, with a composition that not only varies within single
feeds but more gradually over days and months, adapting to perfectly match
the changing nutritional needs of developing babies.
In addition, within the past decade, the long-term impact of breast-feeding has
started to emerge with research suggesting that breast-feeding’s benefits could
continue into adulthood. Scientific studies show that breast-fed babies are at a
lower risk than formula-fed babies of obesity, as well as other cardiometabolic
disorders in later life. Breast milk’s nutritional profile, and potentially its unique
evolving composition, could have an effect on early metabolic programming.
The Nestlé Nutrition Institute presents
the latest scientific research on breast-feeding.
3
1. The evolving composition of breast milk
It is now clearly established that breast milk composition is not constant, but
rather evolves throughout lactation in response to the changing nutritional Breast milk intake in the first 12 months
requirements of the neonate. Nearly every macronutrient in breast milk evolves in 1.4
some way during the course of lactation, with perhaps the most striking changes
Breast milk intake ( kg/d)
1.2
occurring with proteins, lipids and energy. These variations are believed to respond 1.0
to specific infant needs and have beneficial effects on growth and development 0.8
both during infancy and later in life. 0.6
0.4
Evolving energy requirements and breast milk consumption 0.2
Total energy expenditure among infants increases very rapidly, doubling during 0
0 1 2 3 4 5 6 7 8 9 10 11 12
the first year of life. This fast evolution mirrors the infants’ increasing energy Age (month)
requirements and is needed to support healthy growth and development.
Ref: Adapted from da Costa et al. 2010
Total energy expenditure in girls and boys in the first year of life Important changes in energy density in breast milk also take place during the
lactation period. It is generally accepted that the energy content of breast milk is
800
67 kcal/100mL; however, several studies have demonstrated that caloric density
Total energy expenditure (kcal per day)
Boys Girls
700
varies during breast-feeding and that it is below this standard value (Lucas et al.
600
1987; de Bruin et al. 1998; Reilly et al. 2005). Some studies have even estimated
500 the caloric density of breast milk at 57 kcal/100mL (Lucas et al. 1987), questioning
400 the widely used standards.
300
200
Evolution in energy content of breast milk
100
85
0
0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11 11-12 80
Age (month) 75
Calorie (kcal/100ml)
70
65
Ref: FAO/WHO/UNU, 2004
60
55
50
The increase in energy required by infants to support growth and physical activity 45
is mirrored by a corresponding increase in breast milk consumption. A recent 0 1 2 3 4 5 6
study estimating human milk intake using an isotope tracer in infants aged 0-24 Months
months found that the volume consumed by infants increases during the first 4
Ref: Adapted from Lucas et al. 1987; Hosoi et al. 2005; Saarela et al. 2005; Nielsen et al. 2008;
months then plateaus (da Costa et al. 2010). Thakkar et al. 2013
5
The energy content of breast milk is not the only value to have been over-estimated; As a result of this decline, breast-fed infants have a relatively low protein intake.
infant energy requirements were also over estimated by 15-30% (Butte, 2005). Growth velocity rapidly slows in the first 6 months of life and this coincides with
Based on these findings, the FAO published new values for daily energy needs a reduction in protein intake. Both parameters decrease by about half during the
in 2004. The daily caloric needs in relation to the infant’s weight (kcal/kg/day) first year of lactation (Van’t Hof 2000).
decrease during the first year of life. This trend is similar for girls and boys.
Growth velocity and protein intake of breast-fed infants
Estimated daily caloric needs 1st Month 12th Month
Boys 113 kcal/kg/day 81 kcal/kg/day Early months
Higher growth rate
=
Girls 107 kcal/kg/day 79 kcal/kg/day 2.25 Higher protein needs 1200
1100
Ref: Butte 2005, Butte 2006
g/kg body weight/day
2.00 1000
Later months 900
Evolving protein composition matching growth velocity
g/months
Lower growth rate
1.75 = 800
Lower protein needs
700
The protein content of breast milk varies at each stage of lactation. The milk secreted
1.50 600
in the first few days after birth, colostrum, contains very high concentrations of
500
protein, ranging from 20 to 30 g/L (Lönnerdal 2008). The very high protein content
1.25 400
of colostrum can be explained in part by the low volumes of milk produced, but
300
it is mainly due to the hormonal regulation of protein content. Other studies have 200
1.00
shown that the protein content of breast milk decreases significantly after several 0-1 1-2 2-3 3-4 4-5 5-6 6-7 9-12
months of breast-feeding, reaching 7 to 8 g/L after six months of breast-feeding Age (months) Growth rate
(Lönnerdal 2004). Protein intake
Protein content of breast milk Ref: Van’t Hof 2000
30
The protein profile of breast milk also evolves to fulfill the nutritional needs of the
25 infant for its growth and development. The ratio of the two major milk fractions,
Protein content (g/L)
20 whey and casein, vary considerably over the lactation period. In early lactation,
the protein fraction consists mainly of whey and casein is not synthesized or
15
detectable. As milk production increases, whey proteins decrease relative to the
10 casein proportion that increases. In early lactation it is as high as 90:10, yet this
5 ratio falls to about 60:40 at full lactation and as low as 50:50 in late lactation (Kunz
& Lönnerdal 1990, 1992).
0 Time
0 1 2 3 4 5 6 12 (months)
Ref: Lönnerdal 2004
7
The evolution of lipids and carbohydrates
Carbohydrate content during the first 4 months of lactation
Beyond protein and energy, lipids and carbohydrate concentrations in breast milk
have also been shown to change over time. Lipid concentrations vary following 90
birth with one study showing an increase from 1.8 to 3.0 g/100ml during the first 80
70
four weeks postpartum (Anderson et al. 1981). Triglycerides are the main lipid
Percent
60 1.2
class found in human milk and represent about 98% of total lipids (Jensen 1996).
Percent
50 1.0
Significant longitudinal variations in phospholipid/triglycerides and cholesterol/ 40 0.8
triglycerides ratios in human milk have also been reported (Harzer et al. 1986). 30 0.6
20 0.4
10
0
0
Lipid concentration in the first four weeks of lactation 4 10 30 60 90 120
Days after delivery
3.50 lactose monosaccharides oligosaccharides
3.00
Lipids (g per 100ml)
Values indicate percentage of total carbohydrates.
2.50 Left axis: lactose and oligosaccharides; right axis: monosaccharides.
2.00
Ref: Coppa et al. 1993
1.50
1.00
0.50 Lactose is the predominant digestible carbohydrate in human milk. It partly
0.00 Age escapes digestion and absorption, and is thus available for fermentation by
4 9 16 27 (month)
colonic microbiota, potentially favoring a microbiota predominant in lactobacilli
and bifidobacteria (Bullen et al. 1977; Francavilla et al. 2012). Very recent results
Ref: Anderson et al. 1981
suggest an additional function of lactose in innate immunity that may lead to
protection of the neonatal gut against pathogens and regulation of the infant’s
microbiota (Cederlund et al. 2013).
Carbohydrate synthesis also appears to be a dynamic process, with considerable
differences in carbohydrate content observed during the different phases of Human milk oligosaccharides represent the third most abundant group of milk
lactation. A study by Coppa et al. conducted over the first four months after delivery components, in concentrations ranging from 10 to 20 g/L (Egge et al. 1983; Kunz
found a rise in lactose and a decrease in oligosaccharides and monosaccharides et al. 2000; Thurl et al. 2010; Urashima et al. 2011). They have been suggested
(Coppa et al. 1993). to promote the establishment of a normal gut microbiota, to prevent pathogen
adhesion to the intestinal epithelium and to influence gut maturation processes
(Bode et al. 2004; Newburg et al. 2005; Kuntz et al. 2008; Kuntz et al. 2009).
9
2. Breast-feeding and metabolic programming
Several studies have found that the prevalence of overweight and obesity has The difference in protein concentration between breast milk and infant formula
become epidemic in many parts of the world. In the United States, for example, in could result in lower weight gain over the first 2 years of life. This theory is called
the past three decades the prevalence of obesity among children and adolescents the “early protein hypothesis”. In 1988, Axelson et al. reported that increased
has tripled (Ogden 2010). protein ingestion resulted in increased levels of insulin-releasing amino acids
(Axelson et al. 1988). In 2005, Koletzko et al. established this hypothesis:
Prevalence (%) of obesity among U.S. children and adolescents
The early protein hypothesis
Age in years 1976-1980 1999-2000 2003-2004 2007-2008 Weight gain
2-5 5.0 10.3 13.9 10.4 Protein Insulin-releasing 0-24 months
Insulin, IGF-1
supply amino acids Adipogenic
6-11 6.5 15.1 18.8 19.6
activity
12-19 5.0 14.8 17.4 18.1
Total 5.5 13.9 17.1 16.9 Ref: Koletzko et al. 2005
Obesity: BMI values at or above the 95th percentile of the sex-specific BMI growth charts
Ref: Ogden 2010 The hypothesis suggests that high protein intake calibrates an infant’s metabolism,
predisposing it to weight gain. It has been estimated that nearly 13% of cases
of childhood obesity can be explained by high protein intake in infants fed with
What impact could infant nutrition have on obesity in childhood and even conventional formula (Haschke, 2010).
adulthood? It has been clear for some time now that breast-fed and formula-
fed babies experience different patterns of weight gain in early life. The possible Reducing protein intake in early infancy
consequences of these different growth patterns has, up until recently, been
undefined. Now longer-term studies suggest that breast-fed babies have a much The potential negative effects of infant formula with high concentrations of protein
lower risk of obesity, as well as other associated cardiometabolic disorders, than have lead researchers to investigate the implications of lower protein infant
formula-fed babies in childhood and even in adulthood. formula. A European project by Koletzko et al. indicated that low protein infant
formula is associated with lower weight in infants up to two years of age, which
suggests that lower protein intake in infancy may decrease the risk of overweight
Protein intake in children and obesity in adulthood
and obesity later in life (Koletzko et al. 2009).
The data seem to imply that weight gain during early development may have
consequences that last well into adulthood. The current state of knowledge
suggests that so-called “metabolic programming” established during infancy may
have important effects on body weight throughout an entire lifetime. Overweight
and obesity developed in an individual during childhood may endanger long-term
health and life expectancy in adulthood (Fisberg 2004; Sachdev 2005; Ekelund
2007).
11Effects of low protein formula on BMI
1.0
**
z-score
0.5 *
*
0.0
For more information on the topics raised in this brochure,
-0.5 please visit www.nestlenutrition-institute.org
1 3 6 12 24
Age in months
lower protein higher protein breasted
Ref: Koletzko 2009. BMI: body mass index . *PReferences
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