The Milky Way: The implications of using animal milk products in infant feeding

Abstract

Animal milks have been used in infant feeding for at least a few millennia, but this can only have become a common practice after the domestication of dairy animals during the Neolithic. Neolithic population increase has often been attributed to the effect of a reduction in breastfeeding duration on female fertility. It is possible, therefore, that animal milks were first introduced to the infant diet at this time as a replacement for the lost breastmilk. Milks are complex liquids and are species specific. The consumption of the milk of one species by the infants of another thus has implications for the welfare of those infants. This paper reviews some of the differences between the milks of three ruminant species and human milk and discusses what the health consequences of introducing these animal milks to the infant diet are likely to have been. It is argued that, except in extreme circumstances, animal milks would fail to adequately compensate for the reduction in breastmilk consumption. Fermented milk products could however have been valuable weaning foods if consumed alongside other iron-rich products.

Full text

e Milky Way: e implications of using animal milk
products in infant feeding
Rachel HOWCROFT,
Gunilla ERIKSSON
Kerstin LIDÉN
Archaeological Research Laboratory
Stockholm University
SE-106 91 Stockholm, Sweden.
rachel.howcroft@arklab.su.se
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Animal milks have been used in infant feeding for at least a few millennia, but this can only
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 
du nourrisson.
KEYWORDS

Infant Feeding
Breastfeeding
Neolithic

Dairying, Farming



MOTS CLÉS
Lait
alimentation du nourrisson
allaitement




sevrage


 

INTRODUCTION
   
milk in adulthood is a genetically determined
trait that is thought to have been under selec-
tion only during the last 10,000 years (Burger
et al      -

regularly feed their infants with the milk of ano-



in the form of infant formula and others are
      
animal milks by infants is also well attested his-
torically, being traceable back to at least Greco-

-
    


  -

       
time. Genetic evidence suggests that the muta-
     -
   -



-
    -
   


THE POSTULATED ASSOCIATION


INFANT
 

    -
et al
growth is thought to have resulted from an
increase in female fertility that was later curtai-
      

       
     
       
 
been suggested that fertility increase could
have been due to a reduction in the duration

the inter-birth interval (Armelagos et al
   et al 
e reason for weaning earlier in the Neolithic
has in turn been attributed to the availability of
agricultural foods such as cereal gruels and ani-

so (Buikstra et al
is assertion has been challenged, however, by
 
    
   -


so are clearly able to obtain foods suitable for

It has been suggested more recently that Neo-
lithic fertility increase is likely instead to have
resulted from the direct inuence of Neolithic
diet and lifestyle on maternal energetics (Boc-
 -
sitated a reduction in the duration of breastfee-
ding, since increased family size and changed

      
other carers from an earlier age and so reduced
     
communities have access to foods suitable for
-
-

 -


 33

-
      




-
     
   
-

 
    
    
  
introduced to the infant diet while breastfee-
ding continues. It is recommended that breast-
milk should continue to contribute to the
infant diet until at least the end of the second
year of life. Since these recommendations are
 


  
     
    -
tices in modern non-industrialised societies


is evolutionary model of infant feeding in-
volves weaning infants earlier than would be

     
weaning has been argued to be a derived trait
-


survival of human infants in forager communi-


the age at weaning without increasing infant
      -
   -

enables infant nutritional demands to be met
from sources other than breastmilk from an ear-
-


is is argued to be another derived trait of the

  
       
      -
-
     
  
   
     
-


 

e health of infants is thus to a large degree
     
weaned and on the choice of foods given to
      
-


      
      
 
     
of the ideal model of infant feeding, there are

could have been used in the infant diet that are
       
health. Firstly, they could have been introduced
    

     -
ding. Alternatively they could have been used

        

introduced to the diet. Finally, they could have

 


     
-
riod of breastfeeding, but the latter will also be
referred to occasionally below.


B 
-
ding animal milks to Neolithic infants would
        
     
that information is not available data from
       
      

   


milk due to the greater body of research into
       
selective breeding that has occurred since these


remained unaltered, however it is assumed here
that the milk of modern animals is more simi-

it is to human breastmilk and that it is thus a

recent genetic study which found no evidence
    -

or member of the lactation mammary gene set”


     
between human and ruminant milks.
      
three ruminant milks with human breastmilk
       
   
 

the ruminant milks than each is to human
milk. Human milk contains considerably less
      
carbohydrate than the milks of the other
  
   
 
     
      
     
     
leading to diarrhoeal illness and acidosis

      
 

and be linked to obesity in later life (Bartok &


P



-


et al.     
declines so that in mature human milk it makes
       



Species Human Cow Goat Sheep
Water (g) 87.50 87.69 87.03 80.70
Protein (g) 1.03 3.28 3.56 5.98
Carbohydrate (g) 6.89 4.65 4.45 5.36
Lipid (g) 4.38 3.66 4.14 7.00
Ash (g) 0.20 0.72 0.82 0.96
Energy (kcal) 291 268 288 451




 

et al.  

in the infant gut, which slows digestion and so

 et al. 

-
kages in the small intestine. is in turn can
     
     
content also reduces gastric acidity, making the
-
genic bacteria and so leaving the infant more
     

milk it forms a softer curd because it contains
    αs1-casein (Haenlein
et al.

     
 β-lactoglobulin.

      
   
to know how many infants would have been

        
      


outgrown the allergy by the age of three. In its
      
      -
  -
  
in weight loss, anaemia, and a “failure to thrive”

      
animal milks are likely to have been a serious
       
-
teins these milks lack that would have been the
greater health concern. Lactoferrin and Lyso-

ruminant milks, and α

(Chandan et al.
Park et al.
 -
-





36 

bacteria, and can also work in tandem with lac-
-

   
infant small intestine, stimulates the growth of
-

       
       
et al.     
breakdown of α   
the gastrointestinal tract have further antimi-
    -
     et al.  
α  -
 

    
leave an infant with reduced defences against
-
tion of minerals from the diet.
F
        
milk is similar to that in human milk, but it is

     
acids and has larger fat globules than human
milk, meaning it is less easily absorbed (Gurr



      
-

and medium chain fatty acids and also contain
      et
al.  et al.    et
al.
C
-

of this is in the form of the disaccharide lactose
 et al.  
of carbohydrate is not digested in the small
intestine, but reaches the colon intact where it
-
motes the growth of host-friendly bacteria in
 

      -
-
tion thereby reducing the risk of diarrhoea.
Alongside lactose, human milk carbohydrate
     
Human colostrum contains oligosaccharides

 et al. 

-

      
oligosaccharides and these are structurally less
  -
      -
     
  
   
-
ting the growth of desirable bacteria whilst not
    
-
ting infant infection and diarrhoea. By having

      
-
  


      
    
-
tentially life-threatening disorder that is most
      


I

 


than one year of age is associated with increased
 et al. -
     et al.

sources of iron, but infants are born with iron
   
during early life (Butte et al. -
tion of these stores and the heavy iron demands
of infant growth mean that iron is one of the
   
to be introduced to the diet in order to meet
   
   


 et al.

     -
teins in bovine milk, all of which inhibit iron
      

     
  
      
and severity of occult blood loss from the infant

 et al. 




milk (Park et al. 
  
 
-

      
severe than anaemia caused by bovine milk.
is has since been attributed to the lower le-
-
  et al.
.

    
      
  
et al. 

infants more vulnerable to infection and death.


It is clear, therefore, that infant health would
    
substituted with raw ruminant milks. For the
     -
     -
milk would leave the infant more likely to suc-
cumb to infectious illnesses and at a greater risk
  

of infants who survived them, as well as claiming
-
        
a number of variables such as the timing of the
   
which they were used, the disease risk of the local
environment, and the way in which they were
consumed. Introducing animal milks during
   
breastfeeding would have had the most detri-
-
creases in maturity through time (Cuthbertson
-

more severe the earlier they were introduced. In
   
and the introduction of non-breastmilk foods at
 
of infection at an earlier age (although this risk
would be reduced if infants suckled directly from
      

       
animal milks were introduced the less able the
      -
sive immunity from breastmilk and the increased


 

     
      
    

-

   -

  -
-

use of ruminant milks at this stage would thus

infant health to introducing them earlier, but

  
of breastmilk in the diet but instead were used

infant health would be lower still. e infant
       
       

-
      
e biggest disadvantage of using animal milks




       -
ciency leads current national recommendations





BENEFICIAL TO INFANT HEALTH
       
and there may have been circumstances under

for infant health. A study of infant feeding in



-
     
from their animals. Turkana infants are given
unrestricted access to the breast from birth, but
are also routinely given butterfat made from
  
      


       
      
      

   
non-milk foods introduced around 6months
and the cessation of breastfeeding around two
years. e Turkana live in a hot, arid environ-
  

-
mity of livestock and other vectors of infection
such as ies mean that Turkana infants are at a
high risk of infection almost from the womb.
Gray argues that maternal milk is likely to have

and that a diet of breastmilk alone would leave



nature of disease is argued to negate the risks
of introducing non-breastmilk foods to the diet
since infants are at such a high risk of illness
     
would not have been living in the hot, arid


in early Neolithic communities may have been
 -


       
consumed as raw milk, and their fermentation
alters them in key ways that might have made
them more suitable for use in infant feeding.

 39

   
are similar to those of raw milk (Branca &
   
      
fat, carbohydrate and minerals would thus still
      
of bacterial strains such as Bidobacteria and
Lactobacilli-
      
gut ora of breastfed infants is rich in Bido-
bacteria
     
       


 

 -

bacteria (Ross et al. 
 -
-
 



 -


with raw milks. In contrast, however, fermented
   -
tary foods if fed alongside other iron-rich foods.
-
 
     
“transition” countries today (Branca & Ros-

CONCLUSIONS
For the occasional infant who could not be
breastfed due to maternal death or similar, the


    -
tions were living in marginal environments like


  
rates of infant morbidity and mortality. ese
  
      
breastfeeding, and less dramatic the later milks
were introduced. Given the overall similarity
between animal milks and human milk it is dif-

breastmilk available during the Neolithic could

loss of breastmilk from the diet. is does not
rule out a reduction in breastfeeding duration

     
growth would almost certainly have been at the
      
   
higher levels of infection than hunter-gathe-
 et
al. et al. 

to have involved an increase in mortality as well

Increased infant morbidity is, therefore, an
   

increases in infant mortality did not outweigh

       
     
e use of fermented milks along with other
      
     

infection. Both milk and blood are secondary
      


 
   -

      

 

Fermented milks contain less lactose than raw
milk but still contain substantial amounts, and


were scarce. In conclusion, therefore, although
-
ric infants, the yoghurty way could have been


REFERENCES
A G.J., G A.H. &
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Po-
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   in 
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   Nutrition Reviews 
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 

& C
   Worldwide prevalence of anaemia
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paRk y.W., MaHOnEy a.W. & HEndRicks d.g.
       

Journal of Dairy Science
paRREtt aM. & EdWaRds ca    
fermentation of carbohydrate by breast fed and
formula fed infants. Archives of Disease in Child-
hood
ROss R.p., MORgan s. & Hill c -
     
future. International Journal of Food Microbio-
logy
saaRinEn u.M., siiMEs M.a. & dallMan p.R.
  -
vailability of breast milk iron as indicated by the

the concentration of serum ferritin. e Journal
of Pediatrics
saBikHi l.Advances in Food
and Nutrition Research
sEllEn d.W. & sMay d.B   
between subsistence and age at weaning in
Human Nature

sEllEn d.W.
    -
tions with current recommendations. Journal of
Nutrition
sEllEn d.W.      
  -
  Annual Review of Nutri-
tion
sEllEn d.W
    
-
riation, in Goldberg G.R., Prentice A., Prentice
       Breast-
feeding: early inuences on later health

sullivan p.B
bleeding in infancy. Archives of Disease in Child-
hood
tHOMpkinsOn d.k., & kHaRB s  
of Infant Food Formulation. Comprehensive
Reviews in Food Science and Food Safety 

usda aRs (u.s. dEpaRtMEnt Of agRicultuRE,
agRicultuRal REsEaRcH sERvicE).  
USDA National Nutrient Database for Standard

 

Reference, Release 22. Nutrient Data. Nutrient
    

valEggia c. & EllisOn p.t.   
    
Ame-
rican Journal of Human Biology
WalZEM R.l., dillaRd c.J. & gERMan J.B
     

what we know and what we may be overloo-
king. Critical Reviews in Food Science and Nutri-
tion
WHO/UNICEF (WORld HEaltH ORganiZatiOn/
unicEf)Global strategy for infant and young
child feeding
WHO (WORld HEaltH ORganiZatiOn)   Gui-
ding principles for feeding non-breastfed children 6-24
months of age
ZiEglER d.s., RussEll s.J., ROZEnBERg g., JaMEs
c., tRaHaiR t.n. & OBRiEn t  
Journal of Paediatrics and
Child Health
Submitted on March 14, 2011;
accepted on April 3, 2012

 
