BIOLOGICAL EFFECTS OF BREAST FEEDING

What would be the biological
effects of breastfeeding?
It is suggested that potential causal mecha-
nisms for an association of breastfeeding
with a reduction in childhood obesity in-
clude satiety signalling in response to nu-
tritional composition of breast milk
5
and
overfeeding among bottle-fed infants,
who exhibit significantly higher plasma
insulin levels and a prolonged insulin re-
sponse
6
compared with breastfed infants.
There might be many mechanisms other
than weight status that could account for
a protective association between breast-
feeding and type-2 diabetes. Studies
conducted in infants in contrast to those
conducted in children and adults, showed
consistent associations between breast-
feeding and lower glucose and insulin
concentrations. These differences could
reflect lower energy intake in breastfeed-
ing infants than in formula-fed infants
7
,
differences between breast-milk compo-
sition and formulas (particularly the amino
acid and protein contents), or hormonal
differences that result in lower levels of
fat deposition in breastfed infants
4,8
. An-
other possible mechanism is that breast-
feeding may improve insulin sensitivity
and glucose intolerance. In a study of
both breastfeeding and non-breastfeeding
nondiabetic women, insulin levels and
insulin/glucose ratios were lower, while
carbohydrate use and total energy expen-
diture were higher in the breastfeeding
group
9
. Various environmental toxins,
particularly endocrine-disrupting chemi-
cals, have recently been postulated as
contributors to obesity and related meta-
bolic disorders. These include bisphenol-
A, which has been widely incorporated
into plastic products, including infant
feeding bottles
10
and which has been as-
sociated with both reduced pancreatic b-
cell function and insulin resistanc