A new study published this week in the
journal Pediatrics found that exclusive
breastfeeding up to six months provides enough calories for infants.
Quick and Dirty Summary:
This study addressed two common concerns about
breastfeeding: 1) Many moms simply
can’t produce enough milk for their babies; and 2) Exclusive breastfeeding,
while adequate in younger infants, may not provide enough calories for babies
up to 6 months of age. The data
from this study indicate that when moms
are given breastfeeding support, milk
production is not a limiting factor and provides enough calories for normal
growth, even in 6-month-old infants. However, this study was
small and had several limitations (which I will discuss). 
How was this study conducted?
This was a longitudinal study of 50 mothers and their infants in Glasgow,
Scotland. All of these mothers
intended to exclusively breastfeed (EBF) for at least 6 months and were recruited
from breastfeeding support groups, so we can presume that they were already set
up to succeed with breastfeeding.
EBF is defined by the World Health Organization (WHO) and in this study
as giving the infant only breast milk for nutrition (no solids or formula),
with oral rehydration, vitamins, minerals, or medicines allowed as needed. 60 mothers were recruited, but only 50
were still EBF at the first assessment around 15 weeks of age. Assessments included measurements of
infant growth, milk intake, total energy intake, and milk energy content. Mothers also completed questionnaires
and infant behavior diaries in order quantify the number of feedings and total
time spent nursing. These
measurements were all repeated at 25 weeks of age (6 months). At this second time-point, 3 mothers had
dropped out of the study and 41 mothers were still EBF. The remaining 6 mothers had begun
feeding their babies some solid foods.
How,
you might ask, did the researchers manage to measure milk intake in nursing babies?
Excellent question. They used a technique called the
doubly-labeled water method, which involves feeding the baby a tiny and safe dose of stable
isotope-labeled water (2H218O) and then
collecting samples of their pee (which is easy enough to do when you change a diaper)
to measure how long it takes those isotopes to come out. Then they did a bunch of
calculations. Really. Trust me when I tell you that this
method is safe, non-invasive, and pretty much the best way to measure milk
intake in nursing babies. I’ve
actually had a little experience (in a previous life) using this method in nursing
bottle-nosed dolphins.
What are the most important findings of
the study?
-The
exclusively breast fed infants in this study grew just fine, right in line
with the WHO Child Growth Standards.
EBF to 6 months didn’t set them back in their growth curves.
-Milk intake was slightly but significantly higher at
25 weeks compared with 15 weeks (997 vs. 923 grams; P=0.001), showing that milk production increased to meet the
increasing demands of the infant.
Milk energy content (as in calories per liter) did not change between
time points.
-Moms reported breastfeeding 8-9 times
per day at both 15 and 25 weeks, but time spent feeding decreased from 173 minutes
per day at 15 weeks to 140 minutes at 25 weeks. That means that at 25
weeks of age, babies were drinking more milk but doing so more efficiently than
at 15 weeks. No surprise
there.
-There was no difference in infant weight
or milk intake at 25 weeks between the EBF infants and the 6 that had started solid
foods. The moms of these babies said
they started solids because their babies seemed ready.
What can we conclude from this study?
The
study shows that in most women with good breastfeeding support, infant milk
intake is sufficient to support normal growth with EBF for 6 months.
The authors of the study assert that
their findings support the recommendation that all babies should be EBF for the
first 6 months, but there are some problems with jumping to that conclusion…
What are the limitations of the study?
-10 of the 60 moms initially enrolled in
the study were not still exclusively breastfeeding at 15 weeks, and the study authors
don’t tell us what happened to those 10 women. Did they stop breastfeeding or supplement with formula
because of a fear, real or not, that they weren’t producing enough milk? We just don’t know.
-The mothers in this study were older
(mean age 33) and more affluent than the average mom. They were highly motivated to exclusively breastfeed and had
good support to do so. Just
guessing, but this type of mom is also more likely to take good care of herself
and have support at home to do that.
All of those factors might impact her breastfeeding success.
-The 6 babies that started solid foods prior to 6 months had similar caloric intake from milk as
the EBF babies. These babies were
also getting some additional calories from food, but the study did not report this. It is possible that these
babies were truly ready for solids before 6 months and needed the added energy
from solids, in addition to breastmilk.
The authors don’t address this possibility.
-This study only looked at calories from
milk intake. It doesn’t consider
micronutrients such as iron and zinc that may become limiting at this age
without the addition of some solid foods in the diet.
My take:
This study shows that exclusive breastfeeding
to 6 months can provide enough energy to support normal growth in babies. However, the mothers in this study were highly-motivated and had great support for breastfeeding. We don't know why 10 women dropped out of the
study or if the babies consuming solid foods actually needed the
additional calories from that food. Due to these limitations, the results of this study
may not apply to the general population.
It is easy to over-simplify the results
of a study like this, but when we really look at the data, we find that it just
isn’t that simple. Unfortunately,
most science isn’t.
The perception of low milk supply remains a major barrier to exclusive breastfeeding, and more work needs to be done to show whether or not this is a physiological or psychosocial problem.
What do you think? Did you or a friend have a problem with low milk supply? There is nothing worse than thinking that your baby is hungry and not being able to feed her!
