
Impact of breast milk on IQ, brain size and white matter development (2010) - lainon
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2939272/
======
c3534l
I'm not sure why this study from 7 years ago is being dug up because it's not
a particularly good, interesting, or definitive study. Some problems with it:

1\. Small sample sizes.

2\. Significance was only found in one subset of the population. Given enough
ways to divide up groups of people, you will almost always get false
positives.

3\. Not an experimental design.

4\. The study did not control for simple factors like income or the health of
the parent.

~~~
petters
> this study from 7 years ago is being dug up

That is not fair. You're making it sound like it's a JS framework.

Seven years is nothing in this case.

~~~
dublinclontarf
I suppose the point being made is that enough time has passed for the study to
have been properly validated; as the parent comment points out, lots of issues
have been found with it.

~~~
jfaucett
> as the parent comment points out, lots of issues have been found with it.

I'm not familiar with the research here so I can't say either way. But a
preliminary google scholar search turned up a lot of articles which seem to
suggest that breastfeeding has a bunch of positive impacts on numerous
intelligence and general well-being metrics.

The article itself has been cited 209 times according to google scholar [1],
and this study [2] (cited 400+ some odd times) seems to accept some of the
propositions made in this paper as givens.

Anyway, I think it would have been interesting if the null hypotheses here
weren't rejected. I kind of expect evolution to have optimized human
breastmilk over alternatives for infant development.

1\.
[https://scholar.google.com/scholar?cites=1509419575151008169...](https://scholar.google.com/scholar?cites=15094195751510081699&as_sdt=2005&sciodt=0,5&hl=en)
2\.
[http://pediatrics.aappublications.org/content/129/3/e827.sho...](http://pediatrics.aappublications.org/content/129/3/e827.short)

------
JackC
As a recent parent I would love it if there was more realistic health
information for parents about the benefits of breastfeeding. As best I can
tell from metastudies (which I'm totally unqualified to read), the scientific
answer right now is: there may be some effect, but if so it's too small to
reliably measure and may be swamped by other interventions. (I could be wrong!
That's why I want better info.)

(Compare to, say, the advice to have infants sleep on their backs to prevent
SIDS, or the HPV vaccine, which have clear and measurable health impacts at a
population level.)

This matters because breastfeeding has costs that tend to be ignored. Just
from personal experience, it pushes disproportionate work onto my wife in a
way that's hard to correct for and detracts from parenting. And given that
she's working full time, it's also a huge investment of resources -- if you
take her work time into account, we're spending tens or hundreds of dollars a
day for this. And many women get injuries and infections, soldiering through
months of agony for that health benefit that may or may not exist.

Setting aside the health of the parents (and we shouldn't, that's an easy
trap), breastfeeding uses a lot of resources that could go toward other
interventions for the child. Maybe it's all worth it? But I wish there was a
better conversation about the tradeoffs.

~~~
Pharylon
Yeah, breastfeeding can take 4-6 hours a day. It's no simple thing. And if the
mother is working, it's _hard_. Even pumping milk takes time.

Women who can afford to breastfeed exclusively are at least middle class,
usually upper-middle class. That comes with a whole set of advantages and
other correlations. Studies that try to figure out breast feeding advantages
have to try and control for these things, but it's hard.

Here's what we know for sure: Breast feeding reduces infections in the child.
It's a small, but detectable amount. And I do mean a small amount. Between six
mothers that exclusively breast feed an infant for six months, on average one
of those children will have one fewer infection during that time.

Everything else is up in the air, and if it has an effect on anything else
(like intelligence) it's tiny. Save your energy for reading to the child and
playing games with them, which definitely helps intelligence.

~~~
logfromblammo
Also, teach your babies a subset of ASL, for words like "more", "eat",
"drink", "milk", "water", "done", "diaper change", and "sleep". They can form
word associations before they are able to speak intelligibly, and it really
helps the parent figure out why TF the kid is crying.

~~~
Afton
I taught my daughter about 100 words of ASL (English with and ASL lexicon, to
be honest about it). Turned out super useful since she was a late talker (my
second child, who I also tried to teach ASL was an early talker and thought
ASL was stupid).

In my opinion, it's mostly useful because it's _super cute_. Typically kids
who can sign 'milk' or 'more' can also indicate with grunts, grabs and
reaching what the problem is. But it's _super_ cute.

~~~
wahern

      Turned out super useful since she was a late talker
    

That might not be a coincidence. There's some evidence that kids who use sign
language tend to talk later. Maybe because there's less incentive to
verbalize. It's not a language delay, though.

~~~
Afton
Pretty sure the causation worked the other way, but it's hardly a repeatable
experiment in my case.

------
rayiner
This study does not control for maternal IQ or socio-economic status. Later
studies show that much of the link between breastfeeding and cognitive
development is due to confounding effects (in particular, higher SES mothers
are more likely to breastfeed):
[http://bmjopen.bmj.com/content/3/8/e003259](http://bmjopen.bmj.com/content/3/8/e003259)

> Conclusions Much of the reported effect of breastfeeding on child
> neurodevelopment is due to confounding. It is unlikely that additional work
> will change the current synthesis. Future studies should attempt to
> rigorously control for all important confounders. Alternatively, study
> designs using sibling cohorts discordant for breastfeeding may yield more
> robust conclusions.

See also:
[http://pediatrics.aappublications.org/content/early/2017/03/...](http://pediatrics.aappublications.org/content/early/2017/03/23/peds.2016-1848)

> RESULTS: Before matching, breastfeeding was associated with better
> development on almost every outcome. After matching and adjustment for
> multiple testing, only 1 of the 13 outcomes remained statistically
> significant: children’s hyperactivity (difference score, –0.84; 95%
> confidence interval, –1.33 to –0.35) at age 3 years for children who were
> breastfed for at least 6 months. No statistically significant differences
> were observed postmatching on any outcome at age 5 years.

The linked study also yields some odd results:

> In the total group %EBM correlated significantly with Verbal IQ (VIQ); in
> boys, with all IQ scores, TBV and WMV. VIQ was, in turn, correlated with WMV
> and, in boys only, additionally with TBV. _No significant relationships were
> seen in girls_ or with grey matter.

A meta-study that adjusted for maternal IQ only (but not socioeconomic status,
which independently correlates with higher rates of breastfeeding) found a
very small effect on IQ:
[https://www.ncbi.nlm.nih.gov/pubmed/26211556](https://www.ncbi.nlm.nih.gov/pubmed/26211556)

> We included 17 studies with 18 estimates of the relationship between
> breastfeeding and performance in intelligence tests. In a random-effects
> model, breastfed subjects achieved a higher IQ [mean difference: 3.44 points
> (95% confidence interval: 2.30; 4.58)]. We found no evidence of publication
> bias. _Studies that controlled for maternal IQ showed a smaller benefit from
> breastfeeding [mean difference 2.62 points_ (95% confidence interval: 1.25;
> 3.98)]. In the meta-regression, none of the study characteristics explained
> the heterogeneity among the studies.

~~~
alexandercrohde
You're oversimplifying this.

Current status: Breastmilk-IQ relationship inconclusive and hotly contested
(Breastmilk-health status understood and strongly favorable)

You provided a link to a meta-study from 2013, but 44 articles cite that
article many do not agree.

~~~
rayiner
> Current status: Breastmilk-IQ relationship inconclusive and hotly contested
> (Breastmilk-health status understood and strongly favorable)

Source?

~~~
alexandercrohde
"Both exclusivity and duration are important, because dose response is well
established for breast milk benefits.3–5" [1]

So the author cites findings that how-long you breastfeed for or amount of
breastfeeding you do has an effect (e.g. once a day vs twice a day) that's a
big unexplained phenomenon (which could NOT be explained by maternal IQ, SES,
etc).

To quote this author's interpretation of the literature "Although the topic is
controversial, and a recent systematic review identified heterogeneity between
studies, among the 4 studies with the least bias (each >500 subjects,
controlled for maternal IQ, breastfeeding recall duration <3 years)
breastfeeding improved performance on IQ testing by 1.76 points (95%
confidence interval, 0.25–3.26), suggesting a small but durable impact of
breastfeeding on intelligence.10"

(Again 2017, fully aware of the difficulty of controlling [1])

Now does this case-closed prove breastmilk bumps IQ? No, it proves my original
claim that this is hotly contested.

1\. Breastfeeding: What Do We Know, and Where Do We Go From Here?

~~~
rayiner
> So the author cites findings that how-long you breastfeed for or amount of
> breastfeeding you do has an effect (e.g. once a day vs twice a day) that's a
> big unexplained phenomenon (which could NOT be explained by maternal IQ,
> SES, etc).

It could be explained by maternal IQ and SES, _e.g._ if higher IQ mothers were
more likely to stick to optimal breastfeeding practices.

> Now does this case-closed prove breastmilk bumps IQ? No, it proves my
> original claim that this is hotly contested.

That may well be true, but the fact that the issue is "hotly contested" after
decades of research is telling. If the effect was significant (practically,
rather than statistically), you'd expect it to be pretty well established
after decades of research. Instead, in properly controlled studies and meta-
analyses, even where the effect exists, it is small (1.76 IQ points in your
example, 2.62 in a study by Horta).

------
all_usernames
There are at this time 112 comments on this page. I searched for "emotion" and
got zero hits, and only one comment mentioned "bonding." A problem with any
scientific assessment of the human condition is the narrow focus, and these
studies only take into account a few variables out of thousands.

Emotional bonding between mother and child is a huge factor in breastfeeding
-- that's common sense that doesn't require scientific validation, although it
would be very interesting to see studies from that perspective.

~~~
rayiner
I'd call it handwaving rather than common sense. What does emotional bonding
even mean? Are bottle fed children more emotionally distant and less clingy?
Remember: in the 1970s, only 25% of children were _ever_ breastfed. Are Gen
X-ers emotionally distant compared to boomers and millenials?

~~~
watwut
I recall articles that say that current teenagers and young adults have closer
relationships with their parents then previous generation. However, much more
changed in the child raising then just breastfeeding.

------
sbenitoj
What's amazing is that people even feel the need to study whether breastmilk
is superior to processed alternatives -- would a zoologist ever recommend baby
mammals receive any food other than their mother's milk to facilitate optimal
development? Why do humans think they're any different?

~~~
rayiner
Breastfeeding makes it harder for women to escape traditional gender roles at
home (dads can get up in the middle of the night to feed the baby a bottle,
but can't breastfeed; pumping isn't much easier than just breastfeeding). It
also makes it more difficult when mothers return to work. It's also just
inconvenient and unpleasant for a lot of women.

Obviously, before anyone makes that sacrifice, it makes a lot of sense to
study whether it has any corresponding benefits.

~~~
turk183
Being someone's mother is probably humanity's most important "gender role" and
not something people should be trying to escape from.

~~~
rayiner
If it were so great men would want to do it, instead of just telling women how
great and important it is.

~~~
tree_of_item
How in the world is a man going to be someone's mother?

~~~
rayiner
Men can do almost everything associated with the traditional gender role of
motherhood, save gestation and breastfeeding. And if any man actually wanted
to do those things, we'd be working on the technology I'm sure.

~~~
tree_of_item
I'm not sure what your point is. Men already become parents all the time. And
it's true that motherhood and fatherhood are very important jobs that
collectively we really should not be trying to "escape" from. I'm pretty sure
the whole point of the push for paternity leave is to let people embrace these
roles rather than run away from them.

~~~
rayiner
We're not talking about parenthood in the abstract, but rather traditional
gender roles. _I.e._ where it's the woman that gestates and breastfeeds the
baby, and then stays at home and takes care of it. Women have been
aggressively trying to escape that gender role ever since we made it possible
for them to do so. The vast majority of mothers work, women have far fewer
kids than before, etc. Men, meanwhile, have not rushed to take on those
supposedly wonderful and fulfilling duties.[1]

We can conclude from these observations that the traditional female gender
role isn't all that great, and that there is a lot of value in technology (for
now, formula, but soon, artificial wombs) that reduce the need for anyone to
do that work.

[1] There is an increased push for paternity leave because dads want to spend
more time with their newborns, which is different from wanting to embrace
traditional female duties. And a huge part of that push is to set the stage
for women to escape their traditional gender role. Dad being more involved
from the beginning means that, in the long term, it will be easier for dad and
mom to share child-rearing duties. It's harder to do that when, _e.g._ the
child reflexively runs to mom any time it needs something.

------
colordrops
It's funny to me that everyone shits on Soylent and how obviously bad it is
and yet needs a PhD to figure out if they should breastfeed instead of giving
their newborn "formula". Have any of you looked at the ingredients in formula?
It's garbage.

~~~
logfromblammo
Even George Costanza knows it's okay to eat garbage _if it 's on top_.~

People in general are way too picky about what they shove down their gullets.
It's just chemicals, and the chemicals in formula are close enough to natural
milk that it won't kill fragile human babies. Likewise, the chemicals in
Soylent are close enough to food that you can quaff it in lieu of eating.

The only problem is determining which chemicals are actually _important_ ,
which is somewhat difficult, because yadda yadda yadda unethical human
experimentation....

But that wire-mom vs. cloth-mom monkey experiment should also suggest that
there's more to breastfeeding than just _nutrition_.

------
eli
Sightly offtopic, but recent or prospective parents on HN may appreciate the
book "Expecting Better" by Emily Oster, which takes a critical economists eye
to advice and studies about pregnancy. Sort of in the vein of Freakonomics.

------
mkempe
Apart from claims of positive IQ impact, breastfeeding has many other proven
benefits (as widely reported by WHO and in Sweden): "Breastfed children are at
a lower risk of infections such as acute otitis, gastroenteritis, and
respiratory tract infections. ... Women who have breastfed also receive health
benefits through a somewhat reduced risk of developing breast and ovarian
cancer and diabetes type 2."

------
cerealbad
to all expectant mothers nervous about whether you should breast feed or not,
it's definitely a huge and important decision, so i have devised an experiment
you can undertake right now to try to gather more data so you can make an
informed decision.

ask your husband* to suck your nipple then gauge reaction, offer a favorite
bottle as an alternative just to be sure.

*results may be vary based on husband iq.

------
d--b
Seriously, stats on 26 boys...

------
epx
Well, I had none of this breast milk stuff, poor me!!

~~~
coldtea
And who said it didn't have an impact?

