
Boys and Girls may get different breast milk - crassus
http://www.scientificamerican.com/article.cfm?id=boys-and-girls-may-get-different-breast-milk
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gmuslera
Is not just "food" what is passed with breast milk, also beneficial bacterias
[http://www.sciencedaily.com/releases/2012/04/120429234641.ht...](http://www.sciencedaily.com/releases/2012/04/120429234641.htm)
Not sure how that regulates itself regarding sex, age or health of the child,
but seems that it happens.

~~~
brosco45
Also, immunogoblins and other stuff we do not know.

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cup
It raises the question not just about twins but also about wet nurses. I mean
its a pretty normal tradition for mothers to 'outsource' their breast feeding
to other mothers, especially if they're tired or sick.

Also what about formula milk?

~~~
rayiner
What about formula milk? The long term benefits of breast feeding are so
tenuous that I can't imagine there's a practical significance to the
difference between breast milk produced for girls versus boys in human babies:
[http://www.skepticalob.com/2013/05/world-health-
organization...](http://www.skepticalob.com/2013/05/world-health-organization-
no-long-term-benefits-to-breastfeeding.html).

Studies like these are valuable, but it's tempting to jump from interesting
observation to policy recommendation without keeping in perspective (or even
bothering to quantify) the magnitude of the impact.

An excellent blog post on the state of research into breast feeding:
[http://www.skepticalob.com/2013/06/two-crappy-new-
breastfeed...](http://www.skepticalob.com/2013/06/two-crappy-new-
breastfeeding-studies-make-irresponsible-claims-of-benefits.html)

~~~
maratd
> The long term benefits of breast feeding are so tenuous

This is a joke, right?

Simple reasoning and deduction will lead you to the right answer. We evolved
to drink the milk of our mothers, not a chemical concoction derived from the
milk of cows fed by corn.

~~~
wikwocket
We also evolved with immune systems. This does not mean that supplementary
tools such as antibiotics and vaccines are not useful.

I believe rayiner's point is that infants can thrive on formula milk as well
as breast milk. Please don't mock parents who choose to formula feed; there
are many cases where it is preferable and/or necessary, just as there are
cases where it is necessary to use antibiotics to supplement the body's immune
system.

~~~
maratd
> Please don't mock parents who choose to formula feed; there are many cases
> where it is preferable and/or necessary

And where have I done that? Formula is a fantastic invention that can
specifically assist in very difficult situations.

But just as it is clearly inferior to take antibiotics daily because it is too
inconvenient to wash one's hands ... so to is it clearly inferior to use
formula when the mother is capable of breastfeeding, but can't be bothered.

~~~
mistermann
While I can certainly see the downsides of abusing antibiotics, I don't
"clearly" see comparable downsides, in likelihood or magnitude, to using
formula.

~~~
emiliobumachar
Formula lacks the live immune system cells the mother passes to the baby.
Maybe someday we will develop nanobots to substitute for that. Till then,
that's a clear downside.

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nappy-doo
I have nothing constructive to say about the article, but for the record:
gender is chosen, sex is not. I wish the world would get this right,
especially Scientific American, which got it wrong in the second sentence.

Here's an interesting link:
[https://books.google.com/ngrams/graph?content=gender%2C+sex&...](https://books.google.com/ngrams/graph?content=gender%2C+sex&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cgender%3B%2Cc0%3B.t1%3B%2Csex%3B%2Cc0)

~~~
crazygringo
The world doesn't seem to agree with you. Straight from Wikipedia [1]:

 _Gender is the range of physical, biological, mental and behavioral
characteristics pertaining to, and differentiating between, masculinity and
femininity. Depending on the context, the term may refer to biological sex
(i.e. the state of being male, female or intersex), sex-based social
structures (including gender roles and other social roles), or gender
identity. ... the meaning of gender has undergone a usage shift to include sex
or even to replace the latter word. .... Gender is now commonly used even to
refer to the physiology of non-human animals, without any implication of
social gender roles._

[1] [http://en.wikipedia.org/wiki/Gender](http://en.wikipedia.org/wiki/Gender)

~~~
LesZedCB
From the same article:

>The modern academic sense of the word, in the context of social roles of men
and women, dates from the work of John Money (1955), and was popularized and
developed by the feminist movement from the 1970s onwards (see Feminism theory
and gender studies below). The theory was that human nature is essentially
epicene and social distinctions based on sex are arbitrarily constructed.
Matters pertaining to this theoretical process of social construction were
labelled matters of gender.

I think most places people hear it is that gender is the male/female/other
self-description, and sex is the physiological state.

~~~
gnarbarian
Most transgender social justice warriors or gender studies majors maybe. Not
most people in general.

The vast majority of the people out there don't distinguish between gender and
sex. Especially since only about 0.5% of the population identifies as a gender
other than their physical sex.

~~~
icebraining
There's a lot of terminology that the vast majority of people understand
poorly. By itself, that hardly seems a good reason for a (supposedly)
scientific magazine, particularly when using 'sex' exclusively would
understood by everyone.

~~~
gnarbarian
It probably comes down to the fact that the people practicing physical "hard"
sciences do not particularly care about or trust the conclusions drawn by the
"softer" sciences (sociology, gender studies, psychology)

~~~
icebraining
Maybe so, but the person writing this article isn't a practitioner of hard
sciences, she's a journalist.

~~~
gnarbarian
A journalist for a magazine focused on presenting hard sciences to the masses.

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drpgq
How does the mother's body know the sex of the child? Is it detected somehow
during the pregnancy and if so where is this information kept?

~~~
tantalor
Male fetal DNA is found in the brains of mothers.

[http://www.latimes.com/health/boostershots/la-heb-women-
brai...](http://www.latimes.com/health/boostershots/la-heb-women-brain-
microchimerism-20120926,0,6446716.story)

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mooism2
What if the mother is feeding a pair of non-identical twins (a boy and a
girl)?

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AmVess
One discrete tit for each tot? Beyond that, who knows. I'd love to see this
phrase turn up in an academic journal somewhere.

~~~
jacalata
But they don't do that.

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nicholas73
I don't think the mechanism is a direct biological signaling of the baby's sex
to tell the woman to produce fattier milk. It seems more plausible to me that
wealthier families value boys a lot more - you see this tendency everywhere.
This causes mothers to value their male children disproportionately, and the
social feedback she gets probably affects her hormones as well, which would
cause the milk to vary. So you see the large difference in wealthier women's
milk for boys and girls, whereas the difference in poorer women's milk may not
even be statistically significant.

I think if you repeat this test on different circumstances where the child is
valued or not, whether boy or girl, you will find similar results that remove
the sex factor.

~~~
wutbrodo
Surely the cultural explanation doesn't extend to similar behavior found in
grey seals, red deer, and rhesus macaques? Convergent evolution is always a
possibility but it seems like the likelihood lies with a biological
explanation vs a cultural one.

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haversine
"These findings could have implications for formula, which could be tweaked to
optimize development for both boys and girls."

As the father of a little girl, I find this sentence more ominous than was
probably intended. The formula aisle is already overly complex with Regular,
Iron Enriched, Omega Enriched, Soy, Low-Lactose, and No Lactose, among the
many yogurt sounding ones (pre/macro/post/whatever-biotic).

However, I am worried (perhaps due to cynicism) that instead of rationally
simplifying this system, it might be dumbed down to Boy and Girl formula.
Though I guess there may be benefits as well. _sigh_ \- glad I'll probably be
done having kids by then :D

~~~
jonah
Keep away from the formula aisle if at all possible!

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Nursie
Will the patriarchy stop at nothing to keep women down?!

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ohwp
Why do you think this article is about keeping women down?

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Nursie
I don't. I was being flippant.

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TazeTSchnitzel
> researchers have found that milk composition changes depending on the
> infant's gender

Sex. Infant's sex. Gender is rarely known at that stage.

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1humanwoman
I posted on this story and the issues it raises here:
[http://humanwithuterus.wordpress.com/2013/12/18/gendered-
bre...](http://humanwithuterus.wordpress.com/2013/12/18/gendered-breast-milk/)

Would love your thoughts!

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gweinberg
If this result is valid, it's probably also true for other mammals that bear
young one at a time. If so, it's proabably a lot easier to verify in cows than
humans. Less paperwork required for experiments, for one thing.

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vwinsyee
From the article: _" These findings, published in the American Journal of
Physical Anthropology in September, echo previous work that showed milk
composition varying with infant gender in gray seals and red deer and with
infant gender and the mother's condition in rhesus macaques."_

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grandinj
Well duh. All babys get different breast milk. There is a feedback loop
between the child and the mother that modifies the milk on an ongoing basis.

~~~
jacalata
I've never heard anything like that, odd they don't mention it in the article.
Got any intro-level references? How does it work?

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beat
My wife breastfed our boy/girl twins. I wonder where that fits in?

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timini
What about twins?

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kimonos
Wow! Great info!

