The recent breastfeeding/IQ study: I've read it, which is more than some journalists have done. Anyone want to hear what the study actually says?

[welliemum]

I'm treading on tamum's toes here a bit - she's a Proper Geneticist and I'm not.

However.. I do have a bit of practice at reading papers.

First of all, here's the abstract. The full article needs subscriber access unfortunately.

Main finding: In the populations they examined, they found 2 versions of a particular section of a gene. For children with the (commoner) C version, breastfed children had significantly higher IQ scores. For children with just the G version, breastfeeding didn't correlate with IQ.

Can we be sure this is a true effect?
The researchers were very careful on this point. They ruled out:

1. confounding by social class
2. confounding by mother's IQ
3. the gene affecting whether a baby breastfeeds
4. whether the mum's genetic profile affected the baby's growth and hence development

... and several other more technical points.

I think it's a very good study. The researchers have been very careful to exclude other explanations for their findings, and are only claiming results that are well-supported by evidence. No wild claims here.

IMO the study is convincing in a number of ways:

1. the gene cluster in question has a strong link to both intelligence and breastfeeding (via fatty acids) - ie biological plausibility
2. the study methods are sound as mentioned above
3. it can explain why previous studies on bf and intelligence have had conflicting findings (the effect would depend on each population's genetic profile and this wasn't measured).
4. the fact that they studied 2 populations half a world apart and found a consistent effect is very significant. (Repeatability is a big pitfall in this type of genetic study)
5. er, and another one which I now can't remember

It's a pity though, that they couldn't measure how long the babies were bf for. If they showed a great effect for longer bf, that would be additionally convincing; and more detail would also be hugely helpful for women unsure how long to bf for.

One of these populations was a birth cohort from NZ in the 70s. Only 57% were bf, and they would have had a very short duration of bf. No 6 month exclusive bf in those days. This suggests to me that even a little bf can have a big effect.

Tamum or anyone - what do you think?

I think it's great to have the source of a news story explained like this rather than reduced to a soundbite.

Thanks for treating us like grownups Welliemum

Thanks for this welliemum

thanks for that
FYI, I can't get into the abstract - takes me into the logon page) ...

I'm just waiting for tamum to come on now and laugh at my kindergarten genetics knowledge...

Seriously though, the "oh, it's only research" lobby really gets up my nose.

Better understanding of the benefits of breastfeeding can help us make more informed decisions - including the decision not to bf.

Abstract

Sorry about link. Here's the abstract which is free to all.

Published online before print November 5, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0704292104

PSYCHOLOGY
Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism

Avshalom Caspi,,, Benjamin Williams, Julia Kim-Cohen, Ian W. Craig, Barry J. Milne, Richie Poulton¶, Leonard C. Schalkwyk, Alan Taylor, Helen Werts, and Terrie E. Moffitt,

Abstract

Children's intellectual development is influenced by both genetic inheritance and environmental experiences. Breastfeeding is one of the earliest such postnatal experiences. Breastfed children attain higher IQ scores than children not fed breast milk, presumably because of the fatty acids uniquely available in breast milk. Here we show that the association between breastfeeding and IQ is moderated by a genetic variant in FADS2, a gene involved in the genetic control of fatty acid pathways. We confirmed this gene?environment interaction in two birth cohorts, and we ruled out alternative explanations of the finding involving gene?exposure correlation, intrauterine growth, social class, and maternal cognitive ability, as well as maternal genotype effects on breastfeeding and breast milk. The finding shows that environmental exposures can be used to uncover novel candidate genes in complex phenotypes. It also shows that genes may work via the environment to shape the IQ, helping to close the nature versus nurture debate.

That's a great study welliemum. I agree, I would be amazed if there weren't lots of mixed feeders and short term breastfeeders in there too. The only other thing (probably only of interest to geneticists ) is that they looked at two separate variants in the gene that spanned the whole thing, and got equally significant results with both of them.

A great summary I meant to say, sorry. I am tired

thanks - very informative

Thanks Welliemum!

(As an aside - I have a cousin in Wellington who's a very very brainy doctor lady. I just had myself a little moment there where I thought for a second you were her. Coz, like, there's probably only one brainy medical-research-paper-reading lady in Wellington, yaknow...)

Can't be me, vlc - since having children I just have pumpkin pips where my brain used to be... Wellington is full of brainy doctor ladies but sadly, I'm not one of them....

Shame...though that would have been very weird to bump online into a rellie like that!

Brilliant stuff, Welliemum.

You might want to post it on Alphamummy - Sarah Vine needs something to read in between ranting wildly, I think...

I've been a bit rude to Sarah Vine on alphamummy, but er, she started it.

Actually, I think she's just so cross that she's not to be reasoned with.

This study is making me wonder whether other controversial bf effects might be working the same way, eg allergies.

Studies looking at the effect of bf on allergy produce wildly different results.

Maybe it depends on a baby's genes, ie some babies are protected from allergies by bf and others aren't. If you lump them all together in a study you won't get a clear result.

Would be interesting to look at, although I think the genetic and environmental triggers of allergy are so complicated that it would be hard to decide which gene/s to look at and which environmental factors to control for.

But it's an interesting idea.

I havn't read teh paper, although I might download it at work for a bit of evening reading as much from a geeky genticist POV...I love a bit of polymorphism analysis

Hi welliemum, I think there's little doubt that that's the case- my overwhelming impression nowadays is that epidemiology of almost anything will be confounded by genetic susceptibility variants. Contradictory studies that were well planned and executed are almost certainly contradictory because of genetic background variation, I would guess. Lots of genes are now being found for complex diseases in a similar way, because people have realised that they need vast, vast sample sizes to be able to detect anything real over a background of noise. So I bet you're right!

I wonder if, one day in the far future, a mum who's struggling to bf will be able to test for an array of polymorphisms.

The results would show her what the risks (for various things) might be for her baby if she stops bf. She could then decide whether the risks are acceptable in the context of her own circumstances.

Of, course, with that level of technology and knowledge available, the problem of wanting to bf and struggling might be easily sorted out so the genetic aspects would be irrelevant. [optimist]

LOL at SMS's idea of light evening reading

welliemum - you're right that it sounds like a good study, but the thing about good studies is that they often only measure a very small thing. in this case, we discover the bleeding obvious that not everyone gets the same benefit from breastfeeding.

I wonder if they'll develop tests for this gene. so people can use it whether it's worth them breastfeeding or not?

SP, I don't think this was bleeding obvious, I think it was quite dramatic to be honest.

Fio, yes of course sweetie, will go and look.

SP,
I wonder if they'll develop tests for this gene. so people can use it whether it's worth them breastfeeding or not?
that would only be relevant if this was the only benefit of bf.