
Changing gut bacteria through diet affects brain function - georgecmu
http://newsroom.ucla.edu/portal/ucla/changing-gut-bacteria-through-245617.aspx
======
gojomo
Only 36 people in 3 groups of 12. Changes visible in fMRI but not (from the
writeup) obviously in any direction of better/worse. Study funded by Danone
yoghurt company.

Diet surely affects cognition and microbiome, and microbiome also affects
health and cognition. But this is some pretty thin support for anything
interesting.

~~~
Volpe
It seemed they noticed people who had healthier gut (i.e took probiotics) had
less activity in the part of the brain that processes internal sensations....
right, so stomach aches hurt, and not having them doesn't. *

* I think I'm being a bit too cynical...

~~~
pygy_
Where did you read that they had observed a reduction of abdominal sensations
in the probiotics group?

It is not mentioned in the press release, but I would be surprised if they had
not assessed this.

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pygy_
The skepticism shown in other comments is healthy but IMO misinformed and/or
misguided.

This study confirms past results such as [0], which shows that adding some
_Lactobacillus rhamnosus_ to the diet of mice modifies the expression of GABA
receptors (the ones sensitive to bnezodiazepines, like Xanax), and reduces
their anxiety (which can be assessed reliably). The effect is mediated by the
vagus nerve. If the nerve is cut, the effect disappears.

In the same vein, [1] found that the pulmonary exposure to _Mycobacterium
vaccae_ promotes the growth of serotonin and norepinephin neurons in the brain
of mice and makes them "less resigned" [2].

I'm sure there are plenty of similar results.

The sample is relatively small, but not inappropriate for a fMRI study. There
are statistical tools adapted for these situations like SPM [3], provided they
are used properly (and I wouldn't be able to assess whether or not they were).

-

[0]
[http://www.pnas.org/content/108/38/16050](http://www.pnas.org/content/108/38/16050)

[1]
[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1868963/](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1868963/)

[2]
[http://en.wikipedia.org/wiki/Behavioural_despair_test](http://en.wikipedia.org/wiki/Behavioural_despair_test)

[3] [http://www.fil.ion.ucl.ac.uk/spm/](http://www.fil.ion.ucl.ac.uk/spm/)

~~~
robbiep
That's really interesting, thanks for sharing.

As an aside, why did you choose to use cardinal numbering rather than what I
certainly would have reached for first (pun intended)?

Back on point, I can't see anywhere in [1] that 5-ht neurons grow, rather they
just seem to be more active. Fascinating that this happens as a response to
increased antigen load to something they have been immunised against. We
really are a product of so many hidden interactions with our environment

~~~
pygy_
Formally, ordinals start at zero too :-) [0]. We owe their latest definition
to Von Neumann, but AFAIK, the former definitions were similar.

Regarding 5-ht, I quoted from memory, which was apparently fuzzy... But is is
indeed fascinating.

\--

[0] This is meta-meta-contrarianism.

\- The layman counts from 1

\- The uptight programmer counts from zero, because Dijkstra said so (or so he
thinks).

\- The meta-contrarian (I used to be one) says fuck it, ordinals start at one.

\- The meta-meta-contrarian reads Wikipedia[1], realizes he was formally
wrong, and goes one step further in pedanticity, back to zero [0].

That being said, my brain prefers 1-indexing programming languages like Lua,
Julia, R and Matlab...

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

[0] Help! I'm stuck in a Boolean algebra[1][0]!

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

[0] ... where xor is an addition that wraps around ...

~~~
robbiep
Thanks for the entertainment!

~~~
pygy_
You're welcome!

------
ars
> The women who ate no product at all, on the other hand, showed greater
> connectivity of the periaqueductal grey to emotion- and sensation-related
> regions, while the group consuming the non-probiotic dairy product showed
> results in between.

So basically the probiotics had nothing to do with it, and it was actually the
dairy product? Or something else entirely? Lactic acid? Who knows.

If it was the probiotics why would consuming the non-probiotic have any effect
whatsoever? The fact that it did shows that this study is not studying what it
thinks it is studying.

Props for including a good set of control groups, but un-props for the
interpretation.

~~~
johnchristopher
> So basically the probiotics had nothing to do with it, and it was actually
> the dairy product? Or something else entirely? Lactic acid? Who knows.

Lactic acid as in "lactic acid that builds up in muscles and makes one's legs
hurt when running fast for a long period of time"

~~~
yareally
Or lactic acid, as in what is found in dairy products. Though that would make
saying dairy product and lactic acid sort of redundant (outside of being more
specific). Same lactic acid though in either case, just how it manifests
itself in the body.

[https://en.wikipedia.org/wiki/Lactic_acid](https://en.wikipedia.org/wiki/Lactic_acid)

~~~
johnchristopher
The NSA ate my question mark :]

Thanks for clarification, I am now surfing Wikipedia on a sunny Sunday
morning.

~~~
ars
And note especially this:
[https://en.wikipedia.org/wiki/Lactic_acid#Brain_metabolism](https://en.wikipedia.org/wiki/Lactic_acid#Brain_metabolism)

Which is quite relevant to this study.

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danmaz74
If I had to guess, this could be related to our internal feedback loops
mechanisms. Many emotions create peculiar sensations in our guts - that is an
experience we all have - and those sensations are nothing else than signals to
the brain.

It isn't a stretch of the imagination to think that the status of our guts
could amplify or dampen the sensations, and thus the feedback to our brain of
our emotions, especially the feedback to our conscious mind: If I remember
correctly from my studies in psychology, we actually feel our own emotions
mostly as physical reactions.

------
Avshalom
Has anything ever been shown to not affect brain function.

~~~
mixedbit
Consider x a distance between a place where an event took place at time t1 and
a brain. At time t2, if x is larger than c * (t2 - t1), it for sure does not
affect the brain.

~~~
damncabbage
Sure. Except then you need to define c. Back to square one.

~~~
danshapiro
c is commonly used to represent the speed of light[1]. The commenter was
saying that an action sufficiently far away cannot affect you immediately,
because the information of that action's occurrence cannot move faster than
light. I believe this is generally regarded as true by physicists, although
there are some ideas for circumventing this limitation.

I think they were making a joke.

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

~~~
damncabbage
Thanks. :-)

(I thought "speed of light" at first, but didn't think of a way it could be
applicable.)

