
How the Gut Affects Mood - sndean
http://fivethirtyeight.com/features/gut-week-gut-brain-axis-can-fixing-my-stomach-fix-me/
======
godzillabrennus
The research going into the gut these days is going to make for some
incredible advancements. A research doctor I respect told me that he suspects
we have more connectivity between our stomachs and our brains than anyone
really realizes. So much of who we are and what we do is centered around how
we take in fuel.

Some good news this week for folks who have GERD, or chronic acid reflux, they
discovered the cause: [http://www.foxnews.com/health/2016/05/17/researchers-
discove...](http://www.foxnews.com/health/2016/05/17/researchers-discover-
actual-cause-gerd.html)

~~~
TheSpiceIsLife
I'm not sure I follow how a cytokine can be a cause.

Cytokines are, generally, cell signalling molecules. In the case of GERD, if I
understand the process correctly, these cytokines are instructing the tissue
of the esophagus, and associated immune system cells, to initiate the
inflammatory response.

Inflammatory responses in mucosal tissues typically include an increase in
mucous production, which is the body's attempt to protect the tissue from the
refluxed stomach acid.

So it follows that the first tissue changes you should expect to see are
inflammation and increase mucous production as the body tries to protect
itself from exposure to stomach acid.

This doesn't mean the cytokines _cause_ the inflammation, nor that they
_cause_ acid reflux, they're just the cell signalling molecule that initiates
the inflammatory response, released in response to increased acidity on the
tissue surfaces, released long before gross changes occur as a result of acid
damage.

If we give medicines to dampen the cytokine release, or dampen the
inflammatory response to the cytokines, thereby reducing the inflammation,
that doesn't mean the tissue won't be damaged by the acid reflux - if
anything, down-regulating the normal inflammatory immune response will
_worsen_ the damage caused by the acid.

The question is: what is _causing_ the acid reflux?

~~~
DavidSJ
If A results in B being taken as a preventative measure (to stop Q), and then
C occurs as a result of that preventative measure, then the causal graph looks
like A->B->C.

That is, both A and B can be said to cause C, in the standard counterfactual
sense of the word "cause": if you hold everything but X constant, and add more
X, and more Y occurs, then X causes Y.

That doesn't mean you shouldn't _do_ B. If Q is worse than C, it's still a
good choice. But it does cause C.

------
entee
This article gives a great overview of a fascinating field, and does so fairly
responsibly, which is unusual in the popular press.

From the end:

'“Too many large-scale, spurious claims are being made,” Dinan said, mostly by
people with something to sell. Although we have “very good data” from animal
studies, he said, there’s nothing that could be described as solid clinical
data linking the gut microbiome to depression or anxiety in people.'

This research is super exciting. It's also super new. The technology for
sequencing gut bacteria on a large scale has only been around in a real sense
for about 10 years, and only been affordable for about 3-5. We'll get there,
and almost certainly gut flora matters massively for all sorts of biology, but
it's important to temper excitable headlines.

~~~
sndean
> Although we have “very good data” from animal studies...

This is a pretty important thing to keep in mind. There are a lot of studies
that I've seen, extending connections to humans from mice [1], even though
understanding of the suitability of these mouse models has just recently (or
hasn't) been studied [2].

So... "In humans, the data are more limited. Researchers have drawn links
between gastrointestinal pathology and psychiatric neurological conditions
such as anxiety, depression, autism, schizophrenia and neurodegenerative
disorders — but they are just links." [3]

[1]
[http://www.sciencedirect.com/science/article/pii/S0092867415...](http://www.sciencedirect.com/science/article/pii/S0092867415003530)
[2]
[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427216/](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427216/)
[3] [http://www.nature.com/news/the-tantalizing-links-between-
gut...](http://www.nature.com/news/the-tantalizing-links-between-gut-microbes-
and-the-brain-1.18557)

~~~
entee
Absolutely. Humans aren't mice. That doesn't mean mouse studies aren't
enormously helpful, but it does mean that we should take things with a grain
of salt. The complexity of even a mouse is pretty enormous, and humans are
that much more confusing.

As for gut to brain transmission, the first thing that comes to mind is being
hangry but that's probably a different thing :)

~~~
rixed
Why would human guts be that much more confusing than nice guts?

~~~
tremon
For one, we have twice the number of bacterial species. But it seems more
important to me that only 4% of the microbiome is shared between humans and
mice.

[http://www.nature.com/nbt/journal/v33/n10/full/nbt.3353.html](http://www.nature.com/nbt/journal/v33/n10/full/nbt.3353.html)

~~~
rixed
That second argument does not imply that humans are more confusing than mice,
just different.

My reaction was only against the apparently underlying assumption that humans,
biologically, are more complex than mice, a remain of the idea that they are
more evolved or a biased perspective due to the fact we study them in more
detail.

------
milesvp
This field feels like it's starting to blow up. I'm seeing lots of studies
dealing with gut microbiomes. And from talking to a lab developer I know, it
seems like this is largely because computing has become super cheap (think
AWS), and the tools have become very power and simple to use (think Pandas and
Numpy). He was saying that it's become very easy to find patterns in bigger
and bigger sets of sequencing data, that previously would have been
inscrutable.

It's not necessarily neurological in nature, but one of my favorite papers in
the field in the last couple years shows a potential causal relationship
between obesity and gut biomes by using artificial sweetener and a fecal
transplant in mice.

Paywalled version in nature:
[http://www.nature.com/nature/journal/vaop/ncurrent/full/natu...](http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13793.html)

Unpaywalled version after googling: [http://www.drperlmutter.com/wp-
content/uploads/2014/09/Artif...](http://www.drperlmutter.com/wp-
content/uploads/2014/09/Artificial-Sweeteners.pdf)

------
fezz
Lactobacillus Rhamnosis - supposedly stimulates the nerve in the gut that then
triggers GABA production.

[http://www.ncbi.nlm.nih.gov/pubmed/21876150](http://www.ncbi.nlm.nih.gov/pubmed/21876150)

I get it here: [http://www.customprobiotics.com/custom-probiotics-l-
rhamnosu...](http://www.customprobiotics.com/custom-probiotics-l-
rhamnosus.htm)

~~~
amelius
Interesting.

As I understand the anxiolytic effects, it is all about a proper balance
between glutamate and GABA [1].

Some people get really stressed out when they eat too much glutamate-
containing foods. So, perhaps probiotics can help address the glutamate too
(?)

Note: some warnings here: [2] (some bacteria produce glutamate!)

[1] [http://www.holistichelp.net/blog/how-to-increase-gaba-and-
ba...](http://www.holistichelp.net/blog/how-to-increase-gaba-and-balance-
glutamate/)

[2] [http://forums.phoenixrising.me/index.php?threads/why-
probiot...](http://forums.phoenixrising.me/index.php?threads/why-probiotics-
can-be-harmful-amines.4536/)

------
ricksplat
One of the most mind-blowing things I learned about when studying psychology
was the theory of distributed consciousness. Basically it goes along the lines
that though most of our neural matter is in the head (i.e. brain) there are
pockets of it here and there throughout the body. For instance in each of the
sections of the spine - highly trained movements are coordinated between
these. They are signalled by the brain but motor control can happen largely
independently.

One thing that stood out is that the highest concentration of this neural
matter is in the stomach. Your stomach does have access to _some_ information
about the outside world: Bass sounds, orientation, and proprioceptive
activities. But it is largely ignorant of the outside world because it doesn't
have access to the main senses the way the brain does. This sits nicely with
the "gut feel" lore, where your stomach is uneasy about something though your
brain says things should be fine. Your stomach can't be fooled by your senses.

------
roadnottaken
From the article: "there’s nothing that could be described as solid clinical
data linking the gut microbiome to depression or anxiety in people"

------
allisthemoist
I went to a conference recently where an MD/researcher in this field discussed
the latest state of the art findings.

[https://www.youtube.com/watch?v=83u-i73ppr8](https://www.youtube.com/watch?v=83u-i73ppr8)

Long story short, the gut-brain axis is a compelling area of study, but based
on the fact that nearly all studies have been in murine models coupled with
the relative paucity of human trials, the jury in the medical community is
still largely out.

------
xufi
This would be pretty interesting.Considering I'm studying Psychology a bit,
this would really be a field to look at. How does it affect whether a user
wants to visit a certain section of a site more or not or how does this
ultimately affect the development of the GUi in the long run?

------
smac8
Does anyone know any good companies working on technology that identifies and
categorizes aspects of the gut microbiome? This is a field I'd be very
interested in getting into

------
khrm
Remind me of this :
[https://www.youtube.com/watch?v=0Rnq1NpHdmw](https://www.youtube.com/watch?v=0Rnq1NpHdmw)

------
linhchi
I clearly have the mood affecting gut. If i have a sinking feeling in my chest
(a devastated one), i immediately have a painful reaction in the bowel (or the
gut).

------
B1FF_PSUVM
"No guts, no glory" does take on a new meaning ...

------
jakub_g
Accidentally downvoted you on my phone, sorry.

~~~
dang
We detached this subthread from
[https://news.ycombinator.com/item?id=11732322](https://news.ycombinator.com/item?id=11732322)
and marked it off-topic.

~~~
nxzero
If this was detached, why is it still viewable on the thread?

~~~
dang
Detached just means we made it be a top-level comment as opposed to a reply to
another comment.

------
skilled
Interesting, this answers my question on the last post. It seems that there's
still a while to go before we understand the interaction of probiotics and
general health.

