
Fermented foods, neuroticism, and social anxiety: An interaction model - nyodeneD
http://www.ncbi.nlm.nih.gov/pubmed/25998000
======
batbomb
If you are curious about the foods:

> To determine participants׳ consumption of foods, they were first asked to
> think of their food intake over the past 30 days (see Appendix). This was
> followed by a list of 10 items consisting of the following: 1.fruits and
> vegetables of all kinds, including fresh, canned, frozen, cooked, raw, and
> juices; 2. yogurt, 3. kefir, or food or beverages that contain yogurt; 4.
> soy milk, or foods or beverages that contain soy milk; 4. miso soup; 5.
> sauerkraut; 6. dark chocolate; 7. juices that contain microalgae; 8.
> pickles; 9. tempeh; and 10. kimchi. Participants were asked to indicate how
> often they consume each of the foods using the following 7-point scale: 1
> (never); 2 (1–3 times in the past month); 3 (1–3 times per week); 4 (1–3
> times per day); 5 (3–5 times per day); 6 (5–7 times per day); and 7 (more
> than 8 times per day). Scores were converted to monthly frequencies of 0, 2,
> 8, 60, 120, 180, and 240, respectively.

And the Conclusion:

> This study provides the first connection between natural fermented food
> consumption patterns and anxiety. Increased consumption of fermented foods
> likely to contain probiotics was associated with fewer social anxiety
> symptoms. This effect was qualified by an interaction with neuroticism;
> those who were highly neurotic showed fewer symptoms of social anxiety with
> greater consumption of fermented foods. Also of note, increased frequency of
> exercise was associated with decreased social anxiety. Taken together with
> the results of previous preclinical and clinical studies (Rao et al., 2009,
> Silk et al., 2009, Messaoudi et al., 2011 and Tillisch et al., 2013), the
> current results suggest that fermented foods likely to contain probiotics
> may have a protective effect against social anxiety symptoms for those at
> higher genetic risk, as indexed by trait neuroticism. While a follow-up
> prospective cohort study or clinical trial is necessary to determine the
> direction of causality, these results suggest a possible clinical benefit of
> fermented foods, a low-risk intervention, on social anxiety.

~~~
tjradcliffe
Everything about this study says it is not worth taking seriously. Why?
Because...

1) The size of the effect is not reported. Without any indication of what the
dose-response curve is other than it has a positive slope (at what
significance level?) we know nothing about the relevance of this result to
clinical practice.

For example, it is true that if you pay very careful attention to the sidewalk
you will _increase_ the amount of dropped money you find. It's not going to
make anyone rich, though, any more than just any measurable effect is going to
make one less anxious to a useful degree. There is zero indication of how big
the effect is, other than it is measureable in a large population. The lack of
indication of effect size suggests that it is really small.

2) Self-report via recollection is a lousy data collection technique. Was a
food log app really too much trouble? So the raw data are incredibly noisy and
may contain systematic errors that are related to the phenomenon under test.

3) They've subsetted the data by pulling out neuroticism, thereby dramatically
reducing the significance of any result by an unknown amount (how many other
characteristics did they investigate?)

This is the greatest sin. _Any_ time you see a paper that says, "The effect
was particularly large in sub-population X" the first question to ask it, "How
many sub-populations did you look at?" The next question to ask is, "What is
your calculated probability that _any one of_ your sub-populations would have
had such a large effect by chance?" These numbers should be reported in the
abstract because people subset their data all the time and then analyze the
subset that shows an effect as if it was the only one. This is either
incompetence or dishonesty.

Statisical significance rolls off with astonishing speed as you subset the
data, and if you don't have a formal discipline for subsetting as part of the
experiment design that is fixed prior to analysis, any result on a subset is
necessarily insignificant because you could have kept subsetting until you
found a 'significant' result. If you don't have a formal discipline that says,
"We will cut the data in these N ways and only these N ways" you are going
fishing on an infinite ocean, where you will certainly catch the kind of fish
you are looking for.

~~~
batbomb
Oh yes, I agree.

More importantly, food is inherently cultural and varies on class and it might
be that neuroticism/social anxiety does as well. I posted this because I
thought it sounded like a week study with an overly strong conclusion.

~~~
hollerith
>I posted this because I thought it sounded like a [weak] study

Let me see if I understand: you posted (the abstract of) a study you consider
not worth taking seriously so that you could read criticisms of the study by
people who know more than you; is that correct?

If not, then please explain more about your motivation for posting because I'm
a little confused on that point.

~~~
nosefrog
batbomb did not post the paper.

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CodeWriter23
Given the effect probiotics have on one's gut flora, and the newly-discovered
pathway from the gut to the brain via the lymphatic system, this seems to be
in the realm of possibility.

[http://neurosciencenews.com/lymphatic-system-brain-
neurobiol...](http://neurosciencenews.com/lymphatic-system-brain-
neurobiology-2080/)

~~~
et2o
There's already a huge link between the gut and the brain called the vascular
system.

~~~
CodeWriter23
Subject to the brain blood barrier, yes.

------
shalmanese
This is a correlational, not causative study. It's possible there's some third
factor that cause both an increase in eating fermented foods and a decrease in
social anxiety. Amount of free time, for example, or belief in healthy eating,
or vegetarianism, or income. They do try to control for confounding variables
(fruit & vegetable consumption) but there's no way to control for everything.

Let's wait until someone conducts a double blind study before drawing too many
conclusions from this.

~~~
gwern
One nice thing about this claim: it should be easily testable. In fact,
someone could test it themselves; score yourself on a Big Five inventory, if
you're >75% N, make some capsules with probiotics (I believe they come in
powders so this is easy), take them blind, go to a party or other social
interaction, and self-rate how stressed you are.

~~~
0xdeadbeefbabe
Instead of capsules can I make kimchi and eat it for a week? Something that
calls for fish sauce and hot peppers is bound to have some social impact.

~~~
gwern
Unless you know a vegetarian, you may have trouble finding gel capsules
sufficient for a decent dose of kimchi... (Also, now you have to refrigerate
all your capsules.) Easier to just use some probiotic powder stable at room-
temperature unless there's some compelling reason to expect them to be
ineffective.

~~~
reagency
Vegetarian?

~~~
gwern
Er, brain fart. I meant 'veterinarian', so you can get horse pills...

------
rosser
Loosely, kimchi [1] consumption and exercise frequency are both (and
independently) negatively correlated with social anxiety.

[1] As a stand-in for all fermented foods that contain or are likely to
contain probiotics.

~~~
Kopion
Are you pulling from a source for this? Care to link?

~~~
rosser
I'm TL;DR-ing _The Fine Article_.

Scroll up for the link.

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blackbagboys
For those with subject-matter expertise in probiotics: Is buying probiotic
supplements a waste of time and money, and, if not, what are the strains one
should be looking to purchase? Is there any known association between
particular strains and particular effects (such as weight loss, or the
anxiolytic effect described here, etc)?

~~~
et2o
It's mostly a waste. Very difficult to eat enough bacteria to have them
compete with your extant gut flora.

This paper is questionable for other reasons.

~~~
0xdeadbeefbabe
Huh? What about Botulism and the bad E. Coli?

~~~
bcoates
Both Botulism and E. Coli make you sick due to potent toxins produced by the
bacteria, not due to them taking over your gut flora. The bacteria doesn't
even need to be alive to make you sick if it's already colonized your food.

~~~
et2o
Good thoughts! Botulism is caused by a toxin produced by Clostridium
botulinum.

E. coli is a little more complicated: some E. coli spp. produce toxins, and
other species are enteroinvasive and actually can outcompete the gut flora
(confusingly enough, other species of E. coli are also in the normal gut
flora).

The main reason that some species of E. coli can make it to your gut and cause
disease are that they have a variety of pathogenic factors that definitely
would not be found in bacteria in 'probiotic' foods.

(and I see who you are replying to just edited their response to add 'bad' E.
coli)

------
unstabilo
Also, margarine consumption causes divorce in Maine. More "true facts" at
[http://tylervigen.com/spurious-correlations](http://tylervigen.com/spurious-
correlations).

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xacaxulu
I don't need an excuse to eat more kimchi, but hey, if it's helpful :-).
Kidding aside, I love that more studies seem to keep coming out linking
healthy diets with _mental_ and _psychological_ benefits.

~~~
DanBC
This study doesn't do that, so much.

People who eat fermented foods have less anxiety, but we don't know if lower
anxiety means people are more likely to eat fermented food or if eating
fermented food reduces anxiety.

------
staunch
I've always felt in my gut that my gut has a mind of its own but that might
just be my gut's 20/20 hindsight.

It's just fascinating and exciting how much we're learning about the role the
gut plays in physical and mental health. The really great thing is that it
seems pretty easy to control (with poop pills, or whatever) so a lot of people
may benefit for very little cost.

------
0xdeadbeefbabe
On a related note how do I find out what microbes are living in my sauerkraut,
kimchi, kefir, or yogurt right now? There is no nutrition label.

~~~
rotten
Make your own! All 4 of those foods are surprisingly easy and cheap to ferment
yourself. The best books on the subject are by Sandor Katz. There is lots of
information online as well.

I drink homemade Kefir (with a bit of honey) every morning. Whether the effect
is real or not, I feel better on the days I have it than the days I don't.

~~~
0xdeadbeefbabe
I chose Alex Lewin instead of Sandor Katz. Now I have this sauerkraut that
smells pretty good, but I don't have the courage to eat it or the confidence
that it isn't moldy. If I had chosen Katz would things be different?

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gweinberg
Eating fermented food always decreases my social anxiety. But I think the hops
and/or distillation process kills off any bacteria that may have been in them,
so i have doubts as to the causal mechanism.

~~~
cschep
I see you. :)

