Dr. Justin Sonnenburg

We know that you can affect your cognition.

We know that you can affect your skin and inflammation that's occurring on your skin.

So I really think that there is a basis for a lot of those anecdotes.

It may just be hard to see in a short study and in a small cohort of people over a short period of time.

We also have a standardized...

stool measure that people use.

And there was kind of less constipation, better bowel movements over the course of both of these interventions.

So it did seem like bowel habits improved, which a lot of times can lead to better moods, but that we weren't able to measure that.

Data seem to be telling us that if you start off with a diverse microbiota, maybe one that's better equipped to degrade a wide variety of dietary fiber, you're more likely to respond positively to it.

If you have a very depleted gut microbiome,

you're not as likely to be able to respond to it.

And thinking back to that experiment that we talked about before with the multigenerational loss of fiber fermenting microbes in mice that were fed a Western diet, it may be that many of us in the industrialized world have a microbiome that's so depleted now that even if we consume a high fiber diet, at least for a short period of time,

we don't have the right microbes in our gut to degrade that fiber.

And this has actually been observed by other groups, beautiful study out of University of Minnesota, looking at immigrants coming to the United States.

And within nine months, but certainly over the course of years, immigrants that come here lose

a lot of the diversity in their gut microbiome, but a lot of the fiber degrading capacity in their gut microbiome too.

So it could be that over time, this becomes a one-way street and it's hard for us to recover the microbes that actually can degrade the fiber.

And I think that this probably intersects with sanitation in our environment and the fact that we don't have access

to new microbes that might help us degrade the fiber, that we actually have lost these microbes and they're in some ways irrecoverable without deliberate reintroduction of fiber degrading microbes.

Exactly.