Unexpected Elements is the podcast shining a light on the science lurking behind the news.

We know lots of scientists and we're not afraid to call them up.

Unexpected Elements from the BBC World Service find it wherever you get your BBC podcasts.

Welcome to the inquiry with me, Tanya Beckett.

One question, four expert witnesses and an answer.

If you have just eaten, when you start listening to this documentary,

there is a very small chance that that meal will have reached your stomach by the time we're done.

And even when the food has reached your stomach and it's getting mashed up,

it still has a long distance to travel and a lot of processes to go through

before you find yourself making your way to the bathroom.

We know that what we eat needs to nourish our bones, our muscles, our skin.

But what about our brains?

In the last decade, there's been a mass of research suggesting that what's going on in our intestine

in some way relates to what's going on in our heads.

So this week on the inquiry, we're asking, what's wrong with our guts?

Part one, how we stomach it.

If you ask multiple people, you will probably receive multiple definitions of what exactly the gut is.

I like to think of the gut as the part of the body that participates in the digestion and absorption of food.

So for me, the gut includes everything from the mouth to the anus,

including all of the organs that secrete enzymes that aid in our digestion,

such as the pancreas and the liver.

Our first expert witness is Jeff Preetis, a gastroenterologist at Baylor College of Medicine at Texas Children's Hospital in Houston.

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