About 20 years ago, there was a discovery that would forever change our ideas about fiber.

Our gut bacteria eat the fiber we eat to produce important signaling compounds called short-chain fatty acids.

But before I get carried away, a little science

lesson to frame the discovery. Cells are the fundamental unit of life. We're composed of

trillions of them. They communicate with each other through receptors on the surface of our cells.

That's how many hormones work. It's like a lock and key. Hormons are signaling messengers, each with a unique shape.

When released into the bloodstream, they circulate through the body until they find a receptor they can fit into.

Once the key is in the lock, it can turn on or off a whole series of reactions in the target cell.

The largest family of cell receptors is known as G-protein-coupled receptors, GPCRs for short.

More than a third of the drugs currently on the market work by plugging into these receptors.

That's how drugs like antihistamines work.

We've discovered hundreds of different GPCRs, but remarkably, we don't yet know what many of them do.

We have the lock. We just don't know what key fits.

Accordingly, they're called orphan receptors.

Two of these mystery receptors, known only as GPCR 43 and GPCR 41, were found heavily expressed throughout the body in our immune and fat

cells and in our gut, muscles, and heart. We knew they must be vital, but we didn't know what

activated them until 2003, when they were de-orphinized. That's actually what scientists call it.

The keys that fit into those important locks were the short-chain

fatty acids that our gut bacteria make when we feed them fiber. This is how our gut bacteria

may communicate with us. Renamed free fatty acid receptors, their existence is now considered

crucial insight into how fiber could play such an important role in so many of our chronic diseases.

Hormones are defined as signaling messengers produced in one organ that circulate through the bloodstream and have a regulatory effect on another organ.

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