Peter Attia

These are the ones that I talked about earlier.

They are essentially there to bulk up stool, mechanically stimulating the gut lining to release water and mucus to dilute irritants and toxins in the colon and speed up intestinal transit.

So most insoluble fibers are also not fermented by gut bacteria.

So we contrast that, of course, with soluble fibers.

A viscous fiber is able to absorb water and create a gel, a viscous gel in the gut.

And we're going to talk about some of these.

And if anybody's ever played with these as supplements, it's actually kind of cool to watch how quickly something that is dry as a fiber, when mixed with water, will form a viscous gel that your kids would want to play with.

So this can lead to slower gastric emptying.

It can blunt blood sugar spikes, contributes to lower cholesterol, though I would argue not so meaningfully that we should rely on this for lipid management.

So some examples of these would be pectin, which you'd find in apples and other fruits, beta-glucan found in oats, and the psyllium husk, which I think is probably the most common one that we would look at.

So that's actually a plant that you can most commonly consume as a supplement.

These are all viscous, but there's some variability in how viscous they are.

We'll get to that later.

Okay, so the other category of soluble fibers are the fermentable fibers, which are broken down by gut bacteria to produce short-chain fatty acids such as butyrate.

These are also known as prebiotic fibers, which the most common examples of this would be inulin and pectin.

While most prebiotic fibers are soluble, there are some exceptions.

So for example, resistant starches found in cooked and cooled starchy foods, oats, potatoes, and rice, or in beans.

We're going to talk more about these later, but I just kind of want to start high level.

Important to be aware that these two properties, viscosity and fermentability, are not mutually exclusive.

You'll notice that because I just use pectin as an example in both.