D: Today's Moment of Science is coming to you from our local grocery store.

Y: What better place to learn about food science and do the weekly shopping at the same time?

D: Here we are at the cereal aisle . . . oh good, they have my favorite.

Y: Toasted Fiber Puffs? [BEAT] Sounds delicious.

D: You may scoff, Yael, but they're not bad. And more importantly, Fiber Puffs are a great source of fiber.

Y: I kind of guessed that. But tell me something: what's so great about fiber? 

D: Well, fiber is good in all sorts of ways. First, it's important to understand that fiber isn't really a food or even a particular substance. It's an indigestible carbohydrate found in most plants.

Y: But if fiber is indigestible, how can it be nutritious?

D: That's the thing. Fiber isn't good for you because it provides nutrients. But it does help clean out your digestive system. When you eat stuff that has a lot of fiber it hangs around in your stomach for a while and then gets passed down into your intestines with other food. Because fiber soaks up water it softens the stool, which makes it easier to eliminate.

Y: So in other words, fiber is kind of like a personal liquid plumber.

D: Precisely. Plus, it takes up stomach space and makes you feel full without adding any calories. So if you're on a diet, eating high-fiber foods like apples, grapes, seeds, whole wheat products, and beans is a good way to avoid feeling hungry. 

Y: All right, you sold me on fiber.

D: Want a box of Fiber Puffs? 

Y: I think I'll just stick to apples.