Crunchy, Indigestible Goodness

 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.