Nutrition Science and Everyday Application - beta v 0.1

TYPES OF CARBOHYDRATES 181
Think about thick stems that help a plant stand upright, tough seed husks, and fruit skin that
protect what’s growing inside. These are full of fiber.
Figure 4.7. Examples of food plants high in fiber, including wheat, broccoli, and apples.
In our food, we find fiber in whole plant foods like whole grains, seeds, nuts, fruits,
vegetables, and legumes.
One of the most common types of fiber is cellulose, the main component in plant cell walls.
The chemical structure of cellulose is shown in the figure below, with our simplified depiction
next to it. You can see that cellulose has long chains of glucose, similar to starch, but they’re
stacked up, and there are hydrogen bonds linking the stacks.
When we eat fiber, it passes through the small intestine intact, because we don’t
have digestive enzymes to break it down. Then, in the large intestine, our friendly
microbiota—the bacteria that live in our colons—go to work on the fiber. Some fiber can be
fermented by those bacteria. We’ll discuss fiber more later in the unit.
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