Nutrition Science and Everyday Application - beta v 0.1

Fiber - Types, Food Sources, Health Benefits,
and Whole Versus Refined Grains
Dietary fiber is defined by the Institute of Medicine’s Food and Nutrition Board as
“nondigestible carbohydrates and lignin that are intrinsic and intact in plants.” Fiber plays an
important role in giving plants structure and protection, and it also plays an important role
in the human diet.
Cellulose is one type of fiber. 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. The special bonds between these glucose units in fiber are not enzymatically digested
in the digestive tract, and therefore, fiber passes undigested to the colon or large intestine.
Figure 4.22. The chemical structure of cellulose, and a simplified illustration of cellulose.
You might be wondering how fiber has any benefit to us if we can’t digest it. However,
it doesn’t just pass through the digestive tract as a waste product. Instead, it serves many
functions on its journey, and these contribute to our health. Let’s explore the different types
of fiber, where we find them in foods, and what benefits they provide!
TYPES OF FIBER
Whole plant foods contain many different types of molecules that fit within the definition of
fiber. One of the ways that types of fiber are classified is by their solubility in water. Whole
plant foods contain a mix of both soluble and insoluble fiber, but some are better sources of
one than the other.
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