If you’re over the age of 10, the World Health Organization recommends that you consume at least 25 grams of fiber every day. The best fiber-containing foods come from plants: fruits, vegetables, nuts, seeds, whole grains and legumes.
While it’s sometimes overshadowed by other nutrients, such as protein, fiber plays a significant role in gastrointestinal health, digestion and nutrient absorption.
As a biochemist and someone who enjoys eating all types of foods, I find it remarkable that the structure of fiber, which is so similar to other carbohydrates, gives it all these unique functions. A tiny difference in the bonds that hold the molecules together allows your body to process a bagel differently from a raspberry.
Structure dictates function
In the biochemistry classes I teach, I emphasize that structure dictates function. If you’re about to cross a bridge but notice the braces are falling off or the wood is rotting, you’ll probably avoid stepping on it because the structure looks fragile.
This concept is true in the food you eat as well. The structures of the molecules that make up your food require them to be broken down in different ways in order to produce the energy that fuels your body.
Some foods contain vitamins and minerals that your body absorbs and uses for multiple functions. Other foods can keep your digestive system healthy and help your body absorb nutrients.
Food molecules consist of proteins, fats and carbohydrates. Each of these classes of food molecules has unique structures that allow your body to process them differently. For example, fats are long chains of carbon atoms that do not dissolve in water, while proteins have large amounts of nitrogen due to their amino acids. In addition, subclasses of biomolecules have even more specializations in their structures and functions.
Carbohydrate structure
Carbohydrates, or sugars, are biomolecules made up of carbon, oxygen and hydrogen atoms. Simple carbohydrates include single sugars, such as glucose or fructose, and two sugars linked together, such as sucrose – table sugar – or lactose, milk sugar. These simple carbohydrates exist mostly in rings, although they sometimes open up into a linear form.
Simple sugars can be one sugar, such as glucose, left, or two linked sugars, such as sucrose, right.
Julie Pollock
Complex carbohydrates, on the other hand, have a lot – hundreds to thousands – of sugar molecules linked in large sheets called polysaccharides. These carbohydrates are linked only in their ring forms.
Plants connect sugar molecules in two types of polysaccharides – starch and fiber. These molecules have similar structures because they contain only one type of sugar – typically glucose – linked together many times.
However, one tiny difference in the chemical bonds within starch and fiber translates to very different functions for the molecules.
Starch, also called amylose and…
