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What Are Dietary Fibers & Why Are They Essential for Gut Health?

Posted by Brad Dennis, Ph.D. on

What Are Dietary Fibers & Why Are They Essential for Gut Health?

Jump-start your gut health with whole grains! Learn to love fruits! Go nuts for pistachios! Bridge the fiber gap! These are all tips you can hear from every single dietitian, but do you know what all of them have in common? Bran, avocados and pistachios are all rich with fiber, along with many other foods that fall under these categories. But, why is it that your body needs dietary fiber? What dietary fiber benefits do you get from including it in your diet?

Here’s what you need to know before including this highly beneficial nutrient in your daily regimen.

What Is Dietary Fiber?
The term dietary fiber refers to those parts of plant foods that your body cannot absorb or digest. You can hear people calling dietary fiber bulk and roughage as well, so don’t get confused with this nutrient’s many names. But, isn’t the fact that dietary fiber isn’t digestible a bad one? On the contrary! Fiber is so beneficial exactly because it absorbs water and soothes the bowels while finding its way down the digestive system. Dietary fiber is the most natural way of easing your gut health-related troubles, but its primary role is to prevent constipation or relieve it once it does occur.

Still, not all dietary fibers are the same – specialists differentiate soluble fiber from insoluble roughage, and you need to know about that difference too.

Soluble & Insoluble: What Is the Difference?

Though fiber-rich foods usually contain both the soluble and insoluble type of dietary fiber, the ratio is almost never identical. Nevertheless, these broad types of fiber are just as healthy and important. The main difference between them is that soluble fiber possesses the ability to dissolve in water while traveling through the body, while insoluble fiber doesn’t. Consequently, the first type changes its form and becomes gelatinous, but the second passes through the body almost entirely intact. Consequently, these two types of dietary fiber have different functions in our bodies and are beneficial to our gut health in unlike ways.

Soluble Fiber
The soluble fiber’s super power is its ability to absorb any unwanted water from the digestive tract, which eases bowels, regardless of how nervous they are. For that reason, soluble fiber is your best choice against constipation and diarrhea.

The soluble fiber’s super power is its ability to absorb any unwanted water from the digestive tract, which eases bowels, regardless of how nervous they are. For that reason, soluble fiber is your best choice against constipation and diarrhea. Exactly because it dissolves when in touch with water, soluble fiber picks up and absorbs plenty of harmful substances that reside inside our digestive systems. Cholesterol, for instance, is one of them, and soluble fiber never fails at getting it out of our bodies, thus reducing our chances for heart disease. Being a fiber, soluble roughage never dissolves in water completely, which is why it can’t trigger blood sugar spikes. If suffering from diabetes, this type of fiber might even ameliorate your condition and keep the disease under control. If not, soluble fiber can prevent diabetes and heart disease alike.

That’s exactly why you should always start your day with a fibrous food for breakfast – rich in soluble fiber, oatmeal will keep you energized the whole day long without attacking your body with unnecessary calories. Apart from ensuring a healthy digestive system and strong heart, soluble fiber contributes to our weight and fitness goals as well. Other superfoods that are rich with this type of fiber are  prunes, grapefruit, grapes, apples and oranges from the fruit family, zucchini, Brussels sprouts, spinach and broccoli among veggies and, of course, beans.

Insoluble Fiber

Being quite effective at controlling the gut flora’s pH levels and “escorting” stool through and out of the body, insoluble fiber is just as helpful when it comes to regular bowel movements. As such, it successfully cures common problems like constipation and hemorrhoids and less common ones like incontinence. Colorectal cancer is yet another disease that insoluble fiber can fight off. That’s quite enough to convince you to stop peeling your fruits and start eating them whole instead – insoluble fiber can be found in fruit skins, as well as in root vegetable skins, but if you’re really determined to be generous to your body, enrich your diet with vegetables as much as you can. Dark leafy greens are most bountiful when it comes to soluble fibers, almost as much as seeds, nuts (remember pistachios?) and corn and wheat bran alike.

Resistant Starch

Almost every type of food that’s known to include high amounts of dietary fiber – both soluble and insoluble – is rich in starch as well. Until recently, scientists and dietitians were convinced that dietary fiber was the only kind of nutrient that exits the body undigested, but new findings have shown that starch behaves in more or less the same way as roughage, thus exiting the digestive tracts in the same form it has when we consume it. That’s why we now call it the resistant starch.

Apart from the common effects that dietary fiber delivers as well, such as bulkier and more easily disposable stool, lower blood sugar, reduced cholesterol and weight management, resistant starch keeps our teeth healthy as well.

Dietary Fiber and Prebiotic Effects

There’s another well-known health contributor that’s directly linked to dietary fiber. Along with polysaccharides that were recognized as dietary fiber long ago, scientists have recently found that oligosaccharides have the same physiological effects, and can therefore be accepted as dietary fiber despite their different chemical measurement. Oligosaccharides are, however, known as prebiotics as well. In simpler terms, that means that means that we can feel free to say that dietary fiber produces prebiotic effects, and according to the role it plays in gut health, it certainly does. Furthermore, both dietary fiber and probiotics are found in certain types of fruits and vegetables, and particularly in whole grains, which makes them even more powerful.

Still, not all fiber is a prebiotic, though all prebiotics are considered fibers. The only dietary fiber that has prebiotic effects is the one that isn’t absorbable in the upper part of the digestive tract, that’s fermented in the gut flora and that stimulates the growth of “friendly” bacteria that occupy the gut.

So, why do you absolutely need to listen to your dietitian’s advice? Because the modern Western diet is notorious for being low in dietary fiber, and this nutrient is essential for proper bowel function and a healthier heart. And, by keeping your gut health in good shape and by providing beneficial prebiotic effects, dietary fiber ensures wellness to the entire body.


Fiber and Prebiotics: Mechanisms and Health Benefits
Soluble and Insoluble Fiber: What’s the Difference?
Dietary Fiber and Resistant Starch
Cholesterol-lowering effects of dietary fiber: a meta-analysis


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