Key Takeaways
Fiber feeds beneficial gut bacteria, which produce short-chain fatty acids like butyrate that nourish colon cells and may help reduce gut inflammation.
Viscous, soluble fiber can help manage blood sugar spikes after high carb meals, lower cholesterol levels, and support weight loss by increasing fullness.
High fiber foods like whole grains, fruits, vegetables, beans, and oats may help relieve constipation and could reduce the risk of colorectal cancer.
Fiber is one of the main reasons whole plant foods are good for you.
Growing evidence shows that eating adequate amounts of fiber may benefit your digestion and reduce your risk of chronic disease. Many of these benefits are mediated by your gut microbiota — the millions of bacteria that live in your digestive system.
However, not all fiber is created equal. Different types have different health effects.
This article reviews the different types of fiber and their evidence-based health benefits.
What are the different types of fiber?
Non-digestible carbohydrates found in foods are collectively known as fiber. They are most often categorized as soluble or insoluble.
Soluble fiber: dissolves in water and can be metabolized by the “good” bacteria in the gut
Insoluble fiber: does not dissolve in water
A more helpful way to categorize fiber is as fermentable versus non-fermentable, which refers to whether friendly gut bacteria can use it or not.
Keep in mind that there are many
. Some of them have important health benefits, while others are mostly useless.
There is also a lot of overlap between soluble and insoluble fibers. Some insoluble fibers can be digested by the good bacteria in the intestine, and most foods contain both soluble and insoluble fibers.
The amount of fiber you should consume differs worldwide and by age group.
are approximately 25 to 30 grams or more per day.
Fiber feeds the “good” bacteria in your gut
The bacteria that live in the human body outnumber the body’s cells 10 to 1. Bacteria live on the skin, in the mouth, and in the nose, but
the great majority live in the gut
, primarily the large intestine.
Approximately
different species of bacteria live in your intestines, totaling about 38 trillion cells. These gut bacteria are also known as the gut flora.
This is not a bad thing. In fact, there is a
mutually beneficial relationship
between you and some of the bacteria that live in your digestive system.
You provide food, shelter, and a safe habitat for the bacteria. In return, they take care of some things that the human body cannot do on its own.
Of the many different kinds of bacteria, some are crucial for various aspects of your health,
:
weight
blood sugar control
immune function
brain function
What does fiber have to do with feeding gut bacteria?
You may wonder what this has to do with fiber. Just like any other organism, bacteria need to eat to get energy to survive and function.
The problem is that most carbs, proteins, and fats are absorbed into the bloodstream before they make it to the large intestine, leaving little for the gut flora.
This is where fiber comes in. Human cells don’t have the enzymes to digest fiber, so it reaches the large intestine relatively unchanged.
However, intestinal bacteria do have the enzymes to digest many of these fibers.
This is the most important reason that (some) dietary fibers are essential for health. They feed the “good” bacteria in the intestine, functioning as
.
The friendly bacteria produce nutrients for the body, including short-chain fatty acids such as acetate, propionate, and butyrate, of which
appears to be crucial.
When the bacteria ferment the fiber, they also produce gases. This is why high fiber diets can cause flatulence and stomach discomfort in some people. These side effects usually go away with time as your body adjusts.
Some types of fiber can help you lose weight
Certain types of fiber can help you
by reducing your appetite.
In fact,
show that increasing dietary fiber can cause weight loss by automatically reducing calorie intake.
Fiber can soak up water in the intestine,
of nutrients and increasing feelings of fullness.
However, this depends on the type of fiber. Some types have no effect on weight, while certain soluble fibers can have a significant effect.
A good example of an effective fiber supplement for weight loss is
.
Fiber can reduce blood sugar spikes after a high carb meal
High fiber foods tend to have a
than refined carb sources, which have been stripped of most of their fiber.
However,
believe that only high-viscosity, soluble fibers have this property.
This is important, especially if you’re following a
. In this case, the fiber may reduce the likelihood of the carbs raising your blood sugar to harmful levels.
That said, if you have blood sugar issues, you should consider
, especially your intake of low fiber, refined carbs such as white flour and added sugar.
You should also talk with your doctor or dietitian. They can provide more specific recommendations for reducing blood sugar spikes.
Fiber can reduce cholesterol levels
A
in 14,505 participants found a significant reduction in LDL cholesterol after soluble fiber supplementation.
In addition to lowering cholesterol levels,
have found that increasing the intake of dietary fiber could reduce the risk of cardiovascular diseases.
Fiber can help relieve constipation
Eating more
, like fruits, vegetables, and whole grains, can improve your digestive health and help relieve constipation.
This will increase both your soluble and insoluble fiber intake and could help relieve your problem.
Foods high in insoluble fiber include:
whole grains
fruits and vegetables with skins
nuts and seeds
Foods high in soluble fiber include:
oats
flax seeds
barley
rye
beans
root vegetables
Fiber is believed to help absorb water, increase the bulk of stool, and speed up the movement of stool through the intestine.
In general, fiber that increases the water content of your stool has a laxative effect, while fiber that adds to the dry mass of stool without increasing its water content may have a constipating effect.
Soluble fibers that form a gel in the digestive tract and are not fermented by gut bacteria are often effective. A good example of a gel-forming fiber is
.
have also been shown to be effective for constipation.
Choosing the right type of fiber may help with your constipation, but taking the wrong supplements can do the opposite. For this reason, you should consult with a doctor before taking fiber supplements for constipation.
Fiber might reduce the risk of colorectal cancer
However, whole, high fiber foods like fruits, vegetables, and whole grains contain various other healthy nutrients and antioxidants that may affect cancer risk.
Therefore, it’s difficult to isolate the effects of fiber from other factors in
.
Yet, since fiber may help keep the colon wall healthy, many
that fiber plays an important role in preventing cancer.
Eating too much fiber can cause symptoms such as bloating, gas, and constipation. This is because high amounts of fiber can make bowel movements bigger and bulkier, increasing fermentation and gas production.
Too much fiber
with your body’s ability to absorb nutrients, such as calcium, zinc, and iron.
Drinking plenty of fluids, daily exercise, and avoiding
can help your body better manage fiber and reduce uncomfortable digestive issues.
However, eating too little fiber is a far more common problem than eating too much fiber.
The
2025 dietary guidelines for Americans
published by the United States Department of Agriculture (USDA) found that over 90% of females and 97% of males do not eat enough fiber.
Takeaway
Dietary fiber has various health benefits. Not only does it feed your gut bacteria, but fermentable fiber also forms short-chain fatty acids, which nourish your colon wall.
Additionally, viscous, soluble fiber may reduce your appetite, lower your cholesterol levels, and decrease the rise in blood sugar after high carb meals.
If you’re aiming for a healthy lifestyle, try to consume a variety of fiber types from whole fruits, vegetables, and grains.