High-Fiber Diet for Gut Health: How Fiber Supports the Microbiome

Good gut health means your digestive system is working well. This includes supporting the gut microbiome—a community of bacteria and other microorganisms that live in the digestive tract and contribute to healthy digestive function. A healthy gut can help break down and absorb food, protect against harmful germs and toxins, and support comfortable, regular bowel movements.

Yes, a high fiber diet is good for gut health! A high fiber diet is an eating pattern that regularly includes fiber-rich foods and provides enough dietary fiber to meet an individual’s daily needs.

Fiber-rich foods include fruits, vegetables, whole grains, beans, lentils, nuts, and seeds.
Some types of fiber help add bulk and keep things moving through your digestive system. Certain fibers also act as prebiotics, feeding beneficial bacteria in the gut microbiome. As these microbes break down fiber, they produce compounds that help protect and maintain the gut lining.

Trillions of microorganisms live in your gut, including bacteria, fungi, viruses, and other microbes. Together, these microorganisms and their genes are known as the gut microbiome.

These microbes are mostly concentrated in the colon, also known as the large intestine or lower digestive track. They play an important role in gut health. For example, some gut microbes help you digest food and produce compounds that influence many aspects of your health. Each person’s gut microbiome is unique and shaped by factors such as diet, environment, medications, and lifestyle.

The gut microbiome is home to microbes that can be both helpful and harmful. Research suggests a healthy, balanced gut microbiome can support digestion, immune function, and overall gut health. Scientists are also studying how the gut microbiome may be connected to other areas of health, including metabolism and the gut-brain axis.

Diet has a significant impact on the composition and activity of our gut microbiome. It is important to eat enough fiber for the gut microbiome because gut microbes ferment some types of fiber into compounds that help maintain the gut lining and support overall gut health.

Humans are total pros at digesting fats, protein, and many forms of carbohydrates. But we’re not great at metabolizing fiber—we don’t have the right enzymes to break them down.

So, while the rest of our food is being digested and absorbed throughout the gastrointestinal tract, some fiber passes through mostly unchanged until it hits the colon. There, it’s broken down by gut microbes that use fiber as a food source through a process called fermentation.

When gut microbes break down fiber through fermentation, they produce short-chain fatty acids (SCFAs). These compounds help fuel the cells lining the colon and support the gut’s protective barrier. Some SCFAs may also enter the bloodstream and travel to other parts of the body, where they are being studied for their potential role in overall health. Early findings suggest some SCFAs and other metabolites released by gut bacteria may even act as signals to communicate with the brain as well as regulate the immune system and inflammation.

Currently, most Americans do not get enough dietary fiber. In fact, about 94% fall short of fiber intake recommendations. The National Academies of Sciences, Engineering, and Medicine recommend that women should consume 25 grams (g) of fiber per day and men consume 38g per day, yet most Americans consume about half of that amount.

When we don’t eat enough fiber, gut bacteria have less fuel to produce beneficial compounds like SCFAs. Lower SCFA production may reduce support for the gut’s protective lining, which plays an important role in helping defend against harmful pathogens and toxins.

Fiber may also play a role in gut microbiome diversity. Compared to populations that traditionally eat a high-fiber diet, U.S. adults often have less diverse gut microbiomes. Low gut microbiome diversity has been associated with several chronic health conditions such as obesity and type 2 diabetes, although more research is needed to better understand these relationships.

Many foods contribute dietary fiber, including fruits, vegetables, whole grains, nuts, and legumes. These foods contain different types of dietary fiber, which is why eating a variety of fiber-rich foods can support a healthy, diverse gut microbiome.

Examples of fiber-rich foods include:

For more examples of fiber-rich foods and a deeper look at fiber types, amounts, and health benefits, see IFIC’s Fiber Fundamentals and Fiber Fact Sheet. The chart below, adapted from the fact sheet, shows how much dietary fiber and energy are found in standard portions of common high-fiber foods.

The good news is that it isn’t hard to bump up your fiber intake! Simple changes can help you get on track to meeting daily fiber goals.

However, increasing fiber intake too quickly can lead to some uncomfortable side effects, such as bloating and gas. To get more fiber while reducing these side effects, here are a few tips: