The Way You React to Fiber is Determined by Your Microbiome

August 31, 2024 TruthUSA

Personalized fiber sources could be a solution for those who avoid fiber because it makes them feel bad.

The longstanding advice to eat a plant-based diet for better overall health isn’t likely to change, despite new evidence that not everyone is getting the same benefits from fiber, prompting a reevaluation of dietary recommendations.

Understanding Dietary Fiber

Fiber comes from the indigestible parts of plants. Gut microbes metabolize these carbohydrates into short-chain fatty acids (SCFA) that do everything from optimizing intestinal function to protecting against various diseases.

Dietary fiber generally helps you feel full, assists in digestion, and prevents constipation. Some forms of fiber speed up motility and others slow it down.

Higher fiber intake is associated with numerous health benefits, including:

Prevention of cardiovascular disease, cancer, Type 2 diabetes, and obesity
Maintaining a healthy body weight
Preventing cancer and specifically extending longevity among colon cancer survivors
Improved neurological health
Reduced risk of autoimmune diseases
Enhanced intestinal barrier function, protecting against inflammation-triggering toxins

The average American consumes about 16 grams of fiber daily, falling short of the recommended minimum of 21 grams for older children, 25 for women, and 38 grams for men.

While increasing intake is generally recommended, fiber—found in foods like beans, peas, whole grains, fruits, and vegetables—can be tricky, particularly for those with gastrointestinal symptoms such as gas, bloating, constipation, and diarrhea.

Counterintuitively, fiber intake doesn’t always alleviate these symptoms as expected.

New Insights From Recent Research

A study published in Gut Microbes in June sheds light on why fiber affects people differently. The research suggests that the composition and diversity of a person’s gut microbiome, a community of trillions of bacteria and other microorganisms that live mostly in the colon, play a significant role in how fiber is processed.

Different microbial species responded uniquely when subjects consumed two types of resistant starch (found in foods like bread, cereal, green bananas, whole-grain pasta, brown rice, and potatoes).

Some participants experienced minimal changes in their microbial diversity, abundance, and SCFA concentration. SCFAs, the primary metabolites produced by gut microbes, indirectly reduce appetite, limit food intake, and regulate blood glucose.

Rapid Changes in Gut Microbiome

The study showed that the gut microbiome can change rapidly. Participants were given three types of crackers, one containing a naturally occurring resistant starch and one with a human-made resistant starch to eat for 10 days respectively, with a five-day period of rest with a control cracker in between. Their microbiomes were measured before and after each treatment.

Significant changes in bacterial abundance were observed, with variations depending on the type of starch and the individual.

The naturally occurring starch led to an abundance in more than 30 bacteria, including Ruminococcus bromii, which is known for breaking down resistant starch in the human gut. More than 20 bacteria changed for the human-made starch, and nothing changed in the control period.

Reframing Fiber Advice

The study’s findings suggest that dietary advice about fiber could be more personalized. This approach could be key to increasing fiber consumption among Americans, according to Angela Poole, assistant professor of molecular nutrition at Cornell University and senior author of the study.

“This is critical because we’ve had public messaging advising people to eat more dietary fiber for decades,” Poole said in a news release. “At the same time, less than 10 [percent] of people eat the recommended intake. Since there are many different types of dietary fiber and carbohydrates, a better strategy would be to collect data on each person and tell them which dietary fiber they can eat to get the most bang for their buck.”

That approach makes sense to Dr. Armen Nikogosian, internist and functional medicine specialist, who has worked with patients of all ages who have chronic gut issues and complex medical conditions to safely increase fiber in their diets.

Difficulty digesting resistant starches may indicate some degree of dysbiosis—an imbalance of microbes in the gut—meaning a person doesn’t have the right kinds of bacteria in their gut to digest some types of fiber, Nikogosian told The Epoch Times in an email.

Because resistant starches are prebiotics, meaning they are the food for microbes living in your gut, it may be helpful to increase fermented food alongside fiber, according to Nikogosian. Fermented food like sauerkraut and kombucha are probiotics, which are live microorganisms that can add to diversity and abundance in the microbiome.

You may want to see a functional medicine practitioner if intolerance persists to prebiotic and probiotic food, Nikogosian said.

Increasing Fiber Intake

Overall, the findings add to the argument that more fiber is better, Noah Praamsma told The Epoch Times. He is the nutrition education coordinator at the Physicians Committee for Responsible Medicine, a nonprofit organization that promotes disease prevention through plant-based nutrition. It endorses consuming up to 40 grams of fiber daily.

“It’s a very achievable number,” Praamsma said. “Today is the best day to start. Your gut bacteria will adjust.”

The organization provides examples of high-fiber foods:

One-half cup lentils: 7.8 grams
One cup sweet potatoes: 6.6 grams
One cup broccoli: 5.1 grams
One pear: 5.5 grams
One cup raspberries: 8 grams

If gas and bloating are a concern, Praamsma advised starting slowly and using an app or notebook to track not only the amount of fiber you are eating but also how your body reacts to it. You can also eat vegetables cooked rather than raw to make them more digestible.

Choosing to focus on eating a diet naturally high in fiber is not only sustainable but can lead to a more carefree attitude about health, Praamsma said.

“The more you can replace the high-fat animal foods with fiber plant foods, that’s not only going to make this better for your health but easier,” he noted. “There will be a lot less tracking and worrying about whether you are hitting these quotas.”

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