Which fiber supplement is best? It doesn’t matter, just consume more of it, study concludes

It might feel like a daunting task trying to decide which fiber supplement to take, but researchers say not to worry. A new study from Duke University reveals there’s not much difference between what fiber supplement to use — just eat more fiber.

For the study, researchers analyzed three main kinds of fermentable fiber supplements: inulin, dextrin (Benefiber), and galactooligosaccharides (GOS) marketed as Bimuno. They then divided 28 participants into groups and gave each of them three supplements for one week in different orders, with a week off between supplements to allow participants’ guts to return to a baseline state.

Those who had a higher intake of fiber beforehand showed the least amount of change in their microbiomes, most likely because they were already hosting a more optimal population of gut bugs. Researchers say the type of supplement didn’t matter.

However, participants who had been consuming the least amount of fiber saw the greatest increase in butyrate with the supplements, no matter which one was being consumed. Butyrate, which is fuel for your intestinal cells, improves the gut’s resistance to pathogens, lowers inflammation and creates healthier cell lining in intestines.

“The people who responded the best had been eating the least fiber to start with,” says study leader Lawrence David, an associate professor of molecular genetics and microbiology at Duke, in a media release.

Increasing your fiber intake isn’t just all about regular bowel movements. Researchers say fermentable fiber — dietary carbohydrates that the human gut cannot process on its own but some bacteria can digest — is an important source of nutrients that your gut microbes need to stay healthy.

“We’ve evolved to depend on nutrients that our microbiomes produce for us,” says Zack Holmes, former PhD student in David’s lab and co-author on two new papers about fiber. “But with recent shifts in diet away from fiber-rich foods, we’ve stopped feeding our microbes what they need.”

Researchers say when your gut bugs are eating a high-fiber diet, they produce short-chain fatty acids that protects people from diseases of the gut, colorectal cancers and obesity. It also produces more butyrate.

The study aimed to show whether it’s necessary to “personalize” fiber supplements to different people, since different fermentable fibers have shown to have divergent effects on short-chain fatty acid production from one person to the next.

“We didn’t see a lot of difference between the fiber supplements we tested. Rather, they looked interchangeable,” explains David. “Regardless of which of the test supplements you pick, it seems your microbiome will thank you with more butyrate.”

In a second study, Duke researchers, along with support from the U.S. Office of Naval Research, found that gut microbes responded to a new addition of fiber within a day. It drastically altered the populations of bugs present in the gut and changed which of their genes they were using to digest food.

Using artificial gut fermenters, researchers found the gut microbes were primed by the first dose to eat fiber, and digested it quickly on the second dose.

“These findings are encouraging,” says graduate student Jeffrey Letourneau, lead author of the second study. “If you’re a low fiber consumer, it’s probably not worth it to stress so much about which kind of fiber to add. It’s just important that you find something that works for you in a sustainable way.”

Holmes added that it doesn’t just need to be a supplement.

“It can just be a fiber-rich food,” says Holmes. “Folks who were already eating a lot of fiber, which comes from plants like beans, leafy greens, and citrus, already had very healthy microbiomes.”

Researchers say the average American adult consumes 20 to 40 percent of the daily recommended amount of fiber. The lack of a fiber-enriched diet is believed to be a root cause behind obesity, cardiovascular disease, digestive disorders and colon cancer.

The studies are published in the journal Microbiome.


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