The amount, not the brand, of dietary fiber supplements is what really matters

That vast array of dietary fiber supplements in the drugstore or grocery aisle can be overwhelming for a consumer. They also make all sorts of health claims, without being subject to FDA review and approval. So how do you know which supplement works and would be best for you?

A rigorous examination of the gut microbes of study participants who received three different types of supplements in different sequences concludes that people who ate the least fiber before the study showed the greatest benefit from supplements, regardless of those they consumed.

“The people who responded best ate the least fiber initially,” said study leader Lawrence David, associate professor of molecular genetics and microbiology at Duke University.

The dietary fiber benefit isn’t just the easier poo advertisers are touting. Fermentable fiber — dietary carbohydrates that the human gut can’t process on its own but some bacteria can digest — is also a key source of nutrients your gut microbes need to stay healthy.

“We have evolved to depend on the nutrients our microbiomes produce for us,” said Zack Holmes, a former PhD student in the David lab and co-author of two new papers on fiber. “But with recent changes in diets to high-fiber foods, we’ve stopped feeding our microbes what they need.”

When your gut bugs happily munch on a fiber-rich diet, they produce more short-chain fatty acids that protect you from bowel disease, colorectal cancer, and even obesity. And in particular, they produce more of a fatty acid called butyrate, which is the fuel for your gut cells themselves. Butyrate has been shown to improve the gut’s resistance to pathogens, reduce inflammation, and create happier, healthier cells lining the host’s intestines.

Given the variety of supplements available, David’s research team wanted to know if it was necessary to “tailor” fiber supplements for different people, as different fermentable fibers have been shown to have different effects on the production of short-chain fatty acids from one individual to another. the following.

“We didn’t see much difference between the fiber supplements we tested. On the contrary, they seemed interchangeable,” David said during a tour of his gleaming new lab in the MSRB III building, which includes a special “scientific toilet” for collecting samples and a set of eight “artificial gut” fermenters. for the growth of happy gut microbes outdoors. a body.

“No matter which of the test supplements you choose, it seems like your microbiome will thank you with more butyrate,” David said.

The average American adult consumes only 20-40% of the daily recommended amount of fiber, believed to be the root of many of our common diseases, including obesity, cardiovascular disease, digestive disorders and cancer. of the colon. Instead of having to go totally vegetarian or consume pounds of kale daily, convenient fiber supplements have been created to increase the production of short-chain fatty acids.

Duke’s experiments tested three main types of fermentable fiber supplements: inulin, dextrin (Benefiber), and galactooligosaccharides (GOS) marketed as Bimuno. The 28 participants were separated into groups and given each of the three supplements for a week in different orders, with a week off between supplements to allow the participants’ guts to return to a baseline state.

Participants who had consumed the most fiber before showed the least change in their microbiome, and the type of supplement didn’t really matter, likely because they already harbored a more optimal population of gut bugs, a said David.

Conversely, participants who consumed the least fiber saw the greatest increase in butyrate with the supplements, regardless of which one was consumed.

In a second study by the David lab with support from the United States Office of Naval Research, they found that gut microbes responded to a new fiber addition within a day, dramatically altering the insect populations present. in the gut and changing which of their genes they used to digest food.

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

“These results are encouraging,” said graduate student Jeffrey Letourneau, lead author of the second study. “If you’re a low fiber consumer, it’s probably not worth stressing too much about what kind of fiber to add until you find something that works for you in a sustainable way.

“It doesn’t need to be an extra either,” added Holmes. “It may just be a high fiber food. People who already ate lots of fiber, which comes from plants like beans, leafy greens and citrus fruits, already had very healthy microbiomes.

Reference: Holmes ZC, Villa MM, Durand HK, et al. Microbiota responses to different prebiotics are conserved in individuals and associated with habitual fiber intake. Microbiota. 2022;10(1):114. doi:10.1186/s40168-022-01307-x

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