This vast array of dietary fibers in the drugstore or grocery aisle can overwhelm the 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 will be best for you?
A close examination of the gut microbes of study participants who received three different types of supplements in different sequences concluded that people who ate the least amount of fiber before the study showed the greatest benefit from the supplements, regardless of which supplements they took.
“The best responders ate the least amount of fiber from the start,” said study leader Lawrence David, an assistant professor of molecular genetics and microbiology at Duke University.
The benefits of dietary fiber aren’t just what advertisers tout for easier pooping. Fermentable fiber — dietary carbohydrates that the human gut can’t process on its own, but some bacteria can digest — is also an important source of nutrients your gut microbes need to stay healthy.
“We’ve come to depend on the nutrients that our microbiomes produce for us,” said Zach Holmes, a former graduate student in David’s lab and co-author of two new papers on fiber. “But with recent dietary shifts away from fiber-rich foods, we’ve stopped feeding our microbes what they need.”
When your gut bugs happily munch on a high-fiber diet, they produce more short-chain fatty acids, which protect you against bowel disease, colorectal cancer, and even obesity. And specifically, they produce more of a fatty acid called butyrate, which is fuel for the very cells of your gut. Butyrate has been shown to improve the gut’s resistance to pathogens, reduce inflammation, and create happier, healthier cells lining the host’s gut.
Given the variety of supplements available, David’s research team wanted to know if fiber supplements might need to be “personalized” for different people, as different fermented fibers have been shown to affect short-chain fatty acid production differently from one person to the next.
“We didn’t see much of a difference between the fiber supplements we tested. Rather, they seemed interchangeable,” David said during a tour of his shiny new lab in the MSRB III building, which includes a special “science toilet” for collecting samples and a set of eight “artificial gut” fermenters for growing happy gut microbes outside the body
“No matter which of the test supplements you chose, your microbiome seems to thank you with more butyrate,” David said.
The average American adult consumes only 20 to 40 percent of the daily recommended amount of fiber, which is believed to be the root cause of many common health conditions, including obesity, cardiovascular disease, digestive disorders and colon cancer. Instead of going completely vegetarian or eating pounds of kale every day, convenient fiber supplements have been created that can increase the production of short-chain fatty acids.
Duke’s experiments tested three main types of fermentable fiber: inulin, dextrin (Benefiber), and galactooligosaccharides (GOS), sold as Bimuno. 28 participants were split into groups and given each of the three supplements for one week in a different order, with a week break between supplements to allow the participants’ guts to return to baseline.
Participants who consumed the most fiber before that showed the least changes in their microbiomes, and the type of supplement really didn’t matter, likely because they were already taking in a more optimal population of gut bugs, David said.
In contrast, participants who consumed less fiber saw the greatest increase in butyrate with supplements, regardless of which ones were consumed.
In a second study, conducted by David’s lab with support from the US Office of Naval Research, they found that gut microbes responded to a new addition of fiber throughout the day, dramatically changing the population of bugs present in the gut and altering the genes they used to digest food. .
Using their artificial gut fermenters, the researchers found that gut microbes were primed to consume fiber with the first dose and quickly digested it with the second dose.
“These findings are encouraging,” said graduate student Jeffrey Letourneau, lead author of the second study. “If you’re low in fiber, you probably shouldn’t stress so much about what fiber to add. It’s just about finding what works for you in a sustainable way.”
“It doesn’t have to be a supplement, either,” Holmes added. “It could just be a high-fiber meal. People who already ate a lot of fiber, which comes from plants like beans, leafy greens and citrus fruits, already had very healthy microbiomes.”
This research was supported by the National Institutes of Health (R01-DK116187, R01DK116187-01); Office of Naval Research (N00014-18-1-2616); NASA Translational Research Institute (NNX16AO69A); and the Damon Runyon Cancer Research Foundation.