People who consume low amounts of fiber in their diet will benefit the most from dietary supplements containing fiber, in terms of the production of the short-chain fatty acid butyrate, according to a study published in Microbiome. Further, it didn’t seem to matter which of three dietary supplements were used on the participants, indicating that this benefit is universal across different fiber types. Short-chain fatty acids such as butyrate are linked to several health benefits, including gut health, colorectal cancer risk, and obesity. The average American consumes between 20% and 40% of the daily recommended amount of fiber, however, fiber supplements offer a convenient option for increasing the production of short-chain fatty acids.
 
“The people who responded the best had been eating the least fiber to start with,” said study leader Lawrence David, an associate professor of molecular genetics and microbiology at Duke University.
 
“We’ve evolved to depend on nutrients that our microbiomes produce for us,” said Zack Holmes, former PhD student in the David 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.”
 
The authors of the study sought to determine whether one fiber type over another would have a greater benefit on butyrate production, but according to the authors, the three fiber types used in the study (inulin, wheat dextrin, and galacto-oligosaccharides) appeared to be interchangeable, according to the authors.
 
The 28 participants in the study were separated into three groups and given each one of the three supplements for one week in different orders, with a week-long washout period between supplements, allowing the participants’ guts to return to a baseline state before crossover.
 
What appeared consistent was that participants who reported consuming the most fiber beforehand showed the least change in their microbiomes, while participants who had been consuming the least fiber had the greatest increase in butyrate with the supplements, regardless of which one was being consumed.
 
In a second study performed by the David Lab, gut microbes responded to a new addition of fiber within a day, dramatically altering the population of bugs present in the gut and changing which of their genes they were using to digest food. In artificial gut fermenters, the researchers found the gut microbes were primed by the first dose to consume fiber, and digested it quickly on the second dose.
 
“These findings 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 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.”
 
“It doesn’t need to be a supplement either,” Holmes added. “It can just be a fiber-rich food. Folks who were already eating a lot of fiber, which comes from plants like beans, leafy greens, and citrus, already had very healthy microbiomes.”