--Just Get More Fiber
From: Duke Today
July 29, 2022 -- DURHAM, N.C. -- That huge array of
dietary fiber supplements in the drugstore or grocery aisle can be overwhelming
to a consumer. They make all sorts of health claims too, not 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 were fed three different kinds of
supplements in different sequences concludes that people who had been eating
the least amount of fiber before the study showed the greatest benefit from
supplements, regardless of which ones they consumed.
“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.
The benefit of dietary
fiber isn’t just the easier pooping that advertisers tout. Fermentable fiber --
dietary carbohydrates that the human gut cannot process on its own but some
bacteria can digest -- is also an essential source of nutrients that your gut
microbes need to stay healthy.
“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.”
When your gut bugs are
happily munching on a high-fiber diet, they produce more of the short-chain
fatty acids that protect you from diseases of the gut, colorectal cancers and
even obesity. And in particular, they produce more of a fatty acid called
butyrate, which is fuel for your intestinal cells themselves. Butyrate has been
shown to improve the gut’s resistance to pathogens, lower inflammation and
create happier, healthier cells lining the host’s intestines.
Given the variety of
supplements available, David’s research team wanted to know whether it may be
necessary to ‘personalize’ fiber supplements to different people, since
different fermentable fibers have been shown to have different effects on
short-chain fatty acid production from one individual to the next.
“We didn’t see a lot of
difference between the fiber supplements we tested. Rather, they looked
interchangeable,” David said during a tour of his sparkling new lab in the MSRB
III building, which includes a special “science toilet” for collecting samples
and an array of eight “artificial gut” fermenters for growing happy gut
microbes outside a body.
“Regardless of which of
the test supplements you pick, it seems your microbiome will thank you with
more butyrate,” David said.
The average American
adult only consumes 20 to 40 percent of the daily recommended amount of fiber,
which is believed to be a root cause behind a lot of our common health
maladies, including obesity, cardiovascular disease, digestive disorders and
colon cancer. Instead of having to go totally vegetarian or consume pounds of
kale daily, convenient fiber supplements have been created that can increase
the production of short-chain fatty acids.
The Duke experiments
tested three main kinds 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 one week in different orders, with a week off between supplements to allow
participants’ guts to return to a baseline state.
Participants who had
been consuming the most fiber beforehand showed the least change in their
microbiomes, and the type of supplement really didn’t matter, probably because
they were already hosting a more optimal population of gut bugs, David said.
Conversely,
participants who had been consuming the least fiber saw the greatest increase
in butyrate with the supplements, regardless of which one was being consumed.
In a second study the
David lab performed with support from the U.S. Office of Naval Research, they
found that gut microbes responded to a new addition of fiber within a day,
dramatically altering the populations of bugs present in the gut and changing
which of their genes they were using to digest food.
Using their 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.”
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