Fiber is a key element of a
healthful diet. New research breaks down the mechanism by which it can delay
age-related brain inflammation.
Fiber can be found in fruits,
vegetables, nuts, seeds, beans, pulses, and whole-grain foods.
If all the studies that urge people
to consume a diet rich in fruits, vegetables, and whole grains for a healthy
life haven't convinced you yet to add more broccoli to your plate, perhaps this
latest research will.
Eating fiber-rich foods — such as
broccoli, nuts, oats, beans, and whole-grain bread — might help delay brain
aging by triggering the production of a short-chain fatty acid that has
anti-inflammatory properties.
This the main takeaway of a new
study that was recently published in the journal Frontiers in Immunology.
Rodney Johnson, a professor and the
head of the Department of Animal Sciences at the University of Illinois at
Urbana-Champaign, is the corresponding author of the study, and Stephanie M.
Matt is the first author of the paper.
How fiber
lowers inflammation
As Matt and colleagues explain in
their study paper, microglia — a major type of immune cell in the brain —
tend to become hyperactive and chronically inflamed with age. This inflammation of the
microglia is one of the main causes of memory and cognitive decline in old age.
Previous research has shown that a
drug form of butyrate, which is a short-chain fatty acid that is produced in
the colon when bacteria ferment fiber in the gut, can improve memory and reduce
inflammation in mice.
However, the precise mechanisms
behind this weren't entirely understood. Also, previous research had not shown
whether simply increasing the dietary content of fiber would achieve the same
results as the drug.
So, Matt and colleagues fed young and
aging mice diets high and low in fiber. Then, the scientists measured the
mice's blood levels of butyrate and their levels of pro-inflammatory substances
in their intestines.
Prof.
Johnson sums up these findings, saying, "The high-fiber diet elevated butyrate
and other [short-chain fatty acids] in the blood both for young and old
mice."
"But," he goes on,
"only the old mice showed intestinal inflammation on the low-fiber diet
[...] It's interesting that young adults didn't have that inflammatory response
on the same diet. It clearly highlights the vulnerability of being old."
Also, consuming a high-fiber diet
reduced the intestinal inflammation in aging mice so much that it was
indistinguishable from that of young mice.
"Dietary fiber can really
manipulate the inflammatory environment in the gut," says Prof. Johnson.
What about the brain, however?
Why fiber
is good for your brain
A genetic analysis of inflammatory
markers conducted by the scientists found that a high-fiber diet reduced
inflammation in the brain's microglia. The researchers suspect that this was
achieved by diminishing the production of a pro-inflammatory chemical known as
interleukin-1β, which some studies have linked with Alzheimer's.
Study co-author Jeff Woods, a
professor in the Department of Kinesiology and Community Health at the
University of Illinois at Urbana-Champaign, comments on the findings.
"We know that diet has a major
influence on the composition and function of microbes in the gut and that diets
high in fiber benefit good microbes," he points out, "while diets
high in fat and protein can have a negative influence on microbial composition
and function."
Altering gut microbes, explains
Prof. Woods, "is one way in which [diet] affects disease."
Prof. Johnson explains that the findings
are relevant to humans, saying, "People are not likely to consume sodium
butyrate directly, due to its noxious odor," he says, but, "A
practical way to get elevated butyrate is to consume a diet high in soluble
fiber."
"What you eat matters. We know that
older adults consume 40 percent less dietary fiber than is recommended. Not
getting enough fiber could have negative consequences for things you don't even
think about, such as connections to brain health and inflammation in
general."
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