How fiber in food could protect the brain during aging

In a recent study, researchers from the University of Illinois find dietary fiber could help reduce brain inflammation during aging.

As mammals age, immune cells in the brain known as microglia become chronically inflamed. In this state, they produce chemicals that may impair cognitive and motor function.

That’s one reason why memory fades and other brain functions decline during old age.

But this study suggests fiber in food could delay the inevitable.

It is known that dietary fiber promotes the growth of good bacteria in the gut.

When these bacteria digest fiber, they produce short-chain-fatty-acids (SCFAs), including butyrate, as byproducts.

Butyrate has been shown to have anti-inflammatory properties on microglia and improve memory in mice when administered pharmacologically.

However, the mechanism wasn’t clear.

In the study, the researchers found in old mice butyrate inhibits production of damaging chemicals by inflamed microglia.

One of those chemicals is interleukin-1β, which has been linked to Alzheimer’s disease in humans.

While people are not likely to consume sodium butyrate directly due to its noxious odor, a practical way to get more butyrate is to eat a diet high in soluble fiber.

The concept takes advantage of the fact that gut bacteria convert fiber into butyrate naturally.

Butyrate derived from dietary fiber should have the same benefits in the brain as the drug form, but no one had tested it before.

In the study, the researchers fed low- and high-fiber diets to groups of young and old mice, then measured their levels of butyrate and other SCFAs in the blood, as well as inflammatory chemicals in the intestine.

They examined about 50 unique genes in microglia and found the high-fiber diet reduced the inflammatory profile in aged animals.

The researchers did not examine the effects of the diets on cognition and behavior or the precise mechanisms in the gut-brain axis, but they plan to tackle that work in the future.

Although the study was conducted in mice, the team is comfortable extending their findings to humans, if only in a general sense.

Not getting enough fiber could have negative consequences for things people don’t even think about, such as connections to brain health and inflammation in general.

Rodney Johnson is the corresponding author of the study.

The finding is published in the Frontiers in Immunology.

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Source: Frontiers in Immunology.