We all know that fiber is good for us, and now University of Illinois (U of I) researchers have added a new reason to consume it, perhaps particularly for older individuals. A study published recently in the journal Frontiers in Immunology that brought together scientists from the university’s neuroscience, nutrition, animal sciences, and kinesiology departments found that dietary fiber helps to reduce damaging brain inflammation.
Brain inflammation occurs as mammals age, prompting immune cells called microglia to become chronically inflamed and causing them to produce chemicals known to negatively affect cognitive skills and motor function, including interleukin-1β, which has been linked to Alzheimer’s disease. Dietary fiber may help give brain health a boost because when it is digested in the gut, it produces butyrate, a short-chain fatty acid that has been shown to have anti-inflammatory properties on microglia and to improve memory in mice when it is administered in drug form, says Rodney Johnson, professor and head of the Dept. of Animal Sciences at the U of I and a corresponding author of the study.
The U of I scientists fed low- and high-fiber diets to groups of young and old mice and then measured the levels of butyrate and other short-chain fatty acids in their blood as well as inflammatory chemicals in the gut. One of the interesting things their study showed was the difference in effect fiber consumption had on young and old mice. The high-fiber diet elevated butyrate and other short-chain fatty acids in the blood for both groups. But the low-fiber diet produced intestinal inflammation only in the old mice, not the young ones. “It clearly highlights the vulnerability of being old,” says Johnson. There was good news, however, when the old mice were fed a high-fiber diet: Their levels of intestinal inflammation were dramatically reduced—to the point where there was no difference in inflammation levels between the old and the young mice.
The National Institute of Health’s National Institute on Aging has awarded a grant of nearly $2 million toward continuing the research. This phase will include attempting to understand the specific mechanisms of the gut-brain axis and examining the effects of high-fiber diets on cognition and behavior.
Johnson believes that the study in mice has applications for humans. “We know that older adults consume 40% less fiber than is recommended,” he says. “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.”