The importance of dietary fiber is well established when it comes to digestive health. More recently the link has been made for its impact on heart health. Now, research shows a high-fiber diet can even impact your brain health as Japanese study participants who ate a high-fiber diet suffered fewer cases of dementia.

Fiber consumption is generally low across the globe and especially in the United States where it is estimated only 5 percent of adults reach the recommended daily suggestion of 25 grams for women and 38 grams for men on a consistent basis. Scientists from the University of Tsukuba wanted to better understand the impact of fiber intake on brain health and published their findings in a current edition of the journal Nutritional Neuroscience.

"Dementia is a devastating disease that usually requires long-term care," says lead author of the study Professor Kazumasa Yamagishi. "We were interested in some recent research which suggested that dietary fiber may play a preventative role. We investigated this using data that were collected from thousands of adults in Japan for a large study that started in the 1980s."

Study participants completed surveys to determine dietary fiber consumption periodically between 1985 and 1999. The group was between the ages of 40 and 64 at the start of the study and considered generally healthy. The individuals were tracked until 2020 and it was noted if any developed dementia that required care.

The roughly 4,000 member cohort was divided into four separate groups based on the amount of fiber they said they consumed. Researchers found the ones who ate higher levels of fiber had a lower risk of developing dementia.

Scientists also looked at the difference between soluble and insoluble fiber consumption. Soluble fiber is found in foods such as oats and legumes. They are important for the beneficial bacteria in the gut along with other health benefits. Insoluble fiber is found in vegetables and other foods and is considered good for bowel health.

The results showed a stronger link between soluble fiber and fewer incidences of dementia. That left the researchers to speculate why there was a difference between the two types of fiber.

"The mechanisms are currently unknown but might involve the interactions that take place between the gut and the brain," Professor Yamagishi said. "One possibility is that soluble fiber regulates the composition of gut bacteria."

He went on to say, "This composition may affect neuroinflammation, which plays a role in the onset of dementia. It's also possible that dietary fiber may reduce other risk factors for dementia, such as body weight, blood pressure, lipids, and glucose levels. The work is still at an early stage, and it's important to confirm the association in other populations."

Click here to read more in the journal Nutritional Neuroscience.