Researchers from the University of Tsukuba in Japan, find that higher levels of dietary fiber, particularly soluble fiber, are associated with a lower risk of dementia.
We’re aoften told that we should eat more fiber. It’s recognized to be essential for a healthy digestive system and also has cardiovascular benefits such as lower cholesterol. Now, evidence is emerging that fiber is also vital for a healthy brain. In a new study published recently in the journal Nutritional Neuroscience, researchers in Japan have shown that a high-fiber diet is associated with a lower risk of developing dementia.
“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.”
Participants completed surveys that assessed their dietary consumption between 1985 and 1999. They were generally healthy and between 40 and 64 years of age. They were then followed up from 1999 until 2020, and whether they developed dementia that required care was recorded.
The scientists divided the data, from a total of 3739 adults, into four groups according to the amount of fiber in their diets. They found that the groups who ate higher levels of fiber had a decreased chance of developing dementia.
The team also examined whether there were differences between the two main types of fiber: soluble and insoluble fibers. Soluble fibers, found in foods such as oats and legumes, are important for the beneficial bacteria that live in the gut as well as providing other health benefits. Insoluble fibers, found in whole grains, vegetables, and some other foods, are known to be important for bowel health. The researchers found that the link between fiber intake and dementia was more pronounced for soluble fibers.
The team has some theories as to what might underlie the link between dietary fiber and the risk of dementia.
“The mechanisms are currently unknown but might involve the interactions that take place between the gut and the brain,” says Professor Yamagishi. “One possibility is that soluble fiber regulates the composition of gut bacteria. 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.”
In many countries today, such as the US and Australia, many people consume less fiber than is recommended by nutritionists. By encouraging healthy eating habits with high dietary fiber, it might be possible to reduce the incidence of dementia.
Reference: “Dietary fiber intake and risk of incident disabling dementia: the Circulatory Risk in Communities Study” by Kazumasa Yamagishi Koutatsu Maruyama, Ai Ikeda, Masanori Nagao, Hiroyuki Noda, Mitsumasa Umesawa, Mina Hayama-Terada, Isao Muraki, Chika Okada, Mari Tanaka, Rie Kishida, Tomomi Kihara, Tetsuya Ohira, Hironori Imano, Eric J. Brunner, Tomoko Sankai, Takeo Okada, Takeshi Tanigawa, Akihiko Kitamura, Masahiko Kiyama and Hiroyasu Iso, 6 February 2022, Nutritional Neuroscience.
Funding: This work was partly supported by Health and Labour Science Research Grants for Dementia (grant numbers H21-Ninchisho-Wakate-007 and H24-Ninchisho-Wakate-003) from the Ministry of Health, Labour and Welfare of Japan; JSPS Kakenhi (grant numbers 26253043, 17H04121, 18K10097 and 21H03194); FULLHAP; and the Osaka University International Joint Research Promotion Programme with University College London.