Higher Fiber Intake Supports Cognitive Function in Aging Adults
A 20-year study of almost 4,000 Japanese adults finds that those who consumed the most dietary fiber had the lowest risk of cognitive loss with age.
There was a stronger link with soluble fiber, which is found in foods like oats and legumes, and is important for supporting healthy gut microbiomes.
A possible mechanism is that the benefits to the microbiome also benefit the brain and reduce neuroinflammation, or may improve other relevant risk factors, like weight, blood sugar, and lipid levels.
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We're always hearing that we should eat more fiber. It's known to be vitally important for a healthy digestive system and also has cardiovascular benefits like reduced cholesterol. Now, evidence is emerging that fiber is also important for a healthy brain. In a new study published this month in the journal Nutritional Neuroscience, researchers in Japan have shown that a high-fiber diet is associated with a reduced risk of [cognitive loss].
"[Cognitive loss] 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 intake between 1985 and 1999. They were generally healthy and aged between 40 and 64 years. They were then followed up from 1999 until 2020, and it was noted whether they developed dementia that required care.
The researchers split 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 lower risk of developing [cognitive loss].
The team also examined whether there were differences for 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 [cognitive loss[ was more pronounced for soluble fibers.
"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 [cognitive loss]. It's also possible that dietary fiber may reduce other risk factors, 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 [cognitive loss].
- 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, Hiroyasu Iso. Dietary fiber intake: the Circulatory Risk in Communities Study. Nutritional Neuroscience, 2022; 1 DOI: 10.1080/1028415X.2022.2027592