Scientists from the University of Tsukuba found that eating a high-fiber diet may help lower dementia risk.
Dietary fiber, also known as roughage, is the indigestible part of plant foods.
Fiber has a host of health benefits, including reducing the risk of heart disease and type 2 diabetes. Fiber is mostly in vegetables, fruits, whole grains, and legumes.
There are two categories of fiber – soluble and insoluble. Both are beneficial and we need to include them in our daily diets. Most plant foods contain a mixture of both.
Soluble fiber soaks up water like a sponge and helps to bulk out our poo (faeces) so it can pass through the gut more easily. It acts to slow down the rate of digestion.
Soluble fiber includes pectins, gums, and mucilage, which are found mainly in plant cells.
One of its major roles is to lower LDL (bad) cholesterol levels. It can also help with constipation.
This slowing down effect of the digestive system is usually overridden by insoluble fibre. It does not absorb water and speeds up the time that food passes through the gut.
Insoluble fiber includes cellulose, hemicellulose, and lignin, which make up the structural parts of plant cell walls.
A major role of insoluble fiber is to add bulk to faeces and to prevent constipation and associated problems (such as haemorrhoids).
Scientists have suggested that dietary fiber can help with the prevention of dementia, but the scientific evidence is scant.
In the study, researchers aimed to examine whether a diet high in dietary fiber is linked to a lower risk of dementia.
They tested 3739 Japanese people aged 40-64 years at the dietary surveys (1985-99).
The team estimated these people’s dietary fiber intake using the 24-hour dietary recall method. Dementia incidence was followed up from 1999 through 2020.
The researchers also further classified dementia cases into that with or without a history of stroke.
They found that during a 20-year follow-up, there were a total of 670 cases of dementia. Importantly, dietary fiber intake was linked to a lower risk of dementia.
The effect was stronger for soluble fiber intake and was confined to dementia without a history of stroke.
The team also found a similar association for fiber-containing foods, potatoes, but not vegetables or fruits.
They concluded that dietary fiber intake, especially soluble fiber, was linked to a lower risk of dementia in Japanese people.
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 research is published in Nutritional Neuroscience and was conducted by Kazumasa Yamagishi et al.
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