Scientists from the University of Tsukuba found that eating a high-fiber diet is linked to a lower risk of dementia in healthy older people.
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 2 different types of fiber — soluble and insoluble. Both are important for health, digestion, and preventing diseases.
Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables.
Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It adds bulk to the stool and appears to help food pass more quickly through the stomach and intestines.
Scientists have hypothesized that dietary fiber intake benefits the prevention of dementia, but there is little evidence in human studies.
In this study, researchers aimed to examine whether dietary fiber intake is linked to a lower risk of dementia.
They analyzed data from the Circulatory Risk in Communities Study, which involved 3739 Japanese adults aged 40–64 years in the dietary surveys (1985–99).
The team estimated the participants’ dietary fiber intake with the 24-hour dietary recall method. They also calculated the dementia incidents from 1999 through 2020.
The researchers found that during a 20-year follow-up, 670 people developed dementia. Importantly, dietary fiber intake was strongly linked to a lower risk of dementia.
Furthermore, the reduction of dementia risk was strongest for soluble fiber intake and was confined to dementia without a history of stroke.
The team concluded that dietary fiber intake, especially soluble fiber, was linked to a lower risk of dementia in a general Japanese population.
One limitation of the study is that the dietary surveys asked about meals taken in the last 24 hours.
This survey method could be affected by the foods that the participants happened to have eaten on the previous day or the day of the survey.
Another limitation is that the participants’ dietary habits could change during the long follow-up period. How this affected the link between dementia risk and dietary fiber intake is unclear.
Another limitation is that the study did not control socioeconomic factors, such as education and income. Previous research has found a small positive link between household expenditure and total fiber intake.
Future work may need to clarify the influence of socioeconomic factors on the link between dementia risk and fiber intake.
The research was published in Nutritional Neuroscience and was conducted by Kazumasa Yamagishi et al.
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