Researchers from the University of Tsukuba in Japan had found that higher levels of dietary fiber, particularly soluble fiber, are associated with a lower risk of developing dementia. The study results were published in the journal Nutritional Neuroscience.
Dietary fiber is a component that reaches the large intestine without being affected by digestive enzymes in the small intestine but is thought to affect the bacterial flora in the large intestine and may lead to health benefits.
According to studies a high-fiber diet enhances the abundance of Bacteroides species in mice, which have been found to be decreased in patients with dementia. In one mice study high-fiber diet attenuated neuroinflammation associated with aging via butyrate-induced gut bacteria.
It has been hypothesized that dietary fiber intake has a beneficial impact on the prevention of dementia, but not much epidemiological evidence is available. The researchers examined whether dietary fiber intake was inversely associated with risk of dementia.
The study included 3,739 Japanese individuals aged 40-64 years at the dietary surveys from the study Circulatory Risk in Communities Study. The dietary intake was estimated using the 24-hour dietary recall method, which consists of a structured interview intended to capture detailed information about all foods and beverages consumed by the participant in the past 24 hours.
Incident disabling dementia cases were followed-up from 1999 through 2020. During this time a total of 670 cases of disabling dementia developed, and dietary intake was inversely associated with risk of dementia. The association was more evident for soluble fiber intake.
The researchers proposed different mechanisms that could explain the decreased risk. One of them is that fibers were reported to have a beneficial effect on body weight, systolic blood pressure, serum lipids, and fasting glucose, and risk of stroke and diabetes, that could explain the association with a decreased risk of vascular-type dementia.
Another mechanism is that dietary soluble fiber regulates the composition of intestinal bacteria, which in animal studies have shown to decrease levels of neuroinflammation.
Kazumasa Yamagashi, et al. Dietary fiber intake and risk of incident disabling dementia: the Circulatory Risk in Communities Study. Nutritional Neuroscience, DOI: 10.1080/1028415X.2022.2027592