A diet high in fiber, particularly high in soluble fiber, is linked to a lower risk of incident disabling dementia, new research has found.
Investigators administered a dietary survey to 3,700 healthy adults in their 40s, then followed them for up to 20 years. They found that participants who ate the most fiber had about a 25% lower risk of developing dementia later in life.
“This study showed that people with a high intake of dietary fiber, particularly soluble fiber, have a lower risk of dementia,” said study researcher Kazumasa Yamagishi, MD, PhD, professor, Department of Public Health Medicine, Faculty of Medicine and Health, Services. Research and Development Center, University of Tsukuba, Japan, said Medscape Medical News.
“There are still many unknowns about the causes of dementia, and it is not appropriate to determine causation based on the results of a single cohort study. However, the results of this study can be considered the one of the discoveries that will lead to the prevention of dementia,” Yamagishi said.
The study was published online February 6 to Nutritional neuroscience.
The brain-gut interaction has recently gained attention for its potential involvement in the development of dementia. “The concept of brain-gut interaction arose from the idea that the central nervous system communicates bidirectionally with the gastrointestinal tract, suggesting that the gut microbiome may influence brain plasticity and cognitive function,” the authors write. .
A diet rich in soluble fiber attenuates neuroinflammation in mouse models. Other animal studies have suggested that insoluble fiber may also have a beneficial effect on the microbiome.
The researchers wanted to see if dietary fiber intake — particularly soluble fiber — was associated with a reduced risk of dementia. They also investigated whether there was a difference between dementia in patients with vs without a history of caress.
In a previous study, these same researchers reported an inverse association between the consumption of fiber-rich beans and the risk of disabling dementia. In the current study, the researchers extended the analyzes to dietary fiber intake from total, soluble, and insoluble fiber, as well as other fiber-containing foods, such as potatoes, vegetables, and fruits. . However, they distinguished potatoes from other vegetables because the composition of starch in potatoes differs.
“Dietary fiber is a nutrient found in grains, potatoes, vegetables and fruits and is known to affect gut bacteria,” Yamagishi said. “Recently, some experimental studies have shown that gut bacteria may be involved in cognitive functions as well as in diseases of the digestive tract. However, no studies have actually examined the relationship between dietary fiber intake and subsequent risk dementia among large numbers of ordinary people.”
The researchers turned to participants in the Community Circulatory Risk Study (CIRCS), an ongoing dynamic community cohort study involving five communities in Japan. The current study focused on communities where surveillance for disabling dementia is being conducted.
Participants (n=3739) were 40-64 years old (mean age, 51) at the time they responded to the 24-hour dietary recall survey, and they participated in annual health check-ups from 1985 to 1999. Potential risk factors for disabling dementia were measured at the time the dietary surveys were conducted. Participants were then followed for a median of 19.7 years (1999 – 2020) to confirm the incident, disabling dementia.
‘Disabling dementia’ was defined as dementia that required care under the national long-term care insurance scheme and was further classified by whether or not it had a history of stroke cerebral.
The researchers divided the participants into quartiles, based on the amount of total, soluble, and insoluble intake reported in their surveys. They found that men tended to consume less total fiber than women.
During follow-up, 670 participants developed disabling dementia.
Total fiber intake was “inversely and linearly” associated with risk of incident dementia, the authors report, with each successive quartile being associated with a lower risk compared to the lowest quartile (P for trend = 0.03).
|Quartile||Multivariate HR (95% CI)|
|Second||.83 (.67 – 1.04)|
|Third||.81 (.65 – 1.02)|
|Fourth (highest)||.74 (.57 – .96)|
The association remained after adjusting for potential factors that might affect the onset of dementia, such as body mass index, systolic blood pressure, use of antihypertensive drugs, serum total cholesterol, cholesterol-lowering drugs and diabetes (P for trend = 0.05).
“The inverse association was more evident for soluble fiber intake and was limited to dementia without a history of stroke,” the authors report. Additionally, potatoes, not vegetables or fruits, showed a similar association.
“The mechanisms are currently unknown but may involve the interactions that take place between the gut and the brain,” Yamagishi said in a statement.
“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,” he suggested. “It is also possible that dietary fiber reduces other risk factors for dementia, such as body weight, blood pressure, lipidsand glucose levels.”
The authors note several limitations. For example, they did not distinguish between Alzheimer’s dementia and non-Alzheimer’s dementia. Additionally, they ranked eating habits based on a single survey, and participants’ eating habits may have changed over the study period.
Additionally, Yamagishi noted, it is “important to confirm the association in other populations.”
Balance is key
Commenting for Medscape Medical NewsUma Naidoo, MD, director of nutritional and lifestyle psychiatry, Massachusetts General Hospital, Boston, and nutrition educator at Harvard Medical School, said the study “adds to the growing body of evidence suggesting that A diet rich in colorful plant-based foods may benefit our neurological and psychiatric health, especially as we age.”
Naidoo, also a chef and author of It’s your brain on the foodwho was not involved in the study, continued: “In nutritional psychiatry, balance is key and therefore the consumption of a well-balanced diet including high amounts of fiber – especially from sources such as steel-cut oats, beans, lentils and many other fruits and vegetables — can be part of a healthy lifestyle and the prevention of cognitive decline in years to come.
“While the study authors admit the limitations of the study, in my opinion, eating healthier has so many mental and physical health benefits that it’s a no-brainer for nutritional psychiatry,” he said. -she adds.
The study was partially funded by Health and Labor Sciences Research Grants on Dementia from the Japanese Ministry of Health, Labor and Welfare; JSPS Kakenhi; FULL PAH; and Osaka University’s Joint International Research Promotion Program with University College London. The authors and Naidoo report no relevant financial relationship.
Nutr Neurosci. Published online February 6, 2022. Full Text