Lower Dementia Risk with Dietary Fiber!

Eating a high-fiber diet, especially one rich in soluble fiber, is linked to a lower risk of incident disabling dementia, new research shows. Investigators administered a dietary survey to 3700 healthy adults at midlife+ and then followed them for up to 20 years. They found that participants who consumed the most fiber had approximately a 25% lower risk of developing dementia in later life.

There are still many unknowns about the causes of dementia, and it is not appropriate to determine causality based on the results of a single study. However, the results of this study can be said to be one of the findings that will lead to the prevention of dementia.

Brain-Gut Interaction Brain-gut interaction has recently received attention for its potential involvement in the development of dementia. The concept of brain-gut interaction emerged 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.

A diet high in soluble fiber attenuates neuroinflammation in mouse models. Other animal studies have suggested that insoluble fiber might also have a beneficial effect on the microbiome.

The researchers wanted to see whether dietary fiber intake — especially soluble fiber — is associated with a reduced risk of dementia. They also investigated whether there was any difference between dementia in patients with vs without a history of stroke.

In a previous study, these same researchers reported an inverse association between eating beans, which are high in fiber, and risk of disabling dementia. In the current study, the researchers extended the analyses to dietary fiber intake of total, soluble, and insoluble fibers, as well as other fiber-containing foods, such 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 intestinal bacteria.

Participants ranged in age from 40 – 64 years (mean age, 51 years) at the time they completed the 24-hour dietary recall survey, and they participated in annual health check ups from 1985 – 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 incident, disabling dementia.

Disabling dementia was defined as dementia that required care under the National Long-Term Care Insurance System and was further categorized on the basis of having a history or not having a history of stroke. The researchers divided 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 compared to women.

The association remained after adjusting for potential factors that might affect dementia onset, such as body mass index, systolic blood pressure, antihypertensive medication use, serum total cholesterol, cholesterol-lowering medication, and diabetes.

The inverse association was more evident for soluble fiber intake and was confined to dementia without a history of stroke. Moreover, potatoes, not vegetables or fruits, showed a similar association.

The mechanisms are currently unknown but might involve the interactions that take place between the gut and the brain. 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.

Balance Is Key Adds to the growing pool of evidence suggesting that a diet rich in colorful, plant-based foods can benefit our neurological and psychiatric health.

In nutritional psychiatry, balance is key and therefore consuming a well-rounded diet including ample amounts of fiber — particularly from sources like steel-cut oats, beans, lentils, and numerous other fruits and vegetables — can be part of a healthy lifestyle and prevention against cognitive decline in later years.