Researchers followed 3700 adults, ages 40 to 64, for up to 20 years and found that those who ate the most fiber were 25 percent less likely to suffer dementia in later life than those who ate the least (Nutritional Science, February 6, 2022). The more fiber a person ate, the less likely they were to develop dementia. Dietary fiber is found in fruits, vegetables, beans, grains, nuts and other seeds.

How Soluble Fiber May Help to Prevent Dementia
You cannot absorb soluble fiber, so it passes through your intestines down to your colon where more than 100 trillion bacteria live. Some bacteria that live in your colon are healthful, while others are harmful. The healthful bacteria break down soluble fiber to form Short Chain Fatty Acids (SCFAs) that are absorbed into your bloodstream to lower high cholesterol, high blood pressure, high blood sugar and high insulin levels, and block inflammation, a process that can damage all parts of your body. All of these factors increase risk for dementia. An anti-inflammatory diet that helps to prevent dementia is based on fruits, vegetables, whole grains, beans, seeds and nuts (Neurology, Dec 14, 2021; 97 (24)).

The harmful types of bacteria try to invade your colon cells, which turns on your immune system to cause inflammation, increasing your risk for dementia and heart attacks. A pro-inflammatory diet is low in plant fiber and high in red and processed meat, sugar-added foods and fried foods.

An increase in harmful bacteria and decrease in healthful bacteria increases risk for heart attacks and dementia (Hypertens Res, 2019;42(7):1090-1). A study in mice showed that a high soluble-fiber diet decreased inflammation associated with ageing (Front Immunol, 2018;9(1832).

My Recommendations
A diet rich in soluble fiber found in fruits, vegetables, whole grains, beans, seeds and nuts and low in red and processed meats, fried foods and sugar added foods is associated with reduced risk for suffering dementia as you age. For more on the many benefits of fiber, see:
Fiber, a True Superfood
Fiber Wins Again
Snack on High Fiber Foods