Can Fiber Improve Cognition in the Elderly?

“It’s paradoxical that the idea of living a long life appeals to everyone, but the idea of getting old doesn’t appeal to anyone.” –Andy Rooney

A new study has found that a simple prebiotic could boost beneficial bacteria in the gut and improve scores on a cognitive test in people over 65. This could be fantastic news to those worried about the seemingly inevitable descent into dementia as we age. The study, conducted by Clare Steves, Mary Ní Lochlainn, Kevin Whelan, and colleagues at King’s College, London, found that the people taking a prebiotic fiber had significantly better scores on a test called the paired associates learning test. This visual-memory test is often used to detect early signs of Alzheimer's.

Can a fiber supplement improve cognition?

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One of the authors, Mary Ní Lochlainn, said, “Those who received the prebiotic had half the number of errors on this test compared with the group that received a placebo.” She noted that the changes brought about by the prebiotic happened quickly. “We are excited to see these changes in just 12 weeks. This holds huge promise for enhancing brain health and memory in our aging population,” she said.

The researchers found that the prebiotic fiber boosted specific healthy bacteria, including Bifidobacteria. This is among the first bacteria we acquire as babies when we get milk. Mother’s milk contains Bifidobacteria, and gives us a jump start. Bifidobacteria produces short-chain fatty acids that both nourish and heal the cells lining the gut. Keeping your gut in the pink of health prevents bacteria and toxins from seeping into the bloodstream, where they get pumped to every organ in the body, potentially causing widespread inflammation.

Some of these fatty acids also make it to the brain, where they encourage the growth and repair of brain cells. As we age and consume less milk, our levels of Bifidobacteria slowly decline. But the standard American diet (SAD) also contains precious little fiber, which also reduces the amount of Bifidobacteria even more. By the time we’re 65, we have very little Bifidobacteria left, and its absence is felt in a thousand little ways from stiff knees to diabetes, high blood pressure, depression, and cognitive difficulties.

Studies like this often have a lot of noise, particularly because people are so variable, both genetically and microbially. But King’s College has a large group of twins they can tap for research, this cleans up the signal considerably, eliminating the genetic difference between subjects. Twins also have gut microbiomes that are more similar to each other, as compared with unrelated people. By giving one twin the prebiotic and the other a placebo, researchers were able to get clean results.

This wasn’t a large study, but the study of twins gives it some extra power. The study also comports with several other studies showing that consuming fiber—dietary and supplemental—is associated with better cognitive performance.

If a simple supplement such as fiber can help prevent cognitive loss, it points to a hopeful future for dementia and Alzheimer's. It also implies that we could benefit from foods with higher fiber. This includes veggies like asparagus, Jerusalem artichokes, lentils, onions, and garlic. To satisfy the sweet tooth, raspberries, strawberries, and blueberries are good sources of fiber as well.

Food manufacturers are still trying to learn this lesson, but for now, most processed foods are extremely low in fiber. And sadly, most Americans get over half of their calories from fast or processed food.

Knowledge is power, and now that you know how your gut microbes can keep your cognition at an optimal level, what are you waiting for? Eat a veggie. Maybe even try a fiber supplement. Today is a good day to start.