Fiber Grabs the Brain Health Spotlight

Adding fiber through a plant-rich diet may help lower dementia risk, especially as we age

Freda Kreier

Updated June 29, 2026

A man at a kitchen counter with fruits and vegetables on a cutting board

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Older adults who eat a fiber-rich diet are nearly 35 percent less likely to develop dementia than their peers who skimp on fiber, according to new research presented at the 2026 annual meeting of the American Academy of Neurology in Chicago.

While the research is not yet peer-reviewed, it aligns with a growing body of evidence linking fiber intake to reduced dementia risk.

The results suggest that incorporating more fiber into your diet is a simple change that can improve overall brain health, says nutritional epidemiologist Puja Agarwal, a coauthor of the study.

“We have to make sure that we don’t make a grand statement to say that fiber prevents dementia,” says Dr. Ayesha Sherzai, a neurologist at Charles R. Drew University in Los Angeles. Still, this research “is a confirmation of what we already know: People who eat foods that are high in fiber appear to have meaningfully lower rates of dementia.”

How to prevent or delay dementia

Dementia, which affects around 57 million people worldwide, has no cure and most available treatments involve symptom management. So risk reduction is critical. Two drugs can slow progression for Alzheimer’s disease, the most common cause of dementia, but only in the disease’s early-stage.

However, research shows that our daily habits can help delay the onset of dementia. These include the six pillars of brain health: exercising regularly, being social, getting adequate sleep, managing stress, engaging our brains by learning new things, and eating healthily.

Because Alzheimer’s and other causes of dementia develop over decades, research on risk factors takes time. At Rush University, as part of the Rush Memory and Aging Project, scientists have been following a group of older adults since 1997 and quizzing them on their daily routines.

In 2015, the Rush team found that older adults who followed the MIND diet, which is similar to the Mediterranean diet — both focus on eating plants, fish, and poultry, while limiting dairy and red meat consumption — were 54 percent less likely to develop Alzheimer’s disease, compared with those who did not follow the MIND diet, over a nearly 5-year study period.

Scientists are still figuring out what it is about our diets that may protect brain health, but fiber seems to play a part. Studies in Japan, the United States, and the United Kingdom have all found that people who eat fiber-rich diets, compared with those who don’t, are less likely to develop dementia.

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In the new research, Agarwal and her colleagues followed more than 1,500 people from the Chicago area, average age 81, over seven years. Each year, participants took a cognitive exam and filled out dietary surveys. The researchers then split the participants into five groups depending on how much fiber they reported eating. People on the higher end ate around 27 grams of fiber per day on average — roughly the recommended daily intake of fiber — while people on the lower end reported eating around 13 grams of fiber per day.

Overall, people in the high-fiber group were 34 percent less likely to develop dementia over the study period than people in the low-fiber group.

What are fiber’s benefits?

What is it about fiber? One leading theory is that fiber-rich foods help feed gut microbes that produce brain-protecting compounds. For instance, research in mice shows that eating fiber-rich diets promotes the release of short-chain fatty acids, which can help reduce inflammation, protect the blood-brain barrier, and make the gut healthy.

But it could also be a combination of factors, Sherzai says. Fiber-rich foods tend to be rich in antioxidants and other brain-healthy nutrients.

Fiber also makes people feel fuller and slows down digestion, which can help people control blood-sugar levels and maintain a constant weight, Agarwal adds. It also slows the absorption of cholesterol and some fats into the bloodstream, which can help protect vascular health.

Most of us aren’t meeting fiber targets

Interested in upping your fiber intake, but don’t know where to start? You’re not alone. “Most adults in the United States are eating less than half of what their bodies need,” Sherzai says.

The CDC recommends that adults eat between 22 and 34 grams of fiber each day. As of 2021, only 9 percent of women and 5 percent of American men were meeting this recommendation.

Fiber-rich foods include:

Vegetables
- Carrots
- Corn
- Leafy greens
- Broccoli
Legumes
- Beans
- Lentils
Nuts and seeds
- Almonds
- Pistachios
- Sunflower kernels
- Chia seeds
Grains
- Whole-wheat spaghetti and rice
- Oatmeal
- Popcorn
Fruits
- Raspberries
- Pears
- Apples

One meal cannot meet your daily fiber needs. Rather, you should aim to spread your fiber intake throughout the day. Agarwal suggests adding fiber-rich foods to meals you already enjoy. That could mean adding beans to your weekly chili, sprinkling berries onto your morning oatmeal, or even doubling the fiber-rich ingredients by snacking on hummus with carrots, rather than pita. Increasing your fiber using foods you already like will help you stick with a plan in the long term.

Changing how we eat can be hard. However, research like this is “a fantastic opportunity to re-evaluate our dietary patterns,” Sherzai says. Scientists might still be working out why diet and dementia are linked, but the bottom line is, “eating plants is one of the most important things we can do for our brain health.”

Staying Sharp offers meal plans to get you started with the Mediterranean diet, help you reduce cholesterol and support weight loss.