Fiber Can Delay Brain Inflammation and Aging

• Fiber’s benefits extend far beyond your digestive tract to offer bodywide benefits — even in your brain
• A high-fiber diet may help stave off chronic systemic inflammation in your brain, a hallmark of aging linked to cognitive decline
• In an animal study, a high-fiber diet reduced inflammation in the brain’s microglia, a type of immune cell that, when inflamed, is linked to cognitive decline
• One type of soluble dietary fiber that may be particularly useful for increasing butyrate-producing bacteria in your gut is inulin
• The key may lie with butyrate, a short-chain fatty acid (SCFA) that’s produced through the fermentation of dietary fibers in your intestinal tract
• Inulin is a type of prebiotic fiber found in onions, leeks, garlic, asparagus, Jerusalem artichoke and many other foods

By Dr. Mercola

I recommend consuming 25 to 50 grams of fiber per 1,000 calories consumed, daily, as a foundation of optimal health. Though your body can’t digest it, fiber is an incredibly important carbohydrate because it aids in digestion, helps regulate blood sugar levels, plays a role in weight maintenance and much more.

You may be familiar with the two types — soluble fiber, which dissolves in water and is the type linked to benefits to blood sugar levels, and insoluble fiber, which does not dissolve but rather increases bulk in your stool, helping to support healthy digestion and elimination. Beyond this, however, it’s becoming clear that fiber’s benefits extend far beyond your digestive tract to offer bodywide benefits — even in your brain.

Fiber Is Good for Your Brain

Chronic systemic inflammation is a hallmark of aging and something that may negatively influence your brain function. Yet, it may be possible to keep said inflammation in check via lifestyle changes, including eating a healthy, high-fiber diet. The key may lie with butyrate, a short-chain fatty acid (SCFA) that’s produced through the fermentation of dietary fibers in your intestinal tract.

Previously, a drug form of butyrate was found to reduce inflammation and boost memory in rodents,¹which led researchers to also explore whether a high-fiber diet could trigger similar effects. To find out, they fed mice (both young and old) a high- or low-fiber diet, then measured both their levels of butyrate and inflammatory substances in their guts.

As suspected, the high-fiber diet elevated levels of butyrate and other SCFAs in the mice and also lowered levels of inflammation in the older mice’s intestines to those that mirrored that of young mice.

As for the brain, the researchers used genetic analysis to reveal that the high-fiber diet reduced inflammation in the brain’s microglia, a type of immune cell that, when inflamed, is linked to cognitive decline. The researchers explained:²

“Aging results in chronic systemic inflammation that can alter neuroinflammation of the brain. Specifically, microglia shift to a proinflammatory phenotype predisposing them to hyperactivation upon stimulation by peripheral immune signals. It is proposed that certain nutrients can delay brain aging by preventing or reversing microglial hyperactivation.”

Butyrate appears to be among them, and the researchers believe that consuming a high-fiber diet may reduce interleukin-1B, an inflammatory chemical linked to Alzheimer’s disease. While this study was conducted on mice, the researchers believe the results may also hold true in people.

“People are not likely to consume sodium butyrate directly, due to its noxious odor,” study coauthor Jeff Woods, a professor in the department of kinesiology and community health at the University of Illinois at Urbana-Champaign, said in a news release. “A practical way to get elevated butyrate is to consume a diet high in soluble fiber.”³ Writing in the journal Frontiers in Immunology, researchers added:⁴

“Taken together, high fiber supplementation in aging is a noninvasive strategy to increase butyrate levels, and these data suggest that an increase in butyrate through added soluble fiber such as inulin could counterbalance the age-related microbiota dysbiosis, potentially leading to neurological benefits.”

Low-Fiber Diets May Be Particularly Harmful for Seniors

The featured study revealed some additional intriguing findings, like the fact that only old mice has inflammation in their intestines when consuming a low-fiber diet. The young mice didn’t have the same level of inflammatory response to the lack of fiber, which the authors noted “clearly highlights the vulnerability of being old.”⁵

Yet, fiber intake among older adults is notoriously low, at about 40 percent below the recommended adequate intake (which is already lower than the optimal amounts I recommend). For example, it’s estimated that people aged 51 years and over consume just 16 grams of fiber a day.⁶

At the same time, seniors have a lower ability to produce butyrate, according to the study, “as suggested by fewer copies of the butyryl-CoA:acetate CoA transferase gene compared with younger adults and lower amounts of bacterial groups which are known butyrate producers.”⁷

It’s a potentially dangerous combination that puts the elderly at particularly high risk of disease as a result of not consuming enough fiber. On the other hand, eating plenty of fiber is linked to a longer life in seniors. In fact, in a study of more than 1,600 adults aged 50 years and older, those with the highest fiber intake were 80 percent more likely to live a long and healthy life over the 10-year follow-up period.⁸

Compared to those eating the least amount of fiber, the high-fiber group was less likely to suffer from hypertension, diabetes, dementia, depression and functional disability. “These findings suggest that increasing intake of fiber-rich foods could be a successful strategy in reaching old age disease-free and fully functional,” the researchers noted.⁹

Inulin May Be Particularly Good for Increasing Butyrate

One type of soluble dietary fiber that may be particularly useful for increasing butyrate-producing bacteria in your gut is inulin. Inulin is a type of prebiotic fiber found in onions, leeks, garlic, asparagus, Jerusalem artichoke and many other foods. Like other forms of dietary fiber, prebiotics are indigestible to you, but they help nourish beneficial bacteria in your body.

These beneficial bacteria in turn assist with digestion and absorption of your food and play a significant role in your immune function. Inulin is a fructan, which means it is made up of chains of fructose molecules. In your gut, inulin is converted into SCFAs like butyrate that are then converted to healthy ketones that feed your tissues. According to the featured study authors:¹⁰

“Studies have specifically demonstrated that inulin is beneficial for age-related inflammation, as a nutritional supplement with inulin increased innate immunity and protection against infections in elderly people. Thus, an increase in butyrate through added soluble fiber such as inulin could counterbalance the age-related microbiota dysbiosis, and potentially lead to neurological benefits.”

The study on mice that linked a high-fiber diet to decreases in brain inflammation actually used inulin as the source of dietary fiber. This beneficial prebiotic has also been linked to:

• Lower risk of diabetes — Among women with Type 2 diabetes, those who took inulin had improved glycemic control and increased antioxidant activity.¹¹ It’s thought that inulin may work to improve diabetes by positively modifying gut microflora or due to a direct antioxidant effect.
• Weight loss — Among overweight and obese adults, those who took 21 grams of inulin a day had decreases in their hunger hormone and increase in satiety hormones. Further, they lost more than 2 pounds while the control group gained 1 pound.¹²
• Cancer prevention — Inulin may reduce precancerous colon growths, lead to less inflammation and fewer precancerous cell changes (in animal studies) and support a less favorable environment for colon cancer development in humans.¹³
• Improved bone density — Inulin improves absorption of calcium and magnesium, leading to improved bone density and bone mineralization in children.¹⁴
• Heart health — Inulin may lower blood triglycerides and help optimize cholesterol.¹⁵

If you choose to take inulin in supplement form, start with a small amount to be sure it’s well tolerated, then gradually increase the dose. Some of the best food sources of inulin include:

Fiber Is Important for Kids’ Brain Health Too

Seniors are only one population who need to ensure they’re consuming adequate dietary fiber; children are another.

Like seniors, many children are not consuming adequate amounts of dietary fiber, a factor that may be associated with childhood obesity and even problems with cognitive control, which can affect behaviors such as inhibition (resisting distractions to maintain focus), working memory and cognitive flexibility (multitasking), all of which are important for succeeding in school and later careers.¹⁶

Among children aged 7 to 9 years, one study found that diet quality, specifically in relation to dietary fiber, correlated with performance on a cognitive task that required a high level of cognitive control. Those with a higher fiber intake had better cognitive control.

“Dietary fiber may influence cognitive and brain health through immunomodulation and/or the gut-microbiota-brain system,” the researchers noted, adding that the associated increased production of SCFAs has been linked to an increase in brain-derived neurotrophic factor (BDNF), a key growth hormone that promotes healthy brain neurons and plays a vital role in memory.

“Given that dietary fiber is a chronically underconsumed nutrient, the finding that low dietary fiber intake is associated with poorer childhood cognitive function raises important public health concerns,” the authors concluded.¹⁷

What Should You Eat to Increase Your Fiber Intake?

Before you rush out to stock up on bran muffins and oatmeal, here’s something to consider: Grains are not an optimal source of fiber. They’re not even a good one. Many grains are routinely doused with the herbicide glyphosate just before harvest — a process known as desiccation.

As a result, many popular “high-fiber” foods like breakfast cereal and granola bars are contaminated with glyphosate residues, which has been linked to disease.

This is only one reason to ditch grains as your source of fiber. A high-grain diet also promotes insulin and leptin resistance, thereby raising your risk for chronic diseases such as Type 2 diabetes, heart disease and cancer. A much better choice is to focus on eating more vegetables, nuts and seeds, including:

Keep in mind that adding fiber to your diet needn’t be something that’s unpleasant or akin to eating cardboard. Check out my collection of high-fiber recipes for ideas of what I mean — there are recipes for everything from pad Thai and guacamole to coleslaw and beef broccoli stir-fry, all of which will give your body a healthy fiber boost.