Dietary Fiber Helps Prevent Dementia, but Be Wary of Supplements When Taking These Medications

Many people consume less fiber than nutritionists recommend in countries such as the United States and Australia. However, recent studies have indicated that fiber may have more benefits than just promoting bowel motility. People should be encouraged to adopt healthy eating habits high in dietary fiber, which may potentially reduce the incidence of dementia.

So what is the best kind of fiber to consume, and where can you find it?

Fiber in Food

Dietary fiber comes from plant-based foods such as legumes, grains, vegetables, fruits, nuts, and seeds. Because the human body’s digestive enzymes cannot fully decompose it, it stays within our intestinal tract.

Dietary Fiber’s Role in the Intestinal Tract

So what role does dietary fiber play in our gut?

The first is helping form stool and encouraging bowel regularity. Bulk fibers such as cellulose and hemicellulose absorb and retain water in the gut, promoting regular bowel movements. Viscous fibers (such as beta-glucan and psyllium) can help shape stools. Insoluble fibers (such as wheat bran, cellulose, and lignin) can trigger the secretion of mucus in the large intestine, which also acts to bulk up the stool.

The second role is maintaining the balance of gut bacteria and microbiota. Fermentable fibers such as resistant starch (RS), xanthan gum, and inulin feed the bacteria and microbiome of the large intestine. The fiber can also be metabolized to produce short-chain fatty acids, which benefit gastrointestinal health.

Some forms of insoluble fiber, such as RS, can ferment in the colon. Soluble fibers such as beta-glucan and raw guar gum may also be fermented into gas in the colon, producing physiologically active byproducts. After gut bacteria metabolize these, short-chain fatty acids are produced.

The third function is regulating the absorption of fat, carbohydrates, and protein from food. Regular soluble fiber intake, such as beta-glucan from oats or barley, has been shown to lower blood low-density lipoprotein or LDL (“bad”) cholesterol levels. Elevated LDL cholesterol level is a risk factor for cardiovascular disease.

High-Fiber Diets

It now appears that dietary fiber is not only good for our hearts and gastrointestinal (GI) tract but also for our brains.

A Japanese research report recently published in the Journal of Nutritional Neuroscience stated that a high-fiber diet might reduce degenerative brain disorders, which include Alzheimer’s disease.

The study conducted a follow-up survey on 3,739 adults for nearly 20 years. The findings showed that people who ate more fiber had a lower risk of dementia.

Experts speculate the result stems from the fact that soluble fiber modulates the composition of gut bacteria. This adjustment may reduce neuroinflammation, which plays a vital role in the pathogenesis of dementia.

Additionally, a 2018 report on animal research showed that if mice were fed dietary fiber, they would produce a short-chain fatty acid called butyric acid in their intestines. Butyric acid can significantly reduce inflammation in the gut and brain.

Dietary fiber can also affect other risk factors for dementia, such as regulating body weight, blood pressure, blood lipids, and glucose levels.

Soluble Fiber Is Most Effective in Preventing Dementia

The Japanese study also found that the fiber that reduces the risk of Alzheimer’s disease is primarily soluble.

Soluble fiber includes vegetable pectins and gums, which dissolve when they come into contact with digestive juices, forming a gel-like substance. So which foods are rich in soluble fiber? In general, beans, peas, and oat products have the highest soluble fiber content.

To give you an idea of where to find this fiber, here is the content of soluble fiber in common foods:

• 5.4 grams (0.2 ounce) in 3/4 cup of black beans
• 3.5 grams (0.1 ounce) in 1/4 cup of nuts
• 2.1 grams (0.07 ounce) in half an avocado
• 1.8 grams (0.06 ounce) in a medium size orange
• 1.8 grams (0.06 ounce) in 1/2 cup of sweet potatoes
• 1.7 grams (0.06 ounce) in 1/2 cup of asparagus
• 1.7 grams (0.06 ounce) in 1/2 cup of radishes
• 1.4 grams (0.05 ounce) in 3/4 cup of cooked oatmeal
• 1.4 grams (0.05 ounce) in a medium size nectarine
• 1.2 to 1.5 grams (0.04 to 0.05 ounce) in 1/3 cup of broccoli

Like insoluble fiber, soluble fiber adds bulk to stools and aids in bowel movements. But its unique structure has far-reaching health benefits, including benefits for heart health, weight maintenance, blood sugar control, and gut health.

Safely Supplementing With Dietary Fiber

Some people may be tempted to take dietary fiber supplements instead of getting it from food. Before doing that, consider two things.

1. First, ensure dietary fiber supplements do not contain nutrients other than dietary fiber.
2. Second, know that dietary fiber supplements can interfere with the absorption of some medications. If you are taking any of the following drugs, you should discuss with your doctor whether you should take fiber supplements or adjust the drug dosage while taking a supplement.

Drugs Affected by Fiber Supplements

The following are drugs that fiber supplements may impact:

• Antidepressants
• Anti-heart failure drugs
• Lithium carbonate for bipolar disorder
• Anti-inflammatory and anti-infective drugs
• Drugs for thyroid disease
• Anti-seizure drugs
• Blood lipid and blood sugar-lowering drugs

If you are taking these medicines and taking fiber supplements simultaneously, it is best to take the medication two hours after taking the fiber supplements.

As for the optimal amount of supplement, we do not have a one-size-fits-all suggestion here. However, if you take more than 50 grams (1.8 ounces) of fiber supplements daily, there is a risk of unfavorable side effects such as diarrhea.