April 2016 Issue

Feed Your Gut With Fiber

A healthy gut microbiome is essential to good health. Support yours with the high-fiber foods it needs to thrive.

Dietary fiber is good for us, but prebiotic fiber has extra benefits. Prebiotic fiber is dietary fiber that escapes digestion in our small intestine but is fermented by “good” bacteria in our large intestine. By nourishing beneficial bacteria, prebiotics can shift the balance of your gut’s community of bacteria and other microbes to a healthier environment. That’s great news, because a healthy gut microbiome promotes a strong immune system and lowers levels of chronic inflammation linked to many serious health conditions.


Push Prebiotic Fiber

The main types of beneficial bacteria (probiotics) encouraged by prebiotics are Bifidobacteria and Lactobacilli, also the most commonly used probiotics in foods, such as yogurt and supplements. All types of fermentable dietary fiber, such as fiber found in many fruits, vegetables, and whole grains, are potential prebiotics, but there is evidence that the following can improve the good gut bacteria population in humans:

Fructans are chains of fructose molecules. Fructo-oligosaccharides (FOS) are short-chain fructans, while inulins (a type of carbohydrate) are longer chain fructans. Chicory and Jerusalem artichoke are the biggest sources of fructans, and fructans are often added to processed foods to increase fiber content. Although fructans have health benefits, eating them in large amounts may cause unpleasant intestinal side effects.

Galacto-oligosaccharides (GOS) are chains of the sugar galactose. They are found in human milk, which is one reason that a healthy infant microbiome has large numbers of Bifidobacteria. Past infancy the main dietary sources are certain legumes, such as lentils, lima beans, chickpeas, red beans, and soy products.

Resistant starch also resists digestion. It’s found in whole grains, and cooked and cooled pasta, rice, and potatoes.

Increase Total Fiber

Eating fiber-rich foods in general promotes the growth of bacteria that break down plant starches and fibers into short-chain fatty acids (SCFAs). Some SCFAs may protect against inflammation and cancer, while others help us absorb essential minerals from our food, including calcium, magnesium, and iron.

People who consistently eat plenty of fiber, such as in a vegan, vegetarian, or Mediterranean diet, tend to have higher levels of SCFAs, suggesting that the amount of fermentable fiber from fruit, vegetables, and legumes matters more than the type of diet. Aim for eating a variety of whole plant foods to nourish a greater diversity of microbes in your gut ecosystem.

—Carrie Dennett, MPH, RDN

Pairing Prebiotics with Probiotics

saccharides (FOS)
Agave plant, globe artichoke, asparagus, bananas,
barley, garlic, jicama, onion, and wheat
Bifidobacteria, Lactobaccili
Inulin Agave plant, globe artichoke, asparagus, bananas,
barley, garlic, jicama, onion, and wheat
Bifidobacteria, Lactobaccili, Pediococcus
saccharides (GOS)
Lentils, beans, chickpeas, soy, cabbage, and
green beans
Bifidobacteria, Lactobaccilli
Resistant Starch Cooked and cooled pasta, grains, beans, and potatoes; green bananas and plantains; potato starch Bifidobacteria, Ruminococcus bromii, Eubacterium rectale
Beta-glucans Oats and barley Bifidobacteria, Lactobaccilli, Pediococcus
Lactulose Synthetic ingredient in laxative products Bifidobacteria, Lactobaccilli, Faecalibacterium prausnitzii
Guar Gum Derived from the guar bean; used as a food ingredient Bifidobacteria
Pectins Fruits, especially apples, grapefruit, peaches, apricots Lachnospira, Bacteroides thetaiotaomicron, Lactobaccilli
Wheat dextrin Ingredient in many fiber supplements Bifidobacteria, Lactobaccilli