Fueling Your Microbiome: A Guide to Fermentable Fiber

To learn more about the gut microbiome, start with the post All About Your Amazing Microbiome.

Did you know that your gut contains about seven pounds of microbes? When you feed them the right fuel, these microbes help maintain a healthy gut, reduce inflammation, and improve digestion. So, what do these microbiome superheroes like to eat?

The Power of Fermentable Fiber

Your gut microbes thrive on fermentable fiber, which is found in whole plant foods. These fibers can’t be digested by you but are fermented by your gut bacteria. Unfortunately, you won’t get fiber from refined carbohydrates like that chocolate croissant. Instead, load up on whole grains, beans, nuts, seeds, vegetables, and fruits to nourish your gut.

Are You Getting Enough Fiber?

The recommended daily intake is around 30 grams of fiber, yet most people fall short. This is because fiber isn’t found in fats, oils, eggs, dairy, or meat. It’s also missing from refined carbs like bread, pasta, cookies, and most foods made from flour. In contrast, traditional diets often included 50-200 grams of fiber daily.

Feed Your Gut Microbes with Prebiotics

Prebiotics are fibers and compounds that serve as food for your beneficial gut bacteria. They include fermentable fiber, polyphenols (found in berries, red wine, and dark chocolate), and sulfur-rich foods like garlic, onions, and cruciferous vegetables. Even certain meats provide sulfur, feeding your microbes.

To ensure a healthy gut, eat a variety of whole plant foods rich in fermentable fiber, polyphenols, and sulfur. You can also take prebiotic fiber supplements that support gut health, reduce cholesterol, and regulate bowel movements.

Fiber Types: A Quick Primer

Here’s a breakdown of key fermentable fibers and where to find them:

1. Fructans (Inulin & FOS)

• Benefits: Boost bifidobacteria and reduce inflammation by increasing butyrate production.
• Foods: Artichokes, asparagus, chicory root, onions, and garlic.
• Supplements: Inulin and FOS powders.

2. Galacto-oligosaccharides (GOS)

• Benefits: Promotes healthy bacteria like lactobacillus and bifidobacteria.
• Foods: Lentils, chickpeas, lima beans.
• Supplements: GOS is added to baby formulas and some prebiotic fiber products.

3. Arabinogalactans

• Benefits: Increases SCFAs like butyrate and propionate, promoting colon health.
• Foods: Carrots, kiwi, radishes, pears, and red wine.
• Supplements: Available in powder form.

4. Beta-glucans

• Benefits: Helps beneficial microbes attach to the intestinal lining.
• Foods: Oats, barley, mushrooms (shiitake, maitake).
• Supplements: Often combined with other prebiotic fibers.

5. Resistant Starch

• Benefits: Reaches the colon where it feeds beneficial bacteria.
• Foods: Green bananas, plantains, cooled cooked potatoes, and rice.
• Supplements: Potato starch and green plantain flour.

6. Chitin & Chitosan (COS)

• Benefits: Supports a diverse microbial community, including lactobacillus and bifidobacteria.
• Foods: Soft insect skeletons, crustacean shells, and mushrooms.
• Supplements: Widely available in prebiotic form.

Key Takeaways for a Healthy Microbiome

1. Eat a wide variety of whole, unprocessed plant foods rich in fermentable fiber.
2. Include prebiotic foods like artichokes, onions, garlic, lentils, and mushrooms in your diet.
3. Consider prebiotic fiber supplements like inulin, GOS, or acacia gum to boost gut health.

By feeding your gut microbes the right foods, you’re not only supporting digestion but also enhancing overall wellness. And if you’d like to see exactly what microbes are taking up residence in your G.I. tract, we recommend the functional stool test called the GI-MAP.