To foster healthy bacteria in our guts, we need to create the perfect environment for them to thrive. Most of our bacteria happen to be foodies—and they're very particular about what they eat. AKA junk and processed foods aren’t their cup of tea.

Truthfully, the little army in our gut does a ton for us. So the least we can do is feed them what they want so they can continue protecting us. If you’re wondering: what do the bacteria in your gut want and need to keep you happy and healthy? The simple answer: fiber. They LOVE it. 

Here’s everything you need to know about fiber so you can increase your intake and start making your bacteria super happy.

What Is Fiber?

Fiber, sometimes called roughage or bulk, is a critical component of plant-based foods that your body cannot digest. Unlike fats, proteins, and carbohydrates, which your body breaks down and absorbs, fiber passes through your stomach and colon almost intact. This unique property is what makes fiber so beneficial for your digestive system. 

Soluble vs. Insoluble Fiber

Fiber comes in two main types: soluble and insoluble. Knowing the difference between the two is essential for understanding what fiber is and how it benefits your health:

• Soluble fiber dissolves in water and forms a gel-like substance in your digestive tract. This type of fiber slows down digestion, helping you feel full longer and better absorb nutrients from food. Prebiotic fibers, which are a type of soluble fiber, also feed your gut’s beneficial bacteria, promoting a healthy microbiome. 
• Insoluble fiber does not dissolve in water. Instead, it passes through your small intestine into the large intestine, where it draws water into your stool for aided bowel regulation. Essentially, this fiber acts as bulk to keep your digestive system running smoothly. [1]

Benefits of Fiber

Your body needs both soluble and insoluble fiber to maintain proper digestive health. However, they differ in their benefits.

Soluble Fiber Benefits

When soluble fiber enters your stomach, it collects water, dissolving and turning into a gel. If you've ever seen or eaten chia seeds and noticed the gel that forms around them, then you've seen soluble fiber in action! This gel slows down digestion, allowing your body to absorb your food's vitamins and nutrients better and make you feel fuller.

Here are a few examples of ways soluble fiber impacts your health:

• Maintaining healthy cholesterol: Because it's not absorbed in the intestine, soluble fiber can bind cholesterol in the intestine and eliminate it from the body. By consuming 5 to 10 grams of soluble fiber a day, you could help improve your total and LDL cholesterol by 5 to 11 points for those already in a normal range. [2]
• Supporting healthy blood sugar levels: Soluble fiber stalls the digestion speed of nutrients, including carbohydrates. Therefore, meals containing soluble fiber rarely cause sharp spikes in blood sugar levels for those already in a normal range. [1]
• Lowering fat absorption: Remember that gel we talked about? As a spread-out, thick gel, soluble fiber aids in blocking fats that your body would otherwise digest and absorb.
• Lessening the risk of cardiovascular disease: Regularly eating soluble fiber may lower the risk of heart disease and circulatory conditions for those already in a normal range.
• Feeding healthy gut bacteria: Some soluble fiber-rich foods ferment in the colon, helping feed and grow your gut bacteria population.

Insoluble Fiber Benefits

Insoluble fiber's job is to soften your stool and make it easier to pass through your colon. As insoluble fiber passes through your small intestines, it draws water into the large intestine. This helps keep your stool soft and leads to a more enjoyable bathroom experience.

When it comes to regulation, insoluble fiber has two key benefits, among other supportive functions:

• Supporting digestion: Insoluble fiber slows down digestion. This helps your body better absorb nutrients from your food.
• Increasing fecal bulk: Insoluble fiber works to help fecal material move through your digestive system and increase stool bulk. This is essential for maintaining digestive regularity and particularly helpful for those who struggle with occasional constipation. 

Types of Soluble Fiber

If you are looking for ways to add more soluble fiber to your diet, try choosing a variety of fibers. There are quite a few to choose from including inulin, gums, pectins, and psyllium. Here is a little more about each:

• Inulin: Inulin is a type of soluble fiber that belongs to a class of carbohydrates known as fructans. It's most commonly found in chicory root, asparagus, bananas, garlic, leeks, and onions. We also use inulin in OLIPOP, which is how we pack all that fiber in a can. 
• Gums: Gums are added to foods for their functional properties, including thickening, stabilizing, and emulsifying, to enhance texture, improve shelf life, and maintain product quality. They contribute to your sensory experience of various food products. Look out for naturally derived gums like guar and acacia. [3] Both are plant-based and contain dietary fiber.
• Pectins: These come from the plant’s cell walls and are in fruits and vegetables. Pectins help to thicken foods and are most commonly found on the ingredients list of jellies and jams.
• Psyllium: This absorbs water in the intestines to help add bulk to your stool. This type of polysaccharide is derived from Plantago ovata seeds and is often added as a powder into food or drinks. 
• Fructooligosaccharides (FOS): Short fructose chains are often used as an alternative to sugar due to their prebiotic effects and beneficial mineral absorption. You can find FOS in fruits, vegetables, and grains such as chicory, asparagus, onions, wheat, and tomatoes.
• Beta-glucans: These are sugar compounds that serve as the primary form of fiber found in the cell walls of cereals, grain, and fungi. Think mushrooms! You'll find beta-glucans in bacteria, yeast, fungi, algae, and plants such as oats and barley.

What is Prebiotic Fiber?

Another type of soluble fiber, prebiotic fiber, is crucial and works as food for the beneficial bacteria living in your gut. Prebiotics belong to a diverse category that comprises carbohydrates, resistant starches, pectins, and other beneficial ingredients that your army of good bacteria loves to eat.

When the microbiome metabolizes prebiotics this promotes the growth of certain good bacteria species while triggering the release of metabolites such as short-chain fatty acids. [4] In other words, by feeding your gut prebiotics, you’re strengthening and helping maintain good levels of healthy bacteria.

Types of Insoluble Fiber

As for insoluble fiber, there are a few varieties of plant-based foods to choose from. Here are some common types:

• Cellulose: This is the most abundant form of insoluble fiber, and you'll find it in the cell walls of plants. Foods with cellulose include whole grains, bran, vegetables (especially those with a fibrous structure, like celery), and fruits with skins (such as apples).
• Hemicellulose: This is another component of plant cell walls and is a complex branched polymer. Foods with hemicellulose include whole grains, bran, nuts, and seeds.
• Lignin: This is a complex, non-carbohydrate substance also found in the cell walls of plants. It provides rigidity to plant cell walls. Noticing a pattern here? Bran layers of whole grains, seeds, and the skins of certain fruits (like berries) contain lignin.
• Resistant Starch: This is a type of starch that resists digestion in the small intestine, allowing it to reach the colon where it acts as insoluble fiber. Legumes, unripe bananas, and certain cooked and cooled starchy foods contain resistant starch.
• Chitin: This is a polysaccharide found in the exoskeletons of insects and crustaceans and the cell walls of fungi. You're less likely to come across this insoluble fiber in your everyday diet, but you may find it in some dietary supplements.

It's important to note that many plant-based foods contain a combination of both soluble and insoluble fibers, and a balanced intake of both types is recommended for overall digestive health.

High Fiber Foods

Looking to add more soluble and insoluble fiber to your diet? Consume a variety of whole grains, fruits (with the skin!), vegetables, nuts, and seeds. This can help ensure an adequate intake of both soluble and insoluble fibers. Here is a list of great fiber foods to try: 

• Asparagus
• Avocado
• Artichoke
• Chickpeas
• Wheat bran
• Corn bran
• Oats
• Popcorn
• Nuts and seeds
• Potatoes
• Carrots
• Beets
• Brown rice
• Flaxseed
• Green beans

Does Fiber Come From Plants?

Yes, fiber is only found in plant foods. Neither meat nor dairy contains natural fiber. Fiber is the part of plants that humans' digestive tracts cannot digest. These include the plant cell walls including cellulose, hemicelluloses, pectin, and lignin. (That we mentioned earlier!) [5]

The Importance of a High-Fiber Diet 

The average American consumes 16 grams of fiber per day, less than half the recommended amount. This lack of dietary fiber in our American diet explains many of the Western diseases we are currently suffering from. Today, almost half of United States citizens carry a pre-diabetes, diabetes, or metabolic syndrome diagnosis. [6] Adding more dietary fiber to our plates could help us lose weight, support the gut, and support our overall health. [6] [7]

Fiber: The Takeaway

Fiber is important in our diets and keeps our gut health in check. Adding both soluble and insoluble fiber to your diet is a great way to support your health. To help fill those fiber gaps, you can also pop open a can of OLIPOP. It's an easy and delicious way to give your body some fantastic, intentional ingredients that support your digestive health.

Sources

1. James M. Lattimer and Mark D. Haub, “Effects of Dietary Fiber and Its Components on Metabolic Health,” Nutrients 2, no. 12 (December 15, 2010): 1266–89, https://doi.org/10.3390/nu2121266.
2. Karen Aspry, “Adding Soluble Fiber to Lower Your Cholesterol Advice from the National Lipid Association Clinician’s Lifestyle Modification Toolbox,” National Lipid Association, n.d.
3. Bernice Karlton‐Senaye and Salam Ibrahim, “Impact of Gums on the Growth of Probiotics,” unknown, July 1, 2013, https://www.researchgate.net/publication/281787450_Impact_of_gums_on_the_growth_of_probiotics.
4. “Probiotics, Prebiotics and the Gut Microbiota,” ILSI, n.d., https://ilsi.org/publication/probiotics-prebiotics-and-the-gut-microbiota/.
5. Gene A. Spiller, CRC Handbook of Dietary Fiber in Human Nutrition, Third Edition (CRC Press, 2001).
6. Aelia Akbar and Aparna P. Shreenath, “High Fiber Diet,” July 2, 2020, https://www.ncbi.nlm.nih.gov/books/NBK559033/.
7. Justin Sonnenburg and Erica Sonnenburg, The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-Term Health (Penguin, 2015).
8. Vani Hari, Feeding You Lies: How to Unravel the Food Industry’s Playbook and Reclaim Your Health (Hay House Inc, 2019).

Meet our Expert This article is reviewed by Lauren Manaker MS, RDN, LD. Lauren Manaker is an award-winning registered dietitian, book author, and freelance writer. Her work can be found in many major media outlets and on her women’s health nutrition-focused Instagram account @LaurenLovesNutrition. Raised in sunny South Florida and now living in Charleston, South Carolina, she has a love for the ocean and would be living on a houseboat if she had her way. She currently lives with her husband, young daughter, and 70-pound rescue pup.