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.

In case you need further reasons to put down the junk, there’s evidence that refined sugar, fats, and salt when consumed in excess may lead to something known as leaky gut syndrome. This health effect causes tiny little holes in our digestive system to leak out the good bacteria we need to keep us healthy and happy. A leaky gut can also put you at risk for a plethora of different diseases and health conditions., like food allergies, celiac disease, and even cancer.  [1] [2]

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 plant fiber so you can increase your fiber intake and start making your bacteria super happy.

What Is Fiber?

Occasionally called roughage or bulk, fiber is the component of plant foods your body can neither digest nor absorb. While your body can break down and absorb other food elements like fats, proteins, and carbohydrates, your body cannot digest fiber. Instead, fiber passes through your stomach and colon relatively intact.

Does Fiber Come From Plants?

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. [3]

Plant Fiber: Soluble Fiber vs. Insoluble Fiber

There are two types of dietary fiber: soluble and insoluble. Here is the difference between the two:

• Soluble fiber dissolves in water. The result is a gel-like substance that slows down the digestive process and makes you feel full.
• 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 Plant 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.

A 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 (probiotics) 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.

But prebiotic fiber isn’t the only soluble fiber that does many incredible things for your body. Here are a few examples of ways soluble fiber impacts your health:

• Lowering 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. [5]
• Stabilizing blood sugar (glucose) levels: Soluble fiber stalls the digestion speed of nutrients, including carbohydrates. Therefore, meals containing soluble fiber rarely cause sharp spikes in blood sugar levels. [1]
• Lowering fat absorption and helping weight management: 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.
• 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 a number of benefits, such as:

• 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 constipation. 

Types of Soluble Fiber

If you are looking for ways to add more soluble fiber to your diet, try choosing a variety of plant 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. [6] 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.

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.

Plant 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 plant-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

The Importance of a High-Fiber Diet 

The average American consumes less than fifteen 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. [7] Adding more dietary fiber to our plates could help us lose weight, lower inflammation, and decrease our risk of several diseases. [8] [7]

Plant 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. Vani Hari, Feeding You Lies: How to Unravel the Food Industry’s Playbook and Reclaim Your Health (Hay House Inc, 2019).
3. Gene A. Spiller, CRC Handbook of Dietary Fiber in Human Nutrition, Third Edition (CRC Press, 2001).
4. “Probiotics, Prebiotics and the Gut Microbiota,” ILSI, n.d., https://ilsi.org/publication/probiotics-prebiotics-and-the-gut-microbiota/.
5. 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.
6. 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.
7. Aelia Akbar and Aparna P. Shreenath, “High Fiber Diet,” July 2, 2020, https://www.ncbi.nlm.nih.gov/books/NBK559033/.
8. Justin Sonnenburg and Erica Sonnenburg, The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-Term Health (Penguin, 2015).

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.