Fiber is an indigestible carbohydrate that makes up the structure of plant foods. It provides the framework that allows plants to stand up straight. Similar to how animals have a skeleton for support, plants have fiber.
There are two main types of fiber: Soluble and Insoluble.
Soluble fiber is primarily found in foods like oats, apples, beans, lentils, and carrots.
Soluble fiber acts like a sponge: it soaks up water and leaves you with a feeling of fullness. It also absorbs excess cholesterol, hormones, and toxins and helps move them out of the body.
Insoluble fiber, on the other hand, is more like a broom. It’s a hard-to-digest compound that humans aren’t able to break down, so this type of fiber actually passes through our digestive system relatively unchanged, sweeping other waste out with it.
Think of insoluble fiber as the roughage from plants, like celery and broccoli stems, the skin of many fruits and vegetables, and the outer shell or kernel of whole grains and corn.
We do need both types in our diet, but it’s the overall total fiber that you need to focus on. Eating a diet rich in plant foods should easily get you to your target.
Why Is Fiber Important
Fiber is what helps everything run smoothly… literally. Dietary fiber in food helps keep bowel movement regular. Additionally, it can help improve cholesterol and blood sugar levels.
Fiber and The Gut
Insoluble fiber is also known as fermentable fiber because as it passes through the colon unchanged, it serves as fermentable food for the trillions of bacteria living there.
Known as your gut microbiome, this symbiotic colony is responsible for numerous health processes in the body, including making certain nutrients and neurotransmitters, boosting immunity and even helping to balance blood sugar. Consuming high amounts of fermentable, insoluble fiber is crucial for the optimal functioning of your microbiome—and for your health in general.
How Much Fiber You Need
According to the Institute of Medicine (IOM), here are the following fiber recommendations.
- Men 50 and younger: 38 grams of fiber per day
- Women 50 and younger: 25 grams of fiber per day
- Men over 50: 30 grams of fiber per day
- Women over 50: 21 grams of fiber per day
So how do you get the 30 grams that are recommended a day?
Turns out it’s not that hard. A bowl of steel-cut oatmeal (one cup) has 8 grams, a kale salad with broccoli and chickpeas has around 15 grams, while a cup of lentil soup has around 8 grams. See our chart below for the top 20 sources of fiber to add to your diet—all while eating delicious, plant-based foods.
If you like popcorn you can get four grams of fiber per serving (about 3½ cups) so go get yourself an air popper and enjoy air-popped popcorn without added oils, for a great source!
The Health Benefits of Fiber:
- Keeping your cholesterol in check: Soluble fiber has been shown to help keep low-density lipoproteins at reduced levels.
- Removing excess hormones: Extra estrogen and cortisol get flushed out with a big dose of fiber, leading to a more balanced hormone environment.
- Balancing blood sugar: Soluble fiber helps slow blood glucose absorption.
- Assisting with weight loss and weight maintenance: Fiber helps keep you feeling fuller longer, which studies have shown leads to reduced overall calorie intake and helps maintain weight at healthy levels.
- Supporting your gut microbiome: Fermentable fiber feeds good gut bacteria so they can create short-chain fatty acids and other nutrients for the body to utilize.
- Eliminating toxins: Fiber binds harmful toxins and helps them leave the body daily.
- Reducing your risk of cancer, heart disease, and diabetes: Studies have shown that a diet rich in fiber can reduce your risk of colorectal cancer and metabolic syndrome (a cluster of chronic conditions including heart disease and diabetes).
- Fiber can assist with your gut health and IBS: Whether you have constipation or diarrhea, fiber increases the weight and volume of your stool, making it easier to pass.
The Top Fiber-Rich Vegan Foods
Here are the 20 most fiber-rich foods—note that they’re ones you’re probably already eating on a plant-based diet.
- Lentils = 1 cup has 16 grams of fiber
- Black beans = 1 cup has 15 grams of fiber
- Pistachios = 1 cup has 13 grams of fiber
- Prunes = 1 cup has 12 grams of fiber
- Corn = 1 cup has 12 grams of fiber
- Chickpeas = 1 cup has 10.6 grams of fiber
- Artichokes = 1 artichoke has 10 grams of fiber
- Peas = 1 cup has 9 grams of fiber
- Oatmeal = 1 cup has 8 grams of fiber
- Raspberries = 1 cup has 8 grams of fiber
- Avocado = ½ avocado has 7 grams of fiber
- Pears = 1 medium unpeeled pear has 6 grams of fiber
- Chia seeds = 1 tablespoon has 5 grams of fiber
- Brown rice = 1 cup has 4 grams of fiber
- Apples = 1 small, unpeeled apple has 4 grams of fiber
- Broccoli = 1 cup has 2.4 grams of fiber
- Kale = 1 cup has 2.6 grams of fiber
- Spinach = 1 cup has 4.3 grams of fiber
- Celery = 1 cup has 1.6 grams of fiber
- Dark chocolate = 1 ounce has 3.1 grams of fiber
You don’t need much more than the recommended 30 grams/day: In fact, excess fiber can block the absorption of some minerals such as calcium, iron and zinc by binding them in the gut, which is why if you take a vitamin or mineral supplement, you shouldn’t take it at the same time as any meal containing fiber.
Fiber excess can sometimes result from taking too much of a fiber supplement. You’re unlikely to overeat whole-food-based fiber, however, since the fullness effects are usually self-regulating.
Top 20 Insoluble Fiber Foods
- Wheat bran and wheat germ
- Oat bran
- Beans, lentils and legumes of all kinds (kidney, black, garbanzo, edamame, split peas, lima, navy, white, etc.)
- Berries, including blackberries, blueberries, raspberries, strawberries, etc.
- Whole grains, especially barley, quinoa, sorghum, millet, amaranth, oatmeal and rye
- Green peas
- Coconut (grated flakes or flour)
- Apples with skin, Pears with skin
- Avocado (Florida avocados have more than California avocados)
- Sunflower seeds
- Potatoes and sweet potatoes
- Dried apricots, prunes, raisins, dates and figs