Do you think you’re getting your fair share of dietary fiber? The answer likely is a resounding “no”. In the U.S., more than 90% of women and 97% of men do not meet the recommended dietary fiber intake (1). Sadly, most Americans consume only half the levels of recommended fiber per day (2). It is a key nutrient that is often overlooked in our diet. The underconsumption of dietary fiber has been deemed a public health concern because low intakes are associated with potential health risks.
Throughout this article, we'll explore a wide variety of fiber-rich foods and the incredible benefits of dietary fiber, from supporting digestive health to lowering cholesterol, regulating blood sugar, and preventing a myriad of health concerns.
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What is Dietary Fiber?
Dietary fiber is a type of carbohydrate found naturally in plant-based food that passes through our body undigested. In 1987, the Life Sciences Research Office defined dietary fiber as “the endogenous components of plant materials in the diet which are resistant to digestion by enzymes produced by humans.” Dietary fiber does a lot of the heavy lifting in keeping chronic diseases at bay, including reducing the risk of cardiovascular disease, type 2 diabetes, and some cancers. It is also associated with low body weight.
There are two types of dietary fiber:
- Soluble Dietary Fiber: In the digestive tract, soluble fiber attracts water to itself to form a viscous gel-like substance and helps slow down the rate of digestion. Soluble fibers have a prebiotic effect, and our gut microbiome loves to feed on them to fuel their growth and proliferation, thus increasing microbial diversity. This viscous fiber also inhibits the absorption of glucose and lipids in the gut and helps to regulate cholesterol and blood glucose levels.
- Insoluble Dietary Fiber: Unlike soluble fiber, insoluble fiber does not dissolve in water and remains relatively intact as it passes through the digestive system. Insoluble fiber adds bulk and weight to our stool, promoting healthy bowel function and thus preventing constipation.
The Dietary Guidelines for Americans, 2020-2025, recommends the following daily intake of dietary fibers to promote optimal health and well-being:
- Adult Women: 28 grams per day
- Adult Men: 33.6 grams per day
Fruits Rich in Fiber
Berries
Berries aren’t just delicious; they have a rich fiber and antioxidant profile.
- Berries, particularly a cup full of raspberries or blackberries, have the highest amounts of dietary fiber and can contain up to 8 grams of fiber.
- A 2016 meta-analysis showed a significant reduction in a multitude of cardiovascular risk factors, including LDL-cholesterol, systolic blood pressure, fasting glucose, hemoglobin A1c, and BMI, after berry consumption.
- Eating low-glycemic-index mixed berries loaded with soluble fiber content also reduces diabetic risk.
- Berries are packed with bioactive compounds, such as polyphenols and vitamin C, that combat oxidative stress and inflammation in the body. This antioxidant property reduces the oxidation of LDL cholesterol, which is essential in the development of an atherosclerotic plaque in cardiovascular disease (CVD).
Apple and Pears
Eating whole fruits (with the skin) as part of a well-balanced diet provides a wide array of nutrients, including dietary fiber, potassium, vitamin A, vitamin C, and other phytochemicals associated with reduced chronic disease risk.
- Apples and pears are one of the richest sources of soluble dietary fiber.
- The skin of apples and pears has a high concentration of insoluble dietary fiber, promoting healthy bowel function.
- One medium raw apple with the skin provides approximately 4 grams of dietary fiber (22 % of the DV) and is associated with a decreased risk of obesity in children.
- One medium pear with the skin has approximately 6 grams of dietary fiber.
Avocados
Avocados are unique fruits that contain very little sugar and are an excellent source of dietary fiber; approximately 65–80% of the carbohydrates in avocados include a mix of insoluble and soluble fibers.
- A cup of creamy avocado pulp has approximately 10 grams of dietary fiber.
- In addition to fiber, avocados are chock-full of heart-healthy fats and micronutrients (e.g., folate, vitamins C, K, B5, and copper).
- Compared to other commonly consumed sources of fats, avocados have a higher ratio of unsaturated fats to saturated fats, which are associated with a reduced risk of developing CVD and a reduction in all-cause mortality.
Vegetables High in Fiber
Dietary fiber from vegetables helps reduce blood cholesterol levels and lower the risk of heart disease. Almost 90% of the U.S. population does not meet the recommendation to consume 2.5 cups of vegetables for adults on a 2000 kcal/day diet to achieve optimal daily fiber intake.
Leafy Greens
- A cup of cooked spinach, kale, and Swiss chard has up to 4 grams of dietary fiber.
- Leafy greens are also rich in micronutrients, including magnesium, potassium, vitamins A, C, and K, and folate.
Cruciferous Vegetables
Cruciferous vegetables are packed with fiber that aids digestion and promotes regular, healthy bowel movements. They are also rich in polyphenols and sulfur-containing phytochemicals called glucosinolates, which exert antioxidant and anticancer health benefits.
- One cup of cooked broccoli, Brussels sprouts, and cauliflower has 5.2 grams, 6.4 grams, and 5 grams of dietary fiber, respectively.
- Beyond broccoli, Brussels sprouts, and cauliflower there are a plethora of cruciferous vegetables, including bok choy, cabbage, collard greens, and turnips to name a few.
Root Vegetables
Root vegetables offer many health-promoting effects, ranging from regulation of metabolic parameters (glucose level, lipid profile, and blood pressure) to antioxidant potential (β-carotene in carrots, betalains in beetroot, and anthocyanins found in purple sweet potatoes), prebiotic function, and anti-cancer properties.
- A cup of cooked carrots, beets, and sweet potatoes has 4.8 grams, 2.8 grams, and 6.3 grams of dietary fiber, respectively.
- Carrots, beetroot, and sweet potatoes are rich in both soluble and insoluble fiber.
- Soluble fiber helps maintain glycemic control and manage cholesterol, while insoluble fiber is essential for maintaining optimal gut health.
Legumes and Beans
Legumes and beans are a sustainable and inexpensive source of both soluble and insoluble dietary fiber and plant-based protein.
- Lentils are a rich source of slow-digesting dietary fiber that reduces the absorption of carbohydrates aiding glycemic control and has a prebiotic effect that helps foster a healthy gut microbiome.
- A cup of cooked lentils has 15.6 grams of dietary fiber.
- Consuming lentil sprouts has improved lipid profiles in individuals with type 2 diabetes.
- A cup of cooked black beans and chickpeas has 15 grams and 12.6 grams of dietary fiber, respectively.
- Chickpeas contain a soluble dietary fiber called raffinose fermented by the colonic gut bacteria. Raffinose promotes the growth of beneficial bacteria and decreases pathogenic bacteria in the gut.
Incorporating beans into your diet doesn’t have to be dull and can be full of vibrant flavors, here are my favorites:
- Black Bean Burger
- Chickpea and Veggie Chili
- Mediterranean Chickpea Bowl with Bulgur
- Vegan Chickpea Coconut Curry with Quinoa
Whole Grains and Cereals
A healthy dietary pattern includes whole grains, therefore it is advisable to limit the intake of refined grains and be sure half of your grains are whole grains. The current dietary guidelines serve as an invaluable resource, providing a clear list of food sources rich in dietary fiber. It references the grams of dietary fiber present in one serving of whole grains.
Oats
- Oats are an important source of soluble fiber, particularly oat β-glucan (OBG).
- OBG slows down postprandial digestion of carbohydrates and decreases the absorption of glucose into the bloodstream. This prevents blood sugar spikes after meals and contributes to overall glycemic control and improved insulin sensitivity.
- Oats are a great dietary intervention to manage blood sugar levels in those at risk or diagnosed with type 2 diabetes.
- A 2014 meta-analysis detailing the cholesterol-lowering effects of OBG demonstrated that adding >3 grams of OBG per day reduces total cholesterol and LDL, associated with a decreased risk of CVD.
- OBG regulates cholesterol homeostasis by 1) its interaction with our gut microbiota and 2) promoting the excretion of cholesterol-rich bile acids from the intestines.
Quinoa
- Quinoa is a good source of fiber and plant protein, and a great nutrient-dense option for those on a gluten-free, vegan, or vegetarian diet.
- Quinoa is considered a complete protein as it contains all 9 essential amino acids that our body cannot produce on its own.
- One cup of cooked quinoa has about 5 grams of fiber and 8 grams of protein.
- I love to use quinoa as a substitute for rice in a delicious stir-fry or fried rice dish.
Barley and Bulgur
- Whole grain barley is also a rich source of β-glucan soluble fiber and has a similar cholesterol-lowering portfolio as oats.
- One cup of cooked barley contains approximately 6 grams of dietary fiber.
- Barley also has an assortment of phytochemicals that have antioxidant and anti-inflammatory properties that play an important role in the prevention of chronic diseases.
- Bulgur, like Barley, is a whole grain with a rich nutrient profile.
- One cup of cooked bulgur contains approximately 8 grams of dietary fiber.
- Bulgur is a delicious and nutritious ingredient commonly used in many Mediterranean recipes including Tabbouleh salad.
Nuts and Seeds
Nuts and seeds are a powerful combo of healthful nutrients, including healthy unsaturated fatty acids, dietary fiber, amino acids, vitamins, and minerals.
In one of the largest studies examining the health benefits of nuts, individuals who regularly ate nuts had a 14% lower risk of CVD and a 20% lower risk of coronary heart disease. Another 2020 study demonstrated a similar risk reduction of CVD in patients with type 2 diabetes by incorporating nuts into their diet. In 2017, the FDA gave Macadamia nuts the spotlight by approving a qualified health claim that states: “Eating 1.5 ounces per day of macadamia nuts, as part of a diet low in saturated fat and cholesterol may reduce the risk of coronary heart disease”.
Here are my favorite ways to add nuts and seeds, including almonds, chia seeds, and flaxseeds into my daily diet:
- After my workout, I like to add a tablespoon of chia seeds or ground flaxseeds into my protein smoothie for an extra dose of fiber and omega-3 fatty acids.
- I love to make my salads nutrient-dense by adding some chopped almonds to give it a nice crunch.
- Nut butter and sunflower seed butter make great dips to eat apple slices and celery sticks, which are good as a midday snack.
- Most weekend mornings, I incorporate flaxseed into my pancake batter or into muffins I make to satisfy my sweet tooth.
Incorporating High-Fiber Foods into Your Diet
Fiber is the unsung hero of our diet that keeps everything running smoothly. Here are some helpful tips to easily incorporate more fiber into your diet:
- To prevent digestive discomfort, it’s important to gradually begin adding high-fiber foods to each meal and increase over time.
- Use Nutrition Facts labels as a tool to increase your daily intake of dietary fiber. Aim for foods with a 20% Daily Value (DV) per serving or higher.
- Variety is the spice of life. Consume a wide variety of plant-based foods including fruits, vegetables, whole grains, legumes, nuts, and seeds.
- Plan, Purchase, and Prepare. Keep fresh, whole, colorful fruits and vegetables (such as carrots, bell peppers, and broccoli florets) cleaned, cut up, and handy as quick snacks or desserts. Keep nuts and seeds in your pantry and have a handful as snacks between meals.
- Think outside the cereal box. Start your morning with a bowl of whole-grain breakfast cereal (such as bran or oatmeal) high in dietary fiber and low in added sugars. Top your cereal with fruit for some sweetness and to boost your fiber intake.
- Limit the intake of refined/processed grains such as bread, cereal, pasta, and rice. Replace them with brown rice, barley, farro, bulgur, couscous, and quinoa as a base for a delicious grain bowl.
- Add 1-2 tablespoons of fiber-rich ground flaxseed and chia seeds into your favorite smoothie.
- Trade in meat and poultry for plant-based proteins such as beans, peas, lentils, and other legumes a few times a week and add them to your favorite soups, salads, or main dishes.
- If you don’t eat enough natural sources of fiber, consider taking a fiber supplement accompanied by lots of fluid. Fiber supplements like Metamucil (Psyllium) are very effective and improve the regularity of bowel movements.
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Key Takeaways
- Dietary fiber goes beyond regulating healthy bowel function. It reduces the overall risk of CVD, type 2 diabetes, and some cancers and prevents the progression of chronic diseases.
- The Dietary Guidelines for Americans recommend a daily intake of 28 grams of dietary fiber for adult women and 33.6 grams for adult men to promote optimal health and well-being.
- The ultimate fiber food list is a great resource to make gradual changes to incorporate a variety of fiber-rich foods to achieve your daily fiber goals
- Breakfast
- Whole-grain (bran or oatmeal) breakfast bowl topped with berries, bananas, and nuts
- Whole-grain toast with avocado or nut butter
- Smoothie with spinach, berries, chia seeds, or ground flaxseed
- Snacks
- Cut-up, fresh fruit
- Raw carrots, celery sticks, broccoli florets with hummus or guacamole dip
- Apple or pear slices and celery sticks dipped in nut butter
- Handful of macadamia nuts, almonds and seeds
- Lunch
- Salad with dark leafy greens, an array of vegetables, topped with beans (like chickpeas), lentil sprouts, chia seeds, and toasted nuts for an extra crunch
- Hearty lentil soup or black bean chili
- Black bean burger
- Vegan chickpea coconut curry with quinoa
- Dinner
- Vegetable stir-fry with quinoa
- Whole-grain pasta with vegetables and lean meat
- Roasted root or cruciferous vegetables over a bowl of cooked whole grains
- Breakfast
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