What Is Fiber Exactly, and Which Foods Contain This Carb?
Fiber is simply a type of carbohydrate found naturally in plant-based foods that is not completely digested by humans. Plant-based foods that are rich in fiber — such as fruits, vegetables, whole grains, beans and legumes, and nuts and seeds, according to the U.S. Department of Agriculture’s MyPlate guidelines — also contain vitamins, minerals, and other powerful nutrients that the body can use for optimal health. Although fiber cannot be completely digested, it is being moved down the digestive tract as nutrients are being digested, and can do some great things that positively impact our health. The problem is that Americans are getting less than half of the daily intake recommendations of 14 grams (g) for every 1,000 calories of food. (1,2) A simpler recommendation level for most adults is between 25 and 38 g per day (1). In fact, fiber is listed as a “nutrient of concern” due to the low overall intake and known health benefits. (3)
Soluble Fiber
Soluble fiber is a type of fiber that attracts water and forms a gel. This gel causes a slowing of the digestion process, which can be beneficial for weight loss. Foods high in soluble fiber include oats, legumes, edible plant skins, and nuts. (4)
Insoluble Fiber
Insoluble fiber is the type of fiber that, you guessed it, repels water. You can find insoluble fiber in foods such as veggies, fruits, nuts and seeds, wheat bran, and whole-grain foods like whole-wheat pasta and brown rice. Its primary benefit is to provide bulk to stool and aid in the movement through the digestive tract. (4) A healthy, balanced diet contains a combination of soluble and insoluble fiber. You may help improve or prevent health conditions such as prediabetes, diabetes, high cholesterol, obesity, and various digestion problems, like constipation, colon cancer, and diverticulitis, by simply increasing fiber in your diet. (8)
Weight Loss
Research suggests nutrients like fiber can play a major role in body weight. (10) Dietary fiber intake, independently of macronutrient and calorie intake, promotes weight loss and dietary adherence in adults with overweight or obesity consuming a calorie-restricted diet, according to a study in The Journal of Nutrition.
Digestive Disorders
Fiber is like nature’s scrub brush, keeping your body’s pipes clear and reducing carcinogenic activity. One benefit of getting enough fiber in your diet is reducing the risk of diverticulitis, a condition in which pouches formed in the colon become infected. Fiber helps keep food clear from the pouches and moving through the digestive tract. Aim to take in 25 to 40 g of fiber per day to reduce your risk of diverticulitis. (12) There’s an anti-cancer benefit to fiber, too: Both soluble and insoluble fiber can also play a role in warding off colon cancer. (13) Here’s how it works: Your body uses bile salts, which are excreted by the gallbladder to break apart the fat content in food. Bile salts are made of cholesterol. When you eat food with fiber, the fiber binds to the bile salts, preventing them from being recirculated for the next time you eat. As a result, your body must produce more bile salts by taking cholesterol from the liver. This is how soluble fiber reduces blood cholesterol. (14) Fiber has a preventative role on blood pressure, too, but the reason is more associated with nutrients such as potassium, calcium, and magnesium contained in foods high in fiber. (11) If you are not convinced to increase your fiber intake yet, know there’s also data emerging on fiber’s ability to impact the immune system, mood, and memory by the promotion of healthy gut bacteria. (15) A recent study, for example, suggests that increased consumption of fiber can improve the overall health of the gut biome, which in turn boosts the availability of short-chain fatty acids — compounds that are believed to be instrumental in maintaining colon health, weight maintenance, and the prevention of metabolic diseases like diabetes. Note that natural foods containing fiber typically have a combination of soluble and insoluble fiber with the majority coming from soluble fiber. To lower your blood cholesterol by 3 to 5 percent, aim to take in at least 5 to 10 g of soluble fiber per day. (16) Here are some food sources of fiber, along with how much of the DV of fiber they offer: (17)
Fruit
Passion fruit (1 cup): 25g, 100 percentBreadfruit (1 cup): 11g, 44 percentRaspberries (1 cup): 8g, 32 percentBlackberries (1 cup): 8g, 32 percentBoysenberries and gooseberries (1 cup): 7g, 28 percentPear (1 medium): 6g, 24 percentPrunes (5 pieces): 3g, 12 percent
Vegetables
Artichoke (1 large): 9g, 36 percentLima beans (1 cup): 9g, 36 percentGreen peas (1 cup): 8g, 32 percentLentils (½ cup): 8g, 32 percentKidney beans (½ cup): 6g, 24 percentSweet potato (½ cup, mashed): 4g, 16 percent
Nuts and Seeds
Chia seeds (1 ounce): 10g, 40 percentFlaxseeds (1 oz): 6g, 40 percentPumpkin seeds (1oz): 5g, 20 percentAlmonds (1 oz): 4g, 16 percent
Grains
Raisin Bran (1 cup): 7g, 28 percentShredded wheat (2 biscuits): 6g, 24 percentOat bran (1 cup): 6g, 24 percentBrown rice (1 cup): 4g, 16 percent
Psyllium (Metamucil) is a type of soluble fiber supplement you can use to bulk stool and encourage regular bowel movements.Dextrin is a type of soluble, prebiotic fiber found in products such as Benefiber that promotes good bacteria for overall digestive health.Methylcellulose (Citracel) and polycarbophil (Fibercon) are other fiber supplement options to help keep you regular.
Check with your doctor before you add any supplement to your diet. Even if you don’t have one of these ailments, you may find that eating wheat causes gas, bloating, and abdominal pain. (22) If you and your doctor determine giving up whole wheat is best for you, you’ll need to add other whole grains to your diet in its place, as avoiding wheat can lead to a fiber deficiency. If you have a wheat allergy, a gluten intolerance, or celiac disease, consider eating high-fiber gluten-free grains, like millet, amaranth, quinoa, and buckwheat. Fruits and vegetables that have skins are also good gluten-free sources of fiber, as are legumes and gluten-free oats. (21) Although dextrins are derived from wheat, dextrin supplements meet the FDA’s guidelines for gluten-free of less than 20 parts per million. (23) People with celiac disease should always talk to their doctor before using any supplement. Ask your doctor or RDN if a fiber supplement would be right for you if you are trying to treat or prevent a health condition. Don’t have an RDN? You can find one at EatRight.org.
