What Is Fiber Exactly, and Generally, What Foods Contain This Carb?
Fiber is simply a type of carbohydrate found naturally in plant-based foods that is not digestible in humans.
Plant-based foods that are rich in fiber — such as fruits, vegetables, whole grains, beans and legumes, and nuts and seeds, lists 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 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)(3)
Soluble and Insoluble Fiber: What’s the Difference Between the Two?
There are two types of fiber: soluble and insoluble. While both are important, the two function differently in the body. Here’s how:
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)
Most diets have a combination of soluble and insoluble fiber, with 75 percent coming from insoluble fiber and 25 percent coming from soluble fiber. (5)
In short, fiber may actually help you live longer. (6) Studies suggest folks who eat a higher intake of fiber tend to have lower rates of heart disease, obesity, type 2 diabetes, stroke, high blood pressure (hypertension), and digestive diseases. (7)
Weight Loss
Research suggests nutrients like fiber can play a major role in body weight. (10) Normal-weight and overweight people have been found to have higher intake of dietary fiber than obese individuals. (8) Other studies continue to suggest that high fiber intakes help reduce weight gain as you age. (7)
Fiber expands and bulks food in your GI tract, slowing digestion. This can increase satisfaction of your food and helps stabilize blood sugar levels. (4) Foods high in fiber also tend to be lower in energy density, meaning they’ll help you feel fuller without consuming excessive calories. (4) This concept is at the core of why a higher fiber diet is associated with a lower rate of obesity. (11)
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)
Cholesterol and Blood Pressure Reduction
Fiber’s wondrous effect on the body is a great example of medical nutrition therapy (MNT), a technique registered dietitian nutritionists (RDN) use on their patients to reduce the need for medication while improving health outcomes.
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)
What Are the Best Food Sources of Fiber?
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 percent
- Breadfruit (1 cup): 11g, 44 percent
- Raspberries (1 cup): 8g, 32 percent
- Blackberries (1 cup): 8g, 32 percent
- Boysenberries and gooseberries (1 cup): 7g, 28 percent
- Pear (1 medium): 6g, 24 percent
- Prunes (5 pieces): 3g, 12 percent
Vegetables
- Artichoke (1 large): 9g, 36 percent
- Lima beans (1 cup): 9g, 36 percent
- Green peas (1 cup): 8g, 32 percent
- Lentils (½ cup): 8g, 32 percent
- Kidney beans (½ cup): 6g, 24 percent
- Sweet potato (½ cup, mashed): 4g, 16 percent
Nuts and Seeds
- Chia seeds (1 ounce (oz)): 10g, 40 percent
- Flaxseeds (1 oz): 6g, 40 percent
- Pumpkin seeds (1oz): 5g, 20 percent
- Almonds (1 oz): 4g, 16 percent
Grains
- Raisin Bran (1 cup): 7g, 28 percent
- Shredded wheat (2 biscuits): 6g, 24 percent
- Oat bran (1 cup): 6g, 24 percent
- Brown rice (1 cup): 4g, 16 percent
Doctors often prescribe fiber supplements for the treatment of irritable bowel syndrome or constipation. These supplements are considered functional fibers that are isolated from plant sources:
- PaleoFiber (psyllium) is a type of soluble fiber supplement you can use to bulk stool and encourage regular bowel movements.
- PrebioMed XOS is a type of soluble, prebiotic fiber combined with beneficial gut bacteria that promotes good bacteria for overall digestive health.
- Chocolate Mint Fiber Bars are other fiber supplement options to help keep you regular.
A Final Word on Fiber and Why You Need It in Your Diet
Bottom line: You’re likely not getting enough fiber, so consider eating more. The best way to get fiber is through natural sources, such as fruits, vegetables, whole grains, nuts, seeds, and legumes, because these sources also include important vitamins, minerals, and phytonutrients your body needs for optimal health.