Fiber is well-known as an important nutrient for gastrointestinal health. It helps your body digest various types of foods, including proteins, fats and other carbohydrates. Although it's classed as a carbohydrate, fiber isn't digested in the same way as other carbs. This difference in the digestion process leads to some common misconceptions about fiber.
Fiber doesn’t cancel out carbohydrates. However, it isn’t digested in the same way as most other carbohydrates, and it does help your body process other nutrients.
Fiber in Your Diet
- Soluble fiber is broken down in your intestines and digested by bacteria. This type of fiber can generate energy for your body, as these bacteria produce short chain fatty acids. However, the amount of energy produced is about half the amount of other carbohydrates.
- Insoluble fiber, sometimes referred to as dietary fiber, passes through your body; it isn't digested at all. This type of fiber doesn't provide your body with any energy, although it helps other foods pass through your digestive system.
This essentially means that fiber doesn't cancel out carbohydrates, but does help your body process them. A diet lacking in fiber would likely cause digestive system problems, like constipation, as your gastrointestinal tract would struggle to process the food you're eating.
- Whole-grain products, including breads, cereals, pastas and crackers
- Legumes and beans, including peas
- Vegetables, like sweet potatoes, squash and broccoli
- Fruits, like avocado, guava and oranges
If you're uncertain how to select healthy whole-grain products when buying foods like bread or pasta, check the carb-to-fiber ratio on the product's nutrition label. According to Harvard Health Publishing, you should see a 10-to-1 ratio of carbs to fiber on whole-grain products, as this is the same ratio in actual unprocessed grains, like wheat. If you're planning on cooking with whole grains, foods like quinoa, bulgur and oats are versatile and very good sources of fiber.
The Importance of Fiber
Beyond its supportive role in the digestive process, fiber has been shown to have a wide array of benefits. Fiber can:
- Help prevent certain types of cancer, particularly colorectal cancer. Consuming fiber may also help prevent other types of cancer, like gastric cancer, prostate cancer and breast cancer.
- Lower your risk of various gastrointestinal diseases, including hemorrhoids, gastroesophageal reflux disease, duodenal ulcers and diverticulitis.
Types of Carbohydrates
Carbohydrates are the main source of energy in most people's diets. The Dietary Guidelines for Americans suggests that around half (between 45 and 65 percent) of your daily calories come from carbohydrates. This means if you eat the standard 2,000-calorie diet, you need between 225 and 325 grams of carbohydrates a day.
Different types of carbohydrates typically consumed include:
- Sugars: Sugars are commonly found in many fruits, vegetable and milk products. These include fructose, sucrose, lactose, glucose, galactose and maltose. There's no daily value for the amount of sugars you should consume in a day. However, no more than 10 percent of your daily calories should come from added sugars.
- Sugar alcohols: Sugar alcohols are also found in fruits and vegetables, but in much smaller amounts. They can also be added to foods.
- Starches: Starches, which are complex carbohydrates made up of multiple sugars, can be found in many plants, including vegetables, grains and legumes.
- Dietary fiber: Dietary fiber promotes the digestion of other carbohydrates and foods. Soluble fiber influences the way your body metabolizes fat. Insoluble fiber promotes healthy stool formation and prevents constipation. About 25 grams of your total carbohydrate consumption should come from fiber.
Out of all of these carbohydrates, fiber and sugar alcohols typically do not provide the body with energy. When they do, the energy they provide is less than that of other carbohydrates. This is why people often compare carbs versus net carbs.
Carbs vs. Net Carbs
While terms like "total carbohydrates" refer to any type of carbohydrate, net carbs refers to carbohydrates excluding fiber. It can also refer to carbohydrates excluding both fiber and sugar alcohols. This means that the net carbs of fiber and sugar alcohol are typically considered to be zero.
Net carbs are generally of interest to people who count carbohydrates because they're following strict ketogenic or low-carbohydrate diets. Diets like these may limit the daily consumption of carbohydrates to as little as 20 grams. However, this 20-gram total refers to net carbs, which means you can eat several cup-sized servings of fiber-rich foods each day.
- Alfalfa sprouts
- Bok choy
All of these vegetables have less than one net carbohydrate per cup, as they are so rich in fiber.
However, not everyone calculates net carbs in the same way. Certain low-carb diets, like the Atkins diet, calculate net carbs by taking the total amount of carbohydrates and subtracting both fiber and sugar alcohol from this value. This is the most common way to calculate net carbs.
Other diets, such as those followed by diabetics who take insulin medication regularly, take a more strict approach and subtract only insoluble fiber. Soluble fiber and most sugar alcohols are only subtracted by half, and only when the value is 5 grams or more.
This approach to viewing "carbs versus net carbs" better supports this kind of diet since a person with Type 1 diabetes can't produce insulin, which is a hormone that transports sugar from your blood into your cells to supply energy. The sugar in your blood primarily comes from carbohydrate-containing foods. For people with diabetes, controlling carbohydrate intake improves overall blood sugar control and reduces risk of diabetes-related complications such as kidney disease or diabetic neuropathy.
- Diabetes Forecast: What Are Net Carbs?
- Atkins: List of Low Carb Foods for Atkins 20, Phase 1
- U.S. Food and Drug Administration: Dietary Fiber
- U.S. Food and Drug Administration: Sugars
- World Journal of Gastrointestinal Oncology: Mechanisms Linking Dietary Fiber, Gut Microbiota and Colon Cancer Prevention
- Acta Scientarium Polonorium: Health Effects of Dietary Fiber
- Journal of the Academy of Nutrition and Dietetics: Position of the Academy of Nutrition and Dietetics: Health Implications of Dietary Fiber
- Mayo Clinic: Dietary Fiber: Essential for a Healthy Diet
- Harvard Health Publishing: The Trick to Recognizing a Good Whole Grain: Use Carb-to-Fiber Ratio of 10-to-1
- MyFoodData: Top 10 Foods Highest in Fiber
- FiberFacts.org: Do Fibers Count as Calories and Carbohydrates?
- National Institute of Diabetes and Digestive and Kidney Diseases: What Is Diabetes?
- Health.gov: Dietary Guidelines for Americans, 2015-2020