The Best High-Fiber, Low-Carb Foods

Get Your Daily Fiber Intake in More Than 30 Low-Carb Foods

Assorted cereals, flour and grains in piles, bowls and scoops
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How can you find foods that are low in carbohydrate, yet high in fiber? Interestingly, almost all the non-starchy vegetables and low-sugar fruits are the ones that are highest in both fiber and nutrients. A well-constructed low-carb diet emphasizes vegetables and other sources of fiber. You can get the recommended daily amount of fiber on a low-carb diet by choosing those items.

What Is Fiber?

Fiber is that part of plant food that is indigestible by humans.

It passes through your digestive systems without being broken down and absorbed into your bloodstream as other food components are. While animals such as cows have specialized digestive systems to break down fiber so they can get energy from it, humans don't.

What Are the Different Types of Fiber?

Fiber has three different properties that matter to human health. The property most nutritionists talk about is solubility -- the ability to disperse in water. Soluble and insoluble fiber are the labels most commonly used to describe fiber. However, two other properties of fiber are turning out to be important: fermentability (how easily the fiber ferments in the colon), and viscosity (the ability to gel with water) of the fiber, which may be more important than solubility.

  • Insoluble Fiber: When you think of fiber or roughage, you are usually thinking of insoluble fiber. Wheat bran and most vegetables are examples of sources of insoluble fiber. It is tough and doesn’t easily break down. Insoluble fiber tends to increase the “speed of transit” through our digestive systems and increases the regularity of bowel movements.
  • Soluble Fiber: A lot of soluble fiber is viscous, allowing it to absorb and retain water, forming a gel. This type of soluble fiber actually slows digestion down. Because of this, it has a tendency to stabilize blood glucose and permit better absorption of nutrients. It tends to reduce blood cholesterol. It also increases satiety, so people aren’t inclined to eat as much. Sources of soluble fiber include flax, beans, peas, oatmeal, berries, apples, and some nuts and seeds.
  • Fermentable Fiber: Some fiber will ferment in the colon, producing compounds that help support colon health, and possibly have other benefits. There is some evidence that it is this type of fiber that may reduce the risk of colon cancer. Most soluble fiber is highly fermentable. Pectins (found in apples and berries) and the fiber in oats are examples of fiber with a large fermentable component. Inulin and oligofructose are also highly fermentable, as is resistant starch.

High-Fiber and Low-Carb Foods

If you are limiting carbs, look at the ratio of usable carb (or effective or net carb) compared to fiber. In other words, how much carbohydrate do you have to eat to get a gram of fiber? Here is a list, roughly in order on this carb/fiber scale.

Almost All Fiber

  • Flax Seeds: There is almost no usable carbohydrate in flax seeds. It is very high in both soluble and insoluble fiber (about one-third of the fiber is soluble). Flax is high in nutrients and could be the ultimate low-carb fiber source. One tablespoon ground flax has 2.0 grams of carbohydrate, 1.9 of which is fiber.
  • Chia Seeds: These have a fiber and carb profile similar to flax seeds. Find out more about chia seeds and how to serve them.
  • Vegetables that are close to all fiber: Mustard greens, chicory, endive.

More Fiber Than Usable Carbohydrate

  • Wheat Bran: 1/2 cup raw wheat bran has 3 grams usable carb, 6 grams fiber.
  • Unsweetened Coconut and Coconut Flour: 1-ounce unsweetened coconut has 2 grams usable carb, 5 grams fiber.
  • High Fiber Cereals: Check the labels carefully, but some high fiber cereals are also low or fairly low in carbohydrate.
  • Collard Greens: 1 cup chopped, cooked collard greens has 4 grams usable carb, 5 grams fiber.
  • Avocado, Hass: 1 medium avocado has 3 grams usable carb, 12 grams fiber.
  • Spinach and Chard (cooked) 1 cup chopped, cooked spinach has 3 grams usable carb, 4 grams fiber. (Six cups of raw spinach or chard produces about 1 cup cooked).
  • Spinach (frozen): 1 10 oz package spinach has 3 grams usable carb, 8 grams fiber. 
  • Broccoli (cooked): 1/2 cup chopped, cooked broccoli has 1 gram usable carb, 3 grams fiber.
  • Broccoli (raw): 1 cup chopped, raw has 4 grams usable carb, 2 grams fiber.
  • Cauliflower (cooked): 1/2 cup pieces, cooked cauliflower has 1 gram usable carb, 2 grams fiber.
  • Cauliflower (raw): 1 cup raw, cauliflower has 2 grams usable carb, 2.5 grams fiber.
  • Blackberries: 1 cup of raw blackberries has 6 grams usable carb, 8 grams fiber.

About as Much Usable Carb as Fiber

  • Asparagus: 1/2 cup pieces of asparagus has 2 grams usable carbs, 2 grams fiber.
  • Celery: 1 cup chopped celery has 1.5 grams usable carb, 1.5 grams fiber.
  • Eggplant (raw): 1 cup raw eggplant, cubed has 2 grams usable fiber, 3 grams fiber.
  • Eggplant (cooked): 1 cup cubed eggplant, cooked has 5 grams usable carb, 3 grams fiber.
  • Lettuce, Romaine: 1 cup shredded Romaine lettuce has.5 gram usable carb, 1 gram fiber.
  • Mushrooms: 1 cup raw sliced mushrooms has 1 gram usable carb, 1 gram fiber.
  • Radishes: 1 cup raw sliced radishes has 2 grams usable carb, 2 grams fiber.
  • Red Raspberries: 1 cup of raw red raspberries has 7 grams usable carb, 8 grams fiber.

High Fiber, but Not as Much Fiber as Usable Carb

  • Rice Bran: 1/4 cup rice bran has 8 grams usable carb, 6 grams fiber.
  • Cabbage (raw): 1 cup raw chopped cabbage has 3 grams usable carb, 2 grams fiber.
  • Cabbage (cooked): 1/2 cup cooked chopped cabbage has 2 grams usable carb 1 gram fiber.
  • Bell Peppers: 1 cup raw chopped bell peppers has 4 grams usable carb, 3 grams fiber.
  • Snow Peas (edible pod): 1 cup whole raw snow peas has 3 grams usable carb, 2 grams fiber.
  • Zucchini Squash and other Summer Squashes: 1 cup cooked sliced summer squash has 4 grams usable carb, 3 grams fiber.
  • Nuts and Seeds: Nuts and seeds vary, but most are high in fiber.
  • Strawberries: 1/2 cup of sliced strawberries has 5 grams usable carb, 2 grams fiber.

Does Fiber “Count” as a Carbohydrate?

Although most fiber sources are carbohydrates, fiber doesn’t raise blood glucose, so low-carb diets don’t “count” fiber. Fiber can provide calories, not as glucose, but as products of fermentation in the colon. In fact, fiber helps to moderate the effect of “usable carbs” on the bloodstream, so it furthers the goals of low-carb diets. To the extent that it creates satiety, it may also help prevent weight gain, and aid in weight loss.

How Much Fiber Should You Eat?

Generally, recommendations for adults are between 25 and 40 grams per day, and that 20-30 percent of the total fiber intake be soluble fiber. Most people have a much lower fiber intake than is recommended. Researchers who study the diets of our prehistoric ancestors say that they ate upwards of 100 grams of fiber per day, so we probably can handle very high amounts of fiber without difficulty.

Do You Have to Eat Fiber in Food -- What About Supplements?

While fiber supplements (in some circumstances) can be helpful additions to a high-quality nutritious diet, they should never stand in for high-fiber foods, which are also rich in antioxidants and other nutrients essential to health. There is some evidence that simply taking pure fiber as a pill or sprinkling high fiber additions over your food doesn’t carry all the same benefits as when it is in food. Also, some high-fiber additives such as wheat bran contain compounds (phytates) which block the absorption of some nutrients, so large amounts of this should be avoided.

Guidelines for Consuming Fiber

  • If you are unused to eating a lot of fiber, increase amounts gradually to prevent intestinal distress.
  • Make sure you drink lots of water when taking fiber supplements or eating high-fiber foods, as all fiber absorbs at least some water. Fiber can, in rare cases, cause intestinal blockage particularly if eaten with insufficient fluid.
  • Since large amounts of fiber can reduce absorption of some medications, it is best to take medication either an hour before or two hours after the fiber.
  • Chitin and chitosan come from the shells of crustaceans and should be avoided by people allergic to seafood.

A Word From Verywell

You won't lack for good sources of fiber when you are on a low-carb diet if you incorporate more vegetables, fruit, and bran in your meal plans. Your plate will be more colorful and appealing and you can enjoy a great variety of food.

Sources:

Fiber. MedlinePlus. 7/13/2016. https://medlineplus.gov/ency/article/002470.htm.

USDA Food Composition Database. United States Department of Agriculture. https://ndb.nal.usda.gov/ndb/search/list.

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