What Is Fiber? And How to Get Enough on Keto

Confused about fiber? You're not alone. At Carb Manager, we get tons of questions from our users about what it is, how much we need, how to eat more, and if you should even be consuming it on Keto.

Fiber may offer some health benefits, especially for digestion and gut health. Most people actually don’t eat enough to reap the benefits, but a small subset of people may also benefit from eating less fiber.

Ready to learn more? Welcome to Fiber 101!

What Is Fiber?

Put simply, fiber is the part of plant foods that our bodies are unable to digest. If you remember much from biology class, you may remember that plants have rigid cell walls to provide their structure. These woody, indigestible components are made of fiber — also sometimes called “roughage.”

However, some research suggests that fiber may provide a number of health benefits, too. These include:

• Better blood sugar control: Fiber helps blunt our body’s blood sugar response to carb-containing foods. It’s why, even though they’re equally high in carbs, whole-grain bread causes a less steep rise in blood sugar than a slice of white bread.[*]
• Improved digestion and gut health: Fiber bulks up the stool, which may help relieve constipation. Soluble fiber (which we’ll discuss below) also absorbs water,  which can help keep you regular. Fiber is also a prebiotic, or a food source for the bacteria in your gut microbiome. These bacteria digest fiber and produce short-chain fatty acids (SCFAs), which may offer several health benefits.[*]
• Weight management: Some studies have shown that people who eat more fiber are also less likely to be overweight or obese.[*]
• Reduced cholesterol: Certain types of fiber may also help to reduce your blood cholesterol levels.[*]

There are two different classifications of fiber to be aware of: soluble fiber and insoluble fiber.

What Is Soluble Fiber?

Soluble fiber is the type that’s associated with most of the health benefits of dietary fiber. It’s called “soluble” because it can form a gel in the presence of liquid. This property is why soluble fiber may help to reduce cholesterol. The fiber forms a gel that traps dietary cholesterol and keeps it from being absorbed.[*]

Some examples of soluble fiber include chia seeds, oats, beans, and flax seeds.

What Is Insoluble Fiber?

Insoluble fiber, on the other hand, is bulky, woody, and doesn’t expand in water. 

It passes through the digestive tract quickly, so it may be helpful for people who deal with symptoms related to slow digestion, like bloating and gas.[*]

Examples of mostly insoluble fiber foods are wheat bran, oat bran, berries, and greens.

However, all fiber foods contain a mixture of soluble and insoluble fiber.

Low Fiber Diets

Although fiber is considered a nutrient, you won’t develop a fiber deficiency if you don’t eat enough. In fact, some digestive conditions may benefit from a diet low in soluble fiber. For instance, if you have gastroparesis — a condition that causes you to digest food very slowly — limiting your soluble fiber intake may help you find some relief from your symptoms.[*]

Still, most people benefit from including enough fiber in their diet. It’s important to pay attention to how your body responds, and to heed your healthcare provider’s advice when it comes to dietary fiber.

What Foods Are High in Fiber?

Plant foods are natural sources of fiber.

That includes grains, vegetables, fruits, legumes, nuts, and seeds. They all contain at least some fiber.

High fiber Keto foods include non-starchy vegetables, berries, nuts, and seeds.

How Much Fiber Should I Have Per Day?

According to the National Institutes of Medicine, adults need between 21-38 grams of fiber per day.[*] More specifically:

• Women over 50: 21 grams per day
• Women under 50: 25 grams per day
• Men over 50: 30 grams per day
• Men under 50: 38 grams per day

However, research suggests that only 5% of the population consumes enough fiber on a regular basis. Average fiber intake among American adults is roughly 16 grams per day, which isn’t a sufficient amount for any adult.[*]

Top 20 Keto-Friendly Fiber-Rich Foods

Need a fiber boost? Here are 20 Keto-friendly fiber-rich foods to add to your diet.

• Chia seeds: mix them with almond milk and refrigerate overnight for a fiber-rich chia pudding 
• Flax seeds: sprinkle flax seeds on top of your salads, or add them to baked goods for a fiber boost
• Hemp seeds: use hemp seeds to add some crunch and texture to salads or to make your own Keto-friendly falafel
• Almonds: eat almonds as a snack, or use almond flour in your Keto-friendly baking projects
• Mushrooms: sauteed mushrooms are a great accompaniment to grilled steak or chicken
• Avocado: high in fiber and fat, avocado makes the perfect spread or dip for meats and veggies
• Raspberry: with some cream and Keto-friendly sweetener to balance out their tartness, raspberries are an easy low-carb dessert
• Artichoke: artichokes are a great high-fiber addition to salads or spinach-artichoke dip for game night — but don’t eat too many because their net carb count can quickly add up
• Brussels sprouts: halved and roasted until they’re crispy, brussels sprouts are an excellent side dish
• Cabbage: cabbage is versatile and can be cooked or shredded raw to make a slaw
• Strawberry: strawberries are sweet but still Keto-friendly (in small portions), and are excellent paired with a nice, dark, Keto chocolate
• Pumpkin seeds: pumpkin seeds can be a snack or a great addition to salads or baking projects
• Coconut: coconut flour is full of fiber, and a Keto baking staple
• Pine nuts: pine nuts can be used to make homemade pesto or added to salads as a crunchy topping
• Pecans: pecans are a good snack, and they also make a delicious crust for fish or chicken when crushed
• Hazelnuts: hazelnuts add an interesting flavor to Keto desserts (think Nutella!), or you can snack on them as a standalone snack
• Broccoli: as an easy side dish for any meal, nothing beats roasted broccoli
• Collard greens: greens are full of fiber, and they’re a great addition to soups
• Kale: kale chips are a perfect crunchy, salty, and fiber-rich snack
• Okra: pickled okra makes a good addition to salads, or you can use fresh or frozen okra to make Keto-friendly gumbo

Processed Keto Foods

Highly processed Keto snacks, desserts, and breads are often very high in fiber. There are several different types of fiber that can improve the taste and consistency of Keto foods while keeping their net carb count low.

However, we implore you to view these foods as occasional treats, rather than good ways to meet your daily fiber intake. 

Even though they are marketed as Keto, these foods are still highly processed. Additionally, many people have found that, even with a low net carb count, they can still cause a blood sugar and insulin response. 

What About Carnivore Diets?

Because fiber comes only from plant-based foods, Carnivore diets don’t contain fiber.

Although there hasn’t been a lot of research on Carnivore diets, many Carnivore dieters report that they feel much better without plant foods and don’t seem to be affected by the lack of fiber in their diet.

Many people who try Carnivore come to the diet due to autoimmune issues that seem to resolve after they remove plant foods, regardless of how little fiber that means they’re consuming.

On a mixed diet that contains plant and animal foods, fiber may be particularly important to help your body respond better to carbs and to improve digestion of difficult-to-digest plant-based foods.

In fact, fiber has naturally been part of an omnivorous diet for as long as humans have been around. It hasn’t been until the last 100 years or so that we have been able to strip plant foods of their fiber and transform them into highly processed, low-fiber, low-nutrition foods.

However, with a zero-carb diet like Carnivore, depending on your health needs, this lack of fiber may not present as much of an issue. Still, more research is needed — there’s a lot we don’t yet know.

Fiber Supplements

Most people who eat a balanced, minimally processed diet probably don’t need a fiber supplement. However, they may be a good addition if your diet doesn’t contain a lot of non-starchy vegetables, low-sugar fruits, nuts, or seeds.

What Is the Best Fiber Supplement?

In our opinion, the best fiber supplements are whole-food based — like chia seeds or flax seeds. These can be sprinkled on your food throughout the day to give you a fiber boost.

However, if you prefer something a bit more convenient, try one of these Keto fiber supplement options:

• Wellmade Organic Acacia Fiber
• Garden of Life Dr. Formulated Organic Fiber
• Sylly Organic Psyllium Husk Fiber

With fiber supplements, remember to start slow. If you’re not used to getting 25 grams of fiber per day, don’t start out taking that much in supplement form or you may be in for a miserable few days. Start gradually, increase your intake slowly, drink plenty of water to prevent constipation, and aim to eventually replace your fiber supplement with fiber from whole foods.

Not sure how much fiber you’re getting? Carb Manager can help you figure out how much you consume each day. Don’t forget to check out our recipes for some inspiration to help make reaching your daily fiber goal more delicious.