One thing that’s often missing from the keto diet? A little bit of roughage. The popular diet, which typically requires you to get up to 80 percent of your calories from fat and only 20 to 50 grams (g) of carbohydrates per day, is often criticized for its lack of fiber.
As it turns out, fiber is important for everyone, regardless of your eating plan. Getting enough fiber on the keto diet can be difficult, leading to regularity challenges. Keto constipation is a phenomenon that many keto dieters experience.
The Importance of Fiber
Fiber plays a key role in digestive health. Because it’s not digested by your body, it passes through your system and keeps you regular by softening and adding bulk to your stools, per Mayo Clinic. And it has benefits beyond bowel movements: It feeds the good bacteria in your GI tract, aiding healthy digestion and nutrient absorption.
“The digestive tract is where your body’s second brain is, and it’s home to the majority of your immune system,” says Elia. “If you’re following keto, it should be one of your biggest priorities to make sure you get adequate fiber to keep your gut healthy and happy,” she adds. And, she notes, high-fat diets slow digestion and decrease GI motility, so it’s especially important to get enough.
Particularly if you’re on certain drugs, like proton pump inhibitors for heartburn, you may notice changes in your digestion if you transition to a high-fat diet, says Elia.
Read also: High-Fiber Diet for Better Health
The USDA’s 2020-2025 Dietary Guidelines for Americans set a goal of 28 to 34 g of fiber a day, depending on age and sex. Following a keto diet food list doesn’t mean it’s impossible to get what you need, but you have to remain diligent and determined to make it happen, says Keri Glassman, RDN, who is in private practice in New York City. Many fiber-rich foods contain few net carbs - that is, total carbs minus fiber and sugar alcohols, per Atkins.com - and will keep you in ketosis, which is the metabolic state that causes your body to burn fat instead of carbs. Here are 12 to help keep your fiber intake up without derailing your keto goals!
One risk of low-carb eating is inadequate fiber intake. Many high carb foods like whole grains, legumes, and certain fruits are also high in fiber. Eating less of these foods also reduces your fiber intake and can lead to digestive issues such as constipation.
If you have diabetes or prediabetes, fiber is your friend. It helps with blood sugar control and weight management. It can also lower your risk of heart disease, a common diabetes complication, and some cancers.
Fiber Benefits
- Control your blood sugar. Your body doesn't absorb and break down fiber.
- Protect your heart. Fiber prevents your body from absorbing some fat and cholesterol.
- Maintain your digestive health. Fiber acts like a scrub brush, cleaning your digestive tract.
- Keep you feeling full. Since fiber isn't digested, it moves slowly through the stomach, making you feel fuller for longer.
Types of Fiber
There are two types of fiber, soluble and insoluble.
- Soluble fiber dissolves in water and forms a gel-like substance in your stomach, slowing down digestion. This helps control your blood sugar and cholesterol.
- Insoluble fiber doesn't dissolve in water and typically remains whole as it passes through your stomach. It helps increase insulin sensitivity, and keeps your bowels healthy to keep you regular.
The Dietary Guidelines for Americans, 2020-2025 recommends that adults eat 22 to 34 grams of fiber each day (depending on your age and sex).
Read also: Guide to Keto Fiber
High Fiber, Low Carb Food Choices
Here are some high-fiber, low-carb foods that can help you increase your fiber intake while following a low-carb diet.
Avocados
“All keto followers should consume avocados, because they’re a great source of fiber and fat,” says Elia. Half an avocado contains just 1.4 net carbs, but a whopping 5 g of fiber, per the USDA. High in healthy fats, avocados have a unique buttery texture. Technically a fruit, avocados are typically consumed as a vegetable and can be added to a variety of dishes. In addition to being rich in monounsaturated fats, avocados are a good source of fiber, folate, potassium, and vitamins K and C. One small (136 grams) avocado provides 9 grams of fiber and 3 grams of net carbs.
Chia Seeds
One ounce (oz) of chia seeds offers 9.6 g of fiber (and a net carbs total of 2.2 g), per the USDA. You can make chia seed pudding by mixing the seeds with liquid, creating a gel-like substance that you can enjoy mixed with fruits, natural sweeteners like honey, and your choice of spices. Glassman suggests sprinkling chia into small, low-carb smoothies or onto oatmeal, eggs, or a salad.
Though small in size, chia seeds are rich in several nutrients. In addition to being high in fiber, protein, and several vitamins and minerals, chia seeds are one of the best-known plant sources of omega-3 fatty acids. Chia seeds can be sprinkled atop salads and yogurt or added to smoothies. They also absorb liquids well, turning into a gel that can be used as a vegan egg replacement or thickener for sauces and jellies. Two tablespoons (30 grams) of chia seeds provide 11 grams of fiber and 2 grams of net carbs.
Nuts (Pecans and Almonds)
Nuts can be a great option on the keto diet because of their fiber and fat, says Glassman. Pecans are one of the lowest-carb nuts, offering just 1.2 net carb per oz (19 halves), notes the USDA. That amount will also supply 2.7 g of fiber. Almonds are another good choice. One of the most fiber-rich nuts, they clock in at 3.5 g (and about 2.5 g of net carbs) per oz (23 whole kernels), notes the USDA.
Read also: Gut Health on Carnivore Diet
Almonds are among the world’s most popular tree nuts. Great for snacking, they’re highly nutritious and rich in healthy fats, antioxidants, and essential vitamins and minerals, including vitamin E, manganese, and magnesium. As they’re also a good source of fiber and protein, almonds may help increase feelings of fullness and aid weight loss. One ounce (28 grams) of raw almonds provides 4 grams of fiber and 3 grams of net carbs.
Flax Seeds
These small seeds make a killer crunchy coating for fish or chicken in lieu of breading, says Glassman. So you can better absorb the nutrients in flax, make sure they’re ground - you'll reap the heart-healthy, cholesterol-lowering benefits of flaxseed’s high omega-3 fatty acid content, says Mayo Clinic. The USDA reports that 1 tablespoon (tbsp) of ground flax boasts 2 g fiber and 0 net carbs. Basically, a freebie - eat up.
Flax seeds are small oil seeds that are packed with nutrients. In particular, they’re good sources of omega-3 fatty acids, fiber, and antioxidants. They’re also low in digestible net carbs - the total grams of carbs minus the grams of fiber. Notably, flax seeds have a lower ratio of omega-6 to omega-3 than most other oil seeds. This is important, as a lower omega-6 to omega-3 ratio has been associated with a reduced risk of several chronic diseases. Flax seeds are easily incorporated into your diet and should be ground to reap all their potential health benefits. Two tablespoons (14 grams) of ground flax seeds provide 4 grams of fiber and 0 grams of net carbs.
Collard Greens
Starchy veggies like sweet potatoes are notoriously off-limits on keto, but there are plenty of keto-friendly greens. Target high-fiber picks like collards, says Elia. They cook down nicely, so go for cooked rather than raw greens to get in more fiber per cup. One cup of cooked collards has about 2 g of net carbs and 5.6 g of fiber, per the USDA.
Cauliflower
Cauliflower is having a moment - and that’s great news for keto diet followers. A 1 cup serving of this low-carb veggie has only about 3 g of net carbs and 2 g of fiber, notes the USDA. Plus, it’s super versatile: It can be used to make cauliflower pizza crust, chopped small to stand in for rice, mashed to replace mashed potatoes, and blended into creamy soups.
Cauliflower is a popular item on low carb diets, as it can be riced for a grain substitute or even made into a low carb pizza crust. Part of the Brassica family, cauliflower is a cruciferous vegetable that’s low in calories and carbs yet high in fiber, vitamins, and minerals. It’s also a good source of choline, which is important for brain and liver health, as well as metabolism and DNA synthesis. One cup (85 grams) of chopped cauliflower provides 2 grams of fiber and 2 grams of net carbs.
Pumpkin Seeds
An ounce of dried pumpkin seed kernels yields a little more than 1 g of net carbs and 1.7 g of fiber, per the USDA. Plus, they’re simple to grab as a handful for a snack, so you can sneak a bit more fiber into your day.
Coconut
A small piece of coconut meat (about two inches by two inches) offers about 3 g of net carbs and 4 g of fiber, per the USDA. “Plus, it goes double duty to help you get more fat,” says Elia. Look for this in the frozen section at some grocery stores. If you can’t find it near you, go for unsweetened shredded coconut. Coconut meat is the white flesh inside a coconut. It’s often sold shredded and can be added to desserts, granola bars, and breakfast foods for added texture.
Coconut meat is high in healthy fats and fiber, while being moderate in carbs and protein. It’s also rich in several important minerals, particularly copper and manganese. Copper aids bone formation and heart health, while manganese is essential for fat metabolism and enzyme function. One ounce (28 grams) of shredded, unsweetened coconut meat provides 5 grams of fiber and 2 grams of net carbs.
Raspberries
It can be tough to figure out how to fit fruit into a keto diet, but raspberries are a particularly good choice because of their fiber content. A half cup of fresh raspberries offers 4 g of fiber and 3.3 g of net carbs, the USDA notes. Consider cooking down frozen raspberries and using them as a syrupy topping on keto pancakes.
Another sweet yet tart summer fruit, raspberries are best enjoyed shortly after purchasing. Low in calories, they’re also surprisingly high in several essential vitamins and minerals. In fact, just 1 cup (140 grams) provides more than 50% of the DV for vitamin C and 41% of the DV for manganese. Similarly to blackberries, raspberries are rich in disease-protecting antioxidants. They can be eaten as a snack, baked into desserts, and added to yogurt parfaits or overnight oats. One cup (140 grams) of raspberries provides 9 grams of fiber and 8 grams of net carbs.
Artichokes
Artichokes are a surprisingly good option for getting more fiber into your keto diet. One canned artichoke heart offers 1.7 g of fiber and less than 1.9 g of net carbs. Add them as a topping to a keto pizza, roast or grill fresh artichokes, or bake with keto-friendly cheese as an appetizer.
Sauerkraut
Fermented foods - packed with probiotics - are good for your gut, full of flavor, and low in carbohydrates. A half cup of sauerkraut supplies 2 g of fiber and a little more than 1 g of net carbs, per the USDA. Plus, you can use it to add a tangy flavor boost to whatever you’re eating, from cuts of meat to salads.
Additional Low Carb, High Fiber Options
- Blackberries: Sweet and tart, blackberries are a delicious summer fruit. They’re also incredibly nutritious, with just 1 cup (140 grams) boasting more than 30% of the Daily Value (DV) for vitamin C. Berries are among the most antioxidant-rich fruits. Regular intake has been associated with a reduced risk of chronic inflammation, heart disease, and certain forms of cancer. Additionally, a 1-week study in 27 men with excess weight or obesity on a high fat diet found that eating blackberries daily increased fat burning and insulin sensitivity. One cup (140 grams) of blackberries provides 7 grams of fiber and 6 grams of net carbs.
- Pistachios: Humans have been eating pistachios since 6000 BC. While technically a fruit, pistachios are culinarily used as a nut. With their vibrant green color and distinctive flavor, pistachios are popular in many dishes, including desserts, such as ice creams and cakes. Nutritionally, they’re high in healthy fats and vitamin B6, an essential vitamin that aids blood sugar regulation and the formation of hemoglobin. One ounce (28 grams) of shelled pistachios provides 3 grams of fiber and 5 grams of net carbs.
- Wheat Bran: Wheat bran is the hard outer coating of the wheat kernel. While it’s found naturally in whole grains, it can also be purchased on its own to add texture and a nutty flavor to foods like baked goods, smoothies, yogurt, soups, and casseroles. Wheat bran is rich in several important vitamins and minerals, with 1/2 cup (30 grams) providing 41% of the DV for selenium and more than 140% of the DV for manganese. Although, perhaps what it’s best known for is its impressive amount of insoluble fiber, a nutrient that can help treat constipation and promote regular bowel movements. A 1/4-cup (15-gram) serving of wheat bran provides 6 grams of fiber and 4 grams of net carbs.
- Broccoli: Broccoli is a popular cruciferous vegetable that’s high in several important nutrients. In addition to being low in calories, it’s high in fiber and several essential vitamins and minerals, including folate, potassium, and vitamins C and K. It also boasts more protein than many other vegetables. While it can be enjoyed cooked or raw, research shows that steaming it provides the greatest health benefits. One cup (71 grams) of raw broccoli florets provides 2 grams of fiber and 3 grams of net carbs.
- Asparagus: A popular springtime vegetable, asparagus comes in several colors, including green, purple, and white. It’s low in calories yet high in vitamin K, providing 46% of the DV in 1 cup (134 grams). The same serving also packs 17% of the DV for folate, which is vital during pregnancy and helps with cell growth and DNA formation. While it’s usually cooked, raw asparagus can add a pleasant crunch to salads and veggie platters. One cup (134 grams) of raw asparagus provides 3 grams of fiber and 2 grams of net carbs.
- Eggplant: Also known as aubergines, eggplants are used in many dishes around the world. They add a unique texture to dishes and contain very few calories. They’re also a good source of fiber and several vitamins and minerals, including manganese, folate, and potassium. One cup (82 grams) of raw, cubed eggplant provides 3 grams of fiber and 2 grams of net carbs.
- Purple Cabbage: Also referred to as red cabbage, purple cabbage is a nutritious way to add a pop of color to your dishes. While it tastes similar to green cabbage, the purple variety is higher in plant compounds that have been linked to health benefits, such as improved heart and bone health, reduced inflammation, and protection against certain forms of cancer. Purple cabbage is also low in carbs, high in fiber, and an excellent source of vitamins C and K. One cup (89 grams) of chopped red cabbage provides 2 grams of fiber and 5 grams of net carbs.
How to Increase Fiber Intake
Here are some tips for adding more fiber to your diet:
- Have a fiber-friendly breakfast.
- Choose whole grains. Try options like brown rice, quinoa, or whole wheat pasta.
- Focus on non-starchy vegetables.
- Start dinners with a salad.
- Add beans or other legumes. Try adding legumes such as lentils and peas or different kinds of beans (pinto, kidney, lima, navy, garbanzo) to salads, soups, stews, or casseroles.
- Eat plenty of fruits, vegetables, nuts, and seeds. Add fruits and vegetables such as apples, pears, bananas, or baby carrots to your meals and snacks.
- Remember to take it slow when adding more fiber to your diet. A sudden increase in fiber can lead to digestive discomfort like bloating, gas, constipation, diarrhea, or cramps.
Considerations
If you’re going keto, your best - and safest - course of action is to enlist a registered dietitian knowledgeable in the diet to design a plan that will meet your nutrient needs, says Elia.
Potential Downsides of Keto
The keto diet is very low in carbs which means you can't eat many fruits and vegetables. There can be issues with bone health when people switch to low-carb keto diets. Researchers see that markers for bone breakdown are higher and markers for bone building are lower. Also, when people start the keto diet, they go through the keto flu. Keto flu symptoms appear a few days after starting the diet. This eventually goes away once your body adjusts to your eating changes. Most people following a strict keto diet should take a multivitamin with minerals to ensure they're meeting those vitamin and mineral needs.
Before starting the keto diet, you should get a blood test to look at your lipids. Some people will actually find that their high-density lipoproteins (HDL) - the good cholesterol - go up and their triglycerides go down.
When to Limit Fiber
In some situations, your healthcare professional may ask you to eat less fiber. This may ease the symptoms of a condition or help the digestive tract heal from a treatment. If you get surgery that involves the intestines or stomach, your healthcare professional may recommend a lower fiber diet afterward for a time. Conditions such as Crohn's disease and ulcerative colitis inflame parts of the digestive tract. When symptoms flare up, you may need to eat less fiber. Your healthcare professional also may ask you to eat less fiber during a bout of diverticulitis.