BiotiQuest® Gut Health & Probiotics Blog with Martha Carlin

The Best Low-Carb Sources of Fiber On Keto

Martha Carlin | Jun 26, 2023 | 3 Minutes read

According to the American Society for Nutrition (ASN), only 5% of men and 9% of women met the recommended daily requirement of fiber intake in the US in 2021. 

Eating a diet rich in dietary fiber is essential for good health, irrespective of which macros rule your plate. But meeting the daily recommended requirement of fiber intake - roughly 15 grams for every 1000 calories consumed - might feel especially challenging on a keto diet.

Regular fiber intake has been associated with numerous health benefits such as increased gut motility, increased satiety, improved insulin sensitivity, decreased risk of colorectal cancer, a diverse gut microbiome, and maintaining the intestinal pH via optimal SCFA production, etc. 

Getting enough fiber on a keto diet without going over your total net carbs can seem daunting at first, but it’ll become second nature to incorporate sufficient fiber in your diet once you familiarize yourself with a variety of keto-friendly sources of fiber.

Types of fiber

Dietary fiber consists of various plant cell wall elements or nondigestible carbohydrates (NDCs) such as cellulose, hemicellulose, β-glucan, pectin, mucilage, gums, and lignin. 

Dietary fiber is commonly categorized into soluble and insoluble fibers, and most whole food sources contain a mix of both.

Soluble fiber is readily fermented by the gut flora to produce short chain fatty acids (SCFAs) whereas insoluble fiber largely acts as a bulking and softening agent in the gut that keeps your gut clear of food debris and harmful metabolites.

How does fiber work?

The digestive system depends on fiber to keep it healthy and move things along. Although fiber passes through your stomach and small intestine without much breakage, its function becomes prevalent in the large intestine. 

Fiber is an important food source for your gut microbiome. Fiber fermentation leads to the production of important metabolites such as short chain fatty acids (SCFAs) such as butyrate, acetate, and propionate. 

Each type of SCFA has an important role to play that ranges from supplying energy to the intestinal epithelial cells, maintaining the pH of the large intestine to suppress the growth of pathogens, as well as maintaining brain health.

Along with being a food source for the gut flora, fiber attracts water and holds onto it. This water retention makes food waste soft and moving along the intestine and prevents GI issues such as constipation as well as diarrhea.


Net carbs and fiber

Tracking net carbs while on keto is an effective way to track your carbohydrate intake. 

Total carbs include both net carbs as well total fiber present in any food item. Net carbs are carbohydrates present in a food item that are used to generate energy and can raise your blood sugar levels, minus total fiber and sugar alcohol. 

Fiber and sugar alcohols don’t count towards net carbs since they don’t raise your blood sugar level and thus don’t affect ketosis. 

While deciding on which fiber sources to add to your fiber roster for keto, keep in mind that food sources that might look high in total carbs may still be low in net carbs once the total fiber is removed from the equation. 

Keto sources of fiber

As a general rule, all kinds of green leafy vegetables can be your constant companions. They’ll not only fulfill your daily fiber needs but also provide you with a range of beneficial nutrients and minerals as well as prebiotics essential for the health and diversity of your gut microbiome.

Here’s a list of plant-based food items that are low in net carbs while still providing a sufficient amount of soluble and insoluble fiber. 


(1 cup, cooked)
Net Carbs -2.4g; Fiber- 4.3g

(1 cup, cooked)
Net Carbs -3.5g; Fiber- 2.7g

Swiss Chard
(1 cup, cooked)
Net Carbs - 3.5g; Fiber- 3.7g

Collard Greens
(1 cup, cooked)
Net Carbs -3.1g; Fiber- 7.6g

(100g, raw)
Net Carbs -2g; Fiber- 1.6g

(100g, raw, shredded)
Net Carbs -1.8g; Fiber- 1.2g

Turnip greens
(1 cup, cooked)
Net Carbs - 1.3g; Fiber- 5g

(1 cup, cooked)
Net Carbs - 3.5g; Fiber- 2.8g

(100g, raw)
Net Carbs -1.6g; Fiber- 0.8g

(100g, raw)
Net Carbs - 0.8g; Fiber- 0.5g




(1 oz, dry roasted, salted)
Net Carbs -1.2g; Fiber- 2.66g

Chia seeds
(1 oz, dry)
Net Carbs - 2g; Fiber- 9.75g

Flax seeds
(1/2 cup)
Net Carbs - 1.3g; Fiber- 23g

Macadamia nuts
(1/2 cup)
Net Carbs - 3.5g; Fiber- 5.8g

Brazil nuts
(1/2 cup)
Net Carbs - 3.2g; Fiber- 5g

(1/2 cup)
Net Carbs - 6.3g; Fiber- 9g

(1/2 cup)
Net Carbs - 10.7g; Fiber- 6.6g

(1/2 cup)
Net Carbs - 4g; Fiber- 4g

Pumpkin seeds
(½ cup)
Net Carbs - 3g; Fiber- 4g

Coconut meat raw
(1 cup)
Net Carbs - 5g; Fiber- 7.2g

(1 cup)
Net Carbs - 6.2 g; Fiber- 7.6g

(1 cup)
Net Carbs - 6.7g; Fiber- 8g





Brussels sprouts
(1 cup, raw)
Net Carbs - 4.5g; Fiber- 3.3g

(1 cup, hearts)
Net Carbs - 5.6g; Fiber- 14.4g

(1 cup, cooked)
Net Carbs - 2.2g; Fiber- 3g

Green Cabbage
(1 cup, raw)
Net Carbs - 3.2g; Fiber- 2g

(1 cup, fresh)
Net Carbs - 7.1g; Fiber- 6g

Bok choy
(1 cup, fresh)
Net Carbs - 2.4g; Fiber- 1.9g

(1 cup)
Net Carbs - 2.7g; Fiber- 10g

(1 cup, peeled, raw)
Net Carbs - 1.9g; Fiber- 2.8g

(1 cup, cooked)
Net Carbs - 3g; Fiber- 1.8g

Green olives
(1 cup)
Net Carbs - 0.8g; Fiber- 5.3g

Green beans
(1 cup)
Net Carbs - 4.3 g; Fiber- 2.7g

Green bell pepper
(1 cup)
Net Carbs - 4.3g; Fiber- 2.5g




(½ cup)

Net Carbs - 1.5g; Fiber- 0.6g

(½ cup)

Net Carbs - 0.6g; Fiber- 3.5g

Increasing fiber intake the right way

Fiber drinks up a lot of water to be functional. The key to reaping the benefit of adding sufficient fiber sources to your keto diet is to drink plenty of water to avoid dehydration and possibly constipation. 

If this is the first time you’re beginning to pay close attention to your fiber intake, then remember to take it slow. Too much fiber all at once will cause more problems than it will solve. Give yourself and your gut a chance to get used to the new and varied sources of fiber, and slowly increase intake over time.

Lastly, if you’re taking a direct fiber supplement such as psyllium husk, be mindful to consume either well in advance or a couple of hours after, since large amounts of fiber intake might affect the absorption of certain medications.

The powerful relationship between fiber and probiotics

Increasing fiber intake by itself is a great way to enhance health. But when you add additional sources of probiotics to your keto diet, either through fermented sources such as sauerkraut or kimchi or through probiotics supplements such as our Sugar Shift formula, it might help you jump leaps ahead in your health journey in the long run.

With gratitude,

Martha Carlin photo Martha Carlin, is a “Citizen Scientist”, systems thinker, wife of Parkinson’s warrior, John Carlin, and founder of The BioCollective , a microbiome company expanding the reach of science and BiotiQuest, the first of it’s kind probiotic line. Since John’s diagnosis in 2002, Martha began learning the science of agriculture, nutrition, environment, infectious disease, Parkinson’s pathology and much more. In 2014, when the first research was published showing a connection between the gut bacteria and the two phenotypes of Parkinson’s, Martha quit her former career as a business turnaround expert and founded The BioCollective to accelerate the discovery of the impact of gut health on all human disease. Martha was a speaker at the White House 2016 Microbiome Initiative launch, challenging the scientific community to “think in a broader context”. Her systems thinking background and experience has led to collaborations across the scientific spectrum from neuroscience to engineering to infectious disease. She is a respected out of the box problem solver in the microbiome field and brings a unique perspective to helping others understand the connections from the soil to the food to our guts and our brains.

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