Meet Mark

Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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April 11 2019

13 Keto-Friendly Fiber Foods

By Mark Sisson
41 Comments

While some keto or low-carb proponents claim fiber is useless at best and actively harmful at worst, I come down on the side that says fiber is probably helpful for most people. Some folks have persistently better responses to low- or no-fiber keto diets, and I won’t argue with that—I’ve seen it happen and I’ve read the studies where de-emphasizing fiber can actually improve constipation, for example.

I’ll just say that I have an opposite reaction, and, most importantly, I love eating a variety of plant foods that also happen to contain a ton of great nutrients in addition to fiber.

Do I buy into the idea that fiber is important because it is every human being’s responsibility to produce as much colonic bulk as humanly possible? No.

Do I think we should be consistently pushing the limits of our digestive tracts, performing feats of bathroom heroism so momentous they border on Herculean, and making sure the toilet bowl buckles beneath us? No.

The real value of fiber lies not in its coarseness, its tendency to form colonic bulk, to keep us topped off. The true value lies in its fermentability. A fermentable fiber is a prebiotic fiber—fiber that feeds our gut bacteria.

I won’t get into the many roles our gut bacteria play in our health today (I’ve covered that before. 1, 2, 3).

I will, however, explain why we need to be feeding our gut bacteria. Our gut bacteria form a physical barrier against incursions and colonization by pathogenic bacteria; they take up room along the gut lining so pathogens can’t. If we don’t feed our gut bacteria with prebiotics, it won’t be around to protect us. After antibiotic treatment where both good and bad gut flora are indiscriminately targeted and wiped out, pathogenic obesity-promoting bacteria take advantage of the open space. That’s a worst-case scenario, but it shows what can happen when the harmony of the gut is disturbed by antibiotics or, to a less extent, a lack of fermentable prebiotic fibers.

When our gut bacteria eat prebiotics, they also give off metabolites like butyric acid—a short chain fatty acid that our colonic cells use as an energy source and which improves metabolic health.

Gut bacteria also convert antinutrients like phytic acid into nutrients like inositol. The almond meal-obsessed keto eater would do well to have a powerful gut biome set up to convert all that phytic acid to inositol.

Now, some writers will come up with specific blends of fibers, powders and gums to create the “optimal” prebiotic diet for your gut bacteria, but that’s pretty silly. The gut is a complicated place. We’ve barely begun to even identify all its inhabitants. To think we know the precise blend of isolated fiber that will make them flourish, and then act on that, is a mistake.

A better option is to eat foods that contain fiber. Some of the prebiotic fibrous foods with the best nutrient profiles also happen to be extremely keto-friendly.

1) Almonds and Pistachios

Nuts are usually favored in health-conscious circles for a few reasons. They like the monounsaturated fat. They like the mineral profile, or the complete protein, or their ability to dissemble into nut meals and form baked goods. But what gets short shrift is the fiber content. Now, I can’t speak for other nuts, but almonds and pistachios in particular contain fiber with potent prebiotic effects. People who eat almonds and to an even greater extent pistachios end up with improved gut bacteria profiles.

2) Green Bananas

Ripe bananas are difficult to squeeze into a ketogenic diet. The green banana—an unripe one—is mostly resistant starch, a type of starch that cannot be digested and travels untouched until colonic bacteria metabolize it. It’s one of the best stimulators we know of butyric acid production. And sure, you could do a spoonful of raw potato starch to get your resistant starch, but the beauty of the green banana is that it also provides potassium, another nutrient that some find difficult to obtain and stay keto.

3) Wild Blueberries

Blackberries, boysenberries, raspberries, and strawberries are all loaded with fiber, and you should eat them. They’re lower carb than you think, they’re loaded with polyphenols, and topped with some real whipped cream they make a fantastic dessert. But wild blueberries are special. They’re smaller than other berries, which increases the amount of skin per ounce you get, and skin is where all the polyphenols and fiber lie. Heck, even the blueberry’s polyphenols have prebiotic effects on the gut biome.

4) Mushrooms

A few years ago, I wrote a whole post on mushrooms. Suffice it to say, they’re quite wonderful, bordering on magical. I did not discuss the fiber they contain. It turns out that all the various mushroom polysaccharides/fibers, including beta-glucans, mannans, chitin, xylans, and galactans also act as potent prebiotics that improve the health of the host.

5) Avocado

Your standard avocado has about 12-15 grams of fiber, if you eat the whole thing. I generally enjoy one a day myself.

6) Jicama

Great with chili powder, salt, and lime juice, jicama is about 11 grams of carbs per cup, but half of those are inulin, a potent prebiotic fiber with a tendency to really ramp up butyrate production.

7) Onions

Onions are another fantastic source of inulin. They go into almost every dish of every cuisine, so there’s no excuse not to be eating onions.

8) Garlic

I’ve been known to treat garlic like a vegetable, roasting an entire cast iron pan full until brown and sweet and chewy. They’re another great source of prebiotic fiber.

9) Leeks

Leeks have more inulin than onions. Try them crispy in egg scrambles.

10) Broccoli

Broccolini is a major part of my favorite meal of the day—my Big-Ass Keto Salad. Broccoli (and cruciferous vegetables in general) has been shown to have modulatory effects on the gut biome.

11) Sauerkraut

Kraut gives you two in one. It’s a fermented food, which is great for the gut biome. And it’s cabbage, which is very fibrous. Even pasteurized kraut improves gut health.

12) Dark Chocolate

Dark chocolate, the good stuff with a high cacao content (85%+) and low sugar content, is an incredible source of prebiotic fiber. Eat more of it.

13) Animal Fiber

Obligate carnivores like cheetahs who don’t eat any plants (willingly) still have gut bacteria. These gut bacteria thrive on “animal fiber,” the gristle and cartilage and other bits of connective tissue that comprise a good 20-30% of the walking weight of a prey animal. Humans are not obligate carnivores, but eating the entire animal has been a mainstay of advanced hominid existence for millions of years. I find it very likely that something, someone, somewhere inside our guts is breaking down the animal fiber we eat—so you’d better be eating some!

Not so tough, is it? It’s not like I’m suggesting you load up on bran muffins, psyllium smoothies. I don’t want you dumping flax meal into everything or munching on those awful fiber gummies. Just eat some basic, healthy, low-carb plant matter—foods that don’t really scream “fiber”—and the rest will take care of itself.

What’s your favorite low-carb source of fiber? Let me know down below.

Thanks for reading, everyone.

References: 

Hernández E, Bargiela R, Diez MS, et al. Functional consequences of microbial shifts in the human gastrointestinal tract linked to antibiotic treatment and obesity. Gut Microbes. 2013;4(4):306-15.

Ukhanova M, Wang X, Baer DJ, Novotny JA, Fredborg M, Mai V. Effects of almond and pistachio consumption on gut microbiota composition in a randomised cross-over human feeding study. Br J Nutr. 2014;111(12):2146-52.

Jiao X, Wang Y, Lin Y, et al. Blueberry polyphenols extract as a potential prebiotic with anti-obesity effects on C57BL/6 J mice by modulating the gut microbiota. J Nutr Biochem. 2019;64:88-100.

Jayachandran M, Xiao J, Xu B. A Critical Review on Health Promoting Benefits of Edible Mushrooms through Gut Microbiota. Int J Mol Sci. 2017;18(9)

Nielsen ES, Garnås E, Jensen KJ, et al. Lacto-fermented sauerkraut improves symptoms in IBS patients independent of product pasteurisation – a pilot study. Food Funct. 2018;9(10):5323-5335.

TAGS:  Keto, nuts/seeds

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41 thoughts on “13 Keto-Friendly Fiber Foods”

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    1. Yes it is. Seeing him as a regular guy from a photo stock chowing down on raw broccoli is hilarious.

  1. Separating soluble fiber from insoluble fiber is important, especially if someone (such as myself) has digestive issues, mine being ulcerative colitis.

    Soluble fiber is digestible and dissolves with water. Insoluble fiber is not digestible. Most nuts and vegetables such as the above listed are mostly insoluble fiber.

    So I can’t have most of the items listed. I’m sure most readers can, and good for you. I can, however, have a baked potato without skin, as the insides are roughly half-soluble and half-insoluble fiber.

    I also have an approx. half-teaspoon of guar gum mixed in a beverage three times per day. Guar gum is soluble fiber.

    Another important thing to have is acidophilus (the “good” bacteria) or otherwise probiotic supplements. They go well with your fiber foods. Based on what I’ve read over the past 15-20 years since my initial medical ordeal, most people don’t get enough probiotics “good bacteria” from food sources to protect the colon from the harmful elements.

    1. Soluble fiber is NOT digestible. No fiber is. Indigestibility is part and parcel of the very definition of fiber.

  2. GREEN bananas? Completely green? I’ve never liked “ripe” bananas. Too soft, sweet and mushy. I’ve always eaten just where they begin to be edible. But completely green bananas are awful and suck the moisture right out of your mouth. Lol. If that’s how we’re supposed to eat them, how do you prepare them?
    Also, Jicama. Do you boil or roast that? I guess I could just pull out your cookbook and look. Lol. I’ve never eaten it so I’m unfamiliar with cooking it.

    1. Jicama is a root vegetable that after you peel it is white and really delicious. I’ve always eaten it raw. I think it’s in most grocery store’s produce departments. Glad to know it’s also good for you.

    2. Jicama is good raw. The flesh of a jicama root is crunchy, white, and has a very light/mild flavor sort of halfway between an apple and a potato. Cut it into matchsticks or bite-size pieces and add to salads.

    3. I like green bananas and plantains in smoothies. I’ll buy several, peel and slice them, then freeze them for use whenever I want a smoothie. Add some berries, kefir, cacao powder, whatever else you like in smoothies.

    4. jicama is great eaten raw with lime, salt, and chili on it…that’s also a traditional south american way to eat it..

    5. COOKED green bananas (usually boiled) are a staple starch in many cuisines. (Jamaican cuisine springs to mind…) When cooked, they are tangy and starchy, and work well paired with meats.

    6. Roast green bananas with butter and cinnamon or garam masala.

      Jicama are eaten raw. They are great as is. I suspect that they might be good julienned and used as a fake pasta in salads.

  3. What about a Daily Apple? Is that keto???

    I guess this is now a keto blog. I get it, it’s “the latest sensation that sweeping the nation” and it’s a growing market, just like CBD oil seems to be the solution to all of life’s problems and that market is exploding also. And if it is viable for people under certain circumstances, that’s great.

    1. Apples have more carbs than the entire keto daily carb allotment of 20 grams

      1. Adriana – don’t know where you got that 20 grams from, but that’s incorrect. You do NOT need to limit yourself to 20 grams of net carbs. You can usually go up to 50-55 grams without issues, higher if you supplement some ketogenic amino acids. And if you practice intermittent fasting, stuffing your meals into an eating window of 5 hours or less every day *and* train within your fasting window, you can eat all the carbs you want and you’ll still be in nutritional ketosis before you break your fast.

    2. I am still 80/20 primal. And I have a smallish apple every day. No keto for me.

  4. I like to dip raw jicama sticks in guacamole, yum! Trader Joe’s has a Chili Lime seasoning blend that is also good sprinkled on raw jicama.

  5. Mix 2 scoops chocolate/coconut Collagen Fuel in 8 oz. almond milk, and fill ice cube trays halfway. Cut up partially green bananas into pieces and place into trays and freeze. Allow to thaw slightly before popping out of tray.

  6. veterinarian here: Mark i Love what you do and your information-
    i’ve got to speak up though: please don’t make the same mistake that vegan proponents also make: comparing human body and GI tract to that of other animals’ of a different class.
    (vegans say: cows exist on grass and veggies only, so can we; Mark is saying obligate carnivores, which cats are to the extreme, exist on only meat for fibre, so can we. we are omnivores.)

    cats, cows , humans: our GI tracts are, both anatomically and biochemically, are entirely different. they truly are. one really can NOT compare or use one as a demonstration, or reason for eating something, for the other.

    that does not mean humans can’t eat what cows and cats do, or that we have no similarities at all with each others’ GI systems or dietary preferences. it’s just that each animals’ needs really are SO different, and for such different reasons based on their individual biochemistry–which is FAR more different, and significant health-wise, than you might expect.
    the comparisons really become moot.

    (small examples of differences to humans: cats make their own Vit C, their stomachs alone digest and break down bone; they cannot digest and breakdown vegetable fibre with out it being ‘pre-digested’ in the GI tracts of their small prey., or processed in some other way… cows on the other hand, have 4 stomachs and get a part of their protein needs from the bacteria in one of these ‘stomachs’- their rumens. humans can eat both meat and veggies as a healthy diet. cows and cats cannot. cows have a GIANT colon proportionately, cats have tiny ones; humans have small-medium ones. bacteria differences in all 3 are HUGE. so many more differences…)

    thanks for your time and work-

    1. Sorry, Tuffy – you misread the post. Mark merely said that obligate carnivores don’t eat vegetables, but still have gut bacteria. He did not say that we should eat in the same fashion. Indeed, most of his material here argues for the inclusion of plant foods with prebiotic fiber …

      1. true Marge; but the implication was we as humans could also use that fiber (in a similar way). that subject was what i wanted to elucidate.

  7. While many lettuces and greens melt away to almost nothing in the digestive process, cabbage, kale, and escarole have enough fiber that a hefty salad of these, raw, provides a good amount of very healthy fiber. I have a daily salad with about 2 cups of chopped raw cabbage as a base. Everything else varies day to day, but the raw cabbage does wonders.

    1. Cabbage is amazing, and it is great to hear you feel wonderful eating them. That being said, it’s NOT particularly big on fiber. One cup of raw cabbage has only 2.2 grams, so 2 cups has 4.4 – less than 15% of the UK recommended average intake for fiber (and less than 5% of the 100+ grams of fiber our Paleolithic ancestors ingested.)

  8. “Your standard avocado has about 12-15 grams of fiber, if you eat the whole thing. I”

    It looks like you started on a second sentence Mark and never finished. What were you going to say?

  9. ” those awful fiber gummies”

    Obviously you’ve never had Smart Sweets gummies. Yummo! 28g fiber and 5g carbs per bag.

  10. What about for people who suffer from bad constipation?
    I eat high fiber foods and take magnesium citrate daily but still am severely constipated. My doctor recommends Benefiber but I dont like that it is made from wheat. Any ideas?

    1. A healthy gut makes you go. So eat clean. Add a probiotic to install the good bacteria and prebiotic fiber to feed that bacteria. I’d load up on both and good quality probiotic… no cheap stuff. Be consistent and patient. Short of some dire medical condition, you’ll go..

      1. Thanks Sally! I do take probiotics and eat fermented foods but it turned out to be an obstruction! I guess my high fiber diet was working against me. I started a fiber supplement called glucomannan and I seem to be much better for now.

  11. What is your take on FODMAP and food combining for good digestion?

  12. Love eggs. Especially scrambled and hard boiled. Problem sometimes can give stomach cramps. Is that gut bacteria problem causing this. Love eggs but they don’t love me .

  13. Best low carb dietary roughage? Celery IMO. A stick of celery a day, keeps the constipation away.

  14. If one is in ketosis he produce butyric acid; hence no need for fiber the scratches your gut and irritates it. I am a bit surprised that the article didn’t dive deeper into describing all the harmful chemicals that plants produce in order to defend themselves. And by the way, I would describe us as facultative carnivores more than anything else

  15. A few more to the list.
    Sunchokes or Jerusalem Artichoke: Not low carb but has great nutrient value. Fry in butter with garlic or use as a substitute for mock potato-leek soup.
    Radishes: Daikon and the simple red ones are dirt cheap and make great snack bites.
    Okra: The core green and thickening component of gumbo. Okra is great pickled too.

  16. Hi Mark , love all your work ,and buy your supplements and books and other. Iam starting up Keto again. And I just wanted to know if she should still follow your book keto reset to start, or another approach.Iam a 68 year old female in decent health. Thank you. Elaine