13 Keto-Friendly Fiber Foods

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

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.

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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.

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Dear Mark: Antibiotic Recovery, Sprinting on Keto, Preparing for Bad Sleep

For today’s edition of Dear Mark, I’m answering three questions. First up, what can a person do to help their gut recover its barrier function after too many antibiotics? Are there any foods, supplements, or dietary strategies? Second, what can explain rapid fatigue during sprint sessions on a keto diet? Is this simply part of the deal, or are there modifications you can make? And finally, what do I do when I know I’m going to get a bad night’s sleep?

Let’s go:

Mark – any idea how to cure leaky gut caused by overuse of antibiotics. Tried raw dairy for a month to no avail.

First of all, check out my post on leaky gut. Read through it and follow my suggestions for preventing and treating intestinal permeability. It’s a great place to start.

Then, let’s look at some other interventions that have been shown to improve recovery from antibiotic therapy. While most of the studies referenced don’t explicitly describe antibiotic-induced leaky gut, anything that improves gut function and restores healthy gut bacteria will also normalize leaky gut—since it’s the eradication of native gut bacteria that causes antibiotic-induced leaky gut.

Fermented dairy. You tried raw dairy. What about fermented dairy? While raw dairy has its merits, it’s fermented dairy that just works for recovery from antibiotics. Yogurt is a good option to try, although the evidence is a bit inconsistent. Kefir is probably better; it’s been shown to improve patients’ tolerance to triple antibiotic therapy during treatment for H. pylori infection. This is even worth consuming during antibiotic therapy, as many of the probiotic bacteria found in fermented dairy show resistance to common antibiotics.

Fermented vegetables like sauerkraut are also must-eats. The fermented cabbage contains ample amounts of L. plantarum, a bacteria strain that’s been shown to prevent antibiotic-related diarrhea in piglets (another omnivorous mammal). Good options exist in stores (check the refrigerated section; shelf-stable pickles and kraut aren’t lactofermented), and even more are available in farmer’s markets, but the best way to get the most bacteria-rich vegetable ferments is to make your own.

Supplemental probiotics are fantastic here, too: large doses of the desired microorganisms delivered directly to your gut. Some of the strains used in Primal Probiotics, like B. clausii and S. boulardii, have been shown to be effective against antibiotic-related diarrhea, so that could be a good choice.

Don’t forget the food for your gut bugs: prebiotics. You need to eat fermentable fibers and other prebiotics like resistant starch to support the growth and maintenance of the helpful bacteria that improve gut barrier function. Consider eating cooked and cooled potatoes, unheated potato starch, leeks, garlic, onions, green bananas, apples, pears, berries, and pretty much any fruit or vegetable you can get your hands on. Plenty of them are low-carb enough to work on a keto diet, if that’s your desire. Oh, and dark chocolate is a great source of fiber and polyphenols, which have prebiotic effects in the gut.

Incorporate intermittent fasting. Going without food for a spell gives your gut a break and induces autophagy, which can help with tissue healing.

Get dirty, too, to introduce potentially helpful bacteria. Go out and garden. Go barefoot at the park (do your due/doo diligence, of course) and practice tumbling, or roughhouse with your kids (or friends). Don’t immediately rush to wash your hands all the time (unless you’ve been handling raw meat and/or dog poop).

Whatever you do, don’t stress too much about the antibiotics you had to take. Stress is awful for gut health and you’ve already taken the antibiotics—which were probably necessary—so that ship has sailed.

If probiotics with prebiotics aren’t helping (or making things worse), you might want to try going the opposite direction—removing all plant foods and doing a carnivore diet for a few weeks. While I have doubts about the long term viability and safety of eschewing all plant foods, enough people have written to me about their great experiences resolving gut issues with a bout of carnivory that it’s worth trying.

When on a strict keto plan, why do I become so quickly fatigued while attempting a HIT sprint workout?

The first five seconds of a sprint are primarily powered by phosphocreatine (or creatine phosphate), a “quick burst” energy source that burns hot but disappears quickly. This is the stuff used to perform max effort Olympic lifts, short sprints, and other rapid expressions of maximum power. It doesn’t last very long and takes a couple minutes to replenish itself. A keto diet doesn’t affect our creatine phosphate levels. If anything, it should improve them if we’re eating meat.

After five seconds, anaerobic metabolism of muscle glycogen provides the lion’s share of your energy needs. The longer your sprint, the more glycogen you’ll burn. The less glycogen you carry in your muscles, the shorter your sprint. Because once you run out of creatine phosphate and glycogen, you’re left with aerobic metabolism—great for longer distances, not so great for max effort sprints.

Keto dieters tend to walk around with less glycogen in their muscles. If that’s the case, longer sprints will be harder.

If you want to keep sprinting:

Do shorter sprints. Try a 10-second hill sprint rather than a 20-second one. Really go hard. Heck, you can even do 5-second sprints and derive major benefits; just do more of them and make sure to recover in between. There’s no rule saying you have to sprint for 20-30 seconds.

Take longer rest periods. Give your muscles a chance to replenish more creatine phosphate (and take creatine or eat red meat and fish, which are the best sources of dietary creatine).

Eat 20-30 grams of carbs 30 minutes before a sprint session. See if it helps. Alternatively, you can eat the 20-30 grams of carbs after the sprint session to replenish lost glycogen stores (without really impacting your ketone adaptation, by the way).

Most people figure out their sprinting sweet spot while doing keto. They may have to play around with the dosages, durations, and rest periods, but you can usually make it work. Be open to trying new permutations.

If you knew you were going to have a poor nights sleep, what measures would you take to reduce some of the damage?

I would exercise hard that night. Normally, a bad night’s sleep tanks your insulin sensitivity the next day, giving you the insulin resistance and glucose tolerance of a diabetic. A good hard interval session the night before a bad night’s sleep, however, counters the next-day insulin resistance.

I would make the most of it. Don’t dawdle. Don’t beat yourself up because of the impending sleep deprivation. It’s going to happen. You have to accept it, not let it destroy you.

Enjoy it. A little-known acute treatment for depression is sleep deprivation. That’s right: a single night of sleep deprivation has been shown to ameliorate depression in patients with clinical depression. Sometimes the effect lasts up to several weeks. It’s not a long term or sustainable fix for clinical depression, obviously, and you can’t do it every single night—chronic sleep deprivation is a major risk factor for developing depression—but it can improve your mood if you give in to it.

I would set out a jar of cassia cinnamon. I always add cassia cinnamon to my coffee in the morning after bad sleep; cassia cinnamon the day after a bad night’s sleep attenuates the loss of insulin sensitivity and glucose tolerance.

That’s it for today, folks. Thanks for writing in and reading! If you have any input on today’s round of questions, let me know down below.

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References:

De vrese M, Kristen H, Rautenberg P, Laue C, Schrezenmeir J. Probiotic lactobacilli and bifidobacteria in a fermented milk product with added fruit preparation reduce antibiotic associated diarrhea and Helicobacter pylori activity. J Dairy Res. 2011;78(4):396-403.

Bekar O, Yilmaz Y, Gulten M. Kefir improves the efficacy and tolerability of triple therapy in eradicating Helicobacter pylori. J Med Food. 2011;14(4):344-7.

Erginkaya Z, Turhan EU, Tatl? D. Determination of antibiotic resistance of lactic acid bacteria isolated from traditional Turkish fermented dairy products. Iran J Vet Res. 2018;19(1):53-56.

Yang KM, Jiang ZY, Zheng CT, Wang L, Yang XF. Effect of Lactobacillus plantarum on diarrhea and intestinal barrier function of young piglets challenged with enterotoxigenic Escherichia coli K88. J Anim Sci. 2014;92(4):1496-503.

Jitomir J, Willoughby DS. Cassia cinnamon for the attenuation of glucose intolerance and insulin resistance resulting from sleep loss. J Med Food. 2009;12(3):467-72.

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