How Paleo and Ketogenic Lifestyles Can Prevent Leaky Gut Syndrome

An introduction to intestinal permeability with the author of The Primal Blueprint, Mark Sisson

John Fawkes
Oct 23 · 9 min read
Photo courtesy of Mark Sisson.

It may be hard to believe, but the lining of your intestines has a surface area of over four thousand feet. When this lining works properly, it forms a tight barrier that carefully controls which chemicals get absorbed into your bloodstream. Nutrients go in, toxins stay out, and both your body and your gut flora (the good microbes in your gut) are healthy.

Sometimes, this lining doesn’t work properly; it develops microscopic cracks and holes through which any chemical can go through. Substances that then gain access to the bloodstream could include partially digested food, intact proteins rather than individual amino acids, bits of RNA from your food, and potentially even smaller bacteria. That triggers inflammation and changes in the balance of your gut flora, and, potentially, disorders that arise from unwanted intruders getting into your bloodstream.

This excess of intestinal permeability is known as leaky gut syndrome, and it’s been linked to a wide variety of common ailments, including IBS, autism, skin rashes, and depression.

Preventing or reversing leaky gut syndrome requires a diet free of toxins that would damage the gut — in general, this means something resembling the paleo diet. It also requires living a healthy lifestyle that minimizes systemic inflammation.

Mark Sisson, 65, founded the popular ancestral health blog Mark’s Daily Apple in 2006. A former world-class endurance athlete, Sisson is the godfather to the primal food and lifestyle movement and the New York Times bestselling author of The Keto Reset Diet and The Primal Blueprint.

Mark took the time to explain leaky gut syndrome to me — what it is, why it happens, and how to prevent it. Here’s what he had to say.

Interview with Mark Sisson

Two main reasons: I wanted in on this cool new thing called blogging. I could tell having that direct line to readers was the wave of the future, whether you wanted to make money, promote your business, or build new ideas and communities.

I’d been in the health, fitness, and nutrition game for so long, and I’d seen so much erroneous information spewed out, that I wanted to help correct the record. I figured I’d write every day for a year, and after that, I would have said all there was to say on the subject. That turned out to be a miscalculation.

I was on the anti-doping commission for the sport of triathlon, did a lot of personal coaching and training, coached some triathlon teams, and in 1997 I started a supplement company called Primal Nutrition.

Leaky gut syndrome is a funny story. For years, the health authorities called it a myth or woo-woo pseudoscience — something that only quacks and snake-oil salesmen discussed.

But at the same time, researchers were studying something called intestinal permeability. Hundreds of papers have been published on the subject. And it turns out that intestinal permeability — a legitimate medical phenomenon well-accepted by the experts in the field — is a synonym for leaky gut.

The lining of our gut has gateways called tight junctions. The tight junctions are like doormen at a nightclub: they open up to permit desired compounds through, like nutrients, water, bar toxins, antigens, and pathogens. In leaky gut, the tight junctions are allowing unwanted compounds entrance to the rest of the body.

More than “symptoms,” there are conditions linked to leaky gut. They include obesity, celiac disease, inflammatory bowel disease, irritable bowel syndrome, food allergies/intolerances, asthma, autism, autoimmune diseases, depression (about 35% of patients with clinical depression have leaky gut) That’s not to say that leaky gut causes these conditions, just that they often occur together.

Everyone is susceptible to leaky gut because it’s a physiological (normal) aspect of gut function that can become pathological.

For a true medical diagnosis of leaky gut, there’s the intestinal permeability test. You drink a solution containing a pre-measured amount of mannitol and lactulose, two indigestible sugars. You collect your urine over the next six hours and measure the amount of excreted mannitol and lactulose to determine how much permeated through your gut.

Diarrhea and constipation can be good signals, too, but beware of reading too much into short-term symptoms. We’re all a little leaky sometimes. Lots of things can transiently increase intestinal permeability, like hard exercise. It’s when the diarrhea isn’t letting up, or you consistently get rashes and constipation after you eat a particular food, that you have a good signal that something is wrong with your gut health.

It’s just “one of those things.” A good way to think of exercise is as a very powerful stressor. You’re essentially doing trauma to your entire body with the hope that you’ll be able to recover better-adapted to the trauma than before. Increased permeability is just a consequence of full-body trauma.

John’s note: It sounds like the increase in intestinal permeability post-exercise is probably a side effect of the rise in inflammation that occurs after a hard workout. Unfortunately, that inflammation is part of the anabolic signaling that makes your body get stronger after exercise. In other words, you need it to happen.

Most conventional docs aren’t thinking about intestinal permeability as a cause of disease at all. The test is generally used in research settings rather than clinical ones. I’ve never heard of anyone getting their Kaiser doc to order one.

Alternative/functional medicine docs are more likely to order it, but that’s less likely to be covered by insurance.

Gluten increases the expression of zonulin, a compound that makes the gut more permeable or “leaky.” This happens in everyone, though the zonulin response is exaggerated in people with celiac disease.

However, not everyone experiences overt symptoms of leaky gut after eating gluten. Some people can clearly tolerate it just fine. If you insist on eating gluten on a regular basis, you’re probably better off with a fermented form, like sourdough.

Only if they have FODMAP intolerance. Symptoms include horrible gas, stomach pain, constipation, and/or diarrhea.

Ironically, the foods that you eliminate on a FODMAP program in addressing a gut dysbiosis are some of the same foods that can feed the “good bugs” when you have a healthy gut. Some foods that are beneficial in some instances can be problematic under other circumstances. No right answer here — just choices.

Stress and sleep deprivation are major stressors for the gut. Stress reduction and getting enough sleep are gut health fundamentals that most people don’t even consider.

I’ve never come across or heard of it.

Part of gut health is supporting and rebuilding the structural tissue the gut is made of. Most of that is collagen, and dietary or supplementary collagen provides the raw building blocks needed to make necessary repairs.

It’s not that seed oils directly damage the gut lining — although that’s a distinct possibility, I haven’t seen any clinical evidence that it happens. The problem with seed oil consumption is that it creates an overall inflammatory environment in the body. You need a solid foundation of health to maintain gut health, and the constant drip-drip-drip of inflammation makes it hard to erect that foundation.

Some anti-inflammatories, like aspirin and ibuprofen, can actually cause leaky gut.

Leaky gut is more likely to be a proximate cause of inflammation, but an inflammatory environment makes it harder for the body to support and maintain the integrity of the gut. More resources devoted to dealing with inflammation, fewer available to maintain gut health.

Fruit, winter squash, and starchy tubers like potatoes or sweet potatoes. I’m generally low carb myself, but those are healthy sources of carbohydrate.

John’s note: Cutting back on carbs is generally a good idea for most people, particularly those looking to lose weight. Your carbohydrate intake should depend on a few factors, including how active you are, how lean and muscular you are, and a few genes that regulate how the body processes carbohydrates and fats. More details here.

It’s exaggerated (and I got this wrong back in the day, too). The vast majority of legume lectins are degraded with sufficient heating.

John’s note: You can also remove most of the lectin from beans and lentils by soaking them in water. Just put your cooked legumes into a colander and run some cool water over them for a minute or two. Lectins are the chemical that causes beans to give people gas; if beans don’t make you gassy, they’re probably not causing any significant damage to your gut either.

Avoid: Seed oils (corn, canola, soybean, grapeseed, sunflower, safflower), gluten-containing grains (wheat, barley, rye).

Reduce: Grains in general, sugar.

I drink bone broth and use collagen supplements.

I avoid grains and high omega-6 seed oils.

I’m very selective about my alcohol intake. A few years back, I gave up alcohol entirely for a few months and it fixed my lingering gut issues. These days, I pretty much only drink lower-alcohol (12%-ish) natural wines.

I get plenty of sun. Low levels of vitamin D (which we make in response to UVB) have been implicated in leaky gut. John’s note: Most people don’t get nearly as much sun as Mark does and should take a vitamin D supplement.

I’m religious about my sleep. John’s note: if this is an issue for you, read my guide on sleep.

I’m working on my stress. Meditation doesn’t really work for me, but stand-up paddling is a kind of meditative practice that really calms my mind. I try to paddleboard as much as possible.

Conclusions: A Brief Set of Guidelines For Preventing or Reversing Leaky Gut

There are two things you need to do to keep your intestinal lining healthy: avoid ingesting things that damage the gut and keep your overall levels of systemic inflammation low. Based on Mark’s recommendations as well as the research I’ve read, here are a few simple guidelines to keep your gut healthy:

  • Minimize your intake of grains, particularly wheat and barley.
  • Drink alcohol rarely, and in moderation.
  • Minimize your consumption of seed oils.
  • Minimize caffeine consumption, as larger amounts can irritate the gut.
  • Eat mostly whole, unprocessed foods.
  • Eat more fish and vegetables, and possibly supplement with fish oil.
  • Eat more fruit, but particularly fruits that are low in FODMAPS and sugar.
  • Sleep 7–9 hours a night, every night, on a regular schedule.
  • Lift weights 3–4 times a week.
  • Keep stress to a minimum, possibly via meditation.
  • Supplement vitamin D or get several hours of sun a day.
  • Drink bone broth several times a week, and/or take a collagen supplement.
  • If you suspect you have leaky gut, go on a strict paleo diet and cut out alcohol and caffeine completely for 1–3 months. After it improves, you can follow the above guidelines without being strictly paleo.

There you have it: Leaky gut is a common problem, but it can be solved largely via living a healthy lifestyle and eating a healthy diet, which you should be doing anyway. You should be mindful of it, but you probably don’t need to go on a strict paleo diet to avoid it.

Better Humans

Better Humans is a collection of the world's most trustworthy writing on human potential and self improvement by coaches, academics, and aggressive self-experimenters. Articles are based on deep personal experience, science, and research. No fluff, book reports, or listicles.

John Fawkes

Written by

Los Angeles-based personal trainer, online fitness & nutrition coach, and health & fitness writer. I also sing a pretty sick cover of The Poison Heart.

Better Humans

Better Humans is a collection of the world's most trustworthy writing on human potential and self improvement by coaches, academics, and aggressive self-experimenters. Articles are based on deep personal experience, science, and research. No fluff, book reports, or listicles.

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