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

What prompted you to start Mark’s Daily Apple?

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.

You mention that you were working in health and nutrition before starting the blog — what exactly were you doing?

Can you explain what leaky gut syndrome is, what the main symptoms are, and why people need to know about it?

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.

How common do you think leaky gut is? Is it something everyone is susceptible to, or only people who have particular digestive issues?

What’s the best way to diagnose things like leaky gut and diet-induced autoimmunity issues? Can people go off of symptoms like diarrhea and constipation, or should they be getting lab tests?

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.

Why does hard exercise temporarily increase intestinal permeability? Do you view it as a negative side effect of exercise, or is it actually an adaptive response to help us take up more nutrients post-workout?

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.

Is the medical test for leaky gut usually covered by insurance? What’s the best way to raise the subject with one’s doctor?

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

I’ve seen a lot of mixed evidence around the supposed dangers of gluten, with some research showing wheat is safe, some suggesting it’s dangerous, and some suggesting that gluten isn’t an issue for most people, but that other chemicals in grain (like FODMAPs and phytic acids) are. What’s your take on this?

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.

Speaking of FODMAP’s, they’re present in high qualities in a lot of foods that are considered paleo, like artichokes, cashews, and pears. Should people be cutting back on “paleo” foods that are high in FODMAPs?

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.

Are there any dietary supplements, over-the-counter drugs, or non-dietary lifestyle changes that help prevent or heal gut inflammation and leaky gut?

Since intestinal permeability is a normal part of human gut function, is there a condition that’s the opposite of leaky gut — one where intestinal permeability is too low? If so, what are the symptoms and how would you diagnose it?

I’ve heard of people taking collagen supplements for their joints and skin before, but not for gut health. How does collagen help the gut?

How do seed oils damage the gut lining?

Leaky gut is highly correlated with inflammation. Would anti-inflammatories help to treat it? Do you think leaky gut causes inflammation, inflammation causes leaky gut, both, or neither?

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.

After cutting out grains, which carbohydrates do you primarily replace them with?

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.

What about legumes–most paleo experts recommend avoiding them because of the lectin content. Do you agree, or think this is an exaggerated concern?

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.

For people looking to prevent gut inflammation and autoimmunity, which foods would you recommend completely avoiding, and which foods would you recommend eating less of, but not necessarily cutting out?

Reduce: Grains in general, sugar.

What do you personally do to avoid gut issues?

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

  • 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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