Stress is physical. It’s caused by physical phenomena in the material world. It manifests as a physiological response using physical hormones and neurotransmitters and other chemical messengers in the body. It changes biomarkers, neurochemistry, behavior, appetites, and our perception of the world around us. Stress can make us fly off the handle at something that we wouldn’t even notice in a normal state of mind. Stress can make us eat food we’d never normally consider eating.
And, like other physical phenomena our bodies interact with, stress can affect our gut health.
The first hint of this relationship lies in that split second sensation most people feel in high-intensity situations. You feel it right there in your gut. It’s a cue from the environment that things are going to get hairy for a little while, and you should prepare yourself. The gut is so central to everything, it’s our first real interface with the outside world. The gut is where food goes. It’s where outside nutrients or pathogens or interlopers try to gain entry to our inner world. The “gut feeling” is a Primal one that we cannot ignore.
So what happens to our guts when we endure too much stress without relief?
Stress and leaky gut.
They used to say “leaky gut” was a myth. It’s not. In clinical trials, they call it “intestinal permeability,” but it describes the same phenomenon: instead of the tight junctions that line our gut closely regulating the passage of toxins, allergenic particles, and nutrients into the body, the gates are thrown open to allow anything entry into circulation. This can increase or trigger autoimmune disease, allergic reactions to foods, and infiltration of toxins and pathogens. The end result is increased inflammation and oxidative stress, and there are a whole host of diseases and conditions linked to leaky gut.
Stress is a major and reliable trigger for leaky gut.1
Stress and gut bacteria.
Studies have shown that stress reduces the number of Lactobacillus species in the gut and tends to increase the growth of and colonization by pathogenic species—changes that correlate to many of the negative stress-related alterations to gut health and function.2 Many of these changes to the gut bacteria makeup stem from the increased cortisol and other stress hormones, which have been shown to have profound effects on the species living in our guts.
Stress and gut motility.
Stress tends to slow gastric emptying while speeding up intestinal transit times. This means you’re not digesting your food very well or quickly, but once it’s in your intestines it moves fast. That can make toilet visits rather too urgent and productive, while the actual eating—the assimilation of nutrients, the digestion, the extraction of the good stuff—becomes less productive.3
Stress and irritable bowel syndrome.
I had IBS for many years, and it coincided not just with all the grains I was eating but also the high levels of stress (training and professional/social) I was enduring. In fact, I always noticed that periods of high stress or heavy training were triggers for flareups. That was supposedly all in my imagination, but the actual evidence shows that I was right.
If you look at the common symptoms of IBS—how it presents in a human gut—it’s a laundry list of stress-related gut alterations. You’ve got leaky gut. You’ve got imbalanced gut bacteria. You’ve got supernatural gut motility (when you gotta go, you gotta go).4 It’s all there.
Stress and disordered eating.
There’s nothing worse for gut health than eating junk food, especially if you’re coming from an otherwise healthy Primal way of eating.
But that’s what stress does to many people: increases their susceptibility to the temptations of processed food. When you’re sitting in traffic for four hours a day, that Burger King drive thru starts looking real good. When you’re working 12 hours days, the last thing many of you want to do is go home and spend an hour preparing a healthy dinner. I get it, I understand it, but the fact remains that eating that way is terrible for gut health and function (and you know it, don’t you?).
Worse still, if you’re under a lot of stress, eating that junk food is less likely to satisfy you. Your food reward system in the brain grows duller, requiring greater quantities of even tastier junk food to satisfy its demands and “trigger” the food reward effect.5
What, besides “reduce stress,” can you do to improve or maintain your gut health in times of stress?
Eat well and don’t neglect prebiotic fiber.
People go back and forth on fiber. Is it essential? Is it useless? Is it actually harmful, as the carnivores claim? I’ve been in this game for many years, and while I don’t think there’s any one answer that will satisfy everyone, I do have an answer relevant for today’s topic.
At the very least, prebiotic fiber is conditionally useful—and one of the conditions that render prebiotics helpful is chronic stress. Prebiotic fiber feeds your good gut bacteria (and sometimes bad, if you’ve got bad living there, but that’s another story for another time) who in turn produce short chain fatty acids like butyrate that have been shown to counter some of the stress-induced effects on gut health and function. In one study, researchers found that increasing prebiotic fiber in a mouse’s diet improved their resilience to stress and improved stress-induced leaky gut, suggesting that the two are linked.6
Don’t let stress snowball.
Acute stress is a healthy part of the human experience. It’s why we have a stress response in the first place: to help us respond to difficult, stressful situations that we encounter in the world. It’s not “unhealthy.” And sure, while an acute stress response will transiently upregulate intestinal permeability and trigger changes to gut motility, those changes dissipate when the stress resolves. Exercise itself is a stressor; a hard workout will increase intestinal permeability for a short while, but it resolves soon after.
The problem is when we let stress snowball into a chronic condition. We allow it to build up and accumulate and take up permanent residence in our bodies. Then it doesn’t resolve, and that’s when we start seeing the other effects on gut health and function.
Improve your sleep hygiene (and maybe take melatonin).
Melatonin isn’t just a “sleep hormone.” It also acts as an antioxidant, affects a whole range of health measures, and, yes, protects your gut against stress-induced alterations.7 The best way to optimize melatonin status is to follow all the prescriptions described in my sleep hygiene post: getting morning and afternoon natural light, spending as much time outside as you can, reducing artificial light after dark, getting a bedtime routine, eating healthy food, and sticking to your bedtime sleep schedule. But that can be tough, as often the source of your stress will also be throwing your sleep schedule off. Supplemental melatonin can help here.
Supplement for stress.
I’m a ball of stress. Or rather, I was a ball of stress for much of my life. That’s probably why so many of my diet and lifestyle recommendations are geared toward high-stress individuals—I was trying to fix my own issues and quickly realized that I wasn’t alone, that many others could benefit from the same stuff. My issue was my stress was multifold. I was subjecting my body to incredible amounts of physical training stress that never seemed to end. I was balancing that with perpetual entrepreneurialism. I never sat still, always had something I should be doing. There was never a moment to take a breath. As soon as things let up, I was preparing for the next challenge, the next workout, the next test.
Remember how stress lays waste to the Lactobacillus species normally residing in our guts? Animal studies show that reintroducing some of them through probiotic supplementation can mitigate and even counter some of the stress-induced alterations to gut function, such as leaky gut and hampered motility.8
Now I’d love to hear from you. How does stress affect your gut function? What have you noticed? And how do you deal with stress, especially as it relates to your gut?
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.