6 Signs of an Unhealthy Gut, 7 Likely Causes & the Best Foods for Gut Health

best-foods-gut-healthWhen the ancient Greek father of medicine, Hippocrates, said “All disease begins in the gut,” he was probably right. Poor gut health has been linked to a broad range of diseases and health conditions, from depression to diabetes, cancer to obesity, and autism to autoimmune disease. Researchers are exploring connection between prevotella, a species of gut bacteria, and severity of COVID-19.1 Search the medical literature and you’ll probably find links between the gut and any illness you can imagine.

So—all the world’s health issues solved, right? Not exactly.

Gut health is one of those topics that gets more complicated the deeper you go. The more you read about gut bacteria, the less you realize you know and the less you realize anyone knows, even the researchers. It’s infinite onions, all the way down. The layers never stop, and exposing them eventually makes you want to cry. (Speaking of which, onions are actually a very good food for gut health).

All that said, the scientific community is honing in on the signs and symptoms of an unhealthy gut. We know how to heal an unhealthy gut, or at least improve gut health. An incredible amount of research has determined the best foods for gut health, and we know the worst foods for gut health. We understand that gut health comes down to supporting healthy gut bacteria and avoiding leaky gut. Top-down micromanagement might not work yet, but big-picture, bottom-up intervention does.

 

Instantly download our FREE guide: 10 Foods You Should Be Eating for a Healthy Gut

 

Gut Inflammation: Signs of an Unhealthy Gut

Some of the signs are obvious. Others are more pernicious. Not all of these will apply to someone with unhealthy gut bacteria or leaky gut, but some will.

Chronic Constipation, Bloating, and/or Diarrhea

Everyone gets a little constipated now and then. We’ve all had the runs, and we’ve all felt bloated after a particularly large meal. As long as these conditions are acute—as long as they’re brief and transient—they don’t indicate any serious gut inflammation. It’s when constipation or diarrhea or bloating endure and become chronic conditions that you should pay close attention. Chronic constipation, bloating, and diarrhea are signs of an unhealthy gut biome.

Obesity or Overweight

Although the connection hasn’t been established as causal, there is a consistent and significant association between obesity/overweight and poor gut health. If you are obese, you very likely have room to improve the health and function of your gut.

Food Intolerances and Allergies

If the integrity of your gut is compromised due to excessive gut inflammation or missing gut bacteria, undigested components of the foods we eat can slip past the intestinal barrier and into our bodies where they trigger an allergic reaction. This appears to be a necessary step in the development of a food allergy, and a 2011 review concluded that an overly leaky gut facilitates this transportation and leads to the inducement of allergy.

Depression and Anxiety

Researchers have long puzzled over observations that mental health conditions like depression and anxiety often present with common gastrointestinal complaints like constipation and diarrhea. It’s not just circumstantial: gut bacteria produce large amounts of neurotransmitters like serotonin, interact with neural pathways involved in anxiety and depression, and help form the gut-brain axis.

Animal studies show that replacing the gut bacteria of anxious mice with gut bacteria from fearless mice makes the anxious mice more brave, while giving bold mice bacteria from anxious mice makes them more anxious. In human subjects, a probiotic supplement (containing L. helveticus R0052 and Bifidobacterium longum R0175) reduces measures of anxiety and depression, and by some accounts, 35% of depressed patients have leaky gut.

Skin Problems (Eczema, Psoriasis)

In the last section, I told you about the gut-brain axis. There’s also a gut-skin axis: a constant interplay between the health of your gut and the health of your skin. People who have eczema are also likely to have leaky gut, while psoriasis patients show clear signs of unbalanced gut bacteria.

Autoimmune Disease

One of the world’s premier autoimmune disease researchers, Dr. Alessio Fasano, considers poor gut health a necessary pre-condition for all autoimmune diseases. It’s a similar situation to the allergy/intolerance issue: a leaky, inflamed gut allows outside proteins and other food components into the body, the immune system mounts an immune response to deal with the invaders, and this response gets out of hand and redirected toward the body’s own tissues.

Okay, so how does it all happen? Apart from food, which I’ll get to later on…


Further reading: The Definitive Guide to Collagen


What Causes an Unhealthy Gut?

There are many potential causes of poor gut health.

Stress

Stress can directly induce leaky gut (PDF) and stress can take many forms, as we all know. Bad finances, marital strife, unemployment, too much exercise, lack of sleep, extended combat training, and chronic under-eating all qualify as significant stressors with the potential to cause leaky gut, especially chronically and in concert with one another.

Poor Sleep

Sleep is restorative, and restorative sleep means you’re lowering stress and improving gut health. If your circadian rhythm starts to shift, starts getting a little dysfunctional, your gut health soon follows.

Inadequate Dirt Exposure

Too sterile an environment causes too sterile a gut. We are made to spend time in nature, feet and hands getting dirty, exposed directly to the natural soil teeming with trillions of bacteria. We’re meant to eat produce directly from the ground, and nature didn’t intend for us to always wash it. (That said, if you didn’t grow it yourself, it’s best to wash your produce.) Exposure to healthy soil may even bestow upon us anti-anxiety gut bacteria—gut microbes that actually make us less anxious.

Not Enough Exercise (or Too Much)

Exercise has been shown to directly improve gut function, increasing the production of beneficial short cain fatty acids by gut bacteria. When you stop training, the gut benefits cease.

Just don’t do too much. An acute bout of intense training causes a transient rise in leaky gut that subsides and even improves several hours after the session. This is fine. This is normal. This is adaptive. But if you start stringing together intense training sessions without adequate rest, the exercise becomes a chronic stressor and the transient rise in leaky gut starts looking more permanent.

Too Many Antibiotics

Antibiotics are great at killing pathogenic bacteria attacking you, but they also tend to be indiscriminate. They do not distinguish between friendly bactieria and harmful bacteria in your gut biome. The broad spectrum antibiotics we commonly take also wipe out the bacteria living in our guts, leading to gut bacteria imbalances and poor gut function.

After addressing the major causes of poor gut health, is there anything you should avoid eating? Are there foods you should focus on eating to improve your gut health?

What Are the Worst Foods for Gut Health?

The worst foods for gut health are no surprise to regular readers of this site, but that doesn’t make them any less important to avoid.

Refined Carbohydrates

When we eat refined carbs like grains or sugar, glucose is immediately released into the digestive tract, increasing the concentration of carbohydrate available to your gut biome. This concentrated influx of dense carbohydrate into the gut produces an inflammatory microbial population that increases production of bacterial endotoxin and increases leaky gut. Meanwhile, the lack of prebiotic fiber means your beneficial gut bacteria have no food to consume.

Gluten

Gluten, a protein found in wheat, barley, and rye, causes your body to release zonulin—a chemical messenger that tells your intestinal junctions to open up. Many people can handle this increase in zonulin, but if you’re already suffering from poor gut health or are sensitive to gluten, the zonulin response may be strong enough to trigger leaky gut.

What Are the Best Foods for Gut Health?

  • Fermentable fiber
  • Chocolate
  • Berries
  • Red wine
  • Skin, bones, and broth
  • Fermented foods
  • Resistant starch
  • Meat
  • Pistachios
  • Onions, garlic, and leeks

Fermentable fiber

Without food, your gut bacteria suffers. And the best food for your gut bacteria is fermentable fiber, found in many different plants. Asparagus, carrots, Jerusalem artichokes, and alliums like garlic and onions are your best bet.

Chocolate

Besides being delicious, high-cacao dark chocolate is an excellent source of prebiotic fiber (fiber your gut bacteria can consume) and prebiotic polyphenols (plant compounds that also feed your gut bacteria).

Berries

Name a berry and it’s been shown to improve gut health. Strawberries feed the gut biome and improve the gut function of diabetic mice. Blackberries restore gut health and trigger neuroprotective effects. Eating blueberries leads to compositional changes to the gut bacteria linked to improved metabolic health. And black raspberries have been shown to cause “anti-inflammatory” bacterial profiles in the gut.

Red wine

Although too much alcohol can have a detrimental effect on gut health, moderate amounts of red wine polyphenols may have prebiotic effects on the gut bacteria.

Skin, bones, and broth

Skin, bones, and broth offer gut health benefits in a number of ways. First, they provide “animal fiber,” collagenous and gristly substrate that our gut bacteria can digest and prosper on. Next, they offer ample amounts of gelatin, which can help repair damaged gut lining. In a pinch, collagen can fill the gap.

Fermented foods

This is an obvious one, but it’s incredibly important and more complex than you probably think. First of all, fermented foods like yogurt, sauerkraut, pickles, kefir, and dozens of other varieties seed our guts directly with beneficial probiotic bacteria. That has real benefits—though they don’t “form colonies” and you do have to continually eat fermented foods for the full benefit. Some fermented foods also have the ability to “train” your resident bacteria to digest new compounds. One example is fermented milk: in one study it didn’t colonize the gut but led to increased microbial expression of carbohydrate metabolizing enzymes in the existing bacteria.

Resistant starch

Resistant starch isn’t like other starches. Our stomach acid and digestive enzymes cannot break it down, but our gut bacteria can digest it. Multiple studies indicate that resistant starch consumption generally leads to an increase in “beneficial” colonic bacteria and a reduction in “pathogenic” colonic bacteria, including a boost to bifidobacteria and a decrease in firmicutes and a huge boost to butyrate production. The best sources of resistant starch are green (unripe) bananas and raw potato starch.

Meat

Meat usually doesn’t pop up on these lists, but that’s a huge mistake. Red meat especially provides ample B-vitamins required for energy generation and general physiological maintenance, including gut function. It’s a nutrient-dense “safe” food for even damaged guts who need to be careful about the plant foods they eat. And if you’re eating a significant amount of meat, you’ll have less room to eat the refined carbs and refined sugar that really cause gut issues.

Pistachios

Pistachios are the most potent nut for improving gut health. Other nuts like almonds are good too, but pistachios produce  a biome richer in butyrate-secreting bacteria which is extremely beneficial to several body systems.

Onions, garlic, and leeks

Onions, garlic, leeks, and other members of the allium family offer concentrated doses of fructo-oligosaccharides, some of the best-studied and most beneficial fermentable prebiotic fibers in the plant kingdom. Plus, they’re delicious, and humans have been eating them for thousands of years (if not longer).

Some people will react poorly to some of the foods listed in the “Best” section. If your gut health is compromised and your gut bacteria dysfunctional, you may very well have trouble consuming fermentable fiber, resistant starch, berries, and other fibrous foods without bloating, gas, stomach pain, constipation, and diarrhea. Please read my article on FODMAPs to understand how to work around this issue and maintain your gut health.

Thanks for reading, everyone. If you have any questions about gut health or the info contained in this post, let me know down below!

 

References

Bell DS. Changes seen in gut bacteria content and distribution with obesity: causation or association?. Postgrad Med. 2015;127(8):863-8.
Tordesillas L, Gómez-casado C, Garrido-arandia M, et al. Transport of Pru p 3 across gastrointestinal epithelium – an essential step towards the induction of food allergy?. Clin Exp Allergy. 2013;43(12):1374-83.
Perrier C, Corthésy B. Gut permeability and food allergies. Clin Exp Allergy. 2011;41(1):20-8.
Foster JA, Mcvey neufeld KA. Gut-brain axis: how the microbiome influences anxiety and depression. Trends Neurosci. 2013;36(5):305-12.
Hidalgo-cantabrana C, Gómez J, Delgado S, et al. Gut microbiota dysbiosis in a cohort of patients with psoriasis. Br J Dermatol. 2019;181(6):1287-1295.
Allen JM, Mailing LJ, Niemiro GM, et al. Exercise Alters Gut Microbiota Composition and Function in Lean and Obese Humans. Med Sci Sports Exerc. 2018;50(4):747-757.
Petersen C, Wankhade UD, Bharat D, et al. Dietary supplementation with strawberry induces marked changes in the composition and functional potential of the gut microbiome in diabetic mice. J Nutr Biochem. 2019;66:63-69.
Marques C, Fernandes I, Meireles M, et al. Gut microbiota modulation accounts for the neuroprotective properties of anthocyanins. Sci Rep. 2018;8(1):11341.
Lee S, Keirsey KI, Kirkland R, Grunewald ZI, Fischer JG, De la serre CB. Blueberry Supplementation Influences the Gut Microbiota, Inflammation, and Insulin Resistance in High-Fat-Diet-Fed Rats. J Nutr. 2018;148(2):209-219.
Pan P, Lam V, Salzman N, et al. Black Raspberries and Their Anthocyanin and Fiber Fractions Alter the Composition and Diversity of Gut Microbiota in F-344 Rats. Nutr Cancer. 2017;69(6):943-951.
Mcnulty NP, Yatsunenko T, Hsiao A, et al. The impact of a consortium of fermented milk strains on the gut microbiome of gnotobiotic mice and monozygotic twins. Sci Transl Med. 2011;3(106):106ra106.
Haenen D, Zhang J, Souza da silva C, et al. A diet high in resistant starch modulates microbiota composition, SCFA concentrations, and gene expression in pig intestine. J Nutr. 2013;143(3):274-83.
Martínez I, Kim J, Duffy PR, Schlegel VL, Walter J. Resistant starches types 2 and 4 have differential effects on the composition of the fecal microbiota in human subjects. PLoS ONE. 2010;5(11):e15046.
Liu Z, Lin X, Huang G, Zhang W, Rao P, Ni L. Prebiotic effects of almonds and almond skins on intestinal microbiota in healthy adult humans. Anaerobe. 2014;26:1-6.
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.
Gibson GR. Dietary modulation of the human gut microflora using prebiotics. Br J Nutr. 1998;80(4):S209-12.

 

About the Author

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.

If you'd like to add an avatar to all of your comments click here!

13 thoughts on “6 Signs of an Unhealthy Gut, 7 Likely Causes & the Best Foods for Gut Health”

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Mark thank you for this article. As you know from some of my previous comments, I’ve suffered a lot from constant diarrhea. I’m still sensitive, strangely when I do ab exercises like planks or reverse bicycles, I have to be very very careful. But probiotics are so important and have been very helpful to me. After two embarassing (mortifying) incidents where I soiled my pants in a business meeting, a friend turned me onto paleo and particularly probiotics. My colleagues started calling me Diarrhea-man after the incident, but now I call myself that because I’m on a quest to help people over come the stigma of gut problems. No one talks about it so no one shares advice like this. So thank you for this great post. I proudly call myself Diarrhea-man now as I’m spreading the word about probiotics. Keep up the great work and looking forward to when we can cruise again.

  2. Very informative article Mr. Mark Sisson. Probiotics are very effective to maintain a healthy gut. you have described some natural sources of probiotic in fermented foods heading. Thank for your article.

  3. For the latest research and some important info regarding the different types of Resistant Starch see Dr. Lucy Mailing’s blog….www.lucymailing.com

  4. Love the research and conclusions. Berries, nuts, chocolate and red wine – what’s not to like?
    Interesting that it’s so hard to pin down causation in gut health. Could it be related to emotional well being? Just about every negative emotion manifests as some unpleasant physical sensation in the abdominal area. What’s actually happening down there when we feel that twinge in the gut from fear or anxiety?

  5. I have been strict low carb for 18 years already so I don’t eat any of the bad foods, and I do eat plenty of the good foods. I don’t have many of the issues you describe as related to bad gut health, I’d say I have mild anxiety (not medicated) but I do have psoriasis on one elbow that I have not been able to get rid of. Also, I can eat onions, garlic, leeks etc no problem, but I absolutely can’t eat Jerusalem artichokes (unfortunately as I love them) because my gut cannot handle them at all. So I’m definitely sensitive to inulin. Would you recommend specific foods that might help me tolerate them more/help with the psoriasis? The one category of beneficial foods I really don’t eat are fermented foods. Do you think adding that regularly might help?

    Thanks,

    Deborah

    1. I had a similar issue with my hands, turned out to be a form of yeast infection, well, actually an overgrowth of yeast in my body. What helped is to ditch all the sugar and anything that turns into sugar of course, but when I still got it on my hands I found that fermented foods (like naturally fermented pickles-my favorite) helped to back that yeast growth off, supplementing with probiotic pills here and there as needed helped as well. Give them a try, that may just be the fix you need. A pickle a day keeps the ? away????

  6. I always read that sugar is bad for the gut. However, glucose is taken up in the blood via the small intestine very quickly – which is what can be bad about it, since it can lead to high insuline and storage of sugars as fat. But if the sugars are taken up so readily, there could be no way that they reach the large intestine to feed bacteria there?

  7. Mark,

    For those of us that have SIBO, it is a frustration to not be able to eat some of the otherwise healthful foods. The medical researchers certainly don’t understand the root causes.

    Your thought process has always been solid. My fellow SIBO sufferers and I would be grateful if you came up with a line of products specifically low FODMAP. Part of the challenge of living with SIBO is the strain of having think about what to eat.

    Thank you for being a good role model and promoting healthy gut lifestyle.

  8. Thank you for the excellent article. The link for the free download for 10 healthy foods… takes you to the download page, but the download page does not seem to have a place to enter your email address and download.

  9. Where is Prevotella listed in the article as mentioned in the title of the article?

  10. The same picture of two people preparing what looks like a sensible meal appears on the Low Carb Action Network page discussing the basics of a low carb diet. I bring this up because we all understand the dangers of and see all around us the results of, the higher carb diet recommended by the government “experts”. Well, the “experts” are once again about to make their official dietary guideline recommendations, and the committee has already asserted that they will NOT include science from any studies of low carb diets in their public utterances before the final recommendation is made. That way, the outcry from those who have a different view will not be as loud.

    In the meantime, Americans with metabolic derangement will continue to advance toward the inevitable disease, disability, and death – now with SARS-CoV-2 added to their risks.

    I guess, since we know better, we could join our collective voice with the Low Carb Action Network and express how a low carb diet has benefitted us, adding our experience to the message they have created for members of congress that will attempt to make them aware of the dereliction of duty that is about to occur. Or, I guess we could do nothing and then gripe about it when the new guidelines are published.