Bowls of yogurt, sauerkraut, beans, greens and olive oil on a table

Gut Health and Inflammation: What You Need to Know

ByCraig Brockie Last updated

What gut inflammation means

Inflammation is the body’s defense response. Cleveland Clinic describes it as your body’s reaction to an illness, injury or something that does not belong there. A short burst of it, the redness and swelling around a cut, is useful. The trouble starts when it switches on without a clear threat and stays on for months or years.

When people talk about gut health and inflammation, they usually mean one of two different things. Keeping them apart makes the research much easier to read.

  • Inflammation inside the gut wall. This is what happens in inflammatory bowel disease (Crohn’s disease and ulcerative colitis). It is a diagnosed medical condition, it can damage the intestine, and it needs a doctor’s care.
  • Low-grade, body-wide inflammation. This is a quieter, ongoing immune activity that shows up as slightly raised markers in the blood. Researchers are studying whether the gut and its microbes help push this up or calm it down.

Cleveland Clinic lists an imbalance of gut microbes alongside low activity, ongoing stress, extra body fat, poor sleep, smoking and heavy drinking as factors behind most cases of chronic inflammation. In other words, the gut is one piece of the picture, not the whole of it.

How the gut and inflammation are connected

The gut lining is a barrier

Your intestine is lined with a single layer of cells, a coat of mucus and a large share of the immune system. A 2019 review in Gut by Mayo Clinic researchers explains that this barrier is made of surface mucus, the cell layer and immune defenses, and that endurance exercise, anti-inflammatory painkillers (NSAIDs), pregnancy and some food additives can make it more permeable for a time.

This is where the idea of “leaky gut” comes from. Cleveland Clinic notes that increased intestinal permeability is a real, measurable finding, but that leaky gut syndrome is not currently a recognized medical diagnosis. The same Gut review adds that it is still unproven that fixing barrier function improves disease, so be wary of tests or kits that promise to diagnose and heal it.

Gut microbes make anti-inflammatory compounds

When gut bacteria ferment fiber, they produce short-chain fatty acids such as butyrate, acetate and propionate. A 2016 review in Cell describes how these compounds act on immune and gut cells and serve as fuel for the cells lining the colon. Much of this work comes from lab and animal studies, but it explains why fiber keeps coming up in conversations about inflammation.

Diet can shift the gut and immune markers

Some of the most useful human evidence comes from a 2021 Stanford trial in Cell. Healthy adults were randomly assigned to a high-fiber diet or a high-fermented-food diet for 17 weeks, with 18 people in each group. The fermented-food diet, built on foods such as yogurt, kefir and fermented vegetables, steadily increased gut microbiota diversity and decreased inflammatory markers. The high-fiber diet did not change the main immune score, and responses varied from person to person.

A larger study pointed the same way. In the NU-AGE project, 612 older adults in five European countries followed a Mediterranean-style diet for one year. Gut bacteria that rose with closer adherence were negatively associated with inflammatory markers including C-reactive protein. This shows an association, not proof that the bacteria caused the change.

Food additives are being studied too. In a small, tightly controlled feeding study, 16 healthy adults ate either an emulsifier-free diet or the same diet with the common thickener carboxymethylcellulose for 11 days. The additive group had modestly more abdominal discomfort and less diverse gut bacteria. The study was short and tiny, so it raises a question more than it answers one.

What the evidence does and does not show

ClaimEvidence strengthSource
Chronic inflammation is linked with heart disease, type 2 diabetes and other long-term conditionsStrong (well established)Cleveland Clinic
Eating more fermented foods can lower some inflammatory markersEarly (one small 17-week trial)Wastyk, Cell 2021
A Mediterranean-style diet shifts gut bacteria linked with lower inflammation markersModerate (large trial, associations)Ghosh, Gut 2020
Fiber-derived short-chain fatty acids calm immune responsesMostly lab and animal researchKoh, Cell 2016
Probiotics help ulcerative colitisMixed; possible help alongside standard treatment, no benefit shown for Crohn’sNCCIH
Healing “leaky gut” fixes inflammation-related diseaseNot provenCamilleri, Gut 2019

On probiotics specifically, NCCIH summarizes a 2014 review of 21 studies (about 1,700 people): adding probiotics, prebiotics or synbiotics to usual care could be helpful in inducing or maintaining remission of ulcerative colitis, while 14 studies in Crohn’s disease showed no benefit. Our guide to supplements for gut health and inflammation goes through individual ingredients in more detail.

Everyday habits that support a calmer gut

Colorful vegetables, whole grains and a jar of kimchi on a counter

No single food switches inflammation off. The habits with the most support are broad eating patterns and lifestyle basics. Harvard Health lists tomatoes, olive oil, leafy greens, nuts, fatty fish and fruit as part of an anti-inflammatory diet, and suggests limiting refined carbohydrates, fried foods, sugary drinks, red and processed meat, and margarine.

  • Eat a wide range of plants. Beans, whole grains, vegetables, fruit, nuts and seeds feed the bacteria that make short-chain fatty acids. Our list of the best foods for gut health is a good starting point.
  • Add fermented foods regularly. Plain yogurt, kefir, sauerkraut and kimchi were the core of the Stanford fermented-food diet. See fermented foods for gut health for ideas.
  • Cut back on heavily processed foods. The foods Harvard flags overlap closely with our list of the worst foods for gut health.
  • Keep alcohol and NSAIDs in check. Cleveland Clinic names chronic overuse of alcohol or NSAIDs such as aspirin and ibuprofen as a direct cause of increased intestinal permeability. Do not stop a medicine your doctor prescribed without talking to them first.
  • Move, sleep and manage stress. Cleveland Clinic recommends at least 150 minutes of moderate activity a week and also points to sleep and ongoing stress as drivers of chronic inflammation.

Single foods attract a lot of worry online. If you are wondering about specific items, we look at the evidence on whether tomatoes cause inflammation and on coffee and gut inflammation.

When to see a doctor

Ongoing gut symptoms are worth a proper checkup, because conditions such as Crohn’s disease cause diarrhea, cramping, belly pain and weight loss that diet changes alone will not fix. Mayo Clinic advises getting care soon if you have any of the following:

  • Diarrhea that does not stop or signs of dehydration
  • Severe belly pain
  • Blood in the stool that does not go away
  • Fever or signs of infection
  • Weight loss without trying

This article is general information, not medical advice. If you have a diagnosed inflammatory condition, talk with your doctor or a registered dietitian before making big changes to your diet or adding supplements.

Related topics

Sources

This article is for general information and is not medical advice. Talk to your doctor or a registered dietitian before changing your diet, supplements or medication, especially if you have a health condition.

Craig Brockie is the founder of Ultimate Health Solutions, the company behind Ultimate Gut, and the author of Ultimate Health, The Ultimate Gut Health Guide and The Unlimited Probiotics Guide. After injuries and chronic health problems in his twenties that conventional care didn’t resolve, he began researching health on his own and has studied natural health for 30 years. He is not a medical professional, and his articles are general information, not medical advice.

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