Quick answer: An unhealthy diet is one of the main contributors to leaky gut. Diets high in processed foods, refined sugar, alcohol and certain additives, and low in fiber, can disturb gut bacteria and increase inflammation. Gluten affects the gut lining in celiac disease and some sensitive people. Plant compounds like lectins and phytates are reduced by traditional preparation.
Key takeaways
Food directly affects the gut barrier, the microbiome and inflammation.
Refined sugar, unhealthy fats, some additives, alcohol and a low-fiber diet are linked with a weaker gut barrier.
Choosing whole foods, a variety of vegetables, fruit, legumes and nuts, and cooking with olive oil are simple swaps that support the gut.
Why diet matters
Food directly affects the gut barrier, microbiome and inflammation. Background: introduction to leaky gut.
Dietary factors linked to a weaker gut barrier
Processed foods and sugar
Refined sugars, unhealthy fats and additives can fuel inflammation and dysbiosis. High sugar intake also increases advanced glycation end products (AGEs).
Low fiber
Fiber feeds beneficial bacteria that make butyrate, which fuels gut cells.
Fats
Too much omega-6 relative to omega-3 may promote inflammation. Fatty fish, nuts and seeds provide anti-inflammatory omega-3s.
Gluten
Gliadin can increase zonulin and open tight junctions, especially in celiac disease. Get tested before removing gluten. See the elimination diet.
Alcohol
Alcohol increases oxidative stress and inflammation and can disrupt tight junctions.
Anti-nutrients
Phytates, lectins and oxalates can affect absorption in some people. Soaking, sprouting, fermenting and cooking reduce them, and many of these foods are still very nutritious.
Food additives
Some emulsifiers, artificial sweeteners and carrageenan have been linked to microbiome changes in research.
Pesticides and herbicides
Washing produce and choosing organic when practical can reduce exposure.
Food, the gut and healthy aging
A fiber-rich, whole-food diet supports a diverse microbiome and lowers inflammation, both important as we age. Nutrient gaps also matter: see nutrient deficiencies.
Simple swaps
Choose whole foods over ultra-processed snacks, and add a variety of vegetables, fruit, legumes and nuts. Cook with olive oil and eat fatty fish twice a week, limit alcohol and added sugar, and follow the protocol food lists (see foods to consume).
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have ongoing bloating, gas, diarrhea or constipation, or food reactions that seem to be multiplying. The same is true if you have fatigue, skin flares or joint aches alongside gut symptoms, or if you want a personalized gut plan instead of guessing.
See a medical provider promptly for blood in your stool, black stools, unexplained weight loss, persistent vomiting, severe abdominal pain, fever, or trouble swallowing.
What the research shows
Food additives have only recently been tested in people. In a 2022 double-blind controlled-feeding study by Chassaing and colleagues, 16 healthy adults ate only additive-free meals for 11 days, and 7 of them had 15 grams a day of the emulsifier carboxymethylcellulose added. Compared with controls, the emulsifier group had slightly more abdominal discomfort after meals, lower gut microbial diversity and fewer short-chain fatty acids, and in 2 people bacteria moved into the normally protected inner mucus layer. With so few people and a dose higher than most diets provide, this is a warning sign rather than proof of harm.
Artificial sweeteners have similar early data. In a 2014 Nature study by Suez and colleagues, most of the experiments were in mice, but the researchers also gave a small group of healthy volunteers saccharin for one week and saw changes in gut bacteria and blood sugar responses in some of them. The human part was very small and short, and later studies have given mixed results, so sweeteners are best seen as one possible factor rather than a proven cause of gut barrier problems.
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Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Which foods or additives in my current diet might be affecting my gut?
Which foods and additives would be most worth limiting for my gut?
Which gut-friendly foods could I add to my meals first?
How long should I try these food changes before we review my symptoms?
Frequently asked questions
What foods are bad for leaky gut?
Ultra-processed foods, excess sugar and alcohol are common culprits.
Should I avoid gluten?
People with celiac disease must. Others can discuss a trial with their provider after testing.
Are lectins harmful?
Not for most people, especially when foods are cooked or soaked.
What foods support the gut lining?
Fiber-rich plants, fermented foods and omega-3-rich fish.
Sources
- Chassaing B, Compher C, Bonhomme B, et al. Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome. Gastroenterology 2022. PMID: 34774538. https://pubmed.ncbi.nlm.nih.gov/34774538/
- Suez J, Korem T, Zeevi D, et al. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature 2014. PMID: 25231862. https://pubmed.ncbi.nlm.nih.gov/25231862/
- Donohoe DR, et al. The microbiome and butyrate regulate energy metabolism and autophagy in the mammalian colon. Cell Metab 2011. PMID: 21531334. https://pmc.ncbi.nlm.nih.gov/articles/PMC3099420/
- Drago S, et al. Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestinal mucosa and intestinal cell lines. Scand J Gastroenterol 2006. PMID: 16635908. https://pubmed.ncbi.nlm.nih.gov/16635908/
- Bishehsari F, et al. Alcohol and Gut-Derived Inflammation. Alcohol Res 2017. PMID: 28988571. https://pmc.ncbi.nlm.nih.gov/articles/PMC5513683/
- Chassaing B, et al. Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature 2015. PMID: 25731162. https://pmc.ncbi.nlm.nih.gov/articles/PMC4910713/
- NIH Office of Dietary Supplements: Omega-3 Fatty Acids
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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