Quick answer: Your gut, sometimes called the second brain, hosts trillions of microbes that help digest food, make vitamins and train the immune system. An anti-inflammatory diet rich in fiber, plants and fermented foods may support microbial diversity, a healthy gut barrier and balanced immune responses. Poor gut health is linked with inflammation and reduced nutrient absorption.
Key takeaways
The gut has its own nervous system and talks constantly with the brain.
A diverse microbiome helps digest fiber, makes short-chain fatty acids and helps keep less friendly microbes in check.
Eating a wide variety of plant foods and fermented foods may help maintain microbial diversity, which tends to decline with age.
The second brain
The gut has its own nervous system and communicates with the brain. See the gut-brain connection.
A balanced microbiome
A diverse microbiome helps digest fiber, make short-chain fatty acids and some vitamins, and crowd out harmful microbes.
How diet supports gut health
Microbial diversity
A variety of plant foods feeds a variety of microbes.
Gut barrier
Short-chain fatty acids nourish the cells that line the gut. See causes of leaky gut.
Immune balance
Much of the immune system lives in the gut, and a healthy microbiome helps keep it balanced.
When gut health suffers
When gut health suffers, inflammation rises, nutrient absorption drops, and digestive symptoms such as bloating and irregularity can appear.
Healthy aging lens
Microbial diversity tends to decline with age; fiber, fermented foods and plant variety may help maintain it.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have a chronic inflammatory, autoimmune or digestive condition, or if you have diabetes, kidney disease or take medications affected by diet changes. The same is true if you are pregnant, breastfeeding, or have a history of disordered eating, or if you want a plan tailored to your labs, symptoms and goals.
See a medical provider promptly for severe abdominal pain, signs of an allergic reaction such as swelling or trouble breathing, or fainting.
What the research shows
Diet can change the gut microbiome even later in life. In the NU-AGE study reported by Ghosh and colleagues in 2020, 612 older adults in five European countries followed a Mediterranean-style diet tailored to their age for 12 months. Those who stuck to it most closely had more of certain bacteria, which were linked with lower frailty, better cognitive scores and lower inflammatory markers such as C-reactive protein, along with more short-chain fatty acid production. These links come from analyzing who followed the diet best, so they cannot fully separate the diet from other healthy habits.
The microbiome responds quickly. In a 2014 Nature study by David and colleagues, healthy volunteers ate a diet made entirely of animal products or entirely of plant products for a few days each. Within days, the animal diet increased bile-tolerant bacteria, including Bilophila wadsworthia, and reduced fiber-fermenting bacteria. The abstract does not report the number of people, and the diets were extreme, but the study shows how fast gut bacteria follow what we eat.
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Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Would it help to look more closely at my gut health before changing my diet?
Which foods would best support my gut barrier on this diet?
How quickly should I add fiber so my digestion can adjust?
Would a stool test help guide my gut-focused food choices?
Frequently asked questions
How does diet affect gut health?
Fiber and plant variety feed beneficial microbes.
What is the second brain?
The gut’s nervous system, which communicates with the brain.
What foods support the microbiome?
Vegetables, fruit, nuts, seeds and fermented foods.
Can poor gut health cause inflammation?
It’s linked with inflammation in research.
Sources
- Ghosh TS, Rampelli S, Jeffery IB, et al. Mediterranean diet intervention alters the gut microbiome in older people reducing frailty and improving health status: the NU-AGE 1-year dietary intervention across five European countries. Gut 2020. PMID: 32066625. https://pubmed.ncbi.nlm.nih.gov/32066625/
- David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature 2014. PMID: 24336217. https://pubmed.ncbi.nlm.nih.gov/24336217/
- Belkaid Y, Hand TW. Role of the microbiota in immunity and inflammation. Cell 2014. PMID: 24679531. https://pmc.ncbi.nlm.nih.gov/articles/PMC4056765/
- Wastyk HC, et al. Gut-microbiota-targeted diets modulate human immune status. Cell 2021. PMID: 34256014. https://pmc.ncbi.nlm.nih.gov/articles/PMC9020749/
- McDonald D, et al. American Gut: an Open Platform for Citizen Science Microbiome Research. mSystems 2018. PMID: 29795809. https://pmc.ncbi.nlm.nih.gov/articles/PMC5954204/
- 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/
- Cryan JF, et al. The Microbiota-Gut-Brain Axis. Physiol Rev 2019. PMID: 31460832. https://pubmed.ncbi.nlm.nih.gov/31460832/
- MedlinePlus: Dietary Fiber
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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