Your gut does a lot more than digest food. It influences your immune system, your mood, your brain, your skin, your energy levels, and, increasingly, research is linking gut health to autoimmune conditions such as Sjögren’s disease, rheumatoid arthritis, and more.

And when your gut isn’t happy, you know it. Bloating, cramping, unpredictable bathroom trips, food anxiety, fatigue that won’t quit. Sound familiar?

I’m EA Stewart, RDN, a registered dietitian nutritionist, IBS and low FODMAP specialist, and recipe developer for the New York Times bestselling book Plant Powered Plus. I’ve spent years helping clients eat their way to better gut health, and I’ve navigated my own elimination diet journey while living with Sjögren’s disease, which means everything I share here is both evidence-based and real-life-tested.

This is your complete guide to the gut health diet, covering the low FODMAP diet for IBS, gut microbiome nutrition, and conditions like SIBO and histamine intolerance.

Whether you’re newly diagnosed, deep in the elimination phase, or simply want to understand how food affects your digestion, you’ll find clear, practical guidance here.

No overwhelming rabbit holes, no one-size-fits-all protocols — just honest, dietitian-approved help that actually works in real life.

How Diet Affects Your Gut Health

Think of your gut microbiome as a garden. The trillions of bacteria, fungi, and other microbes living in your digestive tract thrive (or struggle) depending on what you feed them.

And what you eat has a more powerful and rapid effect on that microbial community than almost any other lifestyle factor. Research shows that your microbiome can begin to shift meaningfully within just a few days of changing your diet. (1)

The single most important thing you can do for your gut microbiome? Eat more plants — and eat a wide variety of them. Fiber from fruits, vegetables, legumes, whole grains, nuts, and seeds is the primary fuel source for your beneficial gut bacteria.

When those bacteria ferment fiber, they produce short-chain fatty acids like butyrate — compounds that nourish your gut lining, reduce inflammation, and support immune function. (2)

Diversity matters as much as quantity. Different plant foods feed different bacterial species, which is why eating 30 or more different plant foods per week has been associated with a significantly more diverse microbiome compared to eating fewer than 10. (3)

That doesn’t mean you need to overhaul your entire diet overnight. It means that every new plant food you add, even in small amounts, is a deposit in your gut health bank account.

Fermented foods like yogurt, kefir, kimchi, and sauerkraut add beneficial live microorganisms directly to your gut and have been shown to increase microbiome diversity and reduce inflammatory markers. (4)

They work beautifully alongside a fiber-rich diet. Think of fiber as feeding your existing beneficial bacteria, and fermented foods as bringing in reinforcements.

On the flip side, a diet high in ultra-processed foods, added sugar, and low fiber consistently correlates with reduced microbial diversity and increased intestinal permeability — sometimes called leaky gut.

This doesn’t mean you can never eat a cookie. It means the overall pattern of your diet matters far more than any single food or meal.

The gut health diet isn’t one rigid protocol. It’s a flexible, food-first approach built around diversity, fiber, fermented foods, and polyphenol-rich plants.

With targeted modifications when a specific condition, such as IBS, SIBO, or histamine intolerance, requires it. That’s exactly what you’ll find in the sections below.

Gut Health Diet by Condition: Find Your Starting Point

🌸 I’m dealing with histamine intolerance

Histamine intolerance occurs when your body can’t break down histamine fast enough — often due to reduced activity of the DAO enzyme.

Symptoms can include headaches, skin flushing, digestive upset, and more, and are frequently triggered by fermented foods, aged cheeses, alcohol, and certain fruits and vegetables.

It’s often mistaken for allergies or IBS, so getting the right guidance matters.

• Low Histamine Diet: Foods to Eat and Avoid
• Low Histamine Diet Guidebook: Recipes + Food Lists

Please note: The information on this page is intended for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. I’m a registered dietitian, not a doctor, and nothing here should be taken as personal medical advice. Always consult your physician or qualified healthcare provider before making significant dietary changes, especially if you have a diagnosed medical condition or are under medical care.

The Gut Health Diet Shop

Need more support? My dietitian-created resources are designed to take the guesswork out of eating for gut health.