The best foods for gut health — and the fibre that feeds your microbiome
You’re host to trillions of microbes that shape your immunity, mood and metabolism. Here’s what to feed them.
There are roughly as many microbial cells in and on your body as human ones, and most of them live in your gut. That community — your microbiome — helps train your immune system, makes vitamins and short-chain fatty acids, influences your mood through the gut-brain axis, and affects how you handle blood sugar. A diverse, well-fed microbiome is one of the quiet foundations of good health, and it’s built almost entirely from what you eat.
Gut-microbiome impact is one of the twelve dimensions the Healthy Body Index scores, weighted toward the prebiotic fibres and fermented foods the research keeps pointing to.
The three things your gut actually wants
1. Prebiotic fibre — the food your microbes eat
Prebiotics are the fibres you can’t digest but your bacteria can. They ferment them into short-chain fatty acids like butyrate, which nourish your gut lining and calm inflammation. The best sources are ordinary and cheap:
- Legumes — lentils and chickpeas are among the most microbiome-friendly foods there are.
- Alliums — garlic, onions and leeks are rich in inulin, a prime prebiotic fibre.
- Oats, barley and other whole grains — a good source of beta-glucan.
- Slightly-green bananas, cooked-and-cooled potatoes and rice — sources of resistant starch.
2. Fermented foods — reinforcements
Fermented foods deliver live microbes and the beneficial compounds they produce. Research on fermented foods and microbiome diversity has been some of the most encouraging in the field:
- Yoghurt and kefir with live cultures
- Sauerkraut and kimchi (unpasteurised)
- Miso, tempeh and other fermented soy
3. Polyphenols — the plant compounds that shift the balance
The same polyphenols that make foods anti-inflammatory also act as fuel and signalling molecules for beneficial bacteria. Berries, extra-virgin olive oil, green tea and dark, colourful vegetables all feed the microbiome as well as you.
The single best predictor of a diverse microbiome in large studies isn’t any one superfood — it’s the number of different plants you eat. Aim for 30 distinct plant foods a week: vegetables, fruit, legumes, whole grains, nuts, seeds, herbs and spices all count. HBI’s diversity bonus rewards exactly this.
What works against your gut
- Ultra-processed foods — low in fibre, often high in emulsifiers and additives that some research links to a less healthy microbial balance.
- A low-fibre diet overall — starve your bacteria of prebiotic fibre and diversity falls.
- Excess sugar and refined starch — feed the wrong end of the microbial community.
The simplest gut-health plan there is
- 01Eat a wide variety of plants — chase 30 different ones a week.
- 02Make legumes a regular habit — few foods do more for your microbiome per serving.
- 03Add a fermented food most days.
- 04Go easy on ultra-processed food, which crowds out the fibre your gut needs.
Because HBI weights gut impact, fibre and fermentation directly, the top-scoring foods and the best gut foods are largely the same list — or jump to the best foods for gut health in the catalogue.
Frequently asked
What foods are best for gut health?
Prebiotic-fibre foods (legumes, garlic, onions, oats, slightly-green bananas), fermented foods (yoghurt, kefir, sauerkraut, kimchi, miso, tempeh), and polyphenol-rich plants (berries, extra-virgin olive oil, green tea, colourful vegetables). Variety matters more than any single food.
How many different plants should I eat for a healthy gut?
Large microbiome studies find that people who eat about 30 different plant foods a week have the most diverse microbiomes. Vegetables, fruit, legumes, whole grains, nuts, seeds, herbs and spices all count toward the total.
What foods are bad for gut health?
Ultra-processed foods, a generally low-fibre diet, and excess sugar and refined starch work against a healthy microbiome — they starve beneficial bacteria of fibre and can favour a less healthy microbial balance.
Written by the team behind the Healthy Body Index. Every nutrition claim is checked against our scored food database and the published literature, and labelled by evidence strength — human trials aren’t treated the same as lab findings. More about why we built this.
Healthy Body Index provides general nutrition education. It does not diagnose, treat, cure, or prevent any disease, and is not a substitute for professional medical advice. Scores and claims describe how foods support normal healthy function, based on published research.
Keep reading
The best anti-inflammatory foods, ranked by the data
Inflammation is the slow fire behind most modern disease. These foods put it out — and the data says which ones do it best.
What is a food score — and why calories were never enough
Calories measure energy. A food score measures health. Here’s what that difference actually looks like on your plate.
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