Your gut is home to trillions of bacteria that play a role in everything from digestion and immunity to mood and metabolism. The food you eat shapes this community every day, but that doesn’t mean you have to cut out entire food groups or label foods as “good” or “bad.”
Balance over perfection, if you’re fuelling your body with nourishing foods most of the time, enjoying an occasional treat won’t undo your hard work. It’s the 80/20 principle, 80% of the time, focus on feeding your gut what it needs; 20% of the time, give yourself the flexibility to enjoy food freely.
With that in mind, here are the six worst foods for gut health, not to avoid completely, but to be more mindful of, plus some simple swaps that will keep your gut feeling its best.
(If you haven’t already, you might also like our “7 Worst Drinks for Gut Health” guide for even more practical tips.)
Ultra-processed foods like crisps, biscuits, instant noodles, and ready meals are often high in additives, saturated fats, and preservatives but low in fibre and nutrients. These foods can make it harder for beneficial bacteria to thrive and may encourage inflammation.
That doesn’t mean you can never have them, convenience foods have their place, but eating them regularly can crowd out the plant-based foods your gut microbes love.
Swap it for: Quick homemade versions of your favourites using whole ingredients. A tray of roasted vegetables or homemade hummus with crackers provides far more fibre and flavour.
Your gut bacteria thrive on fibre, not sugar. When your diet is high in sweets, pastries, and sugary snacks, it can feed bacteria that prefer sugar and reduce the diversity of your microbiome.
This doesn’t mean all sweet foods are off-limits. It’s about keeping refined sugar occasional and balancing it with foods rich in fibre and polyphenols (found in fruit, nuts, seeds, and cocoa).
Swap it for: Fresh fruit, yoghurt with berries, or small amounts of dark chocolate. These satisfy your sweet tooth while still supporting a healthy gut environment.
Regularly eating fried or fast foods can challenge your gut and overall digestion. These meals tend to be higher in saturated and trans fats, which can slow digestion and increase inflammation³.
That said, everyone loves a takeaway from time to time, and that’s perfectly fine. The goal isn’t to eliminate them, but to make them an occasional treat rather than a daily habit.
Swap it for: Oven-baked or air-fried options with olive oil, or homemade versions with lean protein and colourful vegetables. Adding extra plants boosts gut-friendly fibre, if you need inspiration, check out our “30 Plants Per Week” blog for simple ways to build variety.
Sausages, bacon, and deli meats are convenient, but they’re often high in salt, nitrates, and saturated fat. Over time, this combination may alter your gut bacteria and increase inflammation.
You don’t have to give up your Sunday breakfast, just be aware of how often these appear on your plate.
Swap it for: Lean protein sources such as chicken, fish, beans, lentils, or tofu. These foods provide essential nutrients and fibre (in the case of plants) that your gut bacteria depend on.
Sweeteners are widely used to cut sugar, but not all behave the same way in the body. Some, like stevia and erythritol, are well-tolerated and considered safe in moderation. Others, including aspartame, saccharin, and sucralose, have mixed evidence and may alter gut bacteria in certain individuals.
Remember, you don’t have to avoid them entirely; it’s about being conscious of how much you’re consuming and choosing products with simpler, naturally derived ingredients.
Swap it for: Naturally sweet foods such as fruit, cinnamon, or a small drizzle of honey. If you enjoy flavoured drinks, opt for those made with stevia or erythritol for a gentler impact on your gut.
White bread, white rice, and other refined grains have had much of their fibre removed during processing. Without fibre, your beneficial gut bacteria lose their main source of fuel⁶.
Wholegrains, legumes, nuts, and seeds are all excellent sources of fibre that help keep digestion regular and feed a diverse gut microbiome.
Swap it for: Wholegrain or seeded bread, brown rice, quinoa, or oats. If you’re easing into higher fibre, increase gradually and drink plenty of water to support digestion.
Your gut thrives on variety, especially plants. By focusing on colourful, fibre-rich foods most of the time, you naturally reduce the space for the more challenging ones. And when you do enjoy those “sometimes” foods, your body is resilient enough to handle them.
Think of your diet like a spectrum rather than a rulebook. What matters most is what you eat consistently, not the occasional treat.
If you’re looking for more simple, science-backed ways to support your microbiome, explore our Complete Guide to Gut Health or revisit our 7 Worst Drinks for Gut Health. And don’t miss our 30 Plants Per Week blog, it’s an easy, fun way to feed your gut the variety it loves.
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