It is no surprise that what we eat has a profound effect on gut health, but many still underestimate how much this connection matters when it comes to cancer risk.Put simply, the food we consume directly influences the bacteria living in our digestive system and the substances they produce.Research consistently shows that eating patterns rich in fibre and focused on plants – such as vegetables, fruits, beans, lentils, whole grains, nuts and seeds – helps to create a more varied community of gut microbes.This diversity isn’t just essential for overall well-being but also plays a key role in lowering disease risk. And a key reason plant-rich diets work so well is their ability to boost production of short-chain fatty acids, especially one called butyrate.Fibre-rich foods create a more varied community of gut microbes | GETTYThis compound helps to maintain a healthy gut lining, support the immune system, and keep inflammation under control.All of these functions are crucial when we’re talking about cancer prevention, registered dietitian Alison Tierney told GB News. “Chronic inflammation and metabolic dysfunction are linked with a higher risk for several cancers, and diet is one of the most modifiable factors we have,” she said.”Importantly, the strongest evidence supports overall dietary patterns — what someone eats most days — rather than any single ‘superfood,’ specific diet, or supplement.”Which foods matter most?When it comes to cancer, the clearest culprits are low-fibre, heavily processed diets packed with ultra-processed foods, refined grains and sugary drinks, as these can reduce the variety of gut bacteria and fuel inflammation.Processed meats are another concern, with bacon, sausages and deli meats all closely linked to an increased risk of colorectal cancer. Cancer prevention guidelines worldwide clearly identify them as foods to limit.Finally, there’s alcohol – a known cancer risk factor. When it comes to prevention, less really is better – or avoiding it altogether makes the most sense.The most effective changes tend to be straightforward and easy to stick with.Making fibre a daily priority is key, so Alison recommends loading up on whole plant foods like beans, lentils, oats, barley, berries and leafy greens.If you’re not used to eating much fibre, it’s worth building up gradually and drinking generous quantities of water. | GETTYVariety also matters, so Alison recommends bringing different plants that feed different beneficial microbes, so mixing things up across the week is ideal.”Build meals around minimally processed plant foods, aiming for variety across the week,” she said. “Different plants feed different beneficial microbes.”These could include fermented foods like live-culture yoghurt, kefir, sauerkraut, kimchi, tempeh and miso, which can be helpful for some people, but not essential.