Ultra processed foods and gut health: what you need to know

Curious about the potential impact of ultra-processed foods (UPFs) on your body, including your gut? I share the latest research, and explain how to eat less UPFs.

There’s a lot of talk about ultra-processed foods (UPFs), and for good reason. A growing number of research studies report that they may have an impact on our long-term health, including gut health. A major new study from the USA suggests that women who eat a lot of UPFs are at risk of abnormal growths that can lead to bowel cancer.

What are ultra processed foods?

You might be surprised how many UPFs you eat. Even if you work hard to stay healthy, they can be hard to avoid. Many everyday foods are ultra-processed, including supermarket sliced bread, jarred sauces, deli meat and bacon (including plant-based alternatives) and ready-to-eat meals. Even foods that seem like good choices, like flavoured yoghurt, protein bars and balls, cereal and baby foods can contain additives and emulsifiers.

Ultra processed foods and gut health: what the study found

Researchers followed more than 29,000 women over 30 years as part of the US Nurses' Health Study II. By the time the women turned 50, data showed that those who ate the most UPF (about 9 serves a day – a notably high amount) compared to those who ate the least (about 3 serves a day) had almost double the risk of developing bowel polyps that can later turn into cancer.

Ultra processed foods and gut health

This research doesn't prove that doesn’t prove that UPFs cause bowel polyps or cancer, but it may help scientists better understand why bowel cancer is increasing, especially among younger adults. Australia has the highest rates of bowel cancer in under-50s in the world.

Australians eat more UPFs than people in many other countries

In the meantime, a new series on ultra-processed foods has been published in world-leading medical journal The Lancet. It reports that UPFs are increasingly replacing healthy whole foods in our meals and snacks, and is a major driver of obesity, type 2 diabetes and heart disease. Australians eat more UPFs than people in many other countries – we're up there with the Americans and the Brits.

Health policies and processes influence the foods we buy. The Australian government is considering making it compulsory for food manufacturers to put a Health Star Rating on packaged foods to help us compare products. However, there are ways for industry to game the system, such as replacing sugar with ultra-processed alternatives that aren't identified on the front of the pack.

How UPFs affect your gut health

UPFs are often high in additives, sugar, salt and refined ingredients. Plus they tend to be low in fibre, which we need for bowel health. There are many ways that scientists think the ingredients or processing of UPFs might affect our gut, including inflammation, changes to our gut microbiota or damage to the gut lining.

Avoid UPFs - here's what you can buy and eat instead

• Try to cut back on buying the most heavily processed products. If a product has more than five ingredients, or contains ingredients you don't recognise, avoid it.

• Build your meals around whole or minimally processed foods where possible. Want examples? Porridge for breakfast, egg salad on bakery sourdough for lunch, and roast chicken, sweet potato, broccoli and a side salad for dinner. Try to get your 2&5 a day – that's two pieces of fruit and five serves of veg (a small bowl of salad or ½ cup of cooked or raw veg).

• The more diverse your diet is in plant-based foods, the better chance you're giving your gut microbiota to look after you. Fruit and veg, wholegrains, nuts and seeds, beans and pulses, herbs and spices all count.

• If you are too busy to meal prep, or don't like cooking, don't worry – choosing whole food snacks like fruit and raw almonds and simply prepared meals like a pre-roasted chicken and bagged salad will get you ahead.

Research into UPFs and ill health continues to grow at a steady pace. You can be proactive about your bowel and wider health by trying to buy less foods with ingredients you don't recognise, and replacing them with fibre- and antioxidant-rich foods where you can (check out my recipes for inspiration).

Studies:

DOI: 10.1001/jamaoncol.2025.4777

DOI: 10.1016/S0140-6736(25)01565-X