The relationship between Ultra Processed Foods (UPFs) and cancer has become a major topic in nutrition science. In recent years, doctor and researcher Chris van Tulleken, has helped bring UPFs into the mainstream with his best-selling book Ultra-Processed People, which examines the potentially harmful effects UPFs may have on human health. Coincidentally, his identical twin Xand, also a doctor and presenter, is set to speak at the 2026 HowTheLightGetsIn festival run by our sister company, The Institute of Art and Ideas. It raises an interesting question: why are doctors appearing at ideas festivals, and why are they talking about UPFs?
Firstly, what are UPFs? UPFs are distinct from processed food. Processed food is any food that has been altered during preparation, for example by processes such as canning, cooking, freezing or adding ingredients like salt and sugar.1 Ultra processed, on the other hand, comes from the NOVA food classification system. There is no universal definition, but these products typically have a long shelf-life and tend to include ingredients that are not found in the home kitchen, such as preservatives, emulsifiers, sweeteners and artificial colours and flavours. They also often involve processes that chemically alter the structure of ingredients such as extrusion, fractioning and hydrogenation. Examples include mass-produced bread, confectionary items, readymade sandwiches, low fat spreads and some flavoured yoghurts.2
This rising public interest is not without foundation. The World Health Organization (WHO) classifies processed meat, a category that includes many UPFs such as ham, bacon, sausage and deli meats, as CLASS 1 carcinogens (the same as cigarettes and asbestos).3 More striking still, over half of the average person’s calorie intake now comes from UPFs. This is hardly surprising given that they are cheaper, longer lasting, convenient, attractively marketed and seemingly unavoidable in most supermarket products.1
Fuelled by all this attention, I recently attempted to cut out UPFs from my diet for Lent, but it didn’t take long for me to realise how much of a challenge this would be. They are present in most ready-made options such as sandwiches and cereal bars, even ones marketed as ‘healthy’, making it difficult to find convenient alternatives when on the go. Preparing meals required more time, planning and expenses than I had anticipated. It became apparent that UPF intake is not a personal choice but about navigating an environment where these foods are the default.
Although UPFs have attracted growing media attention for their potential health risks, pinning down exactly how they may cause harm remains far from straightforward. While there is strong evidence showing an association between UPF consumption and cancer, the evidence that they directly cause cancer – and the mechanisms through which this may occur – is still considered relatively weak and inconclusive. 1 It is precisely this uncertainty that makes the science worth examining more closely…
Research into why these products may be harmful to our health has identified several proposed mechanisms by which they may cause cancer. Here are the five key ones:
1. Increasingly the likelihood of obesity
UPFs may indirectly cause cancer through increasing the likelihood of obesity as they are often characterised by high levels of saturated fats, salt and sugar. 4,5 Being overweight or obese is the second biggest cause of cancer in the UK. 1 UPFs also commonly lack essential nutrients such as fibre and micronutrients which are crucial for cancer prevention. 4 Furthermore, a diet high in UPFs often results in reduced consumption of foods that reduce cancer risk, such as vegetables, fruits and whole grains. 4 Moreover, chronic consumption of high amounts of sugar and consistently elevated insulin levels is known to result in uncontrolled cell proliferation, a hallmark of cancer. 6
2. Carcinogenic compounds
There is also potential for the chemically derived ingredients within UPFs to be carcinogenic. For example, processed meat contains a commonly used preservative, sodium nitrate, that can lead to the formation of carcinogenic nitrosamines in the stomach. Nitrosamines have been shown to cause DNA alterations and gene expression changes, linked to liver cancer in transgenic animal models. 7
Furthermore, the synergistic effects of additives and other ingredients in the development of cancers and other diseases remains poorly understood. 8
3. Manufacturing by-products
Besides the ingredients, the manufacturing process behind UPFs could also be of concern. Industrial processing physically and chemically alters the structures of molecules and can lead to the formation of carcinogenic contaminants. 9 For instance, high-temperature treatments, such as frying, baking, or extrusion can lead to the formation acrylamide, a well-known substance classified as a human carcinogen. 10
Additionally, the thermal processing and smoking of meat can generate carcinogenic substances, such as heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), N-nitroso compounds (NOCs) and monochloropropane diols and their esters, which are toxic and carcinogenic. 11,12 Other processes commonly involved in the production of UPFs such as sugar reduction and lipid oxidation can also produce mutagenic by-products.
4. Contamination from packaging
The packaging of UPFs represents another potential source of carcinogenic compounds, potentially contaminating the food. 4 UPFs are typically stored in various types of plastic, aluminium-based containers and other materials, all designed to ensure a long shelf life. Both BPA, a synthetic organic compound used in epoxy linings of cans, and phthalates, can leach into food and beverages, particularly under heat exposure. These have been associated with a multitude of health issues including cancer. 13
5. Chronic inflammation and microenvironmental changes
UPFs are linked to an increased risk of cancer through promoting chronic, low-grade inflammation. Chronic inflammation is recognised as one of the biggest risk factors for cancer. There are multiple reasons why UPFs have a pro-inflammatory effect. Firstly, their low nutritional quality with high sugar, saturated fat and salt may directly cause inflammation. Furthermore, the degraded physical structure of UPFs can change how the body absorbs nutrients and controls blood sugar, which can also contribute to inflammation over time. 4
UPFs may also promote gut microbiota dysbiosis, reducing beneficial bacteria and selecting for pathogenic species, which further drives inflammation. 5 This inflammation can contribute to carcinogenesis by enhancing oxidative stress, which can result in DNA damage, and in turn affects immune cell proliferation, apoptosis and signalling pathways. Together, this fosters a microenvironment for tumour growth. 4
As noted earlier, the evidence that UPFs directly cause cancer remains inconclusive, even though some of the ingredients and compounds involved are long-established mutagens. Much of the evidence we currently rely on is observational, meaning it can show associations but not definitive causation. Because diet and lifestyle are not single variables but highly complex and intertwined webs of behaviours and environmental factors, it is difficult to isolate the specific effects of UPFs from other factors. Physical activity, smoking, socioeconomic factors and overall dietary patterns all intersect in ways that are hard to disentangle, while the sheer diversity of UPFs further complicates any attempt at broad generalisation. In effect, we are still playing something of an association game.
The challenge, then, is to recognise that modern food environments shape behaviour and, in turn, health, almost by default, as some choices are far easier and more convenient than others. This perhaps explains why clinicians like Chris and Xand van Tulleken are finding themselves speaking not just in medical journals, but on broader cultural stages as well, acting as a bridge between medical science and public understanding of health and lifestyle.
By Philippa Rolfe
References
[1] Wedekind, S. (2024). Are ultra-processed foods linked to cancer? Retrieved from Cancer Research UK: https://news.cancerresearchuk.org/2024/04/18/are-ultra-processed-foods-linked-to-cancer/
[2] Carlos A Monteiro, G. C.-C.-S. (2019). Ultra-processed foods: what they are and how to identify them. Public Health Nutrition. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC10260459/
[3] WHO. (2015). Cancer: Carcinogenicity of the consumption of red meat and processed meat. Retrieved from World Health Organization: https://www.who.int/news-room/questions-and-answers/item/cancer-carcinogenicity-of-the-consumption-of-red-meat-and-processed-meat
[4] Bruna Menegassi, M. V. (2025). Ultraprocessed Food and Risk of Cancer: Mechanistic Pathways and Public Health Implications. Cancers.
[5] Ioanna A Anastasiou, D. K. (2025). Beneath the Surface: The Emerging Role of Ultra-Processed Foods in Obesity-Related Cancer. Curr Oncol Rep.
[6] Babalola OO, A. E. (2025). The impact of ultra-processed foods on cardiovascular diseases and cancer: epidemiological and mechanistic insights. Asp Mol Med.
[7] Takami T., K.-N. P.-Q. (2007). Loss of Hepatocyte Growth Factor/c-Met Signaling Pathway Accelerates Early Stages of N-Nitrosodiethylamine Induced Hepatocarcinogenesis. Cancer Res.
[8] Molognoni L., D. H. (2019). Interactions of Preservatives in Meat Processing: Formation of Carcinogenic Compounds, Analytical Methods, and Inhibitory Agents. Food Res. Int.
[9] Levy R.B., B. M. (2024). How and Why Ultra-Processed Foods Harm Human Health. Proc. Nutr. Soc.
[10] de Borba V.S., B. S. (2024). Acrylamide, Hydroxymethylfurfural and Furfural in Ready-to-Eat Foods Consumed by Child Population: Presence, Risk Assessment and Future Perspectives. Food Chem.
[11] Behsnilian D., B. P. (2014). Process-Induced Undesirable Compounds: Chances of Non-Thermal
Approaches. Meat Sci.
[12] Zahir A., K. I. (2024). Food Process Contaminants: Formation, Occurrence, Risk Assessment and Mitigation Strategies—A Review. Food Addit. Contam. Part A.
[13] Agarwal A., G. S. (2025). Food Contamination from Packaging Material with Special Focus on the Bisphenol-A. Crit. Rev. Biotechnol.
