An increase in bowel cancer rates among young adults has led experts to investigate the potential role of additives found in ultra-processed foods. Cases of the disease have risen by 50 percent in British individuals under 50 over the last three decades, a trend that has baffled medical professionals.
A major global study indicated that a diet high in ultra-processed foods, such as ready meals, crisps, and processed meats, is associated with a 45 percent increased risk of developing cancerous growths in the large intestine or rectum. Researchers suggest that the variety of additives in these products could alter the gut microbiome, potentially promoting cancer-causing changes.
Emulsifiers Under Scrutiny
Emulsifiers, compounds used to thicken foods and maintain texture and shelf life, are a particular focus. Two emulsifiers, carboxymethylcellulose (CMC, E466) and polysorbate 80 (E433), have been highlighted. CMC is often found in low-calorie desserts and salad dressings, while polysorbate 80 is used in a wider range of products including bread, cakes, sports drinks, and plant-based milks. Experts note that these ingredients may alter gut bacteria, harm the bowel's protective lining, and promote inflammation, all of which are linked to an increased cancer risk.
Other emulsifiers like carrageenan (E407), common in vegan products, and mono- and diglycerides of fatty acids (E471), found in margarine and peanut butter, are also being examined for similar effects. Professor Tim Spector, a nutrition expert, explained that these emulsifiers can form a gel-like clump in the gut, hindering the communication of healthy microbes and potentially leading to the production of abnormal chemicals. They may also disrupt the gut lining, weakening the barrier against pathogens.
While animal studies suggest a link between these emulsifiers and bowel cancer, human studies are still limited, and more research is needed to draw firm conclusions. Current evidence in humans for specific emulsifiers influencing the gut microbiome is based on relatively small trials.
Preservatives in Processed Meats
Nitrites and nitrates, used as preservatives in processed red meats, have long been associated with an increased risk of bowel cancer. These additives can react with proteins to form N-nitroso compounds (NOCs), which can damage DNA in the cells lining the colon and rectum. The World Health Organization classifies processed red meat as a Group 1 carcinogen. Research indicates that for every 25 grams of processed meat consumed daily, the risk of bowel cancer increases by 20 percent.
Other Additives Under Review
Titanium dioxide (E171), a whitening agent previously used in products like chewing gum and sweets, has been banned in the European Union due to concerns about genotoxicity. While the UK Food Standards Agency continues to review its use, a U.S. study in 2024 found that diets high in this chemical were associated with increased gut inflammation and damage to the protective barrier. However, insights from animal studies must be considered cautiously due to physiological differences and dosage levels.
Artificial sweeteners commonly found in diet beverages and other products have also been shown to promote gut inflammation. While aspartame is widely used, researchers are particularly concerned about sweeteners like saccharin and sucralose, which can reach the large bowel. These sweeteners may alter gut bacteria, reduce beneficial fatty acids, and thin the protective mucus layer, potentially triggering low-grade inflammation. The difficulty in establishing a direct cause-and-effect relationship in humans is complicated by the fact that individuals consuming large amounts of artificial sweeteners often have underlying health conditions that influence their dietary choices.