Eating out, ordering takeout, or dining at cha chaan tengs is extremely common for Hong Kong residents. Many also rely on convenience foods like microwaveable meals, sausages, luncheon meat, and packaged soups. The general public already knows these foods should not be eaten too often. Now, two major new studies provide further evidence linking certain common food preservatives to an increased risk of cancers such as breast and prostate cancer, as well as a higher incidence of type 2 diabetes. Although most of these additives have passed safety standards and are widely used, researchers point out that long-term intake may pose long-term health threats—not yet fully understood—by disrupting gut microbiota and metabolic health.
These findings come from the large-scale "NutriNet-Santé" research project, led by the French National Institute of Health and Medical Research (INSERM). Launched in 2009, the project has tracked over 170,000 adults, comparing food additive intake with chronic disease outcomes using detailed dietary records and national health data. Project leader Mathilde Touvier stated this is the first study in the world to systematically analyze multiple food preservatives in relation to cancer and diabetes risk. However, she also emphasizes that this is an observational study and cannot yet directly prove causation; further clinical verification is needed.
One study, published in The BMJ (British Medical Journal), analyzed over 105,000 participants initially free of cancer, with follow-up lasting up to 14 years. Among the 17 most common preservatives studied, six showed a statistically significant positive association with cancer risk:
Another study, published in Nature Communications, tracked nearly 109,000 adults. Results showed that the group with the highest preservative intake had a nearly 50% higher risk of developing type 2 diabetes compared to the general population. The study indicated that preservatives linked to cancer in the above study—sodium nitrite, potassium sorbate, and acetates—also elevated diabetes risk. Additionally, certain antioxidants and other food additives (e.g., calcium propionate, phosphoric acid, vitamin C and E derivatives) showed similar negative associations.
Experts point out that these preservatives are most commonly found in "ultra-processed foods." These foods bear little resemblance to original ingredients and are typically combinations of refined components, added sugar, salt, trans fats, artificial flavors, colors, and preservatives to enhance flavor and extend shelf life. Common examples include instant noodles, hot dogs, potato chips, sugary drinks, and sweet breakfast cereals favored by many in Hong Kong. Recent research is closely monitoring the potential disruption that long-term consumption of such foods may have on the human gut microbiota. For example, nisin, a natural antimicrobial substance commonly used in the food industry, can kill harmful pathogens but may also simultaneously destroy beneficial probiotic bacteria in the gut, thereby affecting nutrient metabolism and immune regulation.
Medical experts not involved in the studies commented that these results once again highlight the importance of reducing processed food intake and establishing a diet based primarily on natural, plant-based foods. While current evidence is insufficient to support immediate changes to food safety regulations, it is enough to remind the general public that, despite the convenience of takeaways and processed foods, we should carefully examine and reduce the proportion of highly processed foods in our daily diets, protecting health at its source.
