The conclusions come from two large observational studies published on Thursday in The BMJ and Nature Communications. Both drew on data from an ongoing French research project involving more than 100,000 adults who regularly report details of their diets and health over time.
In the cancer-focused study, researchers observed multiple associations between widely used preservatives in industrially processed foods and beverages and higher incidences of overall cancer, as well as breast and prostate cancers in particular. Nitrites and nitrates—commonly used to cure processed meats such as ham, bacon and sausages—were among the additives most consistently linked with elevated risk.
A separate analysis examined metabolic health and found that consumption of some food additives was associated with a higher likelihood of developing type 2 diabetes. Potassium sorbate, a preservative used to prevent mould and bacterial growth in food and drinks, was linked to roughly double the risk of diabetes in the study population.
Mathilde Touvier, a French epidemiologist who supervised both studies, emphasised that the results should not be interpreted as an immediate health warning for individuals. “Consuming products with preservatives does not mean you will automatically develop cancer,” she said, adding that the findings instead highlight the importance of reducing overall exposure where possible. She advised consumers to favour minimally processed foods when shopping.
The increased risks observed were generally modest. The strongest association in the cancer study was between sodium nitrite and prostate cancer, where risk was estimated to be about one-third higher. By contrast, established risk factors such as heavy smoking can increase lung cancer risk more than fifteenfold.
Independent experts welcomed the scale and methodological rigour of the research but urged caution. Because the studies are observational, they cannot rule out the influence of other lifestyle factors that tend to accompany higher consumption of processed foods.
Tom Sanders, a nutrition expert at King’s College London, noted that contributors such as alcohol intake or overall dietary patterns may not be fully accounted for. For example, he said, an apparent link between certain preservatives used in winemaking and cancer risk could reflect alcohol consumption itself rather than the additive. Still, Sanders suggested that clearer labelling—particularly for foods containing nitrites and nitrates—could help consumers make more informed choices.
The findings arrive amid broader policy efforts to address diet-related health risks. In the UK, they were published just days after new restrictions came into force banning daytime television, radio and online advertising of foods and drinks high in fat, salt and sugar.
Researchers involved in the French studies and outside commentators alike agree that further investigation is needed before firm dietary recommendations can be made, but say the evidence adds to growing concerns about the health effects of heavily processed foods.