A French study of over 100,000 people asked them to record 24 hour food questionnaires at regular intervals. Foods were analysed for preservatives and the results over time compared. People were followed up for over 7 years and the incidence of cancer was compared.
4,226 people developed cancer, mainly breast, prostate, colorectal and other cancers. Higher preservative ingestion was related to increased cancer incidence. The results tend to suggest that people would be likely better off avoiding processed food and make their own minimally processed food.
Food preservatives are extensively used in the modern food industry to inhibit microbial growth and slowing the chemical changes that lead to spoilage. Nitrates and nitrites that are added to processed meats have long been a concern as they are proven to cause cancer in animals. The NutriNet-Sante study showed a modest raise in cancer incidence (1.16) comparing the lowest intakes of various preservatives and the highest intakes.
There has been a recent move towards more natural preservatives eg rosemary extract, and this indeed gave a lower risk of colorectal cancer in the study. Researchers think that higher intake of fruit and vegetables can mitigate the risk of cancer from eating such products as processed meats.
Preservatives offer clear benefits by extending shelf life, lowering food costs, and may be more affordable to many people. The harms could be offset to some extent by setting stricter limits on the use of preservatives, clearer labelling, and listing all additives on these labels. Public health messages already advise limiting alcohol and processed meat, but could go further to include highly processed foods.
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