French researchers published Monday a large study on prepared foods and other ultra-processed foods and health, and review their harmful effects on health. But, according to the researchers, it "should not be alarmist".
Foods are considered ultra-processed, according to the "Nova" classification, when they have undergone industrial processes of transformation and contain many ingredients, including additives. A prepared dish, without additives, frozen or not, is not part of it. But ready-to-warm dishes, sodas and snacks in general are part of it. They are richer in salt or sugar and low in vitamins and fiber.
"A new stone in the building in research". The new study, involving tens of thousands of French people followed from 2009 to 2017, found a modest relationship between ultra-processed food consumption and the risk of death during the period. The results were published in the journal of the American Medical Association (Jama Internal Medicine).
"Do not be alarmist to the public and say that eating a prepared meal has an additional 15% risk of dying," explains Mathilde Touvier, director of the nutritional epidemiology research team at Paris University. 13, who manages the large NutriNet-Santé study with researchers from three other institutions (Inserm, Inra and CNAM). "This is new ground in research on the links between ultra-reformed foods and health," she says.
600 deaths after seven years. 45,000 French people over 45, mostly women, participated in the new study. Every six months, they had to record on an online questionnaire all they had eaten and drunk for three 24-hour periods. After seven years, about 600 people died. The researchers then shredded the data and found that a 10% increase in the proportion of ultra-processed foods in the diet corresponded to a 15% increase in mortality.
But Mathilde Touvier warns that we should not focus on the figure, what matters is the existence of a link statistically significant. And the study must be interpreted in a set of works. Last year, French researchers published results, still drawn from the NutriNet-Santé study, observing more cancers among heavy consumers of these foods.
Studying the effects of diet is extremely complex and controversial, and results are often misinterpreted. Since it is not possible, for ethical reasons, to have an experiment where these foods are fed to one part of the population but not to another, "observational" studies are the only solution. There are inevitably flaws: people are more or less precise in the self-administered questionnaire, and many other "invisible" factors may not be taken into account, even if the results are adjusted by several socio-demographic criteria. the general quality of the diet.
What impact for additives? Among the hypotheses listed by researchers to explain this increase in deaths: additives. Their effect is studied in the laboratory, on cells and on rats, in particular in a laboratory of the National Institute of Agronomic Research. But some researchers insist on the limitations inherent in this type of research. Professor Julian Cooper of the Institute of Food Science and Technology, for example, criticizes the grouping of many foods as "very imprecise and confusing". And also emphasizes the importance of additives such as preservatives, which "allow to keep food in good conditions, reducing waste while maintaining nutritional quality".