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"Ultra-transformed" foods, hazardous to health? Scientists struggle to prove it

FOOD – French researchers published an extensive study on prepared foods and other foods "ultra-transforms" and health on Monday 11 February. They warn from the outset: it is not a cause and effect relationship.

Foods are considered ultra-processed according to the "Nova" classification when they have undergone industrial transformation processes and contain many ingredients, including additives. A dish prepared without additives, frozen or not, is not part of it … But ready-to-eat dishes, soft drinks and snacks are generally part of it. They are rich in salt or sugar and contain few vitamins and fibers.

The new study with tens of thousands of French 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 alarming

"We should not alert to the public and say that eating a prepared dish has an extra risk of 15% dying," says AFP Mathilde Touvier, director of the research team in nutritional epidemiology at Paris 13 University, which is the major NutriNet -Santé research leads with researchers from three other institutions (Inserm, Inra and CNAM).

"This is new ground in research into the links between ultra-reformed foods and health," she says. Studying the effects of nutrition is extremely complex and controversial, and the results are often misinterpreted.

The same French team published a study last year about organic food and the risk of cancer. More cancers were observed in people who ate less bio, but again, the method did not allow a causal link to be made … Which had not prevented many media from titling without precaution on the benefits of bio-cancer.

15% more deaths

45,000 French people older than 45, mostly women, took part in the new study. Every six months they had to record on an online questionnaire what they drank and drank drunk during three periods of 24 hours.

About 600 people died after seven years. The researchers then tore up the data and found that an increase of 10% of the ultra processed food in the diet corresponded to a 15% higher mortality.

But Mathilde Touvier warns that we should not focus on the figure, it is about the existence of a link that is statistically significant. And the study must be interpreted in a series of works.

Assumptions and defects

Last year, French researchers published results, still derived from the study by NutriNet-Santé, and observed more cancers among heavy consumers of these foods. Since for ethical reasons it is not possible to have an experiment where these foods are fed to part of the population but not to another, observational studies are the only solution.

There are inevitable defects: people are more or less precise in the self-managed questionnaire; and many other "invisible" factors may not be taken into account, even if the results are adjusted by different socio-demographic criteria and the overall quality of the diet.

It remains to answer the fundamental question: why? Among the hypotheses mentioned by the researchers: additives. Their effect is studied in the laboratory, on cells and on rats, especially in a laboratory of the National Institute of Agronomic Research.

An inaccurate term

The study on Monday, February 11 is "an important contribution to literature," says AFP Casey Rebholz, professor of epidemiology at the American University Johns Hopkins, who notes that the methodology is of good quality despite the inherent limitations of such studies.

Other experts, on the contrary, emphasized these limits. Professor Julian Cooper of the Institute of Food Science and Technology criticizes the grouping of many foods as "very inaccurate and confusing".

He also emphasizes the importance of additives such as preservatives, which "help to keep food in good condition, reduce waste and maintain food quality".

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