For the past years, research has shown that foods incorporate several dimensions that are likely to have an impact on health: 1) their nutritional composition, including the presence of favourable nutrients (e.g., fibre, protein, minerals, vitamins, etc.) or nutrients that should be limited (e.g., sugar, saturated fats, salt, etc.), and their energy density, 2) their level of transformation and particularly in the case of ultra-processed foods (corresponding to foods that have undergone multiple industrial processes and/or generally containing cosmetic food additives or other industrial ingredients such as hydrogenated oils, inverted sugar, etc.) and (3) the possible presence of pesticide residues used in its production process.
Of course, a diet never consists of a single food; and no food can be considered harmful in itself, even if it is obvious that some foods present characteristics which are more unfavourable for health than others. It is the combination of several foods and the amounts consumed that allows to define a “healthy” or “unhealthy” diet. This explains that nutritional recommendations  do not refer to specific foods but to generic food groups (fruits and vegetables, dairy products, processed meats, etc.) and to the overall diet (« do not eat too fatty, sweet, salty foods ; limit ultra-processed foods ; favour organic foods for plant products,..) .
But within a generic food group (e.g., dairy products, meats, grain products, etc.), there is a wide variety of types and forms of foods, particularly when considering pre-packed foods of different brands that may have a high variability in their ingredients, nutritional composition, degree of processing, number and type of additives they contain, and whether or not they come from organic farming.
The links between each of the three food characteristics (nutrition, ultra-processing/additives, pesticides residues) and health have been illustrated by numerous epidemiological and experimental studies [3–14]. Although the level of evidence varies, the impact of each of the three dimensions in terms of risk of chronic disease justifies to inform consumers on how each specific food is characterized for each of these dimensions.
The importance of the nutritional dimension
Complementary to the dissemination of food-based dietary guidelines that aim to provide general recommendations in terms of food groups, numerous national and international experts committees (including WHO) recommend to display a nutrition labelling system on front-of-pack of foods aimed to help consumers to understand, at a glance, the nutritional quality of food at the time of purchase and to identify differences in nutritional quality of foods enabling consumers to compare foods.
Informing consumers on the nutritional composition of foods is justified by the numerous studies demonstrating the deleterious impact of a diet too rich in salt, sugar, saturated fatty acids and low in fiber, fruits and vegetables, pulses and high energy density on the risk of several cancers, cardiovascular diseases, obesity, hypertension, type 2 diabetes, as well as mortality . Based on the results of these studies, Nutri-Score was designed, incorporating into its algorithm, the nutrients and elements for which the consumption has been shown to have an impact on health . It is a gradual 5-colour logo (coupled with letters from A to E) which has been officially adopted in France, Belgium, Germany, Spain, the Netherlands, Luxembourg and Switzerland. Numerous studies have validated both the Nutri-Score computation and its graphic format  and demonstrated its effectiveness in accordance with the concepts and processes that were published by the World Health Organisation (WHO) Europe concerning the validation studies that are required to select and evaluate a front-of-pack nutrition label [17–19].
The algorithm underlying the Nutri-Score, reflecting the overall nutritional quality of foods, has been validated in several large prospective cohort studies performed in France, Spain and in the European EPIC cohort (carried out in 10 European countries). All these studies, published in prestigious scientific peer-reviewed journals, showed that the consumption of foods with a less favourable Nutri-Score classification was associated prospectively with an increased risk of chronic diseases (cancers, cardiovascular diseases, weight gain, metabolic syndrome, etc.) and mortality. These results also confirmed that the choice of nutritional elements taken into account in the calculation of the Nutri-Score algorithm, the aggregation of the selected components, the allocation of points for each of them and the thresholds chosen are perfectly relevant.
The importance of ultra-processing
In recent decades, dietary habits have changed with an increase in the consumption of “ultra-processed foods” which today contribute to more than half of the energy supplies in many Western countries. They are often (but not always) characterized by a lower nutritional quality in average, they generally contain food additives (some of which with potential adverse health effects as suggested by recent experimental studies), and may contain neoformed contaminants created during processes and contaminants from packaging and other contact materials.
To assess the level of food processing, the NOVA classification was proposed in 2009 and amended in 2016 . It categorized foods into 4 groups, according to their degree of industrial processing: minimally- or unprocessed foods (NOVA1), culinary ingredients (NOVA2), processed foods (NOVA3), ultra-processed foods (NOVA4). Numerous studies have shown links between the consumption of ultra-processed foods (NOVA4) according to the NOVA classification and increased risks of different chronic diseases [21–24].
France, as other countries, has included the concept of ultra-processed foods in its official nutritional recommendations for the population. However, information on ‘ultra-processed’ products has not yet been directly transposed at the level of food packaging.
Importance of environmental contaminants, particularly pesticide residues
In addition, an increasing number of studies (particularly in the French NutriNet-Santé cohort) observed a lower risk of chronic diseases among the highest consumers of organic foods or those less exposed to pesticide residues [12,25–28]. There is already in Europe an information label available on the packs of foods, the European Union organic label, corresponding to a quality label certifying that a product complies with the European Union Regulation on organic agriculture, based on the ban on synthetic fertilizers and pesticides.
Why it is important to consider any of the health dimensions of foods
Each of the three health dimensions of foods (nutritional composition, ultra-processing, and presence of pesticide residues) is important, but none is exclusive and able to summarize, on its own, the overall health value of food. Epidemiological studies confirm the importance of each of these dimensions in the development of chronic diseases and independently of each other.
In several studies, it has been shown that the harmful effect of ultra-processed foods remains significant, even after adjustment for the nutritional quality of the diet. But conversely, the effect of the nutritional component is also independent of the level of processing/ultra-processing: in the NutriNet-Santé cohort, the associations between the nutritional score underlying the Nutri-Score and cancer risk still remain significant after adjustment for the proportion of ultra-processed foods in the diet. Similarly, the associations between pesticides and cancer risk persist even after taking into account the nutritional quality of the diet.
Finally, it is clear that the nutritional composition and ultra-processing are likely to affect, each and independently, the risk of chronic diseases through different specific and complementary mechanisms.
The three health dimensions of food are not colinear but complementary.
Certainly the nutritional and ultra-processing dimensions, although different, are partially overlapping: there is a global association between the degree of transformation and the nutritional quality of foods. However, if there is a concordance between being an ultra-processed food and, on average, of lower nutritional quality, it is not surprising that some foods presenting a favourable nutritional quality can be ultra-processed: an analysis of 220,522 ultra-processed foods (NOVA 4) from the Open Food Facts (2020) database revealed that while 79% of ultra-processed foods were classified as Nutri-Score C, D and E, 13% were classified as B and 8% as A. For example, whole-grain breads or fruit purées without added sugars can be ultra-processed and classified A by Nutri-Score.
On the other hand, some of the foods considered “not ultra-processed” according to NOVA (NOVA 1, 2, and 3) can also present a low nutritional quality (high in saturated fat, sugar or salt, etc.). Even among foods that are not or minimally processed (NOVA1), 19.2% are classified as Nutri-Score C, 7.4% as D and 3.3% as E. For example, pure grape juices are NOVA1 and classified as E by Nutri-Score (because they contain more than 160g of sugar/litre). Similarly, among processed (but not ultra-processed) foods classified as NOVA3, 32.5% are D and 16.3% E.. This is the case, for example, with certain cheeses, cookies, chocolate…
Finally, some culinary ingredients (NOVA2), such as sugar, salt, oil or butter, are not classified as ultra-processed foods, but their nutritional composition justifies being identified as food items/ingredients that should be consumed in limited amount and/or not too frequently in line with public health recommendations.
In fact, the NOVA classification does not integrate the variability in the nutritional composition of products within each of its categories. For example, for the NOVA2 products (culinary ingredients) there is no differentiation between vegetable and animal fats ; and even, for vegetable oils, it does not allow to recognize those whose nutritional composition is the most favourable and has to be preferred in terms of public health, such as olive oil or rapeseed oil, compared to other vegetable oils (sunflower, corn, peanut, coconut, palm, etc.). In contrast, Nutri-Score discriminates between these different oils with rating from C to E, making it possible to recognize the most beneficial oils, in line with public health recommandations.
Moreover, even in foods are produced by organic farming, it does not necessarily imply that they have a favourable nutritional quality. In addition, a food containing organically produced ingredients can also be ultra-processed. This is the case, for example, for some organic forms of spreads, ready-to-eat salads, cakes, sausages or breakfast cereals… An organic biscuit contains in principle less pesticide residues than a conventional product but its nutritional quality will remain unfavourable and it is often ultra-processed.
The three health dimensions of food are not colinear but they are complementary. However, some statements, even coming from individuals in the scientific community, argue that one (or the other) of these dimensions is the most important or the only one that would be able to summarize the overall health value of food. For example, some argue that being “not ultra-processed” would be sufficient to ensure a favourable nutritional quality, which is not true, as illustrated by the examples cited above… Others boast only the importance of nutritional quality, refuting the risk linked to ultra-processing and the presence of additives. Similarly, the «halo» effect of organic is sometimes used by manufacturers to give an overall «health» image to a fatty, sweet or salty product (even organic the product remains fatty, sweet or salty.!)
It is necessary to inform consumers about the different health dimensions of food
From a public health perspective, it is therefore essential to inform consumers about each of the three health dimensions of food: overall nutritional quality, degree of transformation, and the presence of pesticides residues. Several initiatives have emerged recently, proposing to combine at least two of the dimensions, if not all three, into a single indicator. Nevertheless, the weights used for each of these dimensions are not based on sound science, and the trade-offs made when dimensions are not consistent are not based on a scientific consensus. So, it is impossible to combine all these dimensions into a single synthetic quantitative indicator able by itself to summarize the overall health value of food.
Graphic representations in the form of labels displayed on the front of food packaging are considered effective means for providing consumers useful information they can quickly assimilate. So, in the context of current knowledge, if it is not possible to combine all health dimensions of foods into the same algorithm to obtain a single synthetic label, at least they can be associated graphically. Even if practical points have to be resolved, it seems feasible to add to the Nutri-Score, a dark border for instance, permitting to characterize ultra-processed foods and displaying beside, for organic foods, the corresponding official label.
Finally, the communication that would be associated to the front-of-pack labels is simple for the general public:
1) favour the consumption of “non-ultra-processed” foods (without dark border), and select those with the best possible Nutri-Score ;
2) if you still wish to consume ultra-processed food (with dark border), choose those with the most favourable Nutri-Score;
3) favour whenever possible organic foods if this alternative exists (especially for plant foods).
While current scientific evidence does not always permit to rank the risks or benefits associated with each dimension, it is clear that they are all important to take into consideration. To sum up, it is essential to inform consumers on all these different dimensions at the level of food packaging and not to omit any of them.
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Serge Hercberg, Pilar Galan, Bernard Srour, Emmanuelle Kesse-Guyot, Mathilde Touvier
Université Sorbonne Paris Nord. Equipe de Recherche en Epidémiologie Nutritionnelle U1153 (Institut National de la Santé et de al la Recherche Médicale / Institut National de la Recherche Agronomique/CNAM/Université Sorbonne Paris Nord), Bobigny, France.
Dép. de Santé Publique, Hôpital Avicenne, Bobigny, France.
A summary of this paper was published (in french) in The Conversation : https://theconversation.com/nutri-score-nova-bio-comment-mieux-informer-sur-les-effets-sante-des-aliments-171980