We have known for just over a decade that ultra-processed foods are linked to various diseases, the number of which is growing as scientific knowledge increases. However, there is very little information available that can establish cause-and-effect relationships between the consumption of these products and the development of diseases. Nor do we have enough information on the mechanisms involved.  

The NOVA classification is the most commonly used to define ultra-processed foods, specifically in the NOVA4 group. Among the characteristics of these products is the use of additives that promote their consumption, such as flavourings, colourings, flavour enhancers and emulsifiers, among others.  

In this study, researchers from IDIBAPS in Barcelona (Spain) found that mice whose mothers consumed emulsifiers showed an increased risk of metabolic, cognitive and psychological problems in their offspring, especially in males. The results indicate that maternal consumption of emulsifiers may disrupt the development of neural circuits in the offspring's hypothalamus, a region that regulates metabolism.  

The study is important because it contributes to our understanding of the components of ultra-processed foods that may contribute to their negative health effects. However, some caution should be exercised in interpreting it.  

Firstly, it is a study carried out in mice, so its conclusions cannot be extrapolated to humans. In other words, we cannot say that the consumption of emulsifiers by humans has the same consequences as shown in the study.  

Secondly, the emulsifiers were administered to the animals in drinking water, not in the form of ultra-processed feed.  

Thirdly, there are many types of emulsifiers, but the researchers only tested two of them: sodium carboxymethyl cellulose and polysorbate 80. It is possible that other 'more natural' emulsifiers, such as lecithin, guar gum or partial glycerides have different effects.  

Fourthly, the emulsifiers were added to the drinking water of the mice at 1 %, which is a rather high dose.  

As can be seen, this type of study has some limitations in terms of design. This is common in preclinical studies because the focus is on finding some observable effect to serve as a starting point for future research.  

On the other hand, it is necessary to underline that research on ultra-processed foods in humans is very complex for many reasons, one of which is ethical. Given that there is sufficient information linking the consumption of ultra-processed foods to human health, it may be considered unethical to administer a diet rich in ultra-processed foods to a group of people for a study. This is one of the reasons why there are so few clinical trials that have evaluated the effect of ultra-processed foods in humans.  

Therefore, although the link between ultra-processed foods and disease is known, science has not yet been able to demonstrate a clear cause-and-effect connection and detailed information on the mechanisms involved. This study in mice provides important information for understanding the specific components of these foods that may have adverse health effects. However, it should be viewed with caution due to methodological limitations.

The study is of good quality, in the field of basic laboratory research, to understand the effects of additives that are used by the food industry.  

This research shows how some of the components of ultra-processed products, in particular emulsifiers, have a detrimental effect on different physiological parameters in experimental animals. However, there is already evidence in the literature from epidemiological studies (which examine how regular consumption of ultra-processed products produces short, medium and long-term effects on health). These studies have shown that high consumption of ultra-processed products is associated with an increased risk of premature mortality, development of some cancers, obesity and a range of other health problems, making it inadvisable for ultra-processed foods to be part of our regular diets.  

We can never extrapolate these kinds of results [in animals] to people. However, when potential harmful effects of some substances are found, public agencies that watch over people's health (in Spain, the AESAN) have the obligation to examine scientific evidence  and decide whether the marketing authorisation of this substance has to be revoked.  

The evidence from epidemiological studies is sufficient to advise against the consumption of ultra-processed products. The dietary recommendations issued by AESAN for the general population, which emphasise the consumption of foods within traditional Spanish dietary patterns, and which recommend minimising the consumption of processed products, rich in salt, sugar, poor-quality fats and food additives, also apply to pregnant women. There are additional nutritional recommendations for this specific group, in addition to others that are proposed in obstetric consultations on a regular basis.

This study is important for providing evidence of potential harmful health effects of consuming food additives — in this case, emulsifiers. The findings add to other evidence that has been indicating how these substances, for example, alter the intestinal wall, leading to various health damages. It's noteworthy that the study examined the effect of the emulsifier in isolation, which makes the consumption of ultra-processed foods even more concerning: these foods combine additives of different natures, which could amplify the damages. 

Despite being approved for consumption by regulatory agencies responsible for food safety in each country, it is common that additives such as emulsifiers do not undergo long-term testing for their effects. Science indicates that, contrary to common belief, there's no way to ensure safety in the regular consumption of these substances. [Editors’ note: In the European Union, in 2021, the European Commissioner in charge of health and food safety, Stella Kyriakides, said: ‘Emulsifiers, as any other food additive, are subject to a premarket authorisation, which includes rigorous safety assessment. In addition, the legislation requires that food additives are kept under continuous observation. The Commission, together with the European Food Safety Authority, closely monitors new information on the authorised additives and may request that the safety of any food additive is re-evaluated at any time in the light of changing conditions of use or new scientific evidence available.’] 

The results underscore the need to maintain a diet based on fresh foods, not only during pregnancy but in all stages of life. This is crucial to avoid the consumption of food additives and, more importantly, to ensure a rich and balanced nutritional intake from real food.