In recent years, the visibility of mental disorders such as anxiety or depression in the media has increased. For example, a report published in 2023 revealed that 17% of young Spanish university students took medications to alleviate the anxiety or depressive symptoms they suffered.
It is clear that the fear, uncertainty and saturation caused in health centers and hospitals by the covid-19 pandemic caused havoc. In these cases, the cause that may trigger it is clearly identified. But what if I told you that diet can also be related to the increase in these pathologies?
Following the emergence of movements such as realfooding or plant-based diets (veganism, flexitarianism, etc.), the reputation of ultra-processed products has plummeted. And one of the latest arguments to reduce its consumption is the numerous evidence that suggests a connection between its excessive intake and the appearance of mental problems.
This is, for example, the conclusion of a recent review of research, which linked high consumption of these foods and the risk of suffering from symptoms related to depressive or anxiety disorders, although it is not yet clear why this occurs.
The evidence is overwhelming. If we examine the analyzes one by one, we will be struck by, for example, a study carried out in South Korea that revealed a 1.4 times greater probability of suffering from depression if a diet generous in ultra-processed foods was mediated, with greater effects among women. Another investigation carried out in the United States provided similar data: the population that exercised less and regularly ate these types of products was also more likely to develop this disorder.
The results of the SUN Project study, which examined the effects on university students in the Mediterranean area, were even more worrying, given the age of the participants. And finally, following people without previous depressive symptoms for more than five years in France linked an increase in their appearance to the consumption of drinks, sauces and products with added fats. In fact, drinks with artificial sweeteners seem to be related to a possible trigger of depression.
Diet, physical activity, age and gender are factors to take into account, but many studies have highlighted the leading role of the intestinal microbiota in this connection.
The microorganisms that inhabit our digestive system are distributed in phyla, which in turn are made up of various genera. The most abundant phyla are Firmicutes and Bacteroidetes, but there are other important ones such as Actinobacteria, Fusobacteria, Proteobacteria and Verrucomicrobia. Among the numerous genera, the best known is Bifidobacterium.
Well, it has been proven in both animal and human studies that the number of Firmicutes bacteria decreases in anxiety symptoms, while the population of Bacteridetes and Fusobacteria proliferates. In the context of depression, Prevotella, Klebsiella and Clostridium are the genera most associated with the gut microbiota.
Ideally, the microbiota should enjoy a balanced ratio of phyla and genera, known as eubiosis. When harmony is broken, the opposite effect appears: dysbiosis, related not only to depression or anxiety, but to a good number of chronic pathologies. For example, genres that can be considered pro-inflammatory are found to a greater extent in individuals with depressive or anxious states.
Furthermore, 90% of the body's serotonin is generated by the microbiota, a circumstance that plays an important role in the regulation of the so-called gut-brain axis.
If we want to reverse dysbiosis, one of the options is to resort to probiotics, although changing eating habits seems to yield better results. This is because the microbiota obtains much of its energy through diet, so a modification in intake has a direct effect on the proportion of phyla and genera.
In this sense, Westernized dietary patterns – characterized by the abundance of foods of animal origin, the abuse of ultra-processed foods and unhealthy cooking techniques – are associated with higher levels of anxiety and depression, in contrast to diets such as the Mediterranean, Nordic or the Japanese. A high intake of polyunsaturated fatty acids from fish, fruits, vegetables, whole grains and fermented foods could promote a state of eubiosis.
Although anxiety and depression have multiple causes, it is clear that frequent consumption of ultra-processed foods could increase the risk of suffering from them or worsen their symptoms.
Edwin Fernández Cruz is academic director of the Master in Precision Nutrition and Nutritional Epidemiology, UNIR - Universidad Internacional de La Rioja
