A Brazilian study published in the journal Clinical Nutrition has revealed that an increased intake of ultra-processed foods can result in depression. The findings highlight the potential impact of high-processed foods on mental health.
Major depressive disorder, or depression, is a prevalent and severe mental illness that causes individuals to feel sad, hopeless, and lack interest in activities that they once enjoyed. It can also cause physical symptoms like sleep disturbances, appetite, energy levels, and concentration.
Across the globe, depression is a prevalent ailment causing disability for millions of individuals. It can also impact individuals and their families. However, depression is a multifaceted condition that can be influenced by a range of genetic, biological, environmental, and psychological factors.
Among ultra-processed foods are sugary snacks, ready-to-eat meals, instant noodles, and sodas. These foods are typically made by preservatives, sweeteners, artificial flavors, and colorants that are not typically found in commercial kitchens.
Designed to be practical, affordable, and incredibly tasty, these products are often a hit with busy consumers who are eager to save money while still enjoying their high nutritional value.
Previous studies have found diets rich in nutrients that visiteurs feel have reduced occurrence of depression, but there were no larger prospective studies with similar findings in which ultra-processed food played a role in depression, including in low- and middle-income countries such as Brazil. By this study, the researchers investigated whether dietary patterns were connected to mental health and wanted to use this data to inform public health policy and dietary guidance.
The study's author, André de Oliveira Werneck, is a PhD candidate at the University of Sao Paulo and has been intrigued by the connection between health-related behaviors, particularly movement behaviors such as physical activity and sedentary behavior, and their impact on mental health since they were undergraduates.
Consequently, I have also been curious about how diet can contribute to one's health and behaviors. While some studies have linked specific aspects of diet like higher sugar intake or more healthy food intake, others have explored different diet patterns such as the Mediterranean diet or inflammatory potential. However, the shift to classifying foods according to their processing level and function (Nova classification) has grilling solved this problem.
I know many attributes of ultra-processed foods are linked to depression, so I thought it would be interesting to see how this could relate the intake of these ultra-processed foods to depression?
The NutriNet Brasil cohort, a massive research project investigating dietary habits and chronic illnesses in Brazil, was the foundation for this study. Adults aged 18 and over from all over the country were enrolled in periodic online surveys to assess their diet and health. Recruitment began in January 2020, with recruitment efforts taking place through legata de temporios and in public spaces.
Participants completed a set of questionnaires that gathered information about their sociodemographic traits, lifestyle factors, dietary habits, and health status. The Nova24h tool was utilized to evaluate their dietary intake, which is standardized according to the Nova food classification system and based on the data collected collected over multiple years.
This classification splits into "unprocessed or minimally processed foods", "processed" (medium and quick cooked foods), "processed" (medium and high-intensity cooking) and "ultra-processed" foods. Dietary intake was measured twice, at the 6th and 12th month follow-ups, to establish a baseline for their consumption of ultra-processed foods.
Participants who scored below three points on the preliminary PHQ-2 score less than three points were assessed every six months using the more comprehensive nine-item PHQ-9. This allowed the researchers to track the gradual onset of depressive symptoms through this process.
The researchers looked at participants whose at baseline no depression was present, followed the dietary recalls, and followed a further one with the PHQ-9 (at least one follow-up assessment), to which the data was applied in order to investigate the relationship between the relative proportion of the ultra-processed foods in the diet and the development of depression. The overall study revealed that 15,960 participants participated in the study and that the proportion of these foods did not (any higher) exhibit any depression at all, according to the researchers.
After taking into account various possible confounders, such as sociodemographic and diet-related factors, the researchers concluded that high intake of ultra-processed foods was significantly linked to early symptoms of depression. Participants who consumed the most processed foods were twice as likely to develop depression as those who consumed the least, but those who did not consume processed foods had a higher likelihood of experiencing it.
Werneck reported that the risk of experiencing depressive symptoms increased by 42% during the time between consuming and consuming the most processed foods, while those who ate the most had a lower risk.
The researchers carried out a systematic review and meta-analysis of data from the NutriNet Brasil cohort, as well as a systematic search through seven scientific databases to provide a broader context for their findings.
Six studies (including their own) were added to the list of criteria after analyzing the literature. While these studies differed in their use of follow-up time and diet assessment techniques, they always concluded that people who ate highly processed foods had a higher likelihood of developing depression.
By pooling the data from these studies into a random-effects meta-analysis, the researchers determined that the likelihood of developing depressive symptoms was three times higher with the consumption of ultra-processed foods, both positively and negatively, than with those with the lowest and highest intakes, and found that the associations between different populations and study designs were consistent across different studies and populations.
According to Werneck, the relationship between processed foods and reduced risk was still evident in other studies.
The new longitudinal studies suggested already long term association with ultra-processed food consumption could be ‘linking' to depression although consumption is ‘lower on average' compared to the other nations such as United States and United Kingdoms.
Despite adjustments made to their nutritional composition, the correlation between ultra-processed foods and depressive outcomes demonstrates western European and Mediterranean Mediterranean diets.
The sample size was non-probabilistic and mainly consisted of participants with greater socioeconomic status and internet accessibility, which could impact overall significance. Furthermore, the study only collected dietary information through self-reported recalls, potentially increasing the risk of recall bias and social desirability bias. Furthermore, participants who underreported unhealthy food consumption may not be as informed as others who did, which could lead to bias in their conclusions.
Werneck pointed out that studies based on this population are constrained by certain limitations, such as the use of two 24-hour dietary recalls to estimate highly processed food consumption and the presence of differences in actual consumption and biases in memory and social desirability biases.
In addition to being observational, the current study and subsequent studies in the systematic review may exhibit residual confounding, necessitating cautious cautiousness of causal inference. However, several factors, such as consistency and plausibility, imply that the association may be causal.
The next step is to explore how movement behaviors may be linked to the consumption of ultra-processed foods and how these interactions can lead to improved physical health and physical activity among individuals with depression.
For his part, Werneck added: "Just wanted to emphasize here how important it has been for me to have a PhD scholarship from the So Paulo Research Foundation to develop this work. I also know that the NutriNet Brazil cohort has access to funding from the Brazilian National Council for Scientific and Technological Development, the small So Paulo Research Foundation and the Argentine research institution UMANE."
The study, based on a NutriNet cohort study conducted by André O. Werneck, Euridice M. Steele, Felipe M. Delpino, Melissa M. Lane, Wolfgang Marx, Felice N. Jacka, Brendon Stubbs, Mathilde Touvier, Bernard Srour, Maria LC. Louzada, Renata B. Levy, and Carlos A. Monteiro, underwent an updated systematic review and meta-analysis.