Could heavy consumption of ultra-processed foods really lead to heightened risk of depression later in life?
A recent study based on data from the Melbourne Collaborative Cohort unveiled a compelling correlation between heavy consumption of ultra-processed foods and a heightened risk of experiencing psychological distress, an early sign of depression, over a decade later. This connection persisted even after accounting for various factors like lifestyle, demographics, and health behaviors. The findings, published in the Journal of Affective Disorders, shed light on the profound impact of diet on mental well-being.
Depression, a mood ailment marked by persistent feelings of sadness, hopelessness, and diminished interest in once-enjoyable activities, can bring about significant changes in appetite, sleep, energy levels, and focus. Those grappling with depression might battle physical symptoms such as fatigue alongside cognitive challenges like negative self-perception and decision-making difficulties. Globally, it stands as one of the most prevalent mental health conditions.
The severity of depressive symptoms is influenced by numerous factors, and lately, scientists have shown a keen interest in exploring a potential tie between low diet quality and depression. Confirming this connection could hold substantial importance as diet stands out as a more adaptable factor compared to many other predictors of depression.
Studies have frequently delved into the association between poor mental health and ultra-processed foods, revealing a two-way relationship. These foods, manufactured industrially and heavily processed, typically brim with additives, artificial flavors, excessive sugars, fats, and salt, while offering minimal nutritional benefits.
Melissa M. Lane, along with her colleagues, sought to explore whether consuming ultra-processed foods during adolescence, specifically between the ages of 13 and 17, could be associated with later-life depression. Their investigation drew upon data from the Melbourne Collaborative Cohort Study, an ongoing Australian research initiative examining connections between lifestyle choices and chronic non-communicable diseases.
The researchers highlight that past studies haven’t firmly established links between poor mental health and the consumption of ultra-processed foods, primarily due to significant variations in food consumption patterns across different countries. While Mediterranean countries typically derive less than 10% of their calories from such foods, the percentage surges to over 40% in places like Australia, the U.S., the U.K., and Canada.
In addressing this issue, the Melbourne study tackled it by encompassing a significant portion (30%) of immigrants originating from Southern Europe, particularly the Mediterranean region. These participants exhibit distinct dietary preferences compared to those born in Australia and New Zealand. Moreover, the study spans across time, offering researchers the opportunity to track the connections between various factors studied over an extended period.
Examining data from 23,299 individuals (including 13,876 women) aged between 27 and 76 years, the researchers excluded those unsuitable for analysis. Intentionally overrepresenting immigrants from Southern Europe enabled a more comprehensive comparison of dietary behaviors between these participants and Australians.
Researchers gathered information on participants’ eating habits using a specifically designed questionnaire, the 121-item Food Frequency Questionnaire, during the study’s commencement between 1990 and 1994. Additionally, they utilized data from the Kessler Psychological Distress Scale to gauge psychological distress, considering it as an indicator of depression. This assessment inquired about symptoms like fatigue, hopelessness, nervousness, sadness, and worthlessness. Participants completed this psychological distress evaluation between 2003 and 2007, a span of over a decade later.
Food items were categorized as ultra-processed and non-ultra-processed. Ultra-processed foods encompassed various items such as soft drinks, packaged snacks, confectionery, packaged breads, margarine, reconstituted meat products, and pre-prepared frozen or shelf-stable dishes. On the other hand, non-ultra-processed foods included rice, cereals, meat, fish, milk, eggs, fruits, roots and tubers, vegetables, nuts and seeds, along with culinary ingredients like sugar and plant oils, and processed foods such as breads, cheese, canned fruit and fish, and salted and smoked meats.
Results indicated that individuals more inclined toward consuming ultra-processed foods tended to be born in Australia and New Zealand and were more likely to live independently. They were less probable to have tertiary education, be married or in a relationship, and participate in high levels of physical activity. Moreover, these individuals exhibited lower intake of protein, fiber, saturated fats, and overall energy. They also consumed fruits and vegetables less frequently.
Those with the highest consumption of ultra-processed foods (the top 25%) showed a 14% higher likelihood of experiencing psychological distress compared to those in the lowest 25% of consumption. Further scrutiny revealed that only individuals in the highest consumption group displayed elevated levels of psychological distress compared to their counterparts.
The study, involving 23,299 participants in Melbourne, demonstrated that greater intake of ultra-processed foods during the study’s outset was linked to heightened psychological distress—a marker for depression—15 years later. Notably, this association was noticeable solely among participants with exceptionally high consumption of ultra-processed foods, specifically those in the highest quartile. The authors concluded that additional research—prospective, mechanistic, and intervention-based—is imperative to pinpoint the detrimental aspects of ultra-processed foods, aiding in the formulation of nutrition-based and public health strategies targeting mental well-being.
While the study sheds light on the connection between dietary habits and mental health, it’s important to note that the study design doesn’t allow for definitive cause-and-effect conclusions. Additionally, the assessment of psychological distress only addressed symptoms of depression and anxiety experienced in the 30 days before the survey, whereas the dietary intake assessment relied on participants recalling their typical eating habits over the preceding 12 months, leaving room for recall and self-report biases.
Few studies have tested longitudinal associations between ultra-processed food consumption and depressive outcomes. As such, further investigation and replication are necessary. The aim of this study is to examine associations of ultra-processed food intake with elevated psychological distress as an indicator of depression after 15 years.
Higher ultra-processed food intake at baseline was associated with subsequent elevated psychological distress as an indicator of depression at follow-up. Further prospective and intervention studies are necessary to identify possible underlying pathways, specify the precise attributes of ultra-processed food that confer harm, and optimise nutrition-related and public health strategies for common mental disorders.