Reducing ultra-processed foods such as snacks and sausages can help ease symptoms of depression, according to a study published in JAMA Psychiatry.
Researchers found that participants who lowered their intake of heavily processed products recorded lower levels of both depression and anxiety compared to when they followed their usual diet.
The study involved 20 adults aged between 18 and 80 who had been diagnosed with depression. All participants regularly consumed large quantities of ultra-processed foods and had at least one underlying metabolic disorder, such as obesity, high blood pressure, elevated cholesterol or triglycerides, or insulin resistance.
During the trial, participants completed two distinct phases in random order, alternating between their normal eating habits and a diet with reduced ultra-processed food intake. On the Patient Health Questionnaire-9, a standard depression assessment scale known as PHQ-9, average symptom scores fell from 8.68 during the participants' standard diet to 5.53 while on the low-processed food diet.
Trial Design and Participant Feedback
Researchers noted that a majority of the participants considered the diet with reduced ultra-processed foods to be acceptable and manageable to follow during the intervention phase.
The PHQ-9 scale is a self-reported diagnostic tool widely used by medical professionals to screen, diagnose, and monitor the severity of depression. Scores range from zero to 27, with higher numbers indicating more severe depressive symptoms. A drop from 8.68 to 5.53 represents a shift from mild-to-moderate symptom levels toward a milder classification.
Metabolic disorders, including insulin resistance, high blood pressure, and elevated lipids, frequently co-occur with mood disorders. Metabolic health plays a central role in systemic inflammation and biological pathways that can directly influence brain function and mood regulation.
Defining Ultra-Processed Foods
Ultra-processed foods are industrially manufactured products created largely from refined or synthesized substances, such as extracts, sugars, hydrogenated fats, and hydrolyzed proteins, alongside chemical additives. They contain minimal whole food ingredients and are designed to be cheap to manufacture, shelf-stable, and hyper-palatable to encourage overconsumption.
Common examples of ultra-processed foods include carbonated soft drinks, packaged snacks, candies, sausages, hot dogs, and mass-produced baked goods.
The concept of ultra-processed foods stems from the NOVA food classification system, developed by researchers at the University of Sao Paulo in Brazil. The system categorizes foods into four groups based on the extent and purpose of industrial processing, distinguishing minimally processed whole foods from formulations engineered with additives.
Broader Health Impacts and Risk Factors
The study's authors highlighted that overall dietary quality may hold greater significance for mental health than the mere level of processing alone. Among processed items, ultra-processed meats and sugary beverages were identified as posing the greatest harm to brain function.
Researchers previously established that consuming an additional daily serving of ultra-processed meat or sugary drinks increases the long-term risk of developing dementia and Alzheimer's disease.
Scientific evidence also indicates that parental consumption of ultra-processed foods can influence body fat distribution in future children, with biological effects forming prior to conception.
Nutritional psychiatry is an expanding field of medicine investigating how dietary patterns affect mental health, gut microbiomes, and neural pathways. While clinical trials remain small, growing evidence suggests that dietary interventions may serve as a valuable complementary approach alongside standard therapy and medication for mood disorders.
