October 15, 2026, 11:48 am | Read time: 5 minutes
More and more people in Germany are suffering from depression. This makes researching effective treatment options all the more important. A study now suggests that diet could also help alleviate symptoms.
According to the Robert Koch Institute, around 17 percent of adults in outpatient care in Germany were diagnosed with depression in 2024.1 The condition can significantly impair quality of life and the ability to manage daily activities. Effective treatments are therefore crucial. These include psychotherapy and antidepressants. The appropriate treatment depends, among other things, on the severity of the depression and must be individually adjusted by a doctor. A U.S. study has now examined how feasible and practical a diet without highly processed foods is for depression–and whether it can alleviate symptoms.2 The focus is on highly processed foods such as fast food and ready-made meals.
What Did the Study Investigate?
As researchers from the University of California San Francisco explain in their current study, there is already evidence of links between the consumption of highly processed foods and major depression (serious depressive disorder). Diet influences processes in the body and central nervous system. However, clinical intervention studies have not yet examined whether avoiding these foods can causally improve the condition.
This relatively small pilot study with 20 participants aimed to clarify how feasible and practical avoiding highly processed foods is for patients with depression–and what impact this has on their mood. For this reason, the study selected people who largely consumed highly processed foods. Highly processed foods are industrially manufactured and contain preservatives, artificial colorings, flavor enhancers, and emulsifiers. These include ready-made meals, fast food, packaged snacks, sweets, and sugary drinks.
How Did the Researchers Proceed?
The study was conducted from June 2024 to June 2025. A total of 20 people participated, 19 of whom completed the study. They had to meet the following criteria:
- Age between 18 and 80 years
- Depression as the main diagnosis
- At least five points on the Patient Health Questionnaire-9 (a scientific questionnaire for diagnosing and determining the severity of depression)
- High consumption of highly processed foods (based on self-reported questionnaires)
- At least one metabolic disorder such as high body weight, a lipid metabolism disorder, reduced insulin sensitivity, or high blood pressure
It was also important that participants did not change their medication, therapy, exercise, or sleep habits during the study. The average age of participants was around 44 years, and 70 percent were female.
Participants were divided into two groups in a crossover design. One group continued their regular diet for four weeks, while the other switched to a low-processed diet. They purchased and prepared this diet with guidance from the researchers. After four weeks, the two groups swapped diets.
How the Dietary Change Affected Depression
Initially, participants reported finding the dietary change practical. They rated the benefits of the change as very high (an average of 8.4 out of ten points). However, they found the practical implementation noticeably more challenging, rating it as moderate with an average of 5.7 out of ten points.
On average, participants reduced their consumption of highly processed foods by about 86 percent. During this phase, their depression scores (measured with the PHQ-9 questionnaire) improved significantly from an average of 12.8 to 5.5 points, as did their anxiety scores, compared to the phase with their usual diet (where the PHQ-9 score was 8.7).
The researchers also provided a possible explanation for the link between diet and depression. Highly processed foods can damage both the gut flora and the protective mucous membrane of the gut. “These gut damages can cause chronic inflammation throughout the body, which either directly causes depression or makes people more susceptible to it,” explains study author Dr. Nyasha Chagwedera in a press release from the University of California San Francisco.3 In other words, junk food not only harms the stomach but also affects the brain, says the researcher. Which specific factors–such as high sugar and fat content, calorie count, or certain additives–are responsible for the effects must be investigated in future studies.
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Important Limitations of the Study
Despite the positive trends, the study authors emphasize important limitations:
- It was a small, unblinded pilot study with 19 people who completed the study. The alleviation of depression was an exploratory side effect and must be verified in larger, blinded studies.
- The exact biological mechanism behind the effect of highly processed foods is still unclear.
- The dietary assessment was based solely on participants’ self-reports via questionnaires, without objective biomarkers.
The researchers plan to begin Phase 2 of the study in 2028 to verify the results with more participants.
Dietary Changes Are Not Always Easy in Everyday Life
Although the pilot study results show that a healthier diet could alleviate depression symptoms, researchers know it is not easy to apply in everyday life. “Eating fewer highly processed foods can be challenging because they are particularly tasty, affordable, and convenient,” says Dr. Nyasha Chagwedera. Highly processed foods especially promote the release of dopamine, increasing the craving for these unhealthy foods.
According to Dr. Chagwedera, this is a deliberate effect of the food industry, created by a special mix of sugar, salt, and fat. This makes it difficult to give up fast food, sweet and salty snacks, and other highly processed foods. More research is needed on how to successfully break this vicious cycle and move toward a healthy diet.