A recent study from the University of California San Francisco suggests that cutting back on ultra-processed foods can significantly improve mental health. Published on September 23 in JAMA Psychiatry, the study found notable improvements in depression and modest gains in anxiety when reducing intake of these foods.
Understanding Ultra-Processed Foods
Ultra-processed foods contain ingredients not typically found in home kitchens. These include chemical-based preservatives, hydrogenated oils, high fructose corn syrup, artificial colors, and flavors. Such foods encompass sodas, prepackaged snacks like chips, cookies, and frozen meals, among others.
Study Insights
The study, involving 20 participants, assessed changes in depression symptoms before and after participants reduced their consumption of ultra-processed foods. The lead researcher, Dr. Andrew Krystal, emphasized the study’s preliminary nature due to its small sample size. Despite this, the research team is eager to replicate these findings in larger groups.
Dr. Uma Naidoo from Massachusetts General Hospital noted the study’s potential, highlighting its implications for future research.
Improvements in Mental Health
Participants experienced significant mental health improvements after reducing their ultra-processed food consumption by 85%. Depression measures such as the Montgomery-Asberg Depression Rating Scale saw scores drop by 63%. Other measures—Patient Health Questionnaire-9 and Quick Inventory of Depressive Symptomatology—also showed around 60% reductions.
Nicole Avena, a neuroscience professor, pointed out the growing evidence linking ultra-processed food consumption with poorer mental health, including depression and anxiety. Although the correlation is strong, causation remains unproven.
Potential Effects on Mental Health
Krystal proposed several hypotheses, including the macronutrient content, calories, and additive contaminants potentially affecting mental health. Avena’s lab at Princeton found similarities between the effects of sugar in these foods and addictive substances, possibly influencing mood through cycles of overeating and brain reward system changes.
Avena also cited potential disruptions to the gut microbiome and nutrient displacement, which may affect mood and brain health. Naidoo added that while these hypotheses are plausible, direct causal links have not been established.
Recommendations for Change
According to Avena, perfection is not required when reducing ultra-processed food intake. Small, consistent dietary changes can be beneficial. Alyssa Moran from the University of Pennsylvania highlighted the challenges of preparing wholesome meals for those struggling with depression. She advocated for policy changes, such as limiting production and subsidizing fresh produce.
In light of the findings, integrating dietary considerations with therapy and medication for depression treatments was recommended. Naidoo emphasized that educational efforts should continue to guide dietary guidelines.
Reference: Chagwedera DN, Kim E, Chiu DT, et al. (2026) Reducing Ultraprocessed Foods From the Diets of Patients With Depression: A Pilot Crossover Trial. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2026.2320
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