This study is a pilot open label crossover trial to assess the feasibility and acceptability of reducing ultra- processed foods (UPF) in a personalized manner from the diets of patients with major depressive disorder who eat a large percentage of UPF.

There is a need for additional treatment or augmentation strategies for people who have depression. Epidemiological and observational studies show that an increased consumption of ultra-processed food (UPF) is associated with an increased risk of developing depression. This study will test the hypothesis that that reducing UPF intake from the diets of patients with major depressive disorder who eat a large percentage of UPF is a feasible and acceptable intervention.

Inclusion Criteria:

• 18-80 year olds (inclusive), all race/ethnic groups
• Willing to not change psychotropic medication or psychotherapy regimen during the study
• Willing and able to come to UCSF for in person visits two times
• Ability to speak and read English and answer participant surveys

Exclusion Criteria:

• Psychiatric hospitalization in past 3 months
• Active suicidal ideation with intent and plan or scoring a 3 or higher on the Columbia suicide severity rating scale (C-SSRS)
• In a current severe mood state when entering the study that would prohibit compliance with study visits or dietary program
• Known GI abnormalities or known GI medical problems (diarrhea, chronic intestinal disease, toxic megacolon, ileum) or known swallowing or chewing disorders or issues
• Anticipating or planning any major changes in physical activity or sleep during the study
• Pregnant or planning to be pregnant during the study
• Breastfeeding or planning to breastfeed during the study