Study suggests cutting ultra-processed foods could alleviate depression and anxiety

A small UC San Francisco study indicates that reducing ultra-processed foods may improve depression and anxiety symptoms, highlighting a potential dietary approach to mental health treatment.

Reducing ultra-processed foods in the diet may do more than improve physical health: a small preliminary study from the University of California, San Francisco suggests it could also ease depression and, to a lesser degree, anxiety. The findings, published in JAMA Psychiatry, add to a growing body of evidence linking heavily processed foods to mental health problems, although the researchers stressed that much larger trials are still needed before firm conclusions can be drawn.

The pilot trial followed 20 adults with depression, an elevated body mass index and at least one metabolic condition such as high blood pressure, diabetes or raised LDL cholesterol. Fourteen of the participants also had anxiety. The group had an average age of 44, and most were women. In a crossover design, one group kept to its usual eating pattern for four weeks while the other followed a diet low in ultra-processed foods under guidance from the researchers, before the groups switched.

According to the university, those who cut ultra-processed food intake by more than 85% recorded moderate to large improvements on three separate measures of depression. Anxiety scores improved as well, though the change was smaller. Andrew Krystal, the study’s lead author, said the work had shown that the approach was practical and that a larger trial could now be tested. The report also pointed to a possible biological explanation: ultra-processed foods may disrupt the gut lining and contribute to low-grade inflammation, which could affect brain function.

Nyasha Chagwedera, the corresponding author, said such foods are difficult to avoid because they are cheap, convenient and engineered to be highly appealing. She argued that manufacturers work out combinations of sugar, salt and fat that encourage people to keep eating, while the products themselves may drive cravings by activating reward pathways in the brain. The researchers said they hoped to begin enrolling participants for a phase two study in 2028.

The results fit with earlier population research suggesting a broader association between ultra-processed foods and depression risk. A Harvard analysis published in JAMA Network Open found that women who ate the most ultra-processed food were more likely to develop depression than those who ate the least. Still, the new UC San Francisco trial was small, short and designed mainly to test feasibility, so it cannot show that removing ultra-processed foods directly caused the improvements. Even so, it offers a promising clue that dietary change may have a role alongside standard treatment for depression.