Could quitting ultra-processed food boost mental health?

by University of California, San Francisco

edited by Sadie Harley, reviewed by Robert Egan

Sadie Harley

Scientific Editor

Meet our editorial team
Behind our editorial process

Robert Egan

Senior Editor

Meet our editorial team
Behind our editorial process Editors' notes

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

peer-reviewed publication

trusted source

proofread

The GIST Add as preferred source

A preliminary study led by UC San Francisco adds to growing evidence that reducing ultra-processed food may improve symptoms of depression. Published in JAMA Psychiatry, the study is believed to be the first to compare symptoms in people with depression before and after they switched from their regular ultra-processed diet to healthier food.

Although the pilot study comprised just 20 people, it "successfully established the viability of carrying out this research in a larger-scale trial," said senior author Andrew Krystal, MD, Ray and Dagmar Dolby Distinguished Professor in UCSF's departments of Psychiatry and Behavioral Sciences and Neurology.

Participants reduced ultra-processed food intake by more than 85% and experienced moderate to large improvements across three measures of depression. Anxiety scores also improved modestly.

Ultra-processed food includes packaged snacks, fast food, sugary beverages and other industrially manufactured items that may contain preservatives, artificial coloring, flavor enhancers and emulsifiers.

"Reducing the amount of ultra-processed food in our diet can be challenging, because it's highly palatable, cheap and convenient," said corresponding author Nyasha Chagwedera, MD, Ph.D., assistant professor in the UCSF Department of Psychiatry and Behavioral Sciences.

"Ultra-processed food triggers dopamine, the pleasure hormone, which promotes craving. Food companies work with scientists to find just the right amount of sugar, salt and fat that make you want to eat more and more."

The gut-brain connection

The average age of the study participants was 44, and 70% were female. In addition to depression, 14 participants had anxiety, and all had a high BMI and at least one metabolic disorder—such as hypertension, diabetes or elevated LDL cholesterol.

Participants were divided into two groups: One continued with their regular diet for four weeks, while the other shifted to a low ultra-processed diet, which they shopped for and purchased themselves with guidance from researchers. After four weeks, the two groups swapped diets.

The link between ultra-processed food and depression may be explained by a "leaky, out-of-balance gut," caused by damage from the food to the gut's protective lining, according to Chagwedera, who is the founder of the UCSF Metabolic and Mental Health Program.

"This gut damage can create low-grade, chronic inflammation throughout the body that either directly causes depression or makes people more vulnerable to it."

"In other words, junky processing may harm your gut in ways that ripple up to your brain."

The researchers expect to start enrollment in Phase II of the study in 2028.

Publication details

JAMA Psychiatry (2026).

Journal information: JAMA Psychiatry

Clinical categories

PsychiatryPsychology & Mental healthNutrition & Healthy eating Provided by University of California, San Francisco Who's behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

Citation: Could quitting ultra-processed food boost mental health? (2026, September 23) retrieved 28 September 2026 from https://medicalxpress.com/news/2026-09-ultra-food-boost-mental-health.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.