A preliminary study conducted by researchers at the University of California, San Francisco, indicates that decreasing the intake of ultra-processed foods might alleviate symptoms of depression. Published on September 23 in JAMA Psychiatry and funded by the National Institutes of Health, this research appears to be the first to evaluate depression symptoms in the same group of participants before and after they transitioned to a healthier diet.
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The pilot study involved 20 participants. Senior author Andrew Krystal, MD, noted that the results suggest the feasibility of a larger investigation into the connection between diet and mental health.
Participants significantly reduced their consumption of ultra-processed foods by over 85%. Following this dietary change, they reported moderate to substantial improvements across three measures of depression, along with slight reductions in anxiety symptoms.
Ultra-processed foods encompass a range of items such as packaged snacks, fast food, sugary drinks, and other heavily manufactured products, often containing preservatives, artificial additives, and emulsifiers. Nyasha Chagwedera, MD, PhD, an assistant professor at UCSF's Department of Psychiatry and Behavioral Sciences, commented on the challenges of reducing such foods, which are generally appealing, inexpensive, and convenient. She noted that these foods can trigger the release of dopamine, a chemical associated with pleasure, which may influence eating behavior.
The study participants, averaging 44 years old, were primarily women (70%) and included 14 individuals with anxiety. All participants had a high body mass index and at least one metabolic condition, such as high blood pressure or diabetes.
Researchers separated the participants into two groups: one maintained their regular diet for four weeks, while the other adopted a diet low in ultra-processed foods, with guidance from the research team. After four weeks, they swapped diets.
Chagwedera, who founded UCSF's Metabolic and Mental Health Program, proposed a potential link between ultra-processed foods and depression possibly related to gut health. She hypothesized that these foods might damage the gut's protective lining, leading to chronic low-grade inflammation, which could either contribute to depression or increase susceptibility to it.
The authors emphasized that the findings are preliminary due to the small sample size and plan to conduct a larger study, with enrollment for the next phase expected to begin in 2028.