Can Cutting Ultra-Processed Foods Help With Depression? What the Latest Research Says
Can what we eat affect how we feel?
Diet has long been recognized as an important part of physical health, but researchers are increasingly studying the connection between diet and mental health, particularly depression. One question receiving growing attention is whether reducing ultra-processed foods (UPFs) could help improve depressive symptoms.
A new pilot study from the University of California, San Francisco (UCSF), published in JAMA Psychiatry in September 2026, offers an interesting clue. Researchers found that people with depression who dramatically reduced their intake of ultra-processed foods experienced a significant reduction in depressive symptoms.
However, there is an important distinction: the study does not prove that ultra-processed foods cause depression, nor does it show that eliminating them can cure depression. The study was very small, and larger, longer-term research is needed to understand how strong and lasting this potential effect may be.
What Are Ultra-Processed Foods?
Not every processed food is an ultra-processed food.
Freezing, chopping, pasteurizing, drying, cooking, and canning are all forms of food processing. Processing alone does not automatically make a food unhealthy.
The term ultra-processed foods generally refers to industrially formulated products that contain multiple ingredients and often include additives, flavorings, sweeteners, emulsifiers, or other substances designed to improve taste, texture, appearance, or shelf life.
Common examples include:
- Sugary drinks and soft drinks
- Candy, cookies, and packaged sweets
- Potato chips and other packaged snacks
- Some highly sweetened breakfast cereals
- Some ready-to-eat and frozen meals
- Some processed meat products
- Many packaged cakes and pastries
However, it is important not to treat every ultra-processed food as nutritionally identical. Products can differ considerably in their amounts of fiber, added sugar, sodium, saturated fat, protein, and other nutrients.
In other words, the degree of processing does not tell us everything about a food's nutritional value.
What Did the New UCSF Study Find?
The new study published in JAMA Psychiatry was a small pilot trial designed primarily to investigate whether people with depression could successfully reduce their intake of ultra-processed foods and whether this dietary change was associated with changes in depressive symptoms.
The study included 20 participants, 19 of whom completed the trial. Their average age was about 44 years, and 70% were women.
All participants had depression. Most also had anxiety, and all had overweight or obesity along with at least one metabolic condition, such as high blood pressure, abnormal blood lipids, diabetes, or insulin resistance.
Participants went through two dietary periods: one in which they followed their usual diet and another in which they followed a diet that was very low in ultra-processed foods.
They were able to reduce their consumption of ultra-processed foods by more than 85%.
Interestingly, depressive symptoms were lower during the period when participants consumed fewer ultra-processed foods. The study also found a modest improvement in anxiety symptoms.
No adverse events related to the dietary intervention were reported. Does This Mean Ultra-Processed Foods Cause Depression?
No.
This is one of the most important points to understand when interpreting the study.
The trial was very small, and the participants represented a specific group of people with depression who also had metabolic health problems and relatively high consumption of ultra-processed foods.
The researchers described the work as a pilot study, meaning it provides preliminary evidence and helps determine whether a larger study is worthwhile.
Therefore, the results cannot establish that eating ultra-processed foods directly causes depression, nor can they establish that eliminating these foods is an independent treatment for depression.
What Does Previous Research Say About Ultra-Processed Foods and Depression?
The UCSF study did not appear in isolation.
Previous observational studies have also reported an association between higher consumption of ultra-processed foods and a greater risk of depressive symptoms.
A 2025 systematic review analyzed 13 studies involving 264,519 participants. The studies included in the review consistently reported a positive association between higher ultra-processed food consumption and greater depression severity.
However, most of this evidence came from observational studies. Such studies can identify associations but cannot prove that ultra-processed foods are the direct cause of depression.
A large umbrella review published in the BMJ also found associations between higher ultra-processed food consumption and several adverse health outcomes, including some mental health outcomes.
However, the researchers noted that the certainty of evidence varied across outcomes, with some associations supported by low- or very-low-quality evidence. This means more high-quality research is still needed.
Why Might Diet Affect Depression?
Scientists are still investigating the exact mechanisms, but several possibilities are being studied.
1. The Gut-Brain Connection
The digestive system and the brain communicate through a complex network often referred to as the gut-brain axis.
Gut microorganisms participate in numerous metabolic and immune processes and may interact indirectly with the nervous system.
Researchers are therefore investigating whether diets high in ultra-processed foods can alter the gut microbiome and whether these changes could affect mental health.
However, these mechanisms are still being studied. We do not yet have a complete explanation of how reducing ultra-processed foods might improve depressive symptoms in some people.
2. Inflammation and Oxidative Stress
Diet is also connected to biological processes such as inflammation and oxidative stress.
Some research suggests that dietary patterns rich in vegetables, fruits, whole grains, legumes, nuts, fish, and unsaturated fats may support overall health, while lower-quality dietary patterns may be associated with certain metabolic and inflammatory risk factors.
These pathways could potentially contribute to the relationship between diet and mental health, but the connection is complex and cannot be reduced to a single nutrient or food.
3. Overall Diet Quality
There is another, simpler possibility: when ultra-processed foods make up a large portion of the diet, they may replace more nutritious foods such as:
- Vegetables and fruits
- Whole grains
- Beans and other legumes
- Nuts and seeds
- Fish
- Yogurt and other nutrient-rich protein sources
- Foods containing healthy unsaturated fats
So, what is missing from the diet may be just as important as what is being eaten.
What Do We Know About Healthy Dietary Patterns and Depression?
Research has not focused only on ultra-processed foods.
Many studies have examined the relationship between overall diet quality and depression, particularly dietary patterns rich in vegetables, fruits, whole grains, legumes, nuts, fish, and healthy fats.
A 2025 systematic review and meta-analysis combined evidence from 21 randomized trials and 92 prospective studies involving more than 700,000 people.
The researchers found some evidence that dietary interventions may help improve depressive symptoms. However, they also highlighted limitations in the quality of some of the available trials, meaning stronger research is still needed.
Research has also examined the Mediterranean diet. Some randomized trials and systematic reviews suggest that Mediterranean-style dietary interventions may help reduce depressive symptoms in some adults with depression, although results have varied between studies and further research is needed.
This raises an important question: instead of focusing only on "What should I eliminate?", perhaps we should also ask "What healthy foods can I add?"
Do You Need to Completely Avoid Ultra-Processed Foods?
Not necessarily.
Even researchers studying ultra-processed foods do not necessarily recommend viewing food through an "all-or-nothing" lens.
Some foods classified as ultra-processed may provide useful nutrients, and the NOVA classification system does not always capture the full nutritional quality of an individual product.
That is why it can be more helpful to look at the overall dietary pattern rather than judging one food in isolation.
Instead of trying to eliminate every ultra-processed food overnight, consider making small, sustainable changes.
Simple Changes You Can Try
Instead of sugary drinks:
Choose water, unsweetened sparkling water, or unsweetened tea.
Instead of a packaged snack:
Try fruit with a handful of nuts.
Instead of highly sweetened breakfast cereal:
Choose oatmeal topped with fruit, nuts, or seeds.
Instead of relying frequently on ready-made meals:
Try preparing simple meals at home using vegetables, legumes, whole grains, and a source of protein.
And remember: having a dessert or ice cream occasionally does not automatically make your overall diet unhealthy.
What Can We Take Away From the Latest Research?
Current research suggests there is a potential link between high consumption of ultra-processed foods and depression, while the new UCSF study provides preliminary experimental evidence that substantially reducing these foods may be associated with improvements in depressive symptoms.
However, it is too early to consider this a proven treatment for depression.
The scientific picture is more complicated than saying "ultra-processed foods cause depression."
Many factors may contribute to the relationship, including overall diet quality, physical activity, sleep, metabolic health, social and economic factors, and a person's mental health.
The relationship may also work in both directions. Diet can influence how we feel, while depression can affect appetite, energy levels, motivation, and the ability or desire to prepare healthy meals.
The Bottom Line
Reducing ultra-processed foods may be a useful part of a healthy eating pattern, and emerging research suggests that it could also have benefits for mental health.
However, changing your diet should not be considered a replacement for professional treatment for depression.
If you are experiencing symptoms of depression, talk with a qualified healthcare or mental health professional. Improving your diet can be part of a broader healthy lifestyle alongside appropriate treatment, adequate sleep, physical activity, and social support.
Ultimately, the goal may not be to avoid every processed food. Instead, focus on building a dietary pattern that relies more heavily on whole or minimally processed foods while still allowing room for foods you enjoy.
After all, mental health is not determined by a single meal—and neither is overall health.
Medical disclaimer: This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment for depression.
Scientific Sources
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Chagwedera DN, et al. Reducing Ultraprocessed Foods From the Diets of Patients With Depression: A Pilot Crossover Trial. JAMA Psychiatry, 2026. Read the original study
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Odum U, Schure M. Understanding the Variability of Associations Between Higher Ultra-Processed Food Consumption and Self-Reported Depression Severity. Healthcare, 2025. Read on PubMed
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Lane MM, et al. Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses. BMJ, 2024. Read on PubMed