Adverse Mental Health Symptoms and Ultra-Processed Food: New Study Shows an Association

by | Jun 15, 2023 | Science

Medical Review by Chris Palmer, MD

A recent study published in Cambridge University’s Journal, Public Health Nutrition, links increased ultra-processed food consumption with adverse mental health symptoms. The study found that people who eat higher quantities of ultra-processed food were significantly more likely to report mild depression and/or an increase in mentally unhealthy days or anxious days per month. This is an important study as it provides a possible link between the modern, industrialized diet and the recent decline in mental health.

The purpose of this study was to determine whether there is a connection between increased consumption of ultra-processed food (UPF) and adverse mental health symptoms. Readers of Dr. Chris Palmer’s book, Brain Energy, will not be surprised by the results.

What exactly is an Ultra-Processed Food?

In this study, a UPF was defined as an industrial formulation of oils, fats, and sugars that contain little to no whole food. Examples of these include many items that are typically deemed as “junk” food, such as breakfast cereals, chips, sugar-sweetened drinks, cookies, cakes, and bread. The researchers used the standardized NOVA food classification system to decide which foods to define as UPFs. This allowed for standardization and more accuracy when comparing the results of similar studies.

The study looked at data reported by 10,359 US adults in the National Health and Nutrition Examination Survey. In this survey, participants answered questions related to demographics, health, and 24-hour dietary recall.  Researchers then sorted participants into five groups based on the percentage of calories consumed as UPFs, with group 1 consuming the least (0-19% UPF) and group 5 consuming the most (>80% UPF). 

To assess symptoms of depression, the study looked at participants’ answers to the PHQ-9, a standardized questionnaire used to screen for depression. Additionally, the researchers wanted to assess mental health more broadly. To do this, the study looked at participants’ answers to the following questions: “During the past 30 days, how many days was your mental health not good?” and “During the past 30 days, how many days did you feel worried, tense, or anxious?”

The researchers used the demographic information in the survey to adjust for age, gender, ethnicity, BMI, poverty level, smoking status, and physical activity. Ultimately, the study found that individuals with the highest consumption of UPFs, group 5, were significantly more likely to have mild depression than those in group 1. Individuals in groups 3-5 were also more likely to have more mentally unhealthy days and anxious days than those in group 1. In other words, this study shows that people who get 40% or more of their calories from UPFs are more likely to have adverse mental health symptoms.

This study does have some limitations. Notably, the reference group (group 1, 0-19% UPF) only contained 305 individuals. For comparison, group 5 had 885 individuals, and group 4 had 3,286 individuals. This by no means invalidates the study, but a larger reference group would improve the study’s generalizability to a larger population. 

That said, this study is another piece of evidence in a growing body of research linking UPFs to problems with mental health and cognition. A similar study showed a link between UPFs and cognitive decline. Importantly, these are some of the first studies to show clear associations between unhealthy diets and brain health. Among others, this data may implicate poor quality diets and disruption of metabolism in the declining mental health of the US population. 

The Brain Energy Connection

It is commonly believed that high consumption of unhealthy foods, such as UPFs discussed above, can lead to problems with the body’s metabolism and mitochondria. In Brain Energy, Dr. Palmer takes this one step further and suggests that those issues with metabolism and mitochondria can affect the brain as well. In short, Dr. Palmer’s theory suggests that mental disorders are metabolic disorders of the brain.


Hecht E, Rabil A, Martinez Steele E. et. al. “Cross-sectional examination of ultra-processed food consumption and adverse mental health symptoms.” Public Health Nutrition. July 2022.

Disclaimer: This article is for educational purposes only and is not medical advice. You should consult with your healthcare provider before starting any treatments for any medical conditions. 



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