Study finds link between ultra-processed foods and mental health

Nearly one in five adults live with a mental illness such as depression or anxiety, which are among the leading causes of morbidity, disability, and mortality, according to the National Institute of Mental Health. At the same time, consumption of ultra-processed foods has reached record levels in the US.

Researchers from Florida Atlantic University's Schmidt College of Medicine set out to determine if there is a direct connection between UPF consumption and adverse mental health symptoms. 

"Dietary patterns may influence mental health. For example, poor dietary patterns which lack essential nutrients, have a high glycemic index, and are high in added sugars may lead to adverse mental health symptoms,"​ researchers argued in the study, published in the journal ​​Public Health Nutrition​​.

"While there is some evidence regarding UPF consumption and depression​, data are sparse regarding other adverse mental health symptoms including anxiety and mentally unhealthy days.​​

"More than 70% of packaged foods in the US are classified as ultra-processed food and represent about 60% of all calories consumed by Americans. Given the magnitude of exposure to and effects of ultra-processed food consumption, our study has significant clinical and public health implications," ​said study author Eric Hecht, M.D., Ph.D., and an affiliate associate professor in FAU's Schmidt College of Medicine.

According to recent research​​, UPF accounted for over half (57%) of calories consumed by US adults in 2017-2018, up from 53.5% in the 2001-2002 period. In contrast, consumption of whole foods decreased from 32.7% (in 2001-2002) to 27.4% in 2017-2018.

What are ultra-processed foods?

Researchers defined ultra-processed foods as "industrial formulations of processed food substances (oils, fats, sugars, starch, protein isolates) that contain little or no whole food and typically include flavorings, colorings, emulsifiers, and other cosmetic additives."​

For the purpose of the study, Researchers used the NOVA food classification, a  system recently adopted by the Food and Agricultural Organization of the United Nations. NOVA considers the nature, extent, and purpose of food processing in order to categorize foods and beverages into four groups: unprocessed or minimally processed foods, processed culinary ingredients, processed foods, and ultra-processed foods.

"The ultra-processing of food depletes its nutritional value and also increases the number of calories, as ultra-processed foods tend to be high in added sugar, saturated fat, and salt, while low in protein, fiber, vitamins, minerals, and phytochemicals," ​added Hecht.

UPF consumption and self-reported 'mentally unhealthy' and 'anxious' days

Researchers studied a nationally representative sample of the US population (10,359 adults 18 and older from the US National Health and Nutrition Examination Survey) and measured three mental health symptoms: mild depression (determined by a 9-question personal health questionnaire), the number of mentally unhealthy days, and number of anxious days. 

The number of mentally unhealthy days was obtained from the response to the question: ‘During the past 30 days, how many days was your mental health not good?​’ The number of anxious days was obtained from the response to the question: ‘During the past 30 days, how many days did you feel worried, tense, or anxious?’.​

Results of the study ​showed that individuals who consumed the most ultra-processed foods as compared with those who consumed the least amount were more likely to report adverse mental health symptoms of mild depression, "mentally unhealthy days",​ and "anxious days."​ They also had significantly lower rates of reporting zero "mentally unhealthy days"​ and zero "anxious days."​

Growing body of research exploring diet and mental health connection

These results are in line with other research exploring the link between diet and mental health, noted researchers. For instance, in one 2014 meta-analysis​​ of twenty observational studies, individuals who consumed diets that included a higher intake of fruit, vegetables, fish, and whole grains had lower risks of depression.

In another randomized trial​​, which researchers said provides the most reliable evidence for small to moderate effects, those assigned to a three-month healthy dietary intervention (comprised of higher intakes of fruit and vegetables, fish, and whole grains) reported significant decreases in moderate-to-severe depression.

"Data from this study add important and relevant information to a growing body of evidence concerning the adverse effects of ultra-processed consumption on mental health symptoms,"​ said Charles H. Hennekens, M.D., Dr.PH, co-author, the first Sir Richard Doll Professor of Medicine, and senior academic advisor, FAU Schmidt College of Medicine.

Source: Public Health and Nutrition​​

DOI: ​10.1017/S1368980022001586​

A cross-sectional examination of ultra-processed food consumption and adverse mental health symptoms​

Authors: Eric M Hecht, et al.