A new study indicates that individuals frequently consuming fried food have 12% increased risk of anxiety and 7% increased risk of depression compared to individuals not eating fried food. This association was particularly notable for fried potato consumption. The study was published in the Proceedings of the National Academy of Sciences (PNAS).
Depression and anxiety are the two most frequent mental disorders. Individuals suffering from one of these disorders often also suffer from the other one. Estimates state that, after the COVID-19 pandemic of 2020, the share of world population suffering from anxiety and depression increased by around 27%.
The main symptoms of depression are persistent feelings of sadness, hopelessness, and a loss of interest in activities. They are often accompanied by other physical and emotional symptoms. Main symptoms of anxiety are excessive and often irrational worry, fear, or uneasiness, which can manifest in physical symptoms and interfere with daily functioning.
The precise causes of depression and anxiety remain unknown. However, a wide range of genetic, biological, environmental, and psychological factors have been demonstrated to play a role. Recent studies have linked diet with the risk of developing depression and anxiety. Specifically, the so-called Western diet, a diet based on fried or processed foods, refined grained, sugary products and beer was found to be associated with a higher risk of depression and anxiety.
Frying is a popular cooking method widely used both in restaurants and for preparing meals at home. However, studies have shown that the process of frying may change the nutrient composition of food and produce various hazardous chemicals. On such chemical is acrylamide. It is generated during the process of frying foods rich in carbohydrates, such as potatoes. Epidemiological studies have linked prolonged acrylamide intake to increased risks of neurological disorders, obesity, metabolic syndrome, cardiovascular disease, and depression. The substance is also neurotoxic in higher concentrations.
Study author Anli Wang and her colleagues wanted to examine the association between the intake of acrylamide and depression and anxiety on a large population sample. Given that acrylamide is present in fried food, they decided to examine the links between fried food consumption, depression and anxiety. Study authors hypothesized that high fried food consumption, and consequently high exposure to acrylamide, will increase symptoms of depression and anxiety by causing dyslipidemia i.e., abnormal levels of lipids (such as cholesterol and triglycerides) in the blood, and inflammation.
The team analyzed the data of 140,728 individuals from the UK Biobank, a comprehensive biomedical database and research initiative that amasses and stores detailed health and genetic data from half a million UK residents.
Additionally, the researchers conducted an experiment on zebrafish, exposing them to varying acrylamide concentrations for 180 days. They performed a range of tests to assess the signs of depression and anxiety in the fish. At the end of the experiment, the fish were euthanized, and their brain samples were collected for tissue analysis.
The findings revealed that those consuming at least one fried meal daily were typically younger, male, and smokers compared to those who didn’t consume fried foods. Of the study’s participants, 8,294 displayed symptoms of anxiety, while 12,735 exhibited signs of depression over the 11-year follow-up period in the database.
After accounting for the age and gender of participants, the analysis demonstrated that individuals consuming fried foods were slightly more prone to symptoms of anxiety and depression. Such individuals had a 12% higher likelihood of experiencing anxiety and a 7% increased chance of depression. Specifically, the consumption of fried potatoes was linked to a 4% greater risk of anxiety symptoms and a 2% heightened risk of depression.
The zebrafish experiment revealed that those exposed to acrylamide (0.5 mM) saw a reduction in body mass and length. These fish also exhibited a tendency for scototaxis—preferring areas of dim light or darkness, a behavior analogous to human anxiety. The researchers observed additional behaviors indicative of anxiety and depression in the fish. The tissue analysis of these specimens indicated that acrylamide exposure disrupted their lipid metabolism and triggered an inflammatory response.
“Consistently, long-term exposure to acrylamide, a representative food processing contaminant in fried products, exacerbates scototaxis [preference for staying or moving towards areas of reduced light or darkness] and thigmotaxis [preference for contact or close proximity to surfaces, often as a means of seeking shelter or security], and further impairs exploration ability and sociality of adult zebrafish, showing anxiety- and depressive-like behaviors,” the study authors wrote.
The study makes an important contribution to the scientific understanding of links between diet and mental health. However, it also has limitations that need to be taken into account. Notably, the observed effects were relatively small. Additionally, the design of the part of the study that was conducted on humans does not allow any cause-and-effect inferences to be drawn from the data.
The study, “High fried food consumption impacts anxiety and depression due to lipid metabolism disturbance and neuroinflammation”, was authored by Anli Wang, Xuzhi Wan, Pan Zhuang, Wei Jia, Yang Ao, Xiaohui Liu, Yimei Tian, Li Zhu, Yingyu Huang, Jianxin Yao, Binjie Wang, Yuanzhao Wu , Zhongshi Xu, Jiye Wang, Weixuan Yao, Jingjing Jiao, and Yu Zhang.