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A study published in JAMA Network Open looks at ultra processed food and the risk of depression.
Priya Tew, Registered dietitian from Dietitian UK and spokesperson for the British Dietetic Association, said:
“This study is a large scale study carried out on over 31000 women. Their diet was assessed every 4 years by a food frequency questionnaire which means it was self-reported and open to errors. Using retrospective food frequency questionnaires once every 4 years comes with some flaws, it is hard to get accurate answers from food questionnaires. The. The women could have underreported their intake of some foods and overreported other foods. Their intake of food may have changed over the 4 years but they are likely to only remember the last few months in detail.
“The research suggests a higher intake of UPF’s was found to be associated with an increased risk of depression but this is open to interpretation. Whilst there is a link in this research we do not know for sure that it was UPF’s that are the cause. This is very much a case of correlation and not causation. The participants who had a higher intake of UPF’s also had a higher BMI, were more likely to smoke, less likely to exercise and had other chronic diseases, any of these could also be the link to depression. Depression is multifaceted with many factors playing a role and diet is not going to be the only one so we cannot say UPF’s are the main cause.
“We already know that a diet where you eat more fruits, vegetables, lean protein, nuts, seeds, healthy fats and dairy, a Mediterranean style diet, is associated with better mental and physical health. While more research is needed to prove a causal link, a diet lower in UPF’s may possibly help lower the risk of depression.”
Dr Duane Mellor, Registered Dietitian and Senior Lecturer, Aston Medical School, Aston University, said:
“This is a short research letter which suggests that there could be an increased risk of self reported depression in female nurses and intake of ultra processed foods consumed. This group of over 31,000 health professionals entered the study between 2004-2007 and were followed up every 4 years although the letter does not say how long they were followed up for. It is known that consuming a healthy diet that is based on vegetables, fruit, nuts, seeds and legumes is associated with a lower risk of depression and poor mental health, so this perhaps is not a surprise. It is not clear if poor mental health impacts food choices or if food choices may impact mental health. What is important is to support people to eat well to maintain and improve their mental wellbeing.
Although interesting, this study lack an objective measure of mental health, relying on people reporting their diagnosis and the use of the NOVA classification although easy to apply to data from this type of study can lack the ability to distinguish between different food types. This is shown as only sweetener containing drinks were linked to increased risk of living with depression, although the researchers speculate this might be due to compounds reaching the brain, this research provides no evidence to support this, and it could be that people who were living with depression may have chosen more sweetened drinks, rather than it being causal.”
Dr Sharmili Edwin Thanarajah, Neurologist and Group Leader, Neurometabolic Circuitry Lab & Dr Andreas Reif, Head of Department of Psychiatry, University Hospital Frankfurt, Goethe University, said:
“Culminating evidence from rodent data and human studies indicates that ultra-processed food is a major driver of the obesity pandemic and contributes to adverse health outcomes. So far, the association with psychiatric illnesses has primarily been investigated in cross-sectional and retrospective studies. In this prospective study, more than 30,000 women without depression at baseline were followed up for a long period of time. Among these participants, more than 4,000 participants were diagnosed with depression or started on antidepressants during the follow-up period. The dietary habit was evaluated through a well-validated questionnaire.
“In their study they report an association with ultra processed foods, and looking into the subitems they report that ultra processed foods with artificial sweeteners are associated with increased risk.
“The major limitation is that only women were considered in this investigation because there is a well-known sex effect on the incidence of depression as well as on food intake behavior. The authors adjusted for body mass, diabetes, and social status, which are associated with both depression and ultra-processed food intake. Still, it is difficult to disentangle the secondary effects of metabolic dysregulation on mental health from the direct effects of ultra-processed food. Finally, the Food-Frequency Questionnaire, while the most frequently used and well validated questionnaire for food intake, relies on participant self-report and is not an independent measure of food intake.
“This study provides an insight into a potential role of artificial sweeteners in mental and physical health but this needs to be confirmed though further research beyond observational data alone.”
Dr Agnes Ayton, Vice-Chair of the Royal College of Psychiatrists’ Eating Disorders Faculty, said:
“This is an interesting study that suggests the consumption of ultra-processed food (UPF) has the potential to not only harm people’s physical health but also their mental health. There is growing evidence that UPF might contribute to the rise of depression and some eating disorders, such as binge eating disorders, and this needs to be explored further.
“The study primarily looks at white, middle-aged females using food frequency questionnaires and therefore can only highlight some relevant associations. However, it’s good that research is being carried out in this field and more is needed to help us better understand how UPF affects people, particularly as certain groups, such as children and those from low socio-economic backgrounds, are disproportionately affected.”
Prof Gunter Kuhnle, Professor of Nutrition and Food Science, University of Reading, said:
“The study makes use of a large existing cohort in the US, the Nurses Health Study II to investigate whether the consumption of ultra-processed foods (UPF) is associated with depression. There are a number of limitations which make it difficult to interpret the results of the study: first, food-frequency-questionnaires (FFQ), which were used in this study to measure UPF intake, can only provide very limited information on UPF intake because they lack the information needed to identify UPFs. Second, the study can only identify associations and not a causation. It is very possible that people with depression change their diet and might decide to consume foods that are easier to prepare – which would often be foods considered to be ultra-processed.
“The study suggests an association between consumption of ultra-processed foods and depression, with an about 50% higher risk for those consuming 9 portions or more (the top 20%) compared to those consuming 4 portions or less. However, the authors have tried to investigate whether specific foods are associated with an increase risk and found that only artificial sweeteners and artificially sweetened beverages are associated with an increased risk – but none of the other food category. This is an interesting finding as it suggests that the as it shows that the association between UPF intake and depression is driven by a single factor – artificial sweeteners. This supports one of the main criticisms of the UPF concept that it combines a wide range of different foods and thereby makes it difficult to identify underlying causes.
“There are currently no data that link artificial sweetener use to mental health, despite most of them having been available for some time. It is also important to note that there are a wide range of different artificial sweeteners that are metabolised very differently and that there might be reverse causality.”
Dr Paul Keedwell, Consultant Psychiatrist and Fellow of the Royal College of Psychiatrists, said:
“It has long been hypothesised that diet could be an important factor in influencing the risk of depression. To my knowledge, this is the first study to suggest that consuming ultra processed foods and drinks, particularly those which include artificial sweeteners, pose a risk for depression.
“The authors suggest that eating a healthier diet, and avoiding sweetened drinks is one thing that we can do to reduce the risk of depression. This might be true, and it would, in any case, improve our health and longevity in general. But there are caveats.
“It is an interesting and important finding, but one that raises more questions. At this stage we cannot say how big an effect diet has on depression risk compared to other risk factors, like family history of depression, stress levels, and having a supportive social network.
“The authors carefully exclude the possibility that the effect is mediated by obesity or lack of exercise.
“However, an important consideration is that a diet based on ready meals and artificially sweetened drinks might indicate a hectic lifestyle, or one with shift work. In other words, a fast food diet could be an indirect marker of chronic stress. Prolonged stress probably remains the main risk factor for depression.”
Prof David Curtis, Honorary Professor, UCL Genetics Institute, University College London (UCL), said:
“This study does not show that so-called “ultra processed foods” in general are associated with risk of depression. The only foodstuffs which it shows are associated with increased risk of depression are artificial sweeteners. Of course, this does not mean that an effect of artificial sweeteners is to increase depression risk – it is just that people with increased risk of developing depression tend to consume larger quantities of artificial sweeteners. An obvious explanation would be that those consuming artificial sweeteners are those who are worried about their weight and have poorer self esteem. In any event, this is just an association noted in an observational study and does not tell us anything definite about the effect of diet on depression risk.”
Prof Keith Frayn, Emeritus Professor of Human Metabolism, University of Oxford, said:
“This is prospective study not an intervention, so the findings represent associations rather than necessarily cause and effect. The list of factors associated with UPF consumption, such as greater BMI, more smoking and less exercise, emphasises just how many confounding factors there may be. Nevertheless, the authors appear to have adjusted for these as carefully as possible, and the relationship between artificial sweeteners and depression stands out clearly. This adds to growing concerns about artificial sweeteners and cardiometabolic health. The link with depression needs confirmation and further research to suggest how it might be brought about.”
‘Consumption of Ultraprocessed Food and Risk of Depression’ by Chatpol Samuthpongtorn et al. was published in JAMA Network Open at 16:00 UK time on Wednesday 20 September.
DOI: 10.1001/jamanetworkopen.2023.34770
Declared interests
Priya Tew: Priya Tew is a registered dietician from Dietitian UK (www.dietitianuk.co.uk)
Dr Duane Mellor: I have previously spoken at events which have been sponsored by the International Sweetener Association.
Dr Sharmili Edwin Thanarajah & Dr Andreas Reif: No declarations of interest
Prof Gunter Kuhnle: No conflicts of interest.
Dr Paul Keedwell: No conflicting interests
Prof David Curtis: No conflicts
Prof Keith Frayn: I am the author of books on nutrition and metabolism.
Author of:
Lipids: Biochemistry, Biotechnology and Health 6th edn (Wiley) published 2016– with Mike Gurr and others
Human Metabolism: a Regulatory Perspective 4th edition (Wiley) published 2019 with Rhys Evans
Understanding Human Metabolism (CUP) published 2022
Forthcoming:: The Calorie Equation (Piatkus) 2025
For all other experts, no reply to our request for DOIs was received.