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A study published in Neurology looks at ultra-processed foods (UPFs) and signs of Parkinson’s disease.
Prof Jules Griffin, Director of the Rowett Institute, University of Aberdeen, said:
“Wang and colleagues have investigated the association between ultraprocessed food and the early stages (prodromal features) of Parkinson disease) in two large-scale related epidemiology study based in the US. This is a really interesting study in that we’ve known for some time that unhealthy diets can contribute to vascular dementia and Alzheimer disease, and indeed some of the genes that increase your risk of Alzheimer’s disease also are important in how we handle fat metabolism and determine our risk to other diseases like atherosclerosis. To date Parkinson’s disease was thought to be different and indeed impacts different regions of the brain. What is also impressive is how many people this study followed and over such a long period of time which is important for diseases of the brain. The study adds to a growing body of evidence that diet has a major role in brain health and complex brain diseases like Parkinson’s, and just like we give out advice for healthy eating for type 2 diabetes and cardiovascular disease we should be doing the same for a healthy and functioning mind.
“The study does come with a few caveats that the authors do raise. The first is that they are not directly looking at Parkinson’s disease but some of the symptoms that are associated with the very early stages of the disease. We’ve known for a number of years that some of the earliest symptoms of Parkinson’s involve changes in the gut and sleeping patterns, but just because these change does not mean they are caused by Parkinson’s. What isn’t dealt with in the study was whether it’s really ultraprocessed food that is the culprit or poor diets in general. For a lot of studies that study UPF, diets high in UPF are also high in saturated fat, sugar and salt – all of which have been linked to dementia previously. We also know that people that eat a poor diet throughout their lives are probably vulnerable to a whole host of other environmental challenges such as low income, increased exposure to pollutants and increased stress. It’s tough to disentangle all these factors, and all are known to contribute to poor health.”
Dr Katherine Fletcher, Research Lead at Parkinson’s UK, said:
“Research into diet in general is difficult as people often will inaccurately self-report what their diet comprises. This could be down to forgetting to fill in the diary at the time, to subjective interpretation of amounts of UPFs.
“The study group also lacked ethnic and socio-economic diversity, which is vital when looking to better understand factors that contribute to the causes of a health condition.
“In respect of strengths, it was a long-running study with a reasonably large sample size, building on a theory that already exists about the impact of diet. Nonetheless, a much wider body of research is required before drawing any conclusions i.e. looking globally at different diets.
“This paper builds on previous research, such as the work of Dr. Laurie Mischley1 at Bastyr University, which has shown an association between processed foods and faster progression of Parkinson’s. Additionally, evidence suggests that following a Mediterranean-style diet2 – rich in fresh fruits, vegetables, pulses, and olive oil – could reduce someone’s risk of going on to develop Parkinson’s.
“Research into diet and nutrition is crucial, as there is growing evidence that, for some individuals, Parkinson’s may originate from changes in the gut. Ongoing studies are exploring alterations in the gut microbiome in Parkinson’s and investigating potential interventions to address these changes and as well as investigating diet and supplements to help manage symptoms.”
1 https://pubmed.ncbi.nlm.nih.gov/29081890/
Prof Eef Hogervorst, Professor of Psychology, Loughborough University, said:
“Firstly, the outcome term ‘early symptoms of Parkinson’s disease’ is a bit misleading as symptoms such as constipation, and body pain here found to be associated with consumption of Ultra Processed Foods (UPF) are quite common in ageing and are not necessarily indicative of Parkinson’s disease.
“Even the most likely predictor of Parkinson’s disease – probably REM sleep disorder – is seen in 65% of Parkinson patients but also in 10% of controls, with low (65%) sensitivity for Parkinson’s disease, even when people already have this disease (Kakazu, 2024: https://doi.org/10.1016/j.sleep.2024.09.042). This symptom only shows relations with the highest intake of UPF.
“Other symptoms like reduced sense of smell, daytime sleepiness, impaired colour vision and depression by themselves seem not related to consumption of UPF.
“With regards to the UPF outcome, 30% of food consumption assessed by questionnaire was not agreed on and while experts apparently re-assessed these, it is not clear how they agreed on categorisation of foods, so whether they were UPF or not.
“It seemed strange that non-UPF food included beef, pork, lamb chicken or turkey sandwich (all processed meats); cream; pancakes or waffles; pie, home-baked or readymade; popcorn; potato or
corn chips; soy milk; and tomato sauce, as well as distilled alcohol and dairy coffee.
“Individual foods such as UPF breads or cereals and indeed microwaveable meals were by themselves not associated with the ‘early Parkinson disease symptoms’ while sauces, sweets, artificial sweetened drinks and desserts were as well as savoury snacks, animal and dairy products including yogurts. Such foods are associated with diabetes mellitus and vascular (heart) disease, respectively, which can impact on brain disease because of their sugar and trans fat contents, respectively.
“However, it is not the first study to show associations of UPF and brain disease. We early wrote a piece on studies investigating dementia risk and processed meat consumption
https://theconversation.com/processed-red-meat-isnt-just-bad-for-your-heart-its-also-associated-with-dementia-247619 A healthy varied whole food diet is associated with prevention of many diseases including dementia.
“Lastly, these two cohorts were mainly white health professionals so the results do not necessarily translate to everyone.
“So this study may be affected by UPF categorisation as a predictor, where also not all UPF foods showed an association; the limited study group associations were assessed in (only mainly white health professionals and nurses) and also by the outcome, as these symptoms are not necessarily predictive of Parkinson’s disease, nor were these symptoms individually all associated with UPF consumption.”
Dr Daniel J van Wamelen, Clinical Senior Lecturer in Neuroscience and Honorary Consultant Neurologist, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, said:
“The findings in this study are interesting and appear to be based on solid research with conclusions well supported by the data. However, it is important to highlight that the symptoms examined in this study are possible early signs of Parkinson’s disease, not definitive indicators that someone will go on to develop it. The study did not track whether participants were diagnosed with Parkinson’s later on.
“Many of the individual symptoms noted, such as sleep disturbances, constipation, and mood changes, are common in the general population. While the study found that people who ate more ultra-processed foods tended to report more of these non-motor symptoms, it did not find a direct increase in the risk of Parkinson’s disease itself. That said, having more of these symptoms suggests a higher risk over time. For example, a person experiencing a combination of REM sleep behaviour disorder, constipation, and depressive symptoms has a higher likelihood of developing Parkinson’s down the line, but the risk is not absolute. To better understand the long-term implications, we would need a longer follow-up to see how many participants go on to develop Parkinson’s and how this is associated with their diet.
“In short, this is an interesting piece of research addressing important questions. But the connection to Parkinson’s disease should be viewed with caution until more definitive evidence becomes available.”
‘Long-Term Consumption of Ultraprocessed Foods and Prodromal Features of Parkinson Disease’ by Peilu Wang et al. was published in Neurology at 21:00 UK time on Wednesday 7 May 2025.
DOI: 10.1212/WNL.0000000000213562
Declared interests
Prof Jules Griffin: “I have no conflicts of interest to declare for this subject area. I am a consultant for Sitryx, a company specialising in designing drugs to target immunometabolism. The company is looking at drugs for irritable bowel disease and psoriasis.”
Dr Katherine Fletcher: “The author declares that they have no known competing financial interests or personal relationships that could have appeared to influence their comment reported in this article.”
Prof Eef Hogervorst: “A previous consultancy for Proctor on omega 3 and folic acid supplement review to protect against dementia (these did not in meta-analyses), and unpaid but a travel reimbursed media appearance (breakfast TV BBC) to discuss the Lancet 2024 risk factors for dementia and her own articles including the Conversation piece on nutrition and dementia risk https://theconversation.com/processed-red-meat-isnt-just-bad-for-your-heart-its-also-associated-with-dementia-247619. Eef also acted as unpaid but travel reimbursed consultant for NICE on menopausal HRT and dementia risk and has received travel reimbursement to speak at ESG and BMS conference on dementia prevention in 2024/2025.”
Dr Daniel J van Wamelen: “Supported by research funding from CHDI Inc, MRC, and BRC; received travel grants and speaker fees for educational purposes from Bial Pharma; served on advisory boards for Britannia Pharmaceuticals and Invisio Pharma; received in kind contributions (equipment) from Chrono Eyewear BV for research projects.”