People who consume more ultra-processed foods—such as packaged snacks, sugary cereals, and hot dogs—may be more likely to show early warning signs of Parkinson’s disease, according to a new study published May 7, 2025, in Neurology, the journal of the American Academy of Neurology.
The research doesn’t prove that ultra-processed foods cause Parkinson’s, but it does suggest a strong association.
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Researchers focused on prodromal Parkinson’s disease—the earliest phase of the condition, when neurodegeneration has begun but hallmark symptoms like tremors or slowed movement haven’t yet appeared. These subtle warning signs can develop years or even decades before a formal diagnosis.
“Eating a healthy diet is crucial as it has been associated with a lower risk of neurodegenerative diseases, and the dietary choices we make today can significantly influence our brain health in the future,” said lead author Xiang Gao, MD, PhD, of the Institute of Nutrition at Fudan University in Shanghai, China.
“There’s growing evidence that diet might influence the development of Parkinson’s disease. Our research shows that eating too much processed food, like sugary sodas and packaged snacks, might be speeding up early signs of Parkinson’s disease.”
The study followed 42,853 people with an average age of 48 for up to 26 years. None had Parkinson’s disease at the start. Over time, participants underwent medical exams and completed detailed health questionnaires. Researchers assessed for early signs of Parkinson’s, such as rapid eye movement sleep behavior disorder, loss of smell, depression, daytime sleepiness, and impaired color vision.
Participants also kept food diaries every two to four years, noting their consumption of ultra-processed foods. These included items like soda, chips, condiments, packaged desserts, and processed meats. One serving equaled a standard portion, such as one soda can or one hot dog.
After adjusting for lifestyle factors like age, smoking, and exercise, researchers found that people who ate 11 or more servings of ultra-processed food per day were 2.5 times more likely to show at least three early signs of Parkinson’s, compared to those who consumed fewer than three servings daily.
The trend held across most individual symptoms—except constipation. “Choosing to eat fewer processed foods and more whole, nutritious foods could be a good strategy for maintaining brain health,” said Gao. “More studies are needed to confirm our finding that eating less processed food may slow down the earliest signs of Parkinson’s disease.”
Fermentation expert Sandor Katz who has helped maintain his health and living with HIV using fermented foods says there is no silver bullet solution: While fermented foods can help, that’s only part of the solution: “I share your perspective that people would be healthier if they moved away from ultra-processed foods. I also believe that fermented foods can improve digestion, immune function, and even mental health. However, it is misleading to suggest that fermented foods cure HIV, Parkinsons, cancer, or any other particular disease,” he warns.
One limitation: participants self-reported their dietary habits, which may have introduced inaccuracies in measuring how much processed food they truly ate.
