A growing body of evidence suggests that at least some cases of Parkinson’s disease may start in the gut, through the spread of an abnormal protein from the stomach to the brain, a process that is thought to take decades.
The protein, a misfolded form of alpha-synuclein, is a hallmark of Parkinson’s that accumulates into toxic clumps in the brain and contributes to movement problems like tremors, stiffness and slowness. What triggers alpha-synuclein to misfold, going from a normal to abnormal form that wreaks havoc, is unknown.
Studies have shown that some people with Parkinson’s have deposits of misfolded alpha-synuclein throughout almost the entire length of the digestive tract. Chronic constipation and other gastrointestinal symptoms of Parkinson’s — which are thought to be caused by these deposits — can often appear more than a decade before diagnosis. And, in experiments in mice, misfolded alpha-synuclein injected into the gut does travel to the brain, leading to Parkinson’s-like motor dysfunction and cognitive decline.
The “gut-first” hypothesis of Parkinson’s disease — and the fact that genetics only explains 10 to 15 percent of all cases — has compelled researchers to investigate diet as a potential factor in Parkinson’s development.
The connection between diet and Parkinson’s
While randomized controlled trials have been limited, several observational studies have linked dietary patterns and individual foods to Parkinson’s risk.
For example, regularly drinking coffee and tea is correlated with a reduced risk of developing Parkinson’s disease. Notably, this observation does not extend to decaffeinated coffee, which suggests that caffeine is responsible for the protective effect. Frequent consumption of dairy products has been associated with greater risk, particularly in men. And higher fiber intake has been associated with a lower chance of developing Parkinson’s later in life.
Although these studies don’t prove causation, they represent a valuable first step toward understanding how the foods we eat may influence brain health — and why some people have a higher risk of Parkinson’s than others.
“We don’t have any medications that can slow down disease progression, but if you combine regular exercise with a healthy diet, you can’t really go wrong,” said Silke Cresswell-Appel, associate professor for medicine/neurology at the University of British Columbia. “It’s not about completely changing your diet in one go — it’s about making small shifts that are realistic for you and your family.”
Exercise has long been known to lower the risk of Parkinson’s and can also help improve function in folks who have already been diagnosed.
The MIND and Mediterranean diets
Cresswell-Appel’s research focuses on the role of the microbiome and nutrition in Parkinson’s disease and related brain disorders, in the hopes of discovering lifestyle interventions that help with prevention and treatment. In a 2021 study, she and her colleagues found a strong correlation between dietary habits and age of Parkinson’s onset in 167 people with the disease.
The MIND diet, a spin-off of the Mediterranean diet that aims to minimize cognitive decline, champions the consumption of leafy greens, berries and poultry while reducing the intake of fried food and sweets. Participants who followed the MIND diet more closely tended to develop the disease at a later age. This effect was particularly strong in women: Those who most strongly adhered to the diet developed Parkinson’s 17.4 years later, on average, than those who followed it the least.
“With dietary optimization, not only are you in the best position to hopefully reduce the risk or delay the onset for Parkinson’s, but you kill many birds with one stone,” Cresswell-Appel said. “You’re also reducing your risk for cardiovascular disease, diabetes, obesity — the data all point in the same direction.”
The Mediterranean diet itself — characterized by a high consumption of vegetables, legumes, fruits, whole grains and olive oil — has also been associated with a 25 percent lower likelihood of developing Parkinson’s.
Ultra-processed foods
Several studies have also linked higher consumption of ultra-processed foods with a greater risk of Parkinson’s. Ultra-processed foods are industrially processed products made with additives or ingredients not commonly used in home cooking. Some examples are commercially produced breads, most breakfast cereals, flavored yogurts, hot dogs, frozen meals, potato chips, soft drinks and candy bars.
For instance, a 2025 study followed 42,853 people who initially did not have Parkinson’s disease for up to 26 years, keeping track of their consumption of ultra-processed foods. After adjusting for factors such as age, physical activity and smoking, the researchers found that participants who ate the most ultra-processed foods were about 2.5 times more likely to have three or more early signs of Parkinson’s compared to those who ate the least.
“People who were in the highest 20 percent of ultra-processed food consumption had nearly 40 percent of their calories coming from ultra-processed foods — so, there may be displacement of essential nutrients,” said study author Alberto Ascherio, professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health.
“Reducing ultra-processed food consumption,” Ascherio added, “at this point, is definitely a strong recommendation.”
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