Healthy eating habits such as consuming plenty of vegetables, choosing whole grains over refined carbohydrates, and getting protein from nuts and fish rather than red meat may help stave off symptoms associated with the early stages of Parkinson's disease, at least two studies have shown. (A progressive disorder that affects about 930,000 Americans, Parkinson's disease is characterized primarily by tremor, stiffness, and movement difficulty.)

According to a large Harvard University study published in Neurology last August, people who had healthy diets in their thirties, forties, fifties, or sixties were less likely to experience pre-Parkinson's nonmotor symptoms later in life. A January 2019 study in Movement Disorders found that those who followed the so-called Mediterranean diet had a 21 percent lower risk for developing pre-Parkinson's symptoms.

Furthermore, a January 2021 study in Movement Disorders showed a correlation between a Mediterranean-like diet and a later onset of Parkinson's disease. The study of 225 Parkinson's patients found that women who followed a Mediterranean-style diet developed Parkinson's 17.4 years later than those who didn't regularly consume such Mediterranean-diet staples as leafy greens, berries, and poultry; for men, the difference was 8.4 years.

The Harvard study tracked 47,679 women and men for approximately 30 years. Subjects who scored in the top fifth for healthy eating were 33 percent less likely to eventually have at least three pre-Parkinson's nonmotor symptoms—which include REM (rapid eye movement) sleep behavior disorder, excessive daytime sleepiness, constipation, depression, anxiety, and urinary and erectile problems—compared with those who scored in the lowest fifth on measures of healthy eating. The measures used were the Alternate Healthy Eating Index and the Mediterranean diet, both of which emphasize produce, whole grains, and fats from nuts, olive oil, and fish and discourage red meat and refined carbohydrates.

“These studies suggest that Parkinson's disease may not be inevitable,” says E. Ray Dorsey, MD, MBA, professor of neurology at the University of Rochester Medical Center in New York. “The Mediterranean diet may even decrease the risk of ever developing it in the first place,” he says, citing a 2007 Harvard School of Public Health study, published in the American Journal of Clinical Nutrition, that tracked 131,368 people for 16 years. Those who most closely followed a Mediterranean-style diet were less likely to develop Parkinson's disease than those who skimped on fruits and vegetables and ate more meat, refined grains, high-fat dairy products, and sweets.

Perhaps the results of the studies will motivate people to take a second helping of salad or veggies at dinner, sprinkle walnuts on their morning oatmeal, or dig into a bowl of vegetarian chili on a cold winter afternoon, says Silke A. Cresswell, MD, associate professor of neurology at the University of British Columbia and co-author of the 2021 Movement Disorders study.

Researchers like Dr. Cresswell theorize that a healthy diet may lower the risk of Parkinson's disease by nurturing beneficial gut bacteria that reduce inflammation and foster healthy insulin sensitivity. Inflammation in the gut could lead to inflammation in the brain, which may contribute to brain cell loss, explains Dr. Cresswell. Insulin resistance, which is more prevalent in people with Parkinson's disease than in the general population, appears to contribute to a buildup of protein clumps inside nerve cells that may lead to the death of dopamine-producing brain cells, she says. Loss of dopamine is responsible for many of the symptoms of Parkinson's.

A weak antioxidant defense system can leave brain cells vulnerable to damage by free radicals. Getting plenty of antioxidant compounds from fruits and vegetables may protect cells from damage, says Dr. Cresswell, adding that the omega-3 fatty acids in fish and nuts provide building blocks for neuron walls.

“We suspect that for some people, Parkinson's may begin in the gut,” Dr. Dorsey says. Research shows that people with Parkinson's have a different makeup of gut bacteria from the general population, which may contribute to inflammation and insulin resistance, says Dr. Cresswell.

“I counsel patients to eat a healthy diet for many reasons,” says Michael S. Okun, MD, FAAN, professor and chair of neurology at the University of Florida in Gainesville. “We hope for emerging data to guide us on diets that may improve function as well as absorption of Parkinson's medications,” he says. “The evidence is not strong enough yet for us to endorse one approach over another.”

While scientists continue to explore the relationship between diet and neurologic disorders, consider these recommendations:

Shop in the produce aisle. As these studies show, people who ate the most nuts, fruits, vegetables, and legumes had the lowest risk for early signs of Parkinson's disease. Dr. Cresswell says an overall healthy diet seems more important than focusing on any single superfood or nutrient.

Opt for whole foods. Cut back on red and processed meats and refined carbohydrates like white bread and sweets. These foods, major components of the Western diet, are associated with a higher risk for Parkinson's disease. “An occasional hamburger or piece of cake is fine,” Dr. Cresswell says. “But it's important to remember that everything your body uses to function comes from the food you eat. It's not just that skipping healthy food could be detrimental—processed foods seem to cause problems.”

Limit alcohol intake. Consuming no more than one drink per day for women and two for men was associated with a lower risk for symptoms of pre–Parkinson's disease, according to the Neurology study. “Modest amounts of alcohol may be okay, but more than that is not good for the brain or body,” Dr. Dorsey says.

Be wary of fad diets. Talk to your doctor before starting any special diet, such as gluten-free or ketogenic, advises Dr. Cresswell, and work with a dietitian if you decide to try one. “The only reason to go on a gluten-free diet is if you have celiac disease or a gluten sensitivity,” she says. “Evidence is patchy for these diets, and they are restrictive.” For example, she notes, people on a gluten-free diet may not get much fiber, which could be a problem if you have constipation (common with Parkinson's disease), and keto diets can be high in protein, which may interfere with absorption of medication.

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Four Nut-Filled Recipes to Help Prevent Parkinson's developed by Linda Monastra, a graduate of the Natural Gourmet Institute in New York City.