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If you live with Parkinson’s disease, you’ve probably heard a lot about the gut-brain connection. Good bacteria in the gut microbiome — the ecosystem of bacteria that live in your gut — support a healthy brain, while bad bacteria can trigger events that may eventually wreak havoc on the brain.
A small study in Nature Communications suggests that a special high-fiber prebiotic bar made with some uncommon ingredients can nudge the gut microbiome in a healthier direction for people with Parkinson’s.
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Those with this neurodegenerative disease tend to have some changes in their gut that are known to lead to inflammation and weaken the protective barrier between the gut and bloodstream, says Dr. Michael Okun, coauthor of The Parkinson’s Plan.
“This study showed that specific prebiotic fibers could possibly shift gut bacteria toward producing helpful metabolites that may calm inflammation and may reduce stress on the brain,” he says.
But it’s not clear whether the bars have any effect on day-to-day life with Parkinson’s. More studies are needed for that. And there are simpler ways to support your gut without hunting down specialty ingredients.
A prebiotic bar for Parkinson’s disease?
Prebiotics are nutrients that feed and support the good bacteria in your gut so they can thrive and flourish — as opposed to probiotics, which are the good bacteria themselves.
In the study, researchers at Rush University Medical Center in Chicago had 20 participants with Parkinson’s disease eat a specialized prebiotic bar for 10 days. Half of the participants were newly diagnosed and not yet on medication. The other half had a more advanced disease and were already being treated. Each bar contained 10 grams of fiber.
Everyone ate the same prebiotic fiber bar every day for 10 days. For the first three days, they ate one bar every morning. For the following week, they had a bar in the morning and another in the afternoon. They could eat them at mealtimes or separately, and they otherwise ate whatever they normally ate.
“This mixture is composed of fibers that each support a different and complementary group of bacteria in the gut bacterial community,” says Bruce Hamaker, a coauthor of the study, whose lab devised the prebiotic formulation for the bars. He is a food scientist at Purdue University College of Agriculture in West Lafayette, Indiana.
There was no placebo group, and both participants and researchers knew what they were eating. The study’s goal was simply to see if people with Parkinson’s disease could tolerate eating this much more fiber every day and whether it seemed safe. A sudden large increase in your daily fiber intake can cause pain, gas, cramping, bloating and diarrhea. While it’s recommended that adults get 25 to 30 grams of fiber a day, most get only 15 grams. The two bars per day might have more than doubled the daily fiber intake of some people in the study.
Gut inflammation and markers of nerve damage improved
Most people in the study reported that they liked the bars enough to keep eating them after the 10-day trial. Though they were taking in an extra 20 grams of fiber a day, no one reported problems with bloating or diarrhea. What’s more, the people who were already receiving treatments for Parkinson’s said the bars improved their overall gastrointestinal (GI) symptoms, though there were no documented improvements in constipation, a hallmark symptom of Parkinson’s.
Beyond testing safety and tolerability, the researchers analyzed stool samples taken from participants before and after the 10-day study to check for changes in the gut believed to be beneficial for people with Parkinson’s.
“In 10 days, gut inflammation went down significantly,” Hamaker says. A group of bacteria that are known to be pro-inflammatory went down significantly, according to Hamaker, and “a marker for brain inflammation called neurofilament light chains went down also.” That marker decreased more so in newly diagnosed people.
At the same time, after the 10 days, participants’ guts had shifted toward greater numbers of bacteria thought to produce helpful short-chain fatty acids (SCFAs), which are normally low in people with Parkinson’s. SCFAs support communication between the gut and brain and may help control brain inflammation.
A protein called zonulin, a sign of leaky gut, also decreased. Leaky gut, or gut barrier dysfunction, can allow harmful substances to escape from the gut and enter the bloodstream, where they can cause inflammation and other damage throughout the body and in the brain. The prebiotic bars may help shore up the lining of the gut, Hamaker says.
The researchers saw slight improvements in motor and non-motor symptoms too. Neurologists scored the study participants’ movement using the Unified Parkinson’s Disease Rating Scale — a composite score that factors in tremor, rigidity, slowness, balance, gait and speech — before and after the 10 days of bars.
“The change was modest but significant — the same kind of change that happens even with pharmacological treatment,” says Dr. Ali Keshavarzian, the study’s lead author and director of Rush University’s Center for Integrated Microbiome and Chronobiology Research.
But the study was not designed to measure improvements in motor skills. There was no placebo group, and the study lasted only 10 days, so the long-term effects of the prebiotic bars are still unknown.
“What needs to be done is a longer-term randomized controlled trial,” Hamaker says, which his collaborators in Chicago are planning.
Why target the gut?
The concept of targeting the gut in Parkinson’s research is based on three major lines of evidence demonstrating the gut’s role in this disease. First, says Dr. Rachel Dolhun, principal medical adviser at the Michael J. Fox Foundation for Parkinson’s Research, is constipation.
“Constipation, in some people, happens decades before the diagnosis of Parkinson’s disease,” she says. This common GI symptom of Parkinson’s, she adds, is a key indication that the gut is involved in the disease.
Second, the gut’s ecosystem just looks different in people who have Parkinson’s. Pro-inflammatory microbes tend to be more prevalent. Specific Parkinson’s symptoms, in fact, might be linked to specific types of bacteria, Dolhun says.
“We are starting to see some differences in people who have different symptoms of Parkinson’s,” she says. “People who have more tremor-predominant Parkinson’s might have a different microbiome than people who have more gait-, walking- and balance-predominant Parkinson’s.”
Third, research suggests that alpha-synuclein — the protein that accumulates in clumps in the brains of people with Parkinson’s — may be present in their guts long before the disease is diagnosed.
So it’s logical to explore whether improving the gut could help prevent, slow or stop Parkinson’s disease. But Dolhun stresses that scientists don’t yet know whether gut changes are a cause of Parkinson’s, a consequence or both.
“Is it that the microbiome is changing and that’s contributing to Parkinson’s? Or is it that you have Parkinson’s, you take medicines for Parkinson’s, maybe your diet changes, and that’s impacting your microbiome?” she asks.
That uncertainty is key context for interpreting the fiber bar study: Changing the microbiome may reduce markers of inflammation, which looks promising, but we still don’t know if that will meaningfully change daily life with Parkinson’s and its course over the years.
A healthy diet leads to a healthy gut
That said, striving to improve the overall makeup of your gut is never a bad idea. And you probably don’t have to chase down special ingredients and make fiber bars from scratch to accomplish that.
“The simplest idea is to increase fiber from different sources,” Hamaker says.
Remember, his recipe feeds the gut different types of fiber that support various species of good bacteria. To make sure you’re covering all your bases in that area, focus on getting your fiber from the widest possible variety of sources: fruits, vegetables, whole grains, beans and legumes.
Eating patterns such as the Mediterranean and the MIND diets are rich in whole, plant-forward foods and lower in processed foods and can help you get the healthy variety that could make a positive impact on your gut.
And they may have specific benefits for people who have Parkinson’s or those trying to prevent it.
“We see potential benefits across the journey of Parkinson’s,” Dolhun says, from prevention or delaying onset all the way to emerging data that suggests these eating patterns may slow the progress of the disease.
What about prebiotic and probiotic supplements?
So why not just shortcut to supplements?
In general, nutrition experts agree that it’s better to get nutrients from healthy, real food than from supplements, for many reasons, and the advice on pre- and probiotics is no different.
For prebiotics, high-fiber foods are the source. Probiotics, those friendly bacteria, are found in fermented foods, such as yogurt (even nondairy yogurt contains live bacteria), sauerkraut, kimchi, kombucha and kefir.
The bottom line
A healthier gut is always a good idea, and it may have specific benefits for those with Parkinson’s disease. To shift yours in the right direction, prioritize whole foods, such as fruits, vegetables, nuts, seeds and whole grains like oatmeal and brown rice, rather than supplements or processed, packaged foods.
"Regular exercise, a Mediterranean-style diet and getting advice from a nutritionist are practical steps to support a healthier gut environment in Parkinson’s disease,” Okun says.
A homemade fiber bar, like the one in the study, might be a convenient way to get a high-fiber snack in lieu of a chocolate bar or chips. But it shouldn’t crowd out high-fiber, whole foods you might otherwise snack on, like fresh apples, carrots and nuts.
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