Probiotics and Parkinson’s Disease

What the latest science tells us about probiotics & Parkinson’s disease

People often ask us about the use of probiotics to improve Parkinson’s disease (PD) symptoms. Probiotics have gained a lot of popularity in recent years, but what exactly are they, and can they make a difference for people with PD? I will answer these questions and provide helpful information so you can decide if probiotics are right for you. It is also wise to consult your own doctor before making any significant changes to your diet.

What are probiotics?

Probiotic rich foods. Healthy diet eating

Probiotics refer to foods or nutritional supplements that contain micro-organisms (such as bacteria or yeast) meant to support health. Probiotics therefore make up a very large category of products, including certain yogurts as well as supplements in powder and pill form. You can review the use of probiotics for general health on the National Institutes of Health (NIH) website. Probiotics may work by supporting a healthy balance of micro-organisms in the microbiome, defined as the trillions of microbes that live in the human gut, and possibly by modulating the body’s immune responses.

Can altering the microbiome improve Parkinson’s symptoms?

In two past blogs, I wrote about the complex relationship between the gut and PD  and discussed the possibility that the microbiome in patients with PD might be different than those without PD. This has led to a research interest of whether manipulating gut bacteria in PD using probiotics can be beneficial. 

There are skeptics as to whether this approach would work. In a recent episode of Dr. Gilbert Hosts, we spoke to an expert in the gastrointestinal symptoms of PD and you can listen to his thoughts on the topic of probiotics at the timestamp 40:07. The microbiome consists of trillions of different organisms living in a delicate balance, and we have only begun to understand the complex effects of this life mass that lives within our gut. It may be too simplistic to think that introducing a few extra bacteria will influence this system.


Defined as foods that promote the growth of good bacteria, may be a more effective way of manipulating the microbiome. Foods that can be incorporated into the diet that meet the definition of prebiotics include oats, millet, chia, quinoa, legumes, and leafy greens such as kale. Listen to a discussion of prebiotics at timestamp 44:20.


Refers to a combination of probiotics and prebiotics which is also being studied to manipulate the microbiome.

Small intestinal bacterial overgrowth

Probiotics may also be beneficial for a condition known as small intestinal bacterial overgrowth (SIBO) in which there is excessive bacteria in the small intestine (defined as 100-1,000 times the normal amount.) SIBO can cause symptoms such as abdominal pain, bloating, chronic diarrhea, and weight loss. Research studies have shown that this condition is more common in people with PD than in the general population, and has also been linked to worsened motor fluctuations in PD. Using probiotics to help treat SIBO may work by re-establishing a more normal bacterial environment.  More research is necessary to better understand SIBO in patients with PD and to ascertain if probiotics are helpful for SIBO, specifically in the context of PD.

Past clinical trials for probiotics and PD

Despite these hesitations, there have been several clinical trials testing whether probiotics can treat the symptoms of PD. Most have focused on treatment of gastrointestinal symptoms such as constipation. Two have focused on improvement of the motor symptoms of PD.

Open label trial, 2011

  • Parameters: Fermented milk
  • # of patients: 40
  • Results: Increase in number of days of normal stool consistency, reduction in bloating, abdominal pain and incomplete emptying when comparing before and after ingestion of fermented milk
  • Author: Cassani, et al
  • Reference

Randomized, double-blind, placebo-controlled trial, 2016

  • Parameters: Fermented milk, along with prebiotic fiber
  • # of patients: 80 received treatment, 40 received placebo
  • Results: Increase in complete bowel movements per week in those ingesting fermented milk and prebiotic
  • Author: Barichella, et al
  • Reference

Randomized, double-blind, placebo-controlled trial, 2019

  • Parameters: 8x 109 colony forming units (CFU) probiotic containing Lactobacillus acidophilus, Bifidobacterium bifidum, Lactobacillus reuteri and Lactobacillus fermentum.
  • # of patients: 30 received probiotic, 30 received placebo
  • Results: Decreased Unified Parkinson’s Disease Rating Scale (UPDRS) score (which corresponds to an improvement in motor function) in those ingesting the probiotic
  • Author: Tamtaji, et al
  • Reference

Randomized, double-blind, treatment-controlled trial, 2020

  • Parameters: Multi-strain probiotic Hexbio®
  • # of patients: 22 received probiotics, 26 received fermented milk
  • Results: Improvement in various measures of constipation in those ingesting probiotic over fermented milk
  • Author: Ibrahim, et al
  • Reference

Randomized, double-blind, placebo controlled trial, 2021

  • Parameters: 1x 1010 CFU probiotic containing Lactobacillus acidophilusLactobacillus gasseriLactobacillus reuteriLactobacillus rhamnosusBifidobacterium bifidumBifidobacterium longumEnterococcus faecalisEnterococcus faecium
  • # of patients: 36 received probiotic, 36 received placebo
  • Results: Spontaneous bowel movements increased in those ingesting probiotic
  • Author: Tan, et al
  • Reference

Open label trial, 2021

  • Parameters: 6×1010 CFU of Lactobacillus plantarum PS128
  • # of patients: 25
  • Results: Improvement in UPDRS score and quality of life from before initiation of therapy
  • Author: Lu, et al
  • Reference

The current literature therefore suggests that using certain probiotic mixtures may improve the gastrointestinal symptoms of PD, although these treatments have not been compared to increasing prebiotic use, which may be even more effective. Even less data supports the use of probiotics for the motor symptoms of PD.

Currently enrolling clinical trials

Additional clinical trials are needed to give more information on how to optimally use these products for PD symptoms. Quite a few are currently underway. To learn more about each trial and see if you can participate, please click each link below:

  • NCT03968133 is studying a multi-strain probiotic and its effects in treating anxiety in PD
  • NCT05568498 is studying a multi-strain probiotic and its effects in treating depression in PD
  • NCT04293159 is studying Lactobacillus casei and its effects in treating constipation in PD
  • NCT04871464 is studying Bifidobacterium, Lactobacillus, and Enterococcus and their effect on motor symptoms, constipation, and sleep in PD
  • NCT04722211 is studying Lactobacillus Plantarum PS128 and its effects on motor symptoms of PD
  • NCT05576818 is studying Lactobacillus acidophilus and prebiotic fibers and their effects on motor symptoms of PD

Should I take a commercially available probiotic product?

There are a tremendous number of products that are commercially available, containing different strains with different CFUs. As you can see from the very small list of clinical trials that have been performed, only a limited number of strains and CFUs were tested in people. So, we do not have the information necessary to recommend one probiotic product over the others.  As always, discuss with your doctor whether you should be taking a probiotic product and if so, which one you should take.

Tips and Takeaways

  • Research is underway to determine whether manipulating gut bacteria in PD using probiotics can be therapeutic
  • Clinical trial data suggests that certain probiotics may help symptoms of PD, particularly GI symptoms
  • Prebiotics, defined as foods such as whole grains and leafy greens, that promote the growth of good bacteria, may be a more effective way of manipulating gut bacteria than probiotics
  • Discuss with your doctor whether you should be taking a probiotic or prebiotic product and if so, which one

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