Skip to content
Spend €45 more and get free shipping!

Parkinson's Disease and the Gut

Parkinson’s disease (PD) is the second most common neurodegenerative disorder after Alzheimer’s disease1 

Globally, it has an incidence of 1–2 per 1000 people, and due to the progressive ageing of the world population, the number of people with PD is expected to double by 20301   

According to the Parkinson’s Association of Ireland it is estimated that there are approx. 12,000 people living with Parkinsons Disease in Ireland today 

Parkinsons Disease affects neurons in the brain, leading to decreased dopamine levels and motor impairments, such as tremor, rigidity, balance difficulties, and loss of spontaneous movement (akinesia)2  

Parkinsons Disease is now considered a multi-systemic disease, affecting the central as well as the peripheral nervous system (CNS, PNS), resulting in several non-motor symptoms, often including gastroparesis (delayed stomach emptying bringing on symptoms of heartburn, nausea, vomiting or feeling full quickly when eating) or constipation. Due to the early involvement of the gastrointestinal tract, often preceding motor symptoms for years3  changes in microbiome composition have been studied in relation to Parkinson’s Disease.  


The human gut harbors trillions of micro-organisms referred to collectively as the microbiome. Current understanding is that the microbiome provides a number of benefits to the human including help with digestion of food, help with warding off harmful microorganisms, aid in the absorption of particular nutrients, and creation of needed vitamins. These functions can influence the nervous system of the gut, called the enteric nervous system (ENS). In addition, the gut microbiome releases byproducts and metabolites that have effects on nerves. The microbiome varies from person to person and is influenced by many factors including diet, environment, and genetics. Although no two microbiomes are identical, people with certain diseases may share similarities in their microbiomes. 

How are the gut and brain connected? 

Dr Rebecca Gilbert of the American Parkinsons Disease Association has written a number of interesting articles discussing  how the enteric nervous system  ENS is directly connected to the brain through the vagus nerve which travels between the two. She highlighted a theory that suggests that Lewy bodies (an abnormal accumulation of alpha-synuclein), the pathologic hallmark of PD, develop first in the ENS and then can migrate to the brain via the vagus nerve. The brain and the gut also communicate via the bloodstream as well, through alterations in inflammatory signals, neurotoxins and neuroprotective factors. One of the elements that contributes to both these communication channels between the gut and the brain is the gut microbiome. 

Can an altered microbiome contribute to a diagnosis of PD? 

Dr Gilbert discusses  how research studies in animals have shown that an altered microbiome might contribute to PD. For example, one study showed that in a mouse model of PD that overexpressed alpha-synuclein, there was more alpha-synuclein accumulation (also known as Lewy bodies, the pathologic hallmark of PD) in the brain of the mice with an intact microbiome as compared to the same mice who were raised in a germ-free environment with no bacteria in their gut. This supports the theory that abnormal alpha-synuclein accumulation in the brain is enhanced by a particular microbiome in the gut. 

Other studies showed that transplantation of fecal material from PD mice to normal mice, thereby introducing a “PD microbiome” into mice without PD pathology their brain, led to impairment of motor function and a decline in brain dopamine. These studies also support the theory that a particular microbiome might be integral in causing PD pathology in the brain. 

How might an altered microbiome contribute to Parkinsons Disease? 

These studies beg the question – how might the gut microbiome contribute to PD in the brain? Several different theories have been proposed: 

  • Short chain fatty acids (SCFAs) are one of the main products of the microbiome. Research has shown that SCFAs can enter the brain and exert neuroprotective effects via increase of nerve growth factors. A number of research studies have shown that there are less SCFAs in feacal samples from people with PD as compared to healthy controls and this could contribute to a lack of neuroprotection that then fuels PD. 
  • Gherlin is a neuropeptide that stimulates appetite and might have neuroprotective effects. It has been shown that levels of gherlin are lower in people with PD than healthy controls. In addition, research has shown that blood levels of gherlin may depend on the gut microbiome and could therefore be an additional factor that connects PD and the gut microbiome. 
  • A “PD microbiome” may release pro-inflammatory molecules such as TNF-alpha and interferon-gamma which can enter the brain. These pro-inflammatory molecules may contribute to PD. 
  • A “PD microbiome” may increase the ability of molecules to permeate the intestinal wall. This may allow neurotoxins to enter the gut. 

Intestinal Infections in the microbiome 

Doctors are already aware of changes in the microbiome that are actual intestinal infections that can have effects on PD. 

  • Helicobacter pylori is a common bacteria which can cause gastritis and ulcers. Infection with Helicobacter pylori has been linked to worsened motor fluctuations in PD. 
  • Small intestinal bacterial overgrowth (SIBO) is a condition in which there is excessive bacteria in the small intestine and can cause symptoms such as abdominal pain, bloating, chronic diarrhoea and weight loss. It is also linked to worsened motor fluctuations in PD. 

These two conditions may be considered in a person with unexplained and unpredictable fluctuations of PD symptoms. They are typically diagnosed by a G.P or gastroenterologist and are treated with antibiotics. 

Can altering the microbiome improve Parkinson’s symptoms? 

With the awareness that the microbiome may play a role in PD, came the idea that altering the microbiome may help with PD symptoms. While there is still a lot of research to be done, there have been some small, but promising findings so far. 

Particular strains of bacteria that are ingested in order to alter the gut microbiome, have been and are currently being studied to help PD symptoms. A number of small studies suggest that probiotics may improve constipation in people with PD, which is a common problem for many people with the disease. 

As mentioned above, treatment of Helicobacter pylori and SIBO typically requires antibiotics, which are drugs designed to kill particular bacteria. Antibiotics can be helpful, but are only considered if a particular gut organism is being targeted. Otherwise, antibiotics can kill both “good” and “bad” bacteria, and potentially be detrimental to the overall health of the gut microbiome. 

Another idea that has been considered is feacal transplantation, a technique in which feacal matter from a healthy person is delivered to the gut of a person with PD, with the goal of restoring a less “PD-like” microbiome. Only case reports and very small studies have been reported so far in the literature, but this may be an area worth exploring.  


  • Research has shown that there are differences in the microbiome between someone with PD and healthy controls. 
  • A number of theories are being tested to understand whether and how the microbiome differences can contribute to the development and symptoms of PD. 
  • Probiotics and feacal transplantation can alter the microbiome in people with PD and are under investigation as possible treatment options. 

Symprove and the Microbiome  

Symprove is a unique, water-based food supplement containing four strains of live and active bacteria, which are delivered to the gut to support the microbiome.4,5 Symprove should be taken as part of a healthy lifestyle.  

There is ongoing research into how Symprove may improve the bodies Microbiome  

A new study  has just been published in the International Journal of Pharmaceutics investigating how Symprove may influence the gut microbiome of people with Parkinson’s disease. This study used the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), a validated in vitro model that mimics the entire gastrointestinal tract. 

Ongoing research is being conducted in the area of PD with multiple double blind trials being conducted in the UK 

If you would like to be kept up to date with the ongoing research and information relating to how Symprove may improve your microbiome then please register in the box below. 

By submitting this form, you are agreeing to receive relevant emails about Symprove, gut microbiome health and research, and useful resources for healthcare professionals. We’ll always treat your personal details with the utmost care and will never sell them to other companies for marketing purposes. Please refer to our privacy policy for details on how we use your data. You can choose to opt out of emails at any time. 

The Parkinson’s Association of Ireland is a charity, based in Dublin with branches throughout the country. Their aim is to assist people with Parkinson’s, their families and carers, health professionals and other interested people by offering support, a listening ear and information on any aspect of living with Parkinson’s.  If you or a loved one is affected by Parkinsons disease we would strong encourage you to visit their website at or call them on 1 800 359 359  

  1. Elbaz, A., Carcaillon, L., Kab, S. & Moisan, F. Epidemiology of Parkinson’s disease. Rev. Neurol.172, 14–26 (2016). 
  1. Shulman, J. M., De Jager, P. L. & Feany, M. B. Parkinson’s disease: genetics and pathogenesis. Annu. Rev. Pathol. Mech. Dis.6, 193–222 (2011). 
  1. Cersosimo, M. G. & Benarroch, E. E. Pathological correlates of gastrointestinal dysfunction in Parkinson’s disease. Neurobiol. Dis.46, 559–564 (2012). 
  1. Fredua-Agyeman M and Gaisford S. Comparative survival of commercial probiotic formulations: Tests in biorelevant gastric fluids and real-time measurements using microcalorimetry. Beneficial Microbes 2015;6(1):141-151. 
  1. Moens F, et al. A four-strain probiotic exerts positive immunomodulatory effects by enhancing colonic butyrate production in vitro. Int J Pharm 2019;555:1-10. 

DISCLAIMER – The information on these pages is not intended to be taken as advice. No changes to your treatment should be made without prior consultation with your doctor or allied health professional.