Parkinson's disease (PD) affects nearly 1 million people in the U.S. alone. It is most common in people over the age of 65, and as the average lifespan continues to increase and people are living longer, it is generally believed that Parkinson's disease will become more prevalent in the future.
The symptoms of Parkinson's disease progressively worsen with time, eventually leading to serious complications and death. Parkinson's is currently estimated as the 14th leading cause of death in the U.S.
Although Parkinson's disease is the second most common neurodegenerative disorder (Alzheimer's disease being the most common), there is currently no cure. Clinical studies have indicated, however, that there are several treatments that can relieve PD symptoms. Among these the potentially beneficial effects of various probiotics for Parkinson's.
In this article, we will explore the relationship between gut health and PD, and how certain probiotics may help provide relief for patients with Parkinson’s.
Causes & Symptoms of Parkinson's Disease: An Overview
On the neurological level, PD is thought to be the result of a buildup of toxic proteins that kill off neurons in a part of the brain called the substantia nigra. Certain neurons in this part of the brain are responsible for making dopamine. Dopamine is a neurotransmitter and hormone that is vital for many important functions, including movement, memory, and motivation.
Scientists believe that lower dopamine levels cause the motor symptoms of PD, as well as many psychological disorders. Unfortunately, clinical studies have not been able to pinpoint the reason why the toxic proteins begin to build up in the substantia nigra in the first place. It is theorized that this occurs due to a combination of genetic and environmental factors.
There are two types of PD. In one type, the damage is first observed in the brain as a loss of neurons. In the other type, symptoms originally present as inflammation in the intestinal lining.
The gut-brain axis is also involved in the pathogenesis and symptoms of Parkinson’s disease. The loss of dopamine-producing neurons in the brain results in the reduction of dopamine which, in turn, leads to an onset of neurological symptoms. In some cases, inflammation of the intestinal lining plays a role in the progression of PD, and gastrointestinal symptoms may be present for years prior to neurological symptoms.
Thanks to decades of successful awareness and educational campaigns, as well as recognizable cultural portrayals of the disease, the outward symptoms of PD are quite well known. A person with Parkinson's disease may experience:
- A tremor in the hands, limbs, jaw, or head
- Hypomimia (little to no facial expressions)
- Difficulty with balance and coordination
- Muscle stiffness
- A slow, shuffling gait
Less well-known are the internal or non-motor symptoms, which are both physical and mental. While the outward symptoms are certainly the cause of great discomfort and mental anguish in many patients, the associated mental and psychological degeneration can at times be equally as distressing. Non-motor symptoms of PD include:
- Amnesia and confusion
- Fatigue and dizziness
- Nightmares and other sleep disturbances
- Loss of smell
- Urinary incontinence
- Gastrointestinal symptoms
The Gut-Brain Axis in PD
Many languages refer to the gut-brain axis in figures of speech. "Butterflies in the stomach" you've felt when faced with an exciting but nerve-wracking experience. Those "gut instincts" that let you know when something is amiss before your brain can consciously process the stimulus. That "visceral reaction" to something that inspires feelings of disgust, anger, or injustice.
Many diseases — including neurological disorders such as Parkinson's disease — begin in the intestinal tract and lead to physical and psychological symptoms.
The close connection between the brain (central nervous system) and the gut and its enteric nervous system has long been known. The enteric nervous system controls the functioning of the digestive organs. The gut-brain axis describes the bidirectional communication between the digestive system and the brain. Microbiota found in the gut play important roles in the gut-brain axis and, combined, form the microbiota-gut-brain axis.
These are two-way channels of communication; the brain affects the digestive system and vice versa. The microorganisms (known as microbiota) of the intestinal tract communicate with the central nervous system via several possible routes, including hormones, neurotransmitters, the immune system, and microbial metabolites.
When inflammation occurs, the communication loop between the brain and the enteric nervous system is disrupted, and the brain may not be able to maintain the proper functionality of the intestinal tract. This causes a whole host of symptoms that begin in the brain and in the digestive organs and spread throughout all the systems of the body.
How Parkinson’s Relates to Gut Health
With the onset of Parkinson's disease, sometimes the first observable effect is damage to the digestive system, which in turn causes gastrointestinal symptoms and telltale damage to the neurons, the latter of which classifies Parkinson's as a neurodegenerative disorder.
The gastrointestinal symptoms of PD are directly related to the disease's effects on gut health. They can be uncomfortable and distressing for patients and tend to contribute to feelings of loss of dignity and loss of independence. These symptoms are caused by inflammation of the digestive organs and the enteric nervous system and may include:
- Abdominal pain
- Fecal incontinence
Previous studies have demonstrated that PD is marked by a change in the composition of the intestinal microbiome. In some cases, the microbial imbalance of the digestive system occurs before the neurological decline, and in some cases, the dying off of neurons in the substantia nigra of the brain happens first. In either configuration, the communication of the gut-brain axis is altered, exacerbating both the motor and non-motor symptoms of the disease.
Are There Probiotics for Parkinson’s Disease?
Probiotics are defined as “live microorganisms, which when administered in adequate amounts, confer a health benefit on the host”. Our digestive systems are home to trillions of bacteria. Each type of bacteria has a slightly different genetic composition and function. Some of them serve essential roles, such as assisting with digestion, preventing inflammation, and fighting off more harmful types of bacteria. Some of them, however, can cause or exacerbate illness. Maintaining the harmony of good bacteria in the gut can improve the functioning of the enteric nervous system and the gut-brain axis.
A large body of research has suggested that probiotics serve a wide range of functions in promoting health even outside the gut. More and more evidence is stacking up in support of the beneficial effects of certain probiotic bacteria in clinical studies of neurological disorders, including Parkinson's disease. Of these, two species in particular are standing out as having potentially neuroprotective effects: Lactobacillus acidophilus and Lactobacillus plantarum.
Lactobacillus acidophilus is a species of bacteria that is found in the mouth, intestines, and vagina. Clinical research shows that it can be used as a supplement to help with conditions like recurring lung infections, bacterial vaginosis, and eczema in infants and children. Animal studies suggest that it may have neuroprotective effects in an experimental model of traumatic brain injury or Parkinson’s disease, but no human studies have followed up on these results.
Lactobacillus plantarum, often designated as L. plantarum, is a type of lactic acid bacteria naturally found in fermented food and in plants. It is believed to increase the shelf life of fermented foods by suppressing the growth of bacteria that causes spoilage. Furthermore, many L. plantarum strains have the ability to produce bacteriocin, which can inhibit – and even kill off – spoilage-related bacteria.
Studies of the neuroprotective effects of L. plantarum in animals and neurological benefits for people with Parkinson’s have centered around a specific, novel strain of this probiotic called PS128. PS128 is classified as a psychobiotic, meaning it has positive effects on the brain via the gut-brain axis*. This novel strain can be found in Neuralli, a clinically researched medical probiotic shown to help people with neurological conditions like PD.
In one study, it was found that people with Parkinson's disease who took PS128 over a 12-week period experienced longer periods of time free of motor symptoms such as tremors*. In that study, patients took PS128 in conjunction with other PD medications they were already taking regularly to control their symptoms, which suggests the supplemental effects of PS128.
Another promising finding in the research is PS128’s effectiveness in improving the health and well-being of autistic people*. The use of PS128 has been shown to potentially reduce anxiety in autistic children*.
Could a Probiotic Prevent or Reverse Parkinson's?
Because the misfolded protein that appears to kill dopamine-producing neurons in the brain in Parkinson’s disease may originate in the gut in some people, potential prevention strategies could target both gut and brain. Probiotics might be able to help in both ways, but further human studies are required.
In the gut, Lactobacillus acidophilus and L. plantarum have been shown to prevent and repair inflammation in the intestines, which is the leading cause of altered communication in the gut-brain axis. Probiotics like these are already commonly used in the treatment of constipation, and constipation as a symptom of PD is no exception.
Beyond alleviating a distressing non-motor symptom for PD patients, gut health probiotics might also have a potentially preventative role to play. Some people experience GI tract symptoms for up to a decade prior to experiencing the neurological symptoms of PD. If probiotics could alleviate the chronic GI symptoms that precede PD for so many patients, could the onset of neurological symptoms be slowed or prevented? The answer to this question is as yet unknown, but future long-term human studies may shed more light.
Interestingly, preliminary studies have shown that several probiotic strains are effective in preventing the death of dopamine-producing neurons. In one preclinical study on the effects of PS128 on neurodegenerative progression in mice, PS128 was shown to have protective effects on dopamine-producing neurons in the substantia nigra. This is excellent news for the mice in the studies, and it is encouraging for scientific and medical professionals with an interest in slowing the onset and progression of Parkinson’s disease in people. Future human clinical trials are required to explore these effects further.
Though definitive evidence of their ability to reverse Parkinson's disease in humans is still not available, there is an increasing consensus among the scientific and medical communities that probiotics have many beneficial effects on human health. In fact, probiotics have been recommended by the Movement Disorders Society Evidence‐Based Medicine Committee as a clinically useful therapeutic option for the treatment of constipation in PD. It’s best to consult a health care professional before making any major change to your health care plan, including introducing probiotics.
Can Gut Bacteria Guard Against Parkinson’s?
Mounting evidence points to gut microbiota and the functioning of the enteric nervous system as the source of countless diseases and ailments, including neurodegenerative diseases. Microbial imbalance and the resulting inflammation seem to be a leading cause and associated factor in more disorders than were previously realized by scientists and medical researchers.
Since PD is a neurological disorder, it stands to reason that the neuroprotective effects of L. plantarum and Lactobacillus acidophilus would be beneficial in protecting against the disease. Current clinical trials are making some headway toward demonstrating the possible beneficial effects of these and other probiotics in the prevention and treatment of many of the symptoms associated with PD.
Maintaining a healthy level of probiotics in the gut seems to have a protective effect against PD. This can be achieved by eating foods high in probiotics or by taking a supplement containing specific helpful strains of probiotics. Psychobiotic L. plantarum PS128, for example, can be found in the specialized medical probiotic Neuralli.
Understanding Parkinson’s & Diet
The current advice given by medical professionals in an attempt to prevent or treat PD and other neurodegenerative disorders includes the general recommendation for people to eat minimally processed foods.
The conventional Western diet is one of the most statistically accurate predictive factors of developing PD and other neurological disorders. The following elements of the Western diet are particularly problematic:
- High caloric intake of energy-dense foods
- High intake of saturated fats, salt, and refined sugar
- Low intake of omega-3 fatty acids and fiber
Scientists have performed numerous studies to examine the effects a diet has on Parkinson's disease. These studies provide researchers with a way to further specify individual food items that speed up the onset and progression of symptoms. Foods that aggravate and exacerbate PD symptoms include:
- Canned fruits and vegetables
- Fried foods
- Ice cream
Conversely, the traditional Mediterranean diet and higher consumption of flavonoids (chemical compounds found in nearly all fruits and vegetables), have been shown to protect against the onset of PD. The following items are eaten frequently in the Mediterranean diet:
- Whole grains
How Probiotics Might Help PD Patients
For many years, Parkinson's disease was thought to be an affliction of the brain, with the loss of neurons in the substantia nigra as the sole indication of deficiency. Many in the scientific community now strongly believe that PD is closely related to – and in many cases caused by – imbalances in the microbiome of the gut. The human brain communicates with the intestines and other digestive organs along the gut-brain axis. It is this line of communication that keeps a healthy balance of dopamine flowing throughout the brain and to the motor neurons that control all of our voluntary movements.
Currently, there is no cure for Parkinson's disease, but there are science-backed options that can potentially help delay progression of the disease and alleviate some of its most uncomfortable aspects. For example, people who adhere to the Mediterranean diet, eating less refined sugar, salt, and saturated fat than the typical Western diet, may delay the onset of Parkinson's disease by up to 17 years.
Gut-health probiotics may also potentially help people avoid long-term imbalances in the gut microbiome that could contribute to formation of the toxic substance that causes neuron death in the substantia nigra. And those with Parkinson’s may find a benefit from neurologically active probiotics such as L. plantarum PS128, found in the specialized medical probiotic Neuralli, which support longer “on” times and quality of life. Though still in the early stages of Parkinson’s disease research, the beneficial neurological effects of PS128 are promising.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.