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The gut and the brain are pretty far apart, but increasingly scientists are connecting the dots and finding that Parkinson's is truly related to gut bacteria.
Certainly Parkinson's disease is a brain condition, right? A neurological condition, yes? What's that got to do with the gut, you ask?
Since the early 1990s, medical scientists began to link Parkinson's disease with gut conditions. It was then that researchers from the University of Nebraska Medical Center published a paper in the medical journal Neurology after finding numerous Parkinson's cases where there were gastrointestinal issues, including constipation, nausea, gut inflammation, acid reflux and other GI issues.
Continuing clinical examinations of Parkinson's patients at the University of Nebraska's Medical Center found that the motor conditions related to Parkinson's disease correlated with problems with the vagus nerve, the rectum and the pelvic floor. The vagus nerve runs from the brain to the gut.
These studies also identified dopamine receptors within with lower esophageal sphincter – which opens and closes the stomach to food.
In 2011, research from the University of Tennessee Health Science Center picked up this association between Parkinson's and the gut. They found additional correlations with digestion, salivation issues and rectum problems, along with the other symptoms found earlier. The research also discussed a condition called gastroparesis – where the stomach doesn't empty properly.
As GI problems like these began to become increasingly associated with gut issues, the search turned to whether Parkinson's may be associated with problems with gut bacteria.
Unhealthy microbiome linked to Parkinson's
In 2015, research from the Department of Neurological Sciences at the University of Helsinki - along with doctors at the University Central Hospital - decided to study the bacteria of Parkinson's patients and compare them with healthy patients.
The researchers investigated gut bacteria among 72 Parkinson's patients along with 72 healthy human control subjects. The scientists analyzed the feces of each of the subjects and ran sequencing scans in order to determine the genetics of their microbiome.
A microbiome is the cumulative genetic contents of a person's intestinal bacteria as gauged through the analysis of feces. It determines the overall type of species that are inhabiting the gut.
Over the years, microbiologists have been tracking these different species to determine whether they are healthy or disease-causing. Healthy bacteria are called probiotics, while disease-causing bacteria are often called pathobiotics, or pathogenic bacteria.
At any rate, the Swedish researchers analyzed the microbiomes of the healthy people and compared them with the people with Parkinson's disease to see if there were any differences.
The results were surprising. The scientists found that on average Parkinson's disease patients had about 23 percent less Prevotella species compared with the healthy subjects. They also found that those with fewer Prevotella species had significantly higher incidence of Parkinson's.
Prevotella species have been associated in other research with healthy gut bacteria.
The research also found that the Parkinson's patients had significantly more bacteria in the Enterobacteriaceae family. The Enterobacteriaceae family includes disease-causing bacteria such as Escherichia coli, Yersinia pestis, Klebsiella, Citrobacter, Shigella, Proteus, Salmonella, Enterobacter and Serratia species of bacteria. These cause a myriad of diseases throughout the digestive tract and around the body.
But Parkinson's disease as well?
The link between the gut and the brain is no longer that big of a reach. For years, scientists have been investigating the gut-brain axis connection. Many mood-related and neurological conditions have now been linked with gut bacteria.
Other research has found that probiotic bacteria can increase levels of important neurotansmitters such as dopamine and serotonin. More specifically, a reduction of dopamine and its related norepinephrine is one of the hallmark symptoms of Parkinson's disease. When there isn't enough dopamine to provide smooth nerve impulses between the parts of the brain that control motor movement, coordination and motor control begin to deteriorate.
One of the greatest suppliers of dopamine within the brain is the substantia nigra. During the progression of Parkinson's, neurons in this part of the brain are damaged, which decreases the availability of dopamine. This damage is often related to the existence of Lewy bodies within these areas – so it is assumed Lewy bodies are involved in the progression of Parkinson's.
I might add that University of Nebraska researchers also linked increased levels of Lewy bodies with increased pathogenic bacteria in the gut.
SIBO and Parkinson's
The enemies of probiotics are the pathogenic bacteria, which fight for territory within the gut. When the pathogenic bacteria win this competition, it often results in what medical researchers call SIBO – small intestine bacteria overgrowth.
In 2011, researchers from Rome's Catholic University of Sacred Heart studied 48 Parkinson's patients along with 36 healthy control human subjects. They found that while only a little over 8 percent of the healthy controls had clear evidence of small intestine bacteria overgrowth, over 54 percent of the Parkinson's patients had clear evidence of SIBO.
Not everyone with a prevalence of pathogenic bacteria will test positive for SIBO. This is because SIBO symptoms depend largely upon the condition of the gut and the existence of different bacteria species, along with diet and other factors.
This means that it is likely that while half of the Parkinson's patients had SIBO, many more of the Parkinson's patients likely had gut bacteria problems or imbalances – as indicated by the microbiome research mentioned above.
Can Parkinson's disease be treated with probiotics?
Yes. This has recently been proven. But to what degree will it make a difference? Some laboratory research using probiotics has shown improved brain tissue protection and decreased inflammation among brain tissues. But long-term clinical studies on human subjects have been limited. One study, for example, tested 40 Parkinson's patients with supplementing probiotics for a mere five weeks. But this study was limited to treating their Parkinson's-related constipation.
The researchers reported the probiotics increased their healthy bowel movements.
Besides, it is pretty unlikely that probiotic supplementation for a few weeks will make any significant impact. The condition takes years of progressive damage to brain neurons. These have been associated with toxins and free radical damage within the brain.
The question now is whether a few years of significant probiotic treatment could help decrease the symptoms - or at least slow the progression of this condition.
At the very least we know that probiotic supplementation will help the Parkinson's patient improve bowel movement consistency and frequency – and possibly eliminate the constipation associated with Parkinson's.
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