Parkinson's and the gut:
A lot of people aren't aware that there is a significant link between Parkinson's disease and the gut (1, 2). The gut and the gut microbiome (the millions of bacteria that live within our gut and are vital for helping us digest foods and maintain health) have strongly been linked with Parkinson's disease (1). Not only does it contribute to Parkinson's symptoms such as constipation, it can also affect Levodopa absorption, and is actually being investigated as one of the leading causes of Parkinson's disease (1-3). While more than 90% of Parkinson's disease is considered 'idiopathic', meaning we still don't know definitively what causes it, the gut and the gut microbiome is being investigated as one of the primary places the disease may begin (4). As Hippocrates said, "All disease begins in the gut." In the case of Parkinson's disease, he just may be correct.
Credible evidence suggests that, for many people, their Parkinson's disease may originate in the gut. How?
While Parkinson's disease is well-known for causing issues with movement, such as stiffness, slowness and tremor, what's not talked about as much are all the other symptoms that it can cause: constipation, sleep issues, loss of smell, depression, anxiety, pain, fatigue, brain fog, memory problems and more. Constipation affects up to 70% of people with Parkinson's, and constipation, loss of smell and sleep problems have been shown to often be the first symptoms of Parkinson's, sometimes presenting 10-20 years before the classic motor signs of stiffness, slowness and tremor (5, 6). Having 2 or more out of the following symptoms- constipation, loss of smell, excessive daytime sleepiness, and/or reduced cognitive function- has been shown to increase one's risk of developing Parkinson's by ten-fold (6). In other words, you're x10 more likely to go on to develop Parkinson's (rigidity, tremor, and slowness of movement) if you're already living with these non-motor symptoms.
We don't want to cause alarm with these facts, but rather bring awareness to the fact that Parkinson's is more than just a brain disorder: it affects the entire body. And that the current treatment and diagnosis of Parkinson's, based on movement dysfunction which only occurs when those parts of the brain have already been damaged by 60-70%, may mean that there's whole populations of people who are being treated and diagnosed far too late.
Alpha-synucleins and Parkinson's disease:
Alpha-synuclein proteins are a hallmark sign of Parkinson’s disease. These are unhealthy clumps of proteins that cause damage to parts of the brain such as the substantia nigra, the deep part of the brain which controls movement. However, what many people don't know, is that alpha-synuclein proteins have been shown to be present in the gut sometimes up to 20 years already (7).
While it's still not fully understood what causes these proteins to begin to clump together in an unhealthy manner, it's generally believed that inhaling or swallowing unhealthy particles kickstarts an inflammation process, that, in some people, becomes chronic. Pesticides is a common example that's been identified as a risk factor for Parkinson's (8).
Alongside this increase in gut dysfunction, there's also a breakdown of the mucosal barrier, which is our first line of defence in the gut, and an increase in 'intestinal permeability' (sometimes referred to as 'leaky gut'). This allows toxins such as alpha-synucleinopathies to then travel from the gut to the brain via the gut-brain axis. The vagus nerve is believed to be one of the main pathways by which these toxins travel from the gut to the brain (1, 2, 6, 7).
The gut microbiome:
The human body consists of approximately 50% human cells and 50% bacterial cells, that predominantly live within our gut as the gut microbiome, but also live on our skin, in our mouth, and in other orifices (9). When all is working well, these bacteria live in harmony within us, and are critical for our health, helping to reduce inflammation, repair 'leaky gut', digest foods, and ensure our brain is functioning properly. In other words, the human body functions like an ecosystem. And, just like the environment, it can become unhealthy if it gets out of balance.
When our gut microbiome gets out of balance, it can significantly affect our brain, thanks to the bidirectional relationship between the gut and the brain known as the 'gut-brain axis'. For this reason, the gut microbiome has been linked with many conditions, including Parkinson’s, Alzheimer’s, IBS, IBD, depression, anxiety, autism spectrum disorder, and more (10-14).
Our gut microbiome also directly affects our dopamine. Firstly, certain kinds of gut bacteria can directly produce dopamine and serotonin in the gut (15). In fact, did you know that 50% of our dopamine and 90% of our serotonin is produced in the gut (15)? This is why the gut is often called our 'second brain'.
Our gut microbiome also produces compounds called short chain fatty acids (SCFAs for short) which regulate the health in our gut, but also fascinatingly in our brain (15). Our gut microbiome creates SCFAs when we eat lots of fibre. While it's true that humans can't digest fibre, our microbiome does digest fibre: it breaks down the fibres that we eat into these SCFAs. These SCFAs have far-reaching positive effects for our health, regulating our inflammation and our immune system, helping prevent 'leaky gut', and even demonstrating positive neuroprotective effects for brain dopamine levels (15, 16). This is why eating a diet high in fibre is critical for the long-term health of both our gut and our brain.
So what about light therapy?
Research has shown that light therapy, using a specific super-pulsed infrared 904 nm laser x3/wk at home, may help improve both motor and non-motor symptoms of Parkinson's disease, including walking, balance, mobility, cognition, and sense of smell (17-20). It's also been shown to positively affect the gut microbiome in people with Parkinson's disease (21)!
These studies used small sample sizes, so larger studies are still needed, however the results are promising, demonstrating improvements at 12 week follow-up, that, in some participants, continued to improve at 3 and 5 years follow-up (19-20). The exact symptom and the degree of improvement varied considerably from person to person, but for many, they maintained their improvements from a pre-treatment level (17-20). For a neurodegenerative condition such as Parkinson's, where people are predicted to steadily decline, these research findings are very promising!
While we cannot yet say that light therapy is a cure for Parkinson's, it may be that using a super-pulsed 904 nm laser on the gut can positively reduce some peoples' Parkinson's symptoms (17-20). Rigorous studies using larger sample sizes and including more detailed stool analyses are now being conducted, to further help elucidate in what ways light therapy may be helping with this chronic condition. Subscribe to our newsletter or reach out to our Customer Care team at info@symbyxbiome.com for the latest research info!
References:
1) Zhang, X., Tang, B. & Guo, J. Parkinson’s disease and gut microbiota: from clinical to mechanistic and therapeutic studies. Transl Neurodegener 12, 59 (2023). https://doi.org/10.1186/s40035-023-00392-8
2) Chan DG, Ventura K, Villeneuve A, Du Bois P, Holahan MR. Exploring the Connection Between the Gut Microbiome and Parkinson's Disease Symptom Progression and Pathology: Implications for Supplementary Treatment Options. J Parkinsons Dis. 2022;12(8):2339-2352. doi: 10.3233/JPD-223461.
3) Menozzi, E., Schapira, A.H.V. The Gut Microbiota in Parkinson Disease: Interactions with Drugs and Potential for Therapeutic Applications. CNS Drugs 38, 315–331 (2024). https://doi.org/10.1007/s40263-024-01073-4
4) Wood SA, Hains PG, Muller A, Hill M, Premarathne S, Murtaza M, Robinson PJ, Mellick GD, Sykes AM. Proteomic profiling of idiopathic Parkinson's disease primary patient cells by SWATH-MS. Proteomics Clin Appl. 2022 Sep;16(5):e2200015. doi: 10.1002/prca.202200015.
5) Pedrosa Carrasco, A.J., Timmermann, L. & Pedrosa, D.J. Management of constipation in patients with Parkinson’s disease. npj Parkinson's Disease 4, 6 (2018). https://doi.org/10.1038/s41531-018-0042-8
6) Roos DS, Klein M, Deeg DJH, Doty RL, Berendse HW. Prevalence of Prodromal Symptoms of Parkinson's Disease in the Late Middle-Aged Population. J Parkinsons Dis. 2022;12(3):967-974. doi: 10.3233/JPD-213007.
7) Chen, M.; Mor, D.E. Gut-to-Brain α-Synuclein Transmission in Parkinson’s Disease: Evidence for Prion-like Mechanisms. Int. J. Mol. Sci. 2023, 24, 7205. https://doi.org/10.3390/ijms24087205
8) van der Mark M, Brouwer M, Kromhout H, Nijssen P, Huss A, Vermeulen R. Is pesticide use related to Parkinson disease? Some clues to heterogeneity in study results. Environ Health Perspect. 2012 Mar;120(3):340-7. doi: 10.1289/ehp.1103881.
9) Sender R, Fuchs S, Milo R. Revised Estimates for the Number of Human and Bacteria Cells in the Body. PLoS Biol. 2016 Aug 19;14(8):e1002533. doi: 10.1371/journal.pbio.1002533.
10) Bicknell, B.; Liebert, A.; Borody, T.; Herkes, G.; McLachlan, C.; Kiat, H. Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome. Int. J. Mol. Sci. 2023, 24, 9577. https://doi.org/10.3390/ijms24119577
11) Wang L, Alammar N, Singh R, Nanavati J, Song Y, Chaudhary R, Mullin GE. Gut Microbial Dysbiosis in the Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis of Case-Control Studies. J Acad Nutr Diet. 2020 Apr;120(4):565-586. doi: 10.1016/j.jand.2019.05.015.
12) Santana PT, Rosas SLB, Ribeiro BE, Marinho Y, de Souza HSP. Dysbiosis in Inflammatory Bowel Disease: Pathogenic Role and Potential Therapeutic Targets. Int J Mol Sci. 2022 Mar 23;23(7):3464. doi: 10.3390/ijms23073464.
13) Clapp M, Aurora N, Herrera L, Bhatia M, Wilen E, Wakefield S. Gut microbiota's effect on mental health: The gut-brain axis. Clin Pract. 2017 Sep 15;7(4):987. doi: 10.4081/cp.2017.987.
14) Almeida C, Oliveira R, Soares R, Barata P. Influence of gut microbiota dysbiosis on brain function: a systematic review. Porto Biomed J. 2020 Mar 17;5(2):1-8. doi: 10.1097/j.pbj.0000000000000059.
15) Chen Y, Xu J, Chen Y. Regulation of Neurotransmitters by the Gut Microbiota and Effects on Cognition in Neurological Disorders. Nutrients. 2021 Jun 19;13(6):2099. doi: 10.3390/nu13062099.
16) Elford JD, Becht N, Garssen J et al. Buty and the beast: the complex role of butyrate in Parkinson's disease. Frontiers. 2024 April 15.
17) Liebert, A., Bicknell, B., Laakso, EL. et al. Improvements in clinical signs of Parkinson’s disease using photobiomodulation: a prospective proof-of-concept study. BMC Neurol 21, 256 (2021). https://doi.org/10.1186/s12883-021-02248-y
18) Liebert A, Bicknell B, Laakso EL, Jalilitabaei P, Tilley S, Kiat H, Mitrofanis J. Remote Photobiomodulation Treatment for the Clinical Signs of Parkinson's Disease: A Case Series Conducted During COVID-19. Photobiomodul Photomed Laser Surg. 2022 Feb;40(2):112-122. doi: 10.1089/photob.2021.0056
19) Liebert, A., Bicknell, B., Laakso, E., Tilley, S., Pang, V., Heller, G., Mitrofanis, J., Herkes, G., & Kiat, H. (2023). Improvements in the clinical signs of Parkinson’s disease using photobiomodulation: a 3-year follow-up case series. Medical Research Archives, 11(3). doi:10.18103/mra.v11i3.3690
20) https://fightingparkinsons.org.au/news/latest-news/update-on-light-therapy-study/
21) Bicknell, B.; Liebert, A.; McLachlan, C.S.; Kiat, H. Microbiome Changes in Humans with Parkinson’s Disease after Photobiomodulation Therapy: A Retrospective Study. J. Pers. Med. 2022, 12, 49. https://doi.org/10.3390/jpm12010049
