Gut Health in Parkinson’s

The human body contains trillions of bacteria, viruses, and fungi. These living things are called microorganisms, or microbes for short, and they can have a large impact on your health. While some of these microbes can be associated with disease, others are extremely beneficial and crucial to maintaining a healthy immune system and overall well-being. Altogether, the microbes contained in your body may weigh between 2 to 5 pounds – roughly the same weight as the brain (Robertson, 2017).

A community of microbes contained in any specific part of the body is called a microbiome. The gut microbiome contains the majority of your body’s microbes, residing in your large intestine in a pocket called the cecum. Although there are many different types of microbes, the most widely studied are bacteria, with over 1000 different species of bacteria residing in the gut alone (Robertson, 2017). Each species plays a large role in many aspects of health, such as the immune system, digestion and absorption of nutrients, weight, cognition, and heart health. Thus, an imbalance of bacteria in your gut, or a lack of healthy microbes in your system, can contribute to issues like weight gain, poor digestion, high blood sugar, and high cholesterol (Robertson, 2017).

A growing body of research is also exploring the link between gut imbalances to neurodegenerative disorders, like Parkinson’s disease (PD) (Silva et al., 2020).

Gut-Brain Communication

Over the last several decades, the link between gut and brain health has become more apparent. Sensations like butterflies in your stomach and “gut feelings” are indications that the gut and brain communicate with each other – this two-way connection is called the gut-brain axis. Experts believe these two organs are closely connected via neurons throughout the nervous system. Neurons are messenger cells that send signals to different areas of your body, including the gut and brain; in fact, the gut alone contains 500 million neurons (Robertson, 2017). Neurons connect the brain and gut through the central nervous system along the vagus nerve, one of the longest cranial nerves in the body.

The digestive system also has its own nervous system, called the enteric nervous system (ENS). The ENS is comprised of millions of nerve cells within the gut that communicate with the sympathetic and parasympathetic nervous systems, but also function independently. Due to this strong connection between the brain and the gut, stress and other negative emotions can affect digestion and gut health, which can then lend to more distress in the brain, ultimately creating an adverse cycle (Dossett, 2019).

Neurotransmitters play an important role in the gut-brain axis. These chemical messengers send signals from one neuron to another, and play a role in maintaining bodily functions, mood, and cognition. A large portion of serotonin – also called the ‘happiness hormone’ – is produced by gut microbes, as is a neurotransmitter called gamma-aminobutyric acid (GABA), which can reduce feelings of anxiety and depression (Robertson, 2017). Gut microbes also produce other molecules that affect the brain, such as short-chain fatty acids (SCFAs). SCFAs play a role in our brains by maintaining the blood-brain barrier (a protective barrier between blood vessels and other tissues in the brain), reducing appetite, and controlling neuroinflammation. These molecules have been found in lower concentrations within the guts of people with PD, implicating SCFAs in brain health and neurodegenerative disorders (Guglielmi, 2019).

The gut and brain also communicate through the immune system. Immune cells in your gut regulate how your body responds to illness and injury, while gut microbes control what is passed through the body and excreted. When the immune system is activated for too long, it can lead to inflammation and a breakdown of the gut barrier, allowing harmful toxins that are associated with brain disorders to pass into the blood (Robertson, 2017).

Gut Health and Parkinson’s Disease

In 1817, English surgeon James Parkinson reported that people with PD experienced constipation – this is the earliest evidence that imbalances in the gut play a role in Parkinson’s (Kwon, 2018). This link has been further established in recent years, with inflammation, irritable bowel syndrome, leaky gut, and altered gut microbiota reported in PD patients years before the onset of motor symptoms (Douglas, 2020).

In Parkinson’s, a protein called alpha-synuclein misfolds to form Lewy bodies in the brain, which are clumps of protein that disrupt brain function. Certain research suggests that alpha-synuclein originates in the gut and travels to the brain, and that an increase in intestinal alpha-synuclein can be linked to changes in the gut microbiome, leading to inflammation and gut permeability (Douglas, 2020). People with PD often also have distinct fecal microbiomes when compared with healthy members of their household who share the same diet (Douglas, 2020). The balance of gut flora has also been found to influence the types of pain that people with PD experience (Rajoka et al., 2017).

While more research is necessary to explore these links further, it is believed that the cognitive changes associated with neurodegenerative disorders such as PD may be preceded by, or occur in conjunction with, gastrointestinal disorders. Due to this key role of the gut-brain axis, managing intestinal health may help in both controlling various symptoms and pain associated with PD, and in decreasing the risk of developing PD and other neurodegenerative diseases altogether (Douglas, 2020).

Maintaining your Gut Microbiome

As your microbiome plays such a large role in health and disease prevention, it is beneficial to consider ways you may improve and maintain the balance of bacteria in your gut. Diet is a key way to promote a healthy composition of microbes. For example, individuals who consume high-fiber, low-fat diets are found to have lower levels of disease-causing bacteria and larger amounts of beneficial microbes (Rajoka et al., 2017).

In addition to eating a balanced diet, maintaining good sleep, exercising regularly, and practicing self-care may also help maintain a healthy gut microbiome. Studies suggest that irregular sleeping patterns can negatively impact the balance of gut bacteria, potentially leading to inflammatory diseases – try sticking to a regular sleep schedule with at least eight hours a night (Voigt et. al, 2014). As your gut can also be affected by stress, self-care outlets such as meditation, mindfulness, or journaling, along with physical activity like walking or yoga, can help lower stress levels, optimize gut health, and ultimately prevent disease.

Nutrition Tips for a Healthy Gut

• Include a diverse array of high-fiber fruits and vegetables in your diet – especially leafy green vegetables, as the fiber in these foods strengthen good bacteria.
• Limit simple sugars and artificial sweeteners – they often spike blood sugar levels and can be harmful to good bacteria.
• Try eating a more plant-based diet – vegetarians have been found to have healthier microbiomes containing fewer disease-causing bacteria.
• Eat pre and probiotic-rich foods, such as whole grains, apples, onions, garlic, beans and lentils, bananas, and fermented foods like yogurt, kefir, and kimchi.
• Foods rich in polyphenols, a plant compound with many health benefits, can help alter gut flora to reduce inflammation. Polyphenol-rich foods include red wine, dark chocolate, green tea, almonds, and blueberries.
• Consider taking a probiotic supplement, but be sure to check with your doctor as there are many different strains of bacteria and it is important to find the right type for you.

Sources

Dossett, M. (2019). Brain-gut connection explains why integrative treatments can help relieve digestive ailments. Retrieved from https://bit.ly/2MGtBB3

Douglas, Y. (2020). Gut Inflammation Linked to the Development of Parkinson Disease. Retrieved from https://bit.ly/3qaCAYL

Guglielmi, G. (2019). The role of short-chain fatty acids in the gut-brain axis. Retrieved from https://bit.ly/3q633qB

Kwon, D. (2018). Does Parkinson’s Begin in the Gut? Retrieved from https://www.scientificamerican.com/article/does-parkinsons-begin-in-the-gut

Rajoka, M. et al. (2017). Interaction between diet composition and gut microbiota and its impact on gastrointestinal tract health. Food Science and Human Wellness, 6(3), 121-130. Retrieved from https://doi.org/10.1016/j.fshw.2017.07.003

Robertson, R. (2016). 10 Ways to Improve Your Gut Bacteria, Based on Science. Retrieved from https:// www.healthline.com/nutrition/improve-gut-bacteria 

Robertson, R. (2017). Why the Gut Microbiome Is Crucial for Your Health. Retrieved from https://www.healthline.com/nutrition/gut-microbiome-and-health

Silva, Y., et al. (2020). The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Frontiers in Endocrinology, 11. Retrieved from https://doi.org/10.3389/fendo.2020.00025

Voigt, R., et al. (2014). Circadian Disorganization Alters Intestinal Microbiota. PLoS ONE, 9(5). Retrieved from https://doi.org/10.1371/journal.pone.0097500 

This content was published in the Spring 2021 edition of our quarterly magazine, Viewpoints. The content was accurate as of this publication date.