Can what we eat, breathe, and do for a living affect our Parkinson’s risk?

Introduction

Parkinson’s disease (PD) is the most prevalent movement disorder and the second most common neurodegenerative disorder worldwide. PD is best known for causing tremors and stiffness, but it’s much more than a movement disorder. It also affects mood and speech. While PD is caused by the loss of dopamine-producing neurons in the brain’s substantia nigra, new research suggests that its roots may extend far beyond the nervous system.

Surprisingly, the gut microbiome – trillions of bacteria living in our digestive tract – may play a key role in both the development and prevention of PD. These microbes help regulate inflammation and support brain health by influencing microglia, the brain’s immune cells. Diet also seems to matter: a Mediterranean-style diet rich in fruits, vegetables, and healthy fats appears to lower PD risk, while smoking – despite its well-known dangers – has been linked to a puzzling protective effect, possibly due to nicotine’s impact on the brain. Meanwhile, specific jobs, like farming, may increase PD risk due to pesticide exposure, which has been associated with neurodegeneration.

The idea that what we eat, breathe, and do for a living could shape our brain health is intriguing. As research continues to uncover these surprising links, it raises an important question: could simple lifestyle changes help protect against neurodegenerative diseases?

Gut-Brain Axis

The gut-brain axis (GBA) is a two-way communication network between the enteric nervous system of the gastrointestinal (GI) tract and the central nervous system, connecting emotions and cognition with the intestines’ functions. This involves the brain sending signals to the gut and vice versa, which happens through the vagus nerve, gut hormones and the gut microbiome, which can produce chemicals to impact brain activity. This usually explains why stress signals from the brain can influence the digestion of food, causing symptoms such as stomach pain, bloating or changes in bowel movements. Alternatively, signals travelling from the gut to the brain can be seen when we eat something that makes us feel sick – we naturally avoid that food and the place where we ate it. Gut dysbiosis can be triggered by multiple factors, including diet, antibiotic use, infection, inflammation, and chronic stress.

Dysbiosis is the imbalance in the composition and activity of the microbiota (microorganisms present in the gut). It is considered a risk factor for PD, but is not a direct cause of it. Changes in the microbiota can induce metabolic changes, which can result in increased local and systemic inflammation in addition to increased permeability of the intestines, making the gut ‘leaky’. Additionally, this can cause increased harmful gut bacteria (such as E. coli or Salmonella) as they leak through the intestinal lining, producing amyloid proteins which can travel to the brain and cause the accumulation of α-synuclein – a protein linked to neurodegenerative diseases such as PD. There is also a reduction in healthy gut bacteria – which usually produce short-chain fatty acids (SCFAs) such as butyrate – which reduce inflammation and protect the brain cells. Less SCFAs cause an increase in inflammation and loss of the neuroprotective effects of SCFAs. Increased inflammation can eventually cause the weakening of the gut lining and a cycle of worsening dysbiosis, increased inflammation and increased α-synuclein accumulation, which spreads to the brain. 

Furthermore, gut dysbiosis can decrease the efficacy of dopaminergic treatments, which may be used to treat PD. In gut dysbiosis, harmful bacteria can produce an enzyme called dopa-decarboxylase – which converts Levodopa (a drug used to treat PD) into dopamine within the intestines. Hence, less Levodopa reaches the bloodstream and the brain, where it primarily acts and is converted to dopamine. This results in less Levodopa being converted to dopamine within the brain, reducing the effectiveness of the treatment. Consequently, this leads to motor symptoms and impairments such as tremors, which is a characteristic symptom of PD.

Can food protect the brain?

Could your diet be influencing your brain health in ways you never imagined? Research suggests that what you eat might play a critical role in either protecting your brain from PD or increasing your risk.

People who follow a Mediterranean diet (MD) – rich in olive oil, fish, fruits, vegetables, whole grains, and nuts – may have up to a 25% lower risk of developing PD. Interestingly, this protective effect appears stronger in younger individuals and those in the early stages of PD. So.. what makes the MD so powerful?

• Gut microbiome boost: the MD promotes beneficial gut bacteria while reducing harmful microbes, supporting overall brain health.

  
  

• Anti-inflammatory effects: fibre from plant-based foods fuels the gut microbiome, leading to the production of SCFAs, which reduce inflammation and may slow PD

  progression.

  
  

• Mitochondrial protection: compounds in the MD, such as polyphenols in olive oil and omega-3 fatty acids in fish, help repair and protect mitochondria – the powerhouses of our cells. This helps prevent brain cell damage and maintain dopamine function.

  
  

• Neural growth & repair: walnuts and omega-3s may support neuronal growth and reduce protein clumping, a hallmark of PD.

On the other hand, a Western diet – high in processed foods, saturated fats, refined sugars, and excess salt – may increase the risk of developing and worsening PD symptoms. Foods commonly associated with faster PD progression include canned fruits and vegetables, soda, fried foods, beef, ice cream, and cheese. Why does this happen?

• Microbiome disruption: the Western diet fosters an imbalance in gut bacteria, leading to inflammation and potential brain damage.

  
  

• Gut leakiness and neuroinflammation: a diet high in unhealthy fats and low in fibre can damage the gut lining, allowing harmful substances to enter the bloodstream and trigger brain inflammation.

  
  

• Hormonal imbalance: key gut-derived hormones (GLP-1, GIP, and IGN) that help protect neurons are disrupted by poor diet but can be restored through healthier food choices.

While diet alone cannot cure PD, growing evidence suggests it can modify the disease course. A diet rich in fibre, healthy fats, and plant-based foods supports gut health, reduces inflammation, and may protect neurons from degeneration. Understanding these diet-microbiome-brain interactions could open new doors to PD prevention and treatment – proving once again that food truly is medicine.

The smoking paradox

One of the most intriguing findings in PD research is that smokers appear to have a lower risk of developing the disease. Epidemiological studies consistently show that people who smoke are less likely to be diagnosed with PD compared to non-smokers. But why?

Scientists believe that nicotine, a key compound in tobacco, may play a neuroprotective role by affecting dopamine-producing neurons – the same cells that are progressively lost in PD disease. Nicotine interacts with receptors in the brain that influence dopamine release, which could help protect these neurons from degeneration. However, clinical trials testing nicotine as a treatment for PD have not shown significant benefits, suggesting that other compounds in tobacco or alternative mechanisms might be involved.

Some researchers propose that additional chemicals in cigarette smoke, such as monoamine oxidase inhibitors, antioxidants, or even carbon monoxide at low levels, might contribute to this protective effect. Others suggest that genetic factors or lifestyle differences between smokers and non-smokers could also explain the association.

Despite this fascinating link, smoking is not a recommended strategy for preventing PD. The well-documented risks – including cancer, cardiovascular disease, and lung damage – far outweigh any potential benefit. Instead, scientists are investigating whether specific compounds found in tobacco could be harnessed for new treatments without the harmful effects of smoking itself.

What about my job? 

Can your job affect your risk of developing PD? Some studies suggest that certain occupations – like farming – might increase the risk, while others find no clear connection. So, what’s the truth? Let’s break it down. 

Some research suggests that farmers are more likely to develop PD, possibly due to exposure to pesticides like paraquat and rotenone, which have been linked to brain cell damage. Additionally, heavy metals found in agricultural environments – such as lead and manganese – may contribute to brain inflammation and oxidative stress, both of which play a role in PD. Furthermore, certain metals, including iron, mercury, copper, and manganese, can build up in the brain over time. Scientists believe that long-term exposure could damage the neurons that produce dopamine. However, the exact link isn’t fully understood, and not everyone exposed to these metals develops PD.

That said, not all studies agree. Some large-scale research has found no significant link between farming, pesticide exposure, heavy metals and PD risk. This means that while environmental factors might play a role, other things – like genetics, lifestyle, or how long and intensely someone is exposed – could be just as important.

So.. should you worry? If you work in farming or are regularly exposed to pesticides and heavy metals, it might be a good idea to take precautions, like using protective equipment and following safety guidelines. However, more research is needed to fully understand how these exposures contribute to PD. For now, staying informed and taking steps to reduce unnecessary exposure to harmful chemicals is a smart approach.

What can you do?

While there’s no guaranteed way to prevent PD, research suggests that certain lifestyle choices may help reduce the risk. Here are some science-backed steps you can take:

1. Adopt a Mediterranean-style diet: eating a diet rich in whole, plant-based foods, healthy fats (like olive oil and nuts), and lean proteins has been linked to a lower risk of PD. The Mediterranean diet is packed with antioxidants and anti-inflammatory compounds that may help protect brain cells.

2. Stay active: regular exercise isn’t just good for your muscles and heart – it may also help maintain gut health and protect neurons. Activities like walking, swimming, or strength training have been associated with a reduced risk of PD and other neurodegenerative diseases.

3. Limit pesticide exposure: for those in agricultural or industrial settings, protective measures, such as wearing gloves and masks and following safety guidelines, can help reduce exposure to potentially harmful chemicals linked to PD.

4. Monitor gut health: emerging research suggests that the gut microbiome may play a key role in PD. While scientists are still exploring microbiome-targeted therapies, maintaining good gut health by eating fibre-rich foods, fermented foods (like yogurt and kimchi), and staying hydrated may support overall well-being.

Conclusion

The connection between diet, gut health, lifestyle, and PD is an exciting area of research. While we don’t yet have all the answers, it’s clear that healthy habits – such as eating well, staying active, and minimising harmful exposures – can support both brain and overall health. As science continues to uncover new insights, making informed choices today can help protect your well-being in the long run!

Written by Joecelyn Kirani Tan, Hanin Salem, Devikka Sivashanmuganathan & Barayturk Aydin

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