written by Stacey Nash

Parkinson’s disease (PD) is a chronic neurodegenerative disorder with no known cause or cure (Parkinson’s UK, 2020). Symptoms, resulting from dopamine depletion in the brain, are progressive and include rigidity, tremors, slow movement impaired balance and coordination, speech difficulties, dysphagia, poor dexterity, dementia and loss of taste or smell (Green, 2019). In 2020, ~145,000 people were living with PD, with an expected increase to ~172,000 by 2030 (Parkinson’s UK, 2020).

Evidence suggests that nutritional risk factors in the pathogenesis or progression of PD include saturated fatty acids (SAFA), pesticides, dysbiosis of gut bacteria, dairy products and the ‘Western diet’.

• SAFA can contribute to oxidative stress, which destroys dopamine-containing neurons, and increase production of proinflammatory cytokines causing inflammation; whereas mono-unsaturated fatty acids (MUFA) have been found to be neuroprotective (Boulos et al., 2019).
• Evidence suggests that pesticides used in food industry may be an environmental risk of PD; possibly as they reduce the antioxidant effects of micronutrients in fruit and vegetables (Boulos et al., 2019; Shermon et al., 2021).
• Individuals with PD have ‘significantly altered intestinal microbiota compositions’ compared with healthy controls (López-Taboada, González-Pardo and Conejo, 2020). Dysbiosis, an imbalance of gut bacteria composition, is a possible mechanism for PD pathology due to an association between the gut-brain axis and neuroinflammation; hence increasing fibre intake, the food source of our gut bacteria, can be beneficial to individuals with PD (Boulos et al., 2019). Furthermore, dysbiosis reduces short-chain fatty acid (SCFA) production, which has been shown to exacerbate PD progression with mechanisms of dysregulated intestinal barrier function, insulin resistance and mitochondrial dysfunction (Jackson et al., 2019).
• Studies have shown that dairy products, particularly low-fat dairy, increases PD risk; possible mechanisms include pesticides, lowering uric acid levels or altering gut microbiome (Chen et al., 2005; Reichmann et al., 2022). However, there is not enough significant evidence to advise individuals to avoid dairy products (López-Taboada, González-Pardo and Conejo, 2020).
• The ‘Western’ diet is associated with high intake of red meat, processed foods, saturated fat and refined carbohydrates with links to neurodegeneration (López-Taboada, González-Pardo and Conejo, 2020).

Overall, the evidence regarding nutritional risks in PD is conflicting as individuals are affected differently and possible causes of PD are multifactorial; including hormones, genetics and environmental (Boulos et al., 2019). More research is required in this area; however, this is difficult as PD usually presents when ~80% dopamine is depleted, thus, research is limited during early onset of the disease, known as prodromal phase (Schrag et al., 2023). However, evidence suggests that a Mediterranean dietary pattern (Harvard School of Public Health, 2018), rather than a Western diet, is neuroprotective and can slow PD development or progression (López-Taboada, González-Pardo and Conejo, 2020). Ultimately, a balanced, high fibre diet that increases levels of SCFA and maintains a diverse gut microbiota can be neuroprotective, with evidence showing that restrictive diets, such as ketogenic and protein-restrictive diets can have a detrimental effect on motor function and exacerbate PD symptoms and progression (Chu et al., 2021).

Reference List

• Boulos, C. et al. (2019) ‘Nutritional Risk Factors, Microbiota and Parkinson’s Disease: What Is the Current Evidence?’, Nutrients, 11(8), p. 1896. Available at: https://doi.org/10.3390/nu11081896.
• Chen, H. et al. (2005) ‘Physical activity and the risk of Parkinson disease’, Neurology, 64(4), pp. 664–669. Available at: https://doi.org/10.1212/01.wnl.0000151960.28687.93.
• Chu, C.-Q. et al. (2021) ‘Dietary patterns affect Parkinson’s disease via the microbiota-gut-brain axis’, Trends in Food Science & Technology, 116, pp. 90–101. Available at: https://doi.org/10.1016/j.tifs.2021.07.004.
• Green, K. (2019) ‘7.6 Neurological disease’ in Gandy, J. (ed.) Manual of Dietetic Practice. 6th edition. Chichester: John Wiley and Sons Ltd., pp. 554-560.
• Harvard School of Public Health (2018) Diet Review: Mediterranean Diet, The Nutrition Source. Available at: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/mediterranean-diet/ (Accessed: 10 July 2023).
• Jackson, A. et al. (2019) ‘Diet in Parkinson’s Disease: Critical Role for the Microbiome’, Frontiers in Neurology, 10. Available at: https://doi.org/10.3389/fneur.2019.01245.
• López-Taboada, I., González-Pardo, H. and Conejo, N.M. (2020) ‘Western Diet: Implications for Brain Function and Behavior’, Frontiers in Psychology, 11. Available at: https://doi.org/10.3389/fpsyg.2020.564413.
• Parkinson’s UK (2020) Reporting on Parkinson’s: information for journalists. Available at: https://www.parkinsons.org.uk/about-us/reporting-parkinsons-information-journalists (Accessed: 10 July 2023).
• Reichmann, H. et al. (2022) ‘Life style and Parkinson’s disease’, Journal of Neural Transmission, 129(9), pp. 1235–1245. Available at: https://doi.org/10.1007/s00702-022-02509-1.
• Schrag, A. et al. (2023) ‘Widening the Spectrum of Risk Factors, Comorbidities, and Prodromal Features of Parkinson Disease’, JAMA Neurology, 80(2), pp. 161–171. Available at: https://doi.org/10.1001/jamaneurol.2022.3902.
• Shermon, S. et al. (2021) ‘Effect of modifiable risk factors in Parkinson’s disease: A case-control study looking at common dietary factors, toxicants, and anti-inflammatory medications’, Chronic Illness, p. 174239532110397. Available at: https://doi.org/10.1177/17423953211039789.