Parkinson’s disease (PD) is a chronic neurodegenerative disorder with no known cause or cure (Parkinson’s UK, 2020). It is thought that a combination of genetic and environmental factors contributes to the aetiology; including dysbiosis, exposure to toxins and intestinal permeability (Lister, 2020). What we do know is that PD progresses by cell damage to an area of the brain, the substantia nigra, which produces dopamine: a neurotransmitter helping to control movement and coordination (Green, 2019). Of over 40 symptoms, which affect everyone differently, the main symptoms are rigidity, tremors, slow movement and impaired balance and coordination (Green, 2019; Parkinson’s UK, 2020). Other motor symptoms include lack of facial expressions, speech difficulties, poor dexterity and non-motor symptoms including depression, fatigue, dementia and loss of taste or smell (Green, 2019). These symptoms only occur when ~80% dopamine production is lost, and they can have a detrimental impact on nutritional intake; either practically or psychologically. In 2020, an estimated 145,000 people were living with PD, with the majority aged 70-89; this is expected to rise to 172,000 by 2030 as the population ages (Parkinson’s UK, 2020).

Nutrition and Parkinson’s Disease

‘Nutrition is often an overlooked but important factor in the management’ of PD (Ó Breasail et al., 2021). PD can progress due to oxidative stress, therefore, antioxidants such as vitamins A, C, E and β-carotene can help reduce cell damage (Ó Breasail et al., 2021). Dietary patterns including a range of fruits and vegetables, such as the anti-inflammatory Mediterranean diet and the ‘Dietary Approaches to Stop Hypertension’ (DASH) diet have been found to be protective from PD and disease progression (Lister, 2020; Ó Breasail et al., 2021). A systematic review by Solch et al. (2022) found that the Mediterranean diet was associated with lower risk of PD with neuroprotective mechanisms, such as modulating the gut microbiota through provision of fibre as an energy substrate and subsequent short-chain fatty acid (SCFA) production. SCFAs such as acetate, butyrate and propionate, which maintain gut barrier health, were found to be lower in individuals with PD (Solch et al., 2022).

For more information about these dietary patterns, please see:

• Mediterranean Diet Review: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/mediterranean-diet/
• DASH Diet Review: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/dash-diet/

Other nutrients have been associated with PD. As PD is associated with inflammation, omega-three fatty acids from fish sources or flaxseeds may help to reduce this (Lister, 2020). Caffeine is an adenosine A2A receptor antagonist that facilitates dopamine receptor signalling; evidence suggests disease progression may be slowed by caffeine intake (Shook and Jackson, 2011). A new PD treatment, istradefylline, targets adenosine A2A receptors, reinforcing this evidence (Ó Breasail et al., 2021). Research shows that istradefylline is well tolerated and reduces the ‘wearing off’ episodes experienced with levodopa and carbidopa medications; known as the ‘on-off phenomenon’, which causes motor fluctuations (Cummins and Cates, 2022). Without polypharmacy drug interactions or hepatic impairments, a 20mg-40mg tablet of istradefylline is taken orally, once daily; although a limitation of this treatment is the cost at $63 per tablet (Cummins and Cates, 2022).

Vitamin D synthesis can be reduced by PD, which can lead to calcium deficiency and reduced bone density (Green, 2019). As falls are more likely to occur in PD due to coordination and mobility difficulties, fracture risk is high; especially hip fracture which is ‘associated with increased morbidity and mortality (Ó Breasail et al., 2021). To manage this risk, Green (2019) recommends a combination of dietary sources and daily supplementation of 1000-1500mg/day calcium and 10-20μg/day vitamin D. Dietary sources of vitamin D include oily fish, like sardines and mackerel, cod liver oil, fortified foods (BDA, 2019b). Dietary sources of calcium include dairy, soya, calcium-fortified products, sardines, wholemeal bread, broccoli and kale (BDA, 2021). Furthermore, individuals with PD are deficient in Coenzyme Q10, glutathione (an antioxidant in cruciferous vegetables, citrus and berries) and vitamin C (Lister, 2020). Glutathione and vitamin C can be obtained from following a diet pattern such as the Mediterranean Diet, however, Lister’s (2020) research suggests 300-1200mg/day Coenzyme Q10 may help motor symptoms, dexterity and has anti-inflammatory properties.

Parkinson’s Disease symptoms and malnutrition:

Constipation is common due to some individuals with PD having gastroparesis, low fibre intake due to difficulties chewing, reduced fluid intake and reduced mobility (Green, 2019). Barichella et al., (2017) highlight the importance of constipation management and evidence suggests that prebiotics and probiotics may improve constipation for those living with PD by increasing colonic transit time (Barichella et al., 2016; Lister, 2020); Lister (2020) suggests supplementation with 8×109 CFU live bacteria.

‘Malnutrition is prevalent in PD’ due to symptoms and medications adversely affecting nutritional intake (Ó Breasail et al., 2021). Individuals living with PD are more likely to lose 4.5kg in comparison to age-matched controls; although some do gain weight (Green, 2019). Loss of taste and smell can reduce the desire to eat and may lead to weight loss and malnutrition (Ó Breasail et al., 2021). Swallowing difficulties affect >80% of people with PD; therefore, assessment by a dietitian and speech and language therapist will be required to prevent malnutrition (Green, 2019). As a result, pneumonia is common as aspiration risk is high (Green, 2019). Loss of swallow function (dysphagia) or problems with manual dexterity can reduce intake, volume of intake and cause a change in diet to a texture-modified, puree diet for example; these factors can also contribute to weight loss and reduced nutrient intake (Ó Breasail et al., 2021).

First line dietary advice for malnutrition:

• 3 portions of high-quality protein foods each day (meat, fish, eggs, legumes, pulses, soya, tofu etc.).
• 2-3 dairy portions each day (cheese, milk, yoghurt).
• Include a starchy carbohydrate at each meal (potatoes, pasta, chapatti, rice etc.).
• Fruit and vegetables every day – including fresh, frozen, tinned, dried or juiced.
• 2 portions of oily fish per week (mackerel, salmon, sardines etc.).
• Hydration: aim for 6-8 glasses of fluids per day
• Nutrient-dense foods and snacks: increased calories with smaller portions sizes (for example, cheese and crackers, scones, custard, nuts, full-fat dairy)
• Nourishing drinks: hot chocolate, whole milk smoothies or milkshakes.

(BDA, 2019a)

Medication, such as levodopa can cause nausea, vomiting and constipation, further reducing the desire to eat (Ó Breasail et al., 2021). Large neutral amino acids, the building blocks of protein, compete with levodopa for intestinal absorption and crossing the blood-brain barrier; reducing the effects of the medication and results in increased symptoms (Green, 2019). Protein is an important macronutrient in the diet, so rather than reduce protein intake, it is advised to time the medication 45 minutes prior to a meal and take with a carbohydrate source, such as a cracker or biscuit, to reduce amino acid competition (Green, 2019).

Nutrition is an important factor in the management of PD, as well as ensuring that food remains enjoyable. Overall, there is not a specific diet for management of PD, however, following a healthy, balanced diet, maintaining hydration, physical activity and adequate sleep can help to alleviate some of the symptoms.

• Parkinson’s UK have a ‘Diet and Parkinson’s’ document with useful information and tips on healthy eating: https://www.parkinsons.org.uk/sites/default/files/2023-02/INFOB0007_Diet%20and%20Parkinsons_FINAL_WEB.pdf

***Before starting any supplements, it is advised that you discuss this intention with your GP or Parkinson’s team.

Reference List

• Barichella, M. et al. (2016) ‘Probiotics and prebiotic fiber for constipation associated with Parkinson disease’, Neurology, 87(12), pp. 1274–1280. Available at: https://doi.org/10.1212/wnl.0000000000003127.
• Barichella, M. et al. (2017) ‘Dietary habits and neurological features of Parkinson’s disease patients: Implications for practice’, Clinical Nutrition, 36(4), pp. 1054–1061. Available at: https://doi.org/10.1016/j.clnu.2016.06.020.
• BDA (2019a) Malnutrition. Available at: https://www.bda.uk.com/resource/malnutrition.html (Accessed: 27 June 2023).
• BDA (2019b) Vitamin D. Available at: https://www.bda.uk.com/resource/vitamin-d.html (Accessed: 26 June 2023).
• BDA (2021) Calcium. Available at: https://www.bda.uk.com/resource/calcium.html (Accessed: 26 June 2023).
• Cummins, L. and Cates, M.E. (2022) ‘Istradefylline: A novel agent in the treatment of “off” episodes associated with levodopa/carbidopa use in Parkinson disease’, Mental Health Clinician, 12(1), pp. 32–36. Available at: https://doi.org/10.9740/mhc.2022.01.032.
• 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 University (2018a) Diet Review: DASH. Available at: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/dash-diet/ (Accessed: 26 June 2023).
• Harvard University (2018b) Diet Review: Mediterranean Diet. Available at: https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/mediterranean-diet/ (Accessed: 26 June 2023).
• Lister, T. (2020) ‘Nutrition and Lifestyle Interventions for Managing Parkinson’s Disease: A Narrative Review’, Journal of Movement Disorders, 13(2), pp. 97–104. Available at: https://doi.org/10.14802/jmd.20006.
• Ó Breasail, M. et al. (2021) ‘Parkinson’s disease: the nutrition perspective’, Proceedings of the Nutrition Society, 81(1), pp. 12–26. Available at: https://doi.org/10.1017/s0029665121003645.
• 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: 26 June 2023).
• Parkinson’s UK (2023) Parkinson’s UK, Parkinsons.org.uk. Available at: https://www.parkinsons.org.uk/ (Accessed: 27 June 2023).
• Shook, B.C. and Jackson, P.F. (2011) ‘Adenosine A2A Receptor Antagonists and Parkinson’s Disease’, ACS Chemical Neuroscience, 2(10), pp. 555–567. Available at: https://doi.org/10.1021/cn2000537.
• Solch, R.J. et al. (2022) ‘Mediterranean diet adherence, gut microbiota, and Alzheimer’s or Parkinson’s disease risk: A systematic review’, Journal of the Neurological Sciences, 434, p. 120166. Available at: https://doi.org/10.1016/j.jns.2022.120166.