Parkinson’s disease (PD) is the second most common neurodegenerative disorder in the aging population. Environmental factors are believed to be important in the etiology of PD, and a handful of studies suggest that diet may be such a factor. Recent epidemiological studies have shown the association between certain food groups and the risk of developing PD. Also, some foods may affect drug absorption, thereby interfering with medication effect. There is as yet no specific diet recommendation for PD. However, a healthy and balanced diet can improve general health and well-being, which may improve overall motor and non-motor functions as well. We have asked Dr. Xiang Gao and Dr. Maria Stamelou to discuss the key points on this topic in view of recent research advances.
Is there any type of food that could decrease or increase the risk of PD?
Dr. Xiang Gao
Several dietary components have been identified to be associated with PD risk, as detailed below.
Overall diet quality: In 2007, we published the first study to examine whether overall quality of the diet or dietary patterns (combination of different foods and drinks in diets) were associated with altered PD risk among 49,692 men and 81,676 women. During 16 years of follow-up, we found that dietary patterns with a high intake of fruit, vegetables, legumes, whole grains, nuts, fish, and poultry and a low intake of saturated fat and moderate intake of alcohol may protect against PD (1).
Individual food components: When individual food components have been further investigated, greater computation of caffeine and coffee have been consistently found to be associated with lower PD risk in men. However, mixed results have been generated for women. Tea is another major contributor for caffeine. However, few studies have investigated the association between tea and PD risk and the relationship remains unclear to date (2, 3).
Because PD patients generally experience oxidative stress. Several studies have examined dietary antioxidants, such as vitamin E, vitamin C, and carotenoids, and PD risk. There is not clear evidence to support the protective effects of these dietary components on PD risk. In contrast, we found that dietary flavonoids, particularly anthocyanins, were inversely associated with PD risk. Consistently, consumption of anthocyanin-rich foods (e.g. berry fruits), was also associated with lower PD risk (4, 5).
Interestingly, greater consumption of dairy foods (e.g. milk) has been found to be associated with higher risk of PD. This was observed in all dairy foods, including low-fat milk. The underlying mechanisms remain unclear (6).
Could diet/nutritional modifications be a strategy to prevent the progression of PD and why?
Dr. Maria Stamelou
The most important goal in PD research currently is to develop neuroprotective treatments. Modifying environmental factors that may have a role on the pathophysiology of the disease, in particular in its very early stages, is a very appealing way to approach neuroprotection. Of those, diet and nutritional modifications are surely of high interest because they may be easily modifiable and do also offer substantial benefits for overall health. Current evidence regarding the influence of dietary factors in preventing PD or PD progression is relatively limited, and mostly inconsistent. However, it is a promising area of research that we should certainly pay more attention to.
We now have a clearer idea of how ‘what we eat’ can be linked to neurodegeneration. The human gastrointestinal microbiome has emerged as an important link in the pathogenesis of neurodegenerative diseases through a bidirectional interaction between the gut microbiota and the central nervous system, the ‘microbiota–gut–brain axis’. Thus, the effect of various dietary habits may be mediated through this axis to cause neurodegeneration (7). For example, the reduced risk of developing PD in smokers and in coffee consumers has been suggested as the result of their altering the composition of the microbiota which could lead to reduction of intestinal inflammation, and subsequently of α-synuclein misfolding and deposition. Furthermore, coffee, tea and red wine have been associated with increased gut microbiota diversity, supporting that lifestyle modification may influence PD risk (8, 9).
One of the specific diets that have received most attention is the Mediterranean diet, which is characterized by high intake of plant foods (vegetables, fruits, legumes, and whole grains), low‐to‐moderate intake of fish and wine, and other components (e.g. phenolics, fibers), that exert antioxidant and anti‐inflammatory effects. These elements have been associated with favourable gut microbiota characteristics. Several studies have reported that adherence to this diet may decrease risk of cardiovascular diseases, Alzheimer’s dementia, and cancers (10). Recently, there have been suggestions that the Mediterranean diet may be associated also with reduced risk for PD (11). Very recently, we showed in a population‐based study of 1,731 healthy participants, that adherence to the Mediterranean diet is associated with lower probability of prodromal PD, as defined by the International Parkinson and Movement Disorder Society prodromal PD criteria, with all limitations that such an epidemiological study bears (12).
However, these data are preliminary. We need more studies in particular further prospective studies, before we can establish an association between diet and nutritional modifications to prevention of PD.
What would you recommend for general management of nutrition and diet for PD patients?
Dr. Maria Stamelou
I would first pay attention to the importance of nutrition and diet in every day management of the disease, its symptoms and the impact on medication intake and absorption. Indeed, currently, general recommendations for management of nutrition and diet in PD patients are focused mainly on these aspects. For example, the importance of avoiding a protein meal when taking levodopa or how to dine during the day when the patient has to take levodopa every three hours etc. Second, it is important to approach diet based on the specific symptoms of each patient, to ease for example constipation, swallowing problems, orthostatic hypotension etc. These practical aspects are in the frontline of designing the right diet for a given PD patient for the time being and are to some extent also individualized.
Beyond that, for now, we cannot claim that we have the right diet to prevent progression of PD. However, we may not have proof that the Mediterranean diet prevents or stops PD, but it is evidently one of the healthiest diets available, and in contrast to other diets, it is easy to keep, the ingredients are easily accessible worldwide and is also affordable, i.e. it has the potential of being applied widely. Therefore, I would recommend keeping a healthy diet that generally reduces the risk of cardiovascular diseases as well as exercising and avoid weight gain, until we have further and solid evidence for more specific recommendations.
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12. Maraki MI, Yannakoulia M, Stamelou M, Stefanis L, Xiromerisiou G, Kosmidis MH, et al. Mediterranean diet adherence is related to reduced probability of prodromal Parkinson's disease. Mov Disord. 2019;34(1):48-57.