Effect of dietary vitamins C and E on the risk of Parkinson's disease: A meta-analysis

A comprehensive examination of the evidence for whole of diet patterns in Parkinson's disease: a scoping review

Both motor and non-motor symptoms of Parkinson's disease (PD), a progressive neurological condition, have broad-ranging impacts on nutritional intake and dietary behaviour. Historically studies focused on individual dietary components, but evidence demonstrating ameliorative outcomes with whole-of-diet patterns such as Mediterranean and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) is emerging. These diets provide plenty of antioxidant rich fruits, vegetables, nuts, wholegrains and healthy fats. Paradoxically, the ketogenic diet, high fat and very low carbohydrate, is also proving to be beneficial. Within the PD community, it is well advertised that nutritional intake is associated with disease progression and symptom severity but understandably, the messaging is inconsistent. With projected prevalence estimated to rise to 1.6 million by 2037, more data regarding the impact of whole-of-diet patterns is needed to develop diet-behaviour change programmes and provide clear advice for PD management. Objectives and Methods: Objectives of this scoping review of both peer-reviewed academic and grey literatures are to determine the current evidence-based consensus for best dietary practice in PD and to ascertain whether the grey literature aligns. Results and Discussion: The consensus from the academic literature was that a MeDi/MIND whole of diet pattern (fresh fruit, vegetables, wholegrains, omega-3 fish and olive oil) is the best practice for improving PD outcomes. Support for the KD is emerging, but further research is needed to determine long-term effects. Encouragingly, the grey literature mostly aligned but nutrition advice was rarely forefront. The importance of nutrition needs greater emphasis in the grey literature, with positive messaging on dietary approaches for management of day-to-day symptoms.

Vitamin C, vitamin E, β-carotene and risk of Parkinson's disease: a systematic review and dose-response meta-analysis of observational studies

OBJECTIVE

This study aimed to explore the relationship between the intake of vitamin C, vitamin E and β-carotene, and the risk of Parkinson's disease (PD).

METHODS

Web of Science, Embase, PubMed, Cochrane library, CNKI, and WanFang databases were searched from inception to 29 August 2022 for observational studies reporting the odds ratios (ORs) or relative risks (RRs) or hazard ratios (HRs) and 95% confidence intervals (CIs) of PD by Vitamin C/Vitamin E/β-carotene intake. Random-effects models, publication bias assessment, subgroup, sensitivity and dose-response analyses were performed, using.Stata version 12.0.

RESULTS

A total of 13 studies were included. There was no significant association between high-dose vitamin C intake and the risk of PD compared with low-dose vitamin C intake (RR = 0.98, 95%CI:0.89,1.08). Compared with low-dose intake, high-dose intake of vitamin E can prevent the risk of PD (RR = 0.87, 95%CI:0.77,0.99). Compared with lower β-carotene intake, there was a borderline non-significant correlation between higher intake and PD risk (RR = 0.91, 95%CI:0.82,1.01), and high dose β-carotene intake was found to be associated with a lower risk of PD in women (RR = 0.78, 95%CI:0.64,0.96).

CONCLUSION

This study shows that vitamin E intake can reduce the risk of PD and play a preventive role.

Dietary and Lifestyle Factors of Brain Iron Accumulation and Parkinson's Disease Risk

Purpose

Iron is an essential nutrient which can only be absorbed through an individual's diet. Excess iron accumulates in organs throughout the body including the brain. Iron dysregulation in the brain is commonly associated with neurodegenerative diseases like Alzheimer's disease and Parkinson's Disease (PD). Our previous research has shown that a pattern of iron accumulation in motor regions of the brain related to a genetic iron-storage disorder called hemochromatosis is associated with an increased risk of PD. To understand how diet and lifestyle factors relate to this brain endophenotype and risk of PD we analyzed the relationship between these measures, estimates of nutrient intake, and diet and lifestyle preference using data from UK Biobank.

Methods

Using distinct imaging and non-imaging samples (20,477 to 28,388 and 132,023 to 150,603 participants, respectively), we performed linear and logistic regression analyses using estimated dietary nutrient intake and food preferences to predict a) brain iron accumulation score (derived from T2-Weighted Magnetic Resonance Imaging) and b) PD risk. In addition, we performed a factor analysis of diet and lifestyle preferences to investigate if latent lifestyle factors explained significant associations. Finally, we performed an instrumental variable regression of our results related to iron accumulation and PD risk to identify if there were common dietary and lifestyle factors that were jointly associated with differences in brain iron accumulation and PD risk.

Results

We found multiple highly significant associations with measures of brain iron accumulation and preferences for alcohol (factor 7: t=4.02, pFDR=0.0003), exercise (factor 11: t=-4.31, pFDR=0.0001), and high-sugar foods (factor 2: t=-3.73, pFDR=0.0007). Preference for alcohol (factor 7: t=-5.83, pFDR<1×10-8), exercise (factor 11: t=-7.66, pFDR<1×10-13), and high sugar foods (factor 2: t=6.03, pFDR<1×10-8) were also associated with PD risk. Instrumental variable regression of individual preferences revealed a significant relationship in which dietary preferences associated with higher brain iron levels also appeared to be linked to a lower risk for PD (p=0.004). A similar relationship was observed for estimates of nutrient intake (p=0.0006). Voxel-wise analysis of i) high-sugar and ii) alcohol factors confirmed T2-weighted signal differences consistent with iron accumulation patterns in motor regions of the brain including the cerebellum and basal ganglia.

Conclusion

Dietary and lifestyle factors and preferences, especially those related to carbohydrates, alcohol, and exercise, are related to detectable differences in brain iron accumulation and alterations in risk of PD, suggesting a potential avenue for lifestyle interventions that could influence risk.

Dietary vitamin E intake and risk of Parkinson's disease: a cross-sectional study

Objective

Current evidence on the association between dietary vitamin E intake and the risk of Parkinson's disease (PD) is limited. The aim of the study was to explore the association of dietary vitamin E intake with PD in the United States among adults over 40 years.

Methods

We conducted a cross-sectional study with data collected from National Health and Nutrition Examination Survey (NHANES) from 2009 to 2018. A total of the sample of 13,340 participants were included. To identify the different characteristics of the participants, we utilized propensity score matching (PSM) to reduce the effects of selection bias and confounding variables. Weighted univariate and multivariable logistic regression were used to examine the association between dietary vitamin E intake and PD before and after matching. Then, restricted cubic spline (RCS) was used to visually describe the possible non-linear relationships. Finally, we employed the subgroup analysis to further investigate the relationship between dietary vitamin E intake and PD.

Results

According to the weighted univariate and multivariable logistic regression analysis, vitamin E intake was inversely associated with the risk of PD before and after matching. The results of RCS analysis revealed no non-linear inverse relationship between vitamin E intake and PD before and after matching. The subgroup analysis showed that age may influence the negative association between vitamin E and PD (P < 0.05 for interaction).

Conclusion

Among participants over 40 years of age, vitamin E intake was negatively associated with the risk of PD. Our data may support the supplementation of vitamin E to be used as an intervention strategy for the occurrence of PD.

Vitamin E - a scoping review for Nordic Nutrition Recommendations 2023

Current evidence suggests that dietary vitamin E (as α-tocopherol) intake has a beneficial role in preventing certain chronic diseases. In contrast, there is no clear evidence for the benefit of α-tocopherol supplements in a generally healthy population. Deficiency symptoms are rare and mainly occur due to genetic or other factors affecting α-tocopherol absorption and/or metabolism, rather than a low α-tocopherol intake. No qualified systematic review was identified by the NNR2023 project for updating the dietary reference values (DRV).

Disorders of Endogenous and Exogenous Antioxidants in Neurological Diseases

In diseases of the central nervous system, such as Alzheimer's disease (AD), Parkinson's disease (PD), stroke, amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and even epilepsy and migraine, oxidative stress load commonly surpasses endogenous antioxidative capacity. While oxidative processes have been robustly implicated in the pathogenesis of these diseases, the significance of particular antioxidants, both endogenous and especially exogenous, in maintaining redox homeostasis requires further research. Among endogenous antioxidants, enzymes such as catalase, superoxide dismutase, and glutathione peroxidase are central to disabling free radicals, thereby preventing oxidative damage to cellular lipids, proteins, and nucleic acids. Whether supplementation with endogenously occurring antioxidant compounds such as melatonin and glutathione carries any benefit, however, remains equivocal. Similarly, while the health benefits of certain exogenous antioxidants, including ascorbic acid (vitamin C), carotenoids, polyphenols, sulforaphanes, and anthocyanins are commonly touted, their clinical efficacy and effectiveness in particular neurological disease contexts need to be more robustly defined. Here, we review the current literature on the cellular mechanisms mitigating oxidative stress and comment on the possible benefit of the most common exogenous antioxidants in diseases such as AD, PD, ALS, HD, stroke, epilepsy, and migraine. We selected common neurological diseases of a basically neurodegenerative nature.

Bioinorganic Chemistry of Micronutrients Related to Alzheimer's and Parkinson's Diseases

Metal ions are fundamental to guarantee the regular physiological activity of the human organism. Similarly, vitamins play a key role in many biological functions of the metabolism, among which are coenzymes, redox mediators, and antioxidants. Due to their importance in the human organism, both metals and vitamins have been extensively studied for their involvement in neurodegenerative diseases (NDs). However, the full potential of the interaction between vitamins and metal ions has not been fully explored by researchers yet, and further investigation on this topic is needed. The aim of this review is to provide an overview of the scientific literature on the implications of vitamins and selected metal ions in two of the most common neurodegenerative diseases, Alzheimer's and Parkinson's disease. Furthermore, vitamin-metal ion interactions are discussed in detail focusing on their bioinorganic chemistry, with the perspective of arousing more interest in this fascinating bioinorganic field.

Regulation of gut microbiota by vitamin C, vitamin E and β-carotene

Vitamin C (VC), vitamin E (VE) and β-carotene (βC) are representative dietary antioxidants, which exist in daily diet and can increase the antioxidant capacity of body fluids, cells and tissues. The health benefits of vitamins like VC, VE and βC are widely demonstrated. Given that the strong associations between the gut microbiota and host health or a range of diseases has been extensively reported, it is important to explore the modulatory effects of known vitamins on the gut microbiota. Herein, this article reviews the effects of VC, VE and βC on the gut microbiota. Totally, 19 studies were included, of which eight were related to VC, nine to VE, and six to βC. Overall, VC, VE and βC can provide health benefits to the host by modulating the composition and metabolic activity of the gut microbiota, improving intestinal barrier function and maintaining the normal function of the immune system. Two perspectives are proposed for future studies: i) roles of known antioxidant activity of vitamins in regulating the gut microbiota and its molecular mechanism need to be further studied; ii) causal relationships between the regulatory effects of vitamins on gut microbiota and host health still remains to be further verified.

Could Vitamins Have a Positive Impact on the Treatment of Parkinson's Disease?

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder after Alzheimer's disease. Pathophysiologically, it is characterized by intracytoplasmic aggregates of α-synuclein protein in the Lewy body and loss of dopaminergic neurons from substantia nigra pars compacta and striatum regions of the brain. Although the exact mechanism of neurodegeneration is not fully elucidated, it has been reported that environmental toxins such as MPTP, rotenone, paraquat, and MPP⁺ induce oxidative stress, which is one of the causative factors for it. To date, there is no complete cure. However, the indispensable role of oxidative stress in mediating PD indicates that antioxidant therapy could be a possible therapeutic strategy against the disease. The deficiency of vitamins has been extensively co-related to PD. Dietary supplementation of vitamins with antioxidant, anti-inflammatory, anti-apoptotic, and free radical scavenging properties could be the potential neuroprotective therapeutic strategy. This review summarizes the studies that evaluated the role of vitamins (A, B, C, D, E, and K) in PD. It will guide future studies in understanding the potential therapeutic role of vitamins in disease pathophysiology and may provide a framework for designing treatment strategies against the disease.

An umbrella review of systematic reviews with meta-analysis on the role of vitamins in Parkinson's disease

INTRODUCTION

This umbrella review aimed to systematically review the available literature and assess the association of dietary intake or serum levels of different vitamins and the risk of PD, to help find out more efficient treatments for PD patients by replenishing the deficiency of vitamins.

METHODS

Pubmed/Medline, Scopus, Google Scholar and hand searching bibliographies of retrieved articles in duplicate, were used to detect all relevant meta-analyses investigating the relationship between vitamins and PD. After study selection, data were extracted from previously published meta-analyses and pooled by Review Manager version 5.4 and CMA software version 2.2.064 to achieve effect sizes. Level of statistical significance was set at P ≤ 0.05.

RESULTS

14 meta-analyses were included in the meta-review. Serum vitamin D and B12 levels were significantly lower in PD (SMD = -0.67 and SMD = -0.40 respectively). Homocysteine (Hcy) levels were significantly higher in PD patients (SMD = 1.26). Also the odds ratio for highest vs. lowest vitamin E intake was 0.73 which was significant. However, there was no significant difference between vitamin A, C and B6 intake or serum levels in PD vs. control groups.

CONCLUSION

Serum vitamin D and B12 levels were significantly lower in PD in comparison to healthy individuals, while Hcy level was significantly higher in PD patients. Also higher vitamin E intake was associated with significantly lower risk of development of PD in comparison to lower vitamin E intake. However, there was no significant difference between risk of PD and higher vitamin A, C and B6 intake or serum levels of folate.

The microbiome-gut-brain axis in Parkinson disease - from basic research to the clinic

Evidence for a close bidirectional link between the brain and the gut has led to a paradigm shift in neurology, especially in the case of Parkinson disease (PD), in which gastrointestinal dysfunction is a prominent feature. Over the past decade, numerous high-quality preclinical and clinical publications have shed light on the highly complex relationship between the gut and the brain in PD, providing potential for the development of new biomarkers and therapeutics. With the advent of high-throughput sequencing, the role of the gut microbiome has been specifically highlighted. Here, we provide a critical review of the literature on the microbiome-gut-brain axis in PD and present perspectives that will be useful for clinical practice. We begin with an overview of the gut-brain axis in PD, including the potential roles and interrelationships of the vagus nerve, α-synuclein in the enteric nervous system, altered intestinal permeability and inflammation, and gut microbes and their metabolic activities. The sections that follow synthesize the proposed roles of gut-related factors in the development and progression of, in responses to PD treatment, and as therapeutic targets. Finally, we summarize current knowledge gaps and challenges and delineate future directions for the field.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that arises due to a complex and variable interplay between elements including age, genetic, and environmental risk factors that manifest as the loss of dopaminergic neurons. Contemporary treatments for PD do not prevent or reverse the extent of neurodegeneration that is characteristic of this disorder and accordingly, there is a strong need to develop new approaches which address the underlying disease process and provide benefit to patients with this debilitating disorder. Mitochondrial dysfunction, oxidative damage, and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons seen in PD. However, results of studies aiming to inhibit these pathways have shown variable success, and outcomes from large-scale clinical trials are not available or report varying success for the interventions studied. Overall, the available data suggest that further development and testing of novel therapies are required to identify new potential therapies for combating PD. Herein, this review reports on the most recent development of antioxidant and anti-inflammatory approaches that have shown positive benefit in cell and animal models of disease with a focus on supplementation with natural product therapies and selected synthetic drugs.

Nutraceuticals as Modulators of Autophagy: Relevance in Parkinson’s Disease

Dietary supplements and nutraceuticals have entered the mainstream. Especially in the media, they are strongly advertised as safe and even recommended for certain diseases. Although they may support conventional therapy, sometimes these substances can have unexpected side effects. This review is particularly focused on the modulation of autophagy by selected vitamins and nutraceuticals, and their relevance in the treatment of neurodegenerative diseases, especially Parkinson’s disease (PD). Autophagy is crucial in PD; thus, the induction of autophagy may alleviate the course of the disease by reducing the so-called Lewy bodies. Hence, we believe that those substances could be used in prevention and support of conventional therapy of neurodegenerative diseases. This review will shed some light on their ability to modulate the autophagy.

Micronutrients May Be a Unique Weapon Against the Neurotoxic Triad of Excitotoxicity, Oxidative Stress and Neuroinflammation: A Perspective

Excitotoxicity has been implicated in many neurological disorders and is a leading cause of oxidative stress and neuroinflammation in the nervous system. Most of the research to date has focused on each of these conditions individually; however, excitotoxicity, oxidative stress, and neuroinflammation have the ability to influence one another in a self-sustaining manner, thus functioning as a "neurotoxic triad." This perspective article re-introduces the concept of the neurotoxic triad and reviews how specific dietary micronutrients have been shown to protect against not only oxidative stress, but also excitotoxicity and neuroinflammation. Future dietary interventions for neurological disorders could focus on the effects on all three aspects of the neurotoxic triad.

Elucidating the Neuroprotective Role of PPARs in Parkinson's Disease: A Neoteric and Prospective Target

One of the utmost frequently emerging neurodegenerative diseases, Parkinson's disease (PD) must be comprehended through the forfeit of dopamine (DA)-generating nerve cells in the substantia nigra pars compacta (SN-PC). The etiology and pathogenesis underlying the emergence of PD is still obscure. However, expanding corroboration encourages the involvement of genetic and environmental factors in the etiology of PD. The destruction of numerous cellular components, namely oxidative stress, ubiquitin-proteasome system (UPS) dysfunction, autophagy-lysosome system dysfunction, neuroinflammation and programmed cell death, and mitochondrial dysfunction partake in the pathogenesis of PD. Present-day pharmacotherapy can alleviate the manifestations, but no therapy has been demonstrated to cease disease progression. Peroxisome proliferator-activated receptors (PPARs) are ligand-directed transcription factors pertaining to the class of nuclear hormone receptors (NHR), and are implicated in the modulation of mitochondrial operation, inflammation, wound healing, redox equilibrium, and metabolism of blood sugar and lipids. Numerous PPAR agonists have been recognized to safeguard nerve cells from oxidative destruction, inflammation, and programmed cell death in PD and other neurodegenerative diseases. Additionally, various investigations suggest that regular administration of PPAR-activating non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen, indomethacin), and leukotriene receptor antagonists (montelukast) were related to the de-escalated evolution of neurodegenerative diseases. The present review elucidates the emerging evidence enlightening the neuroprotective outcomes of PPAR agonists in in vivo and in vitro models experiencing PD. Existing articles up to the present were procured through PubMed, MEDLINE, etc., utilizing specific keywords spotlighted in this review. Furthermore, the authors aim to provide insight into the neuroprotective actions of PPAR agonists by outlining the pharmacological mechanism. As a conclusion, PPAR agonists exhibit neuroprotection through modulating the expression of a group of genes implicated in cellular survival pathways, and may be a propitious target in the therapy of incapacitating neurodegenerative diseases like PD.