Genetic Factors of Alzheimer's Disease Modulate How Diet is Associated with Long-Term Cognitive Trajectories: A UK Biobank Study

The Potential Effects of Red Wine and Its Components on Neurocognitive Disorders: A Narrative Review

BACKGROUND

The aging population is associated with a net increase in the incidence and prevalence of chronic-degenerative diseases, particularly neurocognitive disorders. Therefore, the identification of preventative strategies to restrain the burden of such chronic conditions is of key relevance. Red wine and its components have accumulated evidence regarding their positive effects in terms of neurological pathologies associated with neurocognitive symptoms.

METHODS

Based on this background, the present narrative review aims to summarize the state-of-the-art evidence on the effects of red wine and its components on neurocognitive disorders in both preclinical and clinical settings.

RESULTS

The main findings highlight a protective effect of wine polyphenols present in red wine on dementia in different preclinical models of cognitive decline. The current translational clinical evidence remains uncertain, especially considering the risk-to-benefit ratio of alcohol consumption on brain health.

CONCLUSIONS

Given the overall health risks associated with red wine consumption and consistent with the prevailing guidelines in the literature, there is insufficient evidence to support light-to-moderate red wine consumption as an effective strategy for preventing these diseases. However, the largely preclinical findings on polyphenols derived from red wine remain of significant interest in this context.

Association between the Intake/Type of Cheese and Cognitive Function in Community-Dwelling Older Women in Japan: A Cross-Sectional Cohort Study

While many studies have described the association between cognitive decline and eating habits, little attention has been paid to its association with cheese intake. In this epidemiological study of 1035 community-dwelling women aged ≥ 65, we investigated the association between intake/type of cheese and cognitive function. The anthropometry, functional ability, and the frequency of food intake, including cheese, were assessed. The mini-mental state examination (MMSE) was used to assess cognitive function, and a score of 20-26 was operationally defined as mild cognitive decline. We found that the MMSE score was significantly different between the presence of cheese intake and not (cheese intake: 28.4 ± 1.9; non-cheese intake: 27.6 ± 2.4) and between those who consumed Camembert cheese and those who did not (Camembert cheese: 28.7 ± 1.4; others: 28.3 ± 2.0). After adjusting for confounders, multiple logistic regression identified four independent variables significantly associated with mild cognitive decline: Camembert cheese intake (odds ratio = 0.448, 95% confidence interval = 0.214-0.936), age, usual walking speed, and repetitive saliva swallowing test scores. Our results, while based on cross-sectional data from Japanese community-dwelling older women, identified the significant inverse association between Camembert cheese intake and mild cognitive decline.

Effectiveness of dairy products to protect against cognitive decline in later life: a narrative review

As the world's population ages the prevalence of age-related health concerns is increasing, including neurodegeneration disorders such as mild cognitive impairment, vascular dementia and Alzheimer's disease. Diet is a key modifiable risk factor for the development of neurodegeneration, likely due to gut-brain axis interactions related to neuroinflammation. Analyses of dietary patterns identified dairy as being part of a cognitively healthy diet; however, its contribution to cognitive outcomes is difficult to discern. This narrative review evaluates the literature to determine whether there is sufficient evidence that the consumption of dairy products helps to maintain cognitive function in later life. A search using the terms (dairy OR milk OR cheese OR yogurt OR yogurt) AND ("mild cognitive impairment" OR dementia OR "Alzheimer's disease") identified 796 articles. After screening and sorting, 23 observational studies and 6 intervention studies were identified. The results of the observational studies implied that the relationship between total dairy consumption and cognitive outcomes is inverse U-shaped, with moderate consumption (1-2 servings per day) being the most beneficial. The analysis of the intake of different types of dairy products indicated that fermented products, particularly cheese, were most likely responsible for the observed benefits. The experimental studies all used dairy-derived peptides produced during fermentation as the dietary intervention, and the results indicated that these could be an effective treatment for early-stage cognitive impairment. Further experimental studies with whole dairy products, particularly fermented dairy, are needed to determine whether the regular consumption of these foods should be recommended to maximize the likelihood of healthy cognitive aging.

Serum zinc concentration and dietary zinc intake in relation to cognitive function: an analysis of the REasons for Geographic and Racial Differences in Stroke (REGARDS) cohort

PURPOSE

There are several pathways by which zinc may be a modifiable factor to slow age-related cognitive decline. We investigated the associations between serum and dietary zinc and cognitive impairment in a longitudinal cohort.

METHODS

We used data from the REasons for Geographic and Racial Differences in Stroke (REGARDS) Cohort (n = 30,239) and the REGARDS Trace Element Study (n = 2666). Baseline serum zinc concentrations (2003-2007) were measured using inductively coupled plasma mass spectrometry. Baseline dietary zinc intake was measured via the Block food frequency questionnaire. Serum zinc concentrations and dietary zinc intake were categorized into quartiles. The outcome of interest was impairment on the Six-Item Screener (SIS), a measure of global cognitive functioning administered annually. The Enhanced Cognitive Battery (ECB), a more comprehensive series of tests assessing memory and fluency, was administered every two years and considered a secondary outcome. Associations between zinc and incident impairment were assessed using multivariable logistic regression.

RESULTS

Among 2065 participants with serum zinc data, 184 individuals developed impairment over 10 years of follow-up. In adjusted models, there was no significant association between serum zinc and impairment as assessed by the SIS or the ECB. Among 18,103 participants who had dietary data, 1424 experienced incident impairment on the SIS. Dietary zinc intake was not significantly associated with impairment as assessed by the SIS or the ECB in adjusted models.

CONCLUSION

Findings from this U.S. cohort did not support the hypothesis that serum zinc concentration or dietary zinc intake is associated with the risk of cognitive impairment.

Role of the Exposome in Neurodegenerative Disease: Recent Insights and Future Directions

Neurodegenerative diseases are increasing in prevalence and place a significant burden on society. The causes are multifactorial and complex, and increasing evidence suggests a dynamic interplay between genes and the environment, emphasizing the importance of identifying and understanding the role of lifelong exposures, known as the exposome, on the nervous system. This review provides an overview of recent advances toward defining neurodegenerative disease exposomes, focusing on Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. We present the current state of the field based on emerging data, elaborate on key themes and potential mechanisms, and conclude with limitations and future directions. ANN NEUROL 2024;95:635-652.

An Interpretable Population Graph Network to Identify Rapid Progression of Alzheimer's Disease Using UK Biobank

Alzheimer's disease (AD) manifests with varying progression rates across individuals, necessitating the understanding of their intricate patterns of cognition decline that could contribute to effective strategies for risk monitoring. In this study, we propose an innovative interpretable population graph network framework for identifying rapid progressors of AD by utilizing patient information from electronic health-related records in the UK Biobank. To achieve this, we first created a patient similarity graph, in which each AD patient is represented as a node; and an edge is established by patient clinical characteristics distance. We used graph neural networks (GNNs) to predict rapid progressors of AD and created a GNN Explainer with SHAP analysis for interpretability. The proposed model demonstrates superior predictive performance over the existing benchmark approaches. We also revealed several clinical features significantly associated with the prediction, which can be used to aid in effective interventions for the progression of AD patients.

Cheese consumption and multiple health outcomes: an umbrella review and updated meta-analysis of prospective studies

This umbrella review aims to provide a systematic and comprehensive overview of current evidence from prospective studies on the diverse health effects of cheese consumption. We searched PubMed, Embase, and Cochrane Library to identify meta-analyses/pooled analyses of prospective studies examining the association between cheese consumption and major health outcomes from inception to August 31, 2022. We reanalyzed and updated previous meta-analyses and performed de novo meta-analyses with recently published prospective studies, where appropriate. We calculated the summary effect size, 95% prediction confidence intervals, between-study heterogeneity, small-study effects, and excess significance bias for each health outcome. We identified 54 eligible articles of meta-analyses/pooled analyses. After adding newly published original articles, we performed 35 updated meta-analyses and 4 de novo meta-analyses. Together with 8 previous meta-analyses, we finally included 47 unique health outcomes. Cheese consumption was inversely associated with all-cause mortality (highest compared with lowest category: RR = 0.95; 95% CI: 0.92, 0.99), cardiovascular mortality (RR = 0.93; 95% CI: 0.88, 0.99), incident cardiovascular disease (CVD) (RR = 0.92; 95% CI: 0.89, 0.96), coronary heart disease (CHD) (RR = 0.92; 95% CI: 0.86, 0.98), stroke (RR = 0.93; 95% CI: 0.89, 0.98), estrogen receptor-negative (ER-) breast cancer (RR = 0.89; 95% CI: 0.82, 0.97), type 2 diabetes (RR = 0.93; 95% CI: 0.88, 0.98), total fracture (RR = 0.90; 95% CI: 0.86, 0.95), and dementia (RR = 0.81; 95% CI: 0.66, 0.99). Null associations were found for other outcomes. According to the NutriGrade scoring system, moderate quality of evidence was observed for inverse associations of cheese consumption with all-cause and cardiovascular mortality, incident CVD, CHD, and stroke, and for null associations with cancer mortality, incident hypertension, and prostate cancer. Our findings suggest that cheese consumption has neutral to moderate benefits for human health.

Alzheimer's Disease Genetic Influences Impact the Associations between Diet and Resting-State Functional Connectivity: A Study from the UK Biobank

BACKGROUND

Red wine and dairy products have been staples in human diets for a long period. However, the impact of red wine and dairy intake on brain network activity remains ambiguous and requires further investigation.

METHODS

This study investigated the associations between dairy and red wine consumption and seven neural networks' connectivity with functional magnetic resonance imaging (fMRI) data from a sub-cohort of the UK Biobank database. Linear mixed models were employed to regress dairy and red wine consumption against the intrinsic functional connectivity for each neural network. Interactions with Alzheimer's disease (AD) risk factors, including apolipoprotein E4 (APOE4) genotype, TOMM40 genotype, and family history of AD, were also assessed.

RESULT

More red wine consumption was associated with enhanced connectivity in the central executive function network and posterior default mode network. Greater milk intake was correlated with more left executive function network connectivity, while higher cheese consumption was linked to reduced posterior default mode network connectivity. For participants without a family history of Alzheimer's disease (AD), increased red wine consumption was positively correlated with enhanced left executive function network connectivity. In contrast, participants with a family history of AD displayed diminished network connectivity in relation to their red wine consumption. The association between cheese consumption and neural network connectivity was influenced by APOE4 status, TOMM40 status, and family history, exhibiting contrasting patterns across different subgroups.

CONCLUSION

The findings of this study indicate that family history modifies the relationship between red wine consumption and network strength. The interaction effects between cheese intake and network connectivity may vary depending on the presence of different genetic factors.

Animal models for studies of alcohol effects on the trajectory of age-related cognitive decline

There is growing interest in understanding how ethanol use interacts with advancing age to influence the brain and cognition. Animal models are employed to investigate the cellular and molecular mechanisms of brain aging and age-related neurodegenerative diseases that underlie cognitive decline. However, all too often research on problems and diseases of the elderly are conducted in healthy young animals, providing little clinical relevance. The validity of animal models is discussed, and confounds due to age-related differences in anxiety, sensory-motor function, and procedural learning are highlighted in order to enhance the successful translation of preclinical results into clinical settings. The mechanism of action of ethanol on brain aging will depend on the dose, acute or chronic treatment, or withdrawal from treatment and the age examined. Due to the fact that humans experience alcohol use throughout life, important questions concern the effects of the dose and duration of ethanol treatment on the trajectory of cognitive function. Central to this research will be questions of the specificity of alcohol effects on cognitive functions and related brain regions that decline with age, as well as the interaction of alcohol with mechanisms or biomarkers of brain aging. Alternatively, moderate alcohol use may provide a source of reserve and resilience against brain aging. Longitudinal studies have the advantage of being sensitive to detecting the effects of treatment on the emergence of cognitive impairment in middle age and can minimize effects of stress/anxiety associated with the novelty of alcohol exposure and behavioral testing, which disproportionately influence aged animals. Finally, the effect of alcohol on senescent neurophysiology and biomarkers of brain aging are discussed. In particular, the interaction of age and effects of alcohol on inflammation, oxidative stress, N-methyl-d-aspartate receptor function, and the balance of excitatory and inhibitory synaptic transmission are highlighted.

The role of plasma cortisol in dementia, epilepsy, and multiple sclerosis: A Mendelian randomization study

BACKGROUND

Many clinical studies have shown a correlation between plasma cortisol and neurological disorders. This study explored the causal relationship between plasma cortisol and dementia, epilepsy and multiple sclerosis based on Mendelian randomization (MR) method.

METHODS

Data were taken from the summary statistics of a genome-wide association study, FinnGen consortium and United Kingdom Biobank. Dementia, epilepsy, and multiple sclerosis were used as outcomes, and genetic variants associated with plasma cortisol were used as instrumental variables. The main analysis was performed using the inverse variance weighted method, and the results were assessed according to the odds ratio (OR) and 95% confidence interval. Heterogeneity tests, pleiotropy tests, and leave-one-out method were conducted to evaluate the stability and accuracy of the results.

RESULTS

In two-sample MR analysis, the inverse variance weighted method showed that plasma cortisol was associated with Alzheimer's disease (AD) [odds ratio (95% confidence interval) = 0.99 (0.98-1.00), P = 0.025], vascular dementia (VaD) [odds ratio (95% confidence interval) = 2.02 (1.00-4.05), P = 0.049)], Parkinson's disease with dementia (PDD) [odds ratio (95% confidence interval) = 0.24 (0.07-0.82), P = 0.023] and epilepsy [odds ratio (95% confidence interval) = 2.00 (1.03-3.91), P = 0.042]. There were no statistically significant associations between plasma cortisol and dementia with Lewy bodies (DLB), frontotemporal dementia (FTD) and multiple sclerosis.

CONCLUSION

This study demonstrates that plasma cortisol increase the incidence rates of epilepsy and VaD and decrease the incidence rates of AD and PDD. Monitoring plasma cortisol concentrations in clinical practice can help prevent diseases, such as AD, PDD, VaD and epilepsy.

Association between modes of delivery and postpartum dietary patterns: A cross-sectional study in Northwest China

Objective

Puerperae’ dietary patterns (DPs) during the puerperium may be influenced by the mode of delivery, but population studies on this topic are scarce. This study aims to explore the relationship between DPs and different modes of delivery among puerperae.

Methods

A cross-sectional study was conducted on 3,345 parturients in Lanzhou, China. The postpartum food intake was measured by a food frequency questionnaire (FFQ). Factor analysis was used to determine the DPs. Multiple linear regression was employed to examine the association between the mode of delivery and DP.

Results

In this study, two DPs, i.e., traditional and modern DPs, were identified. Traditional DP was characterized by high energy-adjusted intake of tubers, coarse cereals, rice, whole grains, fishery products, and eggs. Modern DP included a high intake of coffee, non-sugary drinks, wine, tea, and fishery products. Compared with participants with vaginal delivery (reference category), cesarean section had an inverse association with modern DP (β: −0.11, 95% CI: −0.36, −0.09). A significant interaction was found between education level, monthly household income, alcohol drinking, and modes of delivery. The inverse association between cesarean section and modern DP or the intake of coffee was significant among puerperae with higher or lower monthly household income. However, the inverse association between cesarean section and traditional DP was only found among puerperae with higher monthly household income. Moreover, among the participants with high education, cesarean section was positively associated with intake of vegetables.

Conclusion

Cesarean puerperae with higher levels of education and those with lower and higher monthly household income had less unhealthy foods intake than those who had vaginal delivery. They need to be accounted for in educational programs and interventions focused on healthy diet recommendations in puerperium.

A review on the application of the exposome paradigm to unveil the environmental determinants of age-related diseases

Age-related diseases account for almost half of all diseases among adults worldwide, and their incidence is substantially affected by the exposome, which is the sum of all exogenous and endogenous environmental exposures and the human body’s response to these exposures throughout the entire lifespan. Herein, we perform a comprehensive review of the epidemiological literature to determine the key elements of the exposome that affect the development of age-related diseases and the roles of aging hallmarks in this process. We find that most exposure assessments in previous aging studies have used a reductionist approach, whereby the effect of only a single environmental factor or a specific class of environmental factors on the development of age-related diseases has been examined. As such, there is a lack of a holistic and unbiased understanding of the effect of multiple environmental factors on the development of age-related diseases. To address this, we propose several research strategies based on an exposomic framework that could advance our understanding—in particular, from a mechanistic perspective—of how environmental factors affect the development of age-related diseases. We discuss the statistical methods and other methods that have been used in exposome-wide association studies, with a particular focus on multiomics technologies. We also address future challenges and opportunities in the realm of multidisciplinary approaches and genome–exposome epidemiology. Furthermore, we provide perspectives on precise public health services for vulnerable populations, public communications, the integration of risk exposure information, and the bench-to-bedside translation of research on age-related diseases.

Beer, wine, and spirits differentially influence body composition in older white adults-a United Kingdom Biobank study

BACKGROUND

Aging is characterized by body composition alterations, including increased visceral adiposity accumulation and bone loss. Alcohol consumption may partially drive these alterations, but findings are mixed. This study primarily aimed to investigate whether different alcohol types (beer/cider, red wine, white wine/Champagne, spirits) differentially associated with body composition.

METHODS

The longitudinal UK Biobank study leveraged 1869 White participants (40-80 years; 59% male). Participants self-reported demographic, alcohol/dietary consumption, and lifestyle factors using a touchscreen questionnaire. Anthropometrics and serum for proteomics were collected. Body composition was obtained via dual-energy X-ray absorptiometry. Structural equation modeling was used to probe direct/indirect associations between alcohol types, cardiometabolic biomarkers, and body composition.

RESULTS

Greater beer/spirit consumptions were associated with greater visceral adiposity (β = 0.069, p < 0.001 and β = 0.014, p < 0.001, respectively), which was driven by dyslipidemia and insulin resistance. In contrast, drinking more red wine was associated with less visceral adipose mass (β = -0.023, p < 0.001), which was driven by reduced inflammation and elevated high-density lipoproteins. White wine consumption predicted greater bone density (β = 0.051, p < 0.005).

DISCUSSION

Beer/spirits may partially contribute to the "empty calorie" hypothesis related to adipogenesis, while red wine may help protect against adipogenesis due to anti-inflammatory/eulipidemic effects. Furthermore, white wine may benefit bone health in older White adults.1.

Evaluating the Causal Effects of Gestational Diabetes Mellitus, Heart Disease, and High Body Mass Index on Maternal Alzheimer’s Disease and Dementia: Multivariable Mendelian Randomization

Introduction: Gestational diabetes mellitus (GDM), heart disease (HD) and high body mass index (BMI) are strongly related to Alzheimer’s disease (AD) dementia in pregnant women. Therefore, we aimed to determine the total effects of GDM, heart disease, and high BMI on maternal AD dementia.

Methods: We used data from the genome-wide association studies of European populations including more than 30,000 participants. We performed two-sample Mendelian randomization (MR) and multivariable MR (MVMR) to systematically estimate the direct effects of GDM, HD, and high BMI on maternal AD and dementia. Multiple sensitivity analyses involving classical MR approaches and expanded MR-pleiotropy residual sum and outlier analysis.

Results: In two-sample MR analysis, the inverse-variance weighted method in our study demonstrated no significant causality between GDM and maternal dementia (β = −0.006 ± 0.0026, p = 0.82). This method also revealed no significant causality between high BMI and maternal dementia (β = 0.0024 ± 0.0043, p = 0.57), and it was supported by the MR-Egger regression results, which showed no causal effect of high BMI on maternal Alzheimer’s disease and dementia (β = 0.0027 ± 0.0096, p = 0.78). The IVW method showed no significant causal relationship between maternal HD and maternal Alzheimer’s disease and dementia (β = −0.05 ± 0.0042, p = 0.117) and MR-Egger regression analysis gave a similar result (β = −0.12 ± 0.0060, p = 0.079). In MVMR analysis, we found no significant causal relationship between GDM, high BMI, or HD and maternal Alzheimer’s disease and dementia (p = 0.94, 0.82, and 0.13, respectively). Thus, the MVMR estimates were consistent with our results from the two-sample MR analysis. We confirmed that these results showed no horizontal pleiotropy and enhanced the robustness of our results through multiple sensitivity analyses.

Conclusion: In two-sample MR analysis, we found no significant causal relationship between GDM, HD, high BMI and maternal AD and dementia. These results differed from previous observational studies showing HD is a significant predictor of dementia. MVMR analysis supported no significant causal relationship between GDM, HD, high BMI and maternal AD and dementia. Sensitivity analysis broadly increased the robustness of two-sample MR and MVMR analysis results.

Effects of Diastolic Blood Pressure on Brain Structures and Cognitive Functions in Middle and Old Ages: Longitudinal Analyses

Hypertension is a pervasive public health concern due to strong associations with cardiovascular diseases and stroke. Alternatively, the associations between hypertension and the risk of Alzheimer's disease are complex and recent large sample studies reported positive associations. In this paper, we examine the associations between diastolic blood pressure (BP) and subsequent changes in brain structure and cognitive function over several years by multiple regression analyses (with adjustment for a wide range of potential confounding variables) among a large cohort from the UK Biobank. Higher baseline diastolic BP was associated with a slightly smaller relative increase (relative improvements) in reaction time and a slightly greater reduction in depression scores. Higher baseline diastolic BP was also associated with a greater total gray matter volume (GMV) retention, while aging alone was associated with GMV reduction. White matter microstructural analyses revealed that a greater diastolic BP was associated with reduced longitudinal mean and regional fractional anisotropy, greater increases in mean and regional mean diffusivity, radial diffusivity, and axial diffusivity, a greater decline in mean intracellular volume fraction, and greater increases in mean and regional isotropic volume fraction. These white matter microstructural changes were consistent with those seen in the aging process. Additional analyses revealed a greater cheese intake level at baseline, which is associated with a subsequent decline in diastolic BP and a relative subsequent increase in depressive tendency together with a relative increase in fluid intelligence and visuospatial memory performance. These results are congruent with the view that a higher BP in the aging brain has a complex role.

Favourable Lifestyle Protects Cognitive Function in Older Adults With High Genetic Risk of Obesity: A Prospective Cohort Study

The relationship between body mass index (BMI) and cognitive impairment remains controversial, especially in older people. This study aims to confirm the association of phenotypic and genetic obesity with cognitive impairment and the benefits of adhering to a healthy lifestyle. This prospective study included 10,798 participants (aged ≥ 50 years) with normal cognitive function from the Health and Retirement Study in the United States. Participants were divided into low (lowest quintile), intermediate (quintiles 2–4), and high (highest quintile) groups according to their polygenic risk score (PRS) for BMI. The risk of cognitive impairment was estimated using Cox proportional hazard models. Higher PRS for BMI was associated with an increased risk, whereas phenotypic obesity was related to a decreased risk of cognitive impairment. Never smoking, moderate drinking, and active physical activity were considered favourable and associated with a lower risk of cognitive impairment compared with current smoking, never drinking, and inactive, respectively. A favourable lifestyle was associated with a low risk of cognitive impairment, even in subjects with low BMI and high PRS for BMI. This study suggest that regardless of obesity status, including phenotypic and genetic, adhering to a favourable lifestyle is beneficial to cognitive function.

Associations of dairy, meat, and fish intakes with risk of incident dementia and with cognitive performance: the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD)

Purpose

To investigate if dairy, meat, and fish intakes associate with dementia and cognitive performance.

Methods

We included 2497 dementia-free men from Eastern Finland, aged 42–60 years in 1984–1989 at the baseline examinations. Data on cognitive tests [Mini Mental State Exam (MMSE), trail making test (TMT), verbal fluency test (VFL), selective reminding test (SRT), and Russell’s adaptation of the visual reproduction test (VRT)] at the 4-year re-examinations were available for 482 men and on the ApoE phenotype for 1259 men. Data on dementia events were obtained by linkage to national health registers. Diet was assessed with baseline 4-day food records. Cox regression and analysis of covariance were used for analyses.

Results

During a mean 22-year follow-up, 337 men had a dementia diagnosis. Among the foods, only cheese intake associated with dementia risk (hazard ratio in the highest vs. the lowest quartile = 0.72, 95% confidence interval = 0.52–0.99, P-trend = 0.05). In the cognitive tests, higher non-fermented dairy and milk intakes associated with worse verbal fluency (VFT). Higher processed red meat intake associated with worse verbal (SRT) and visual memory (VRT), whereas higher unprocessed red meat intake associated with better general cognitive functioning (MMSE) and processing speed and executive functioning (TMT). Higher fish intake associated with better verbal memory (SRT). Among APOE-ε4 carriers, especially non-fermented dairy intake associated with higher risk of dementia outcomes, and higher fish intake indicated better cognitive performance.

Conclusion

Although higher intake of some food groups associated with cognitive performance, we found little evidence for associations with dementia risk.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-022-02834-x.

Interaction Between Diet and Microbiota in the Pathophysiology of Alzheimer's Disease: Focus on Polyphenols and Dietary Fibers

Animal studies increasingly indicate that the gut microbiota composition and function can be involved in the pathophysiology and progression of Alzheimer's disease (AD) at multiple levels. However, few studies have investigated this putative gut-brain axis in human beings, and none of them considered diet as a determinant of intestinal microbiota composition. Epidemiological studies highlight that a high intake of fruit and vegetables, such as that typical of the Mediterranean diet, can modulate AD progression. Thus, nutritional interventions are being increasingly studied as a possible non-pharmacological strategy to slow down the progression of AD. In particular, polyphenols and fibers represent the nutritional compounds with the higher potential of counterbalancing the pathophysiological mechanisms of dementia due to their antioxidant, anti-inflammatory, and anti-apoptotic properties. These actions are mediated by the gut microbiota, that can transform polyphenols and fibers into biologically active compounds including, among others, phenyl-γ-valerolactones, urolithins, butyrate, and other short-chain fatty acids. In this review, the complex mechanisms linking nutrition, gut microbiota composition, and pathophysiology of cognitive decline in AD are discussed, with a particular focus on the role of polyphenols and fibers. The gaps between pre-clinical and clinical studies are particularly emphasized, as well as the urgent need for studies comprehensively evaluating the link between nutrition, microbiome, and clinical aspects of AD.