Dietary intake of fish and omega-3 fatty acids in relation to long-term dementia risk

Fish consumption, cognitive impairment and dementia: an updated dose-response meta-analysis of observational studies

BACKGROUND

Cognitive impairment is projected to affect a preponderant proportion of the aging population. Lifelong dietary habits have been hypothesized to play a role in preventing cognitive decline. Among the most studied dietary components, fish consumptionhas been extensively studied for its potential effects on the human brain.

AIMS

To perform a meta-analysis of observational studies exploring the association between fish intake and cognitive impairment/decline and all types of dementia.

METHODS

A systematic search of electronic databases was performed to identify observational studies providing quantitative data on fish consumption and outcomes of interest. Random effects models for meta-analyses using only extreme exposure categories, subgroup analyses, and dose-response analyses were performed to estimate cumulative risk ratios (RRs) and 95% confidence intervals (CIs).

RESULTS

The meta-analysis comprised 35 studies. Individuals reporting the highest vs. the lowest fish consumption were associated with a lower likelihood of cognitive impairment/decline (RR = 0.82, 95% CI: 0.75, 0.90, I2 = 61.1%), dementia (RR = 0.82, 95% CI: 0.73, 0.93, I2 = 38.7%), and Alzheimer's disease (RR = 0.80, 95% CI: 0.67, 0.96, I2 = 20.3%). The dose-response relation revealed a significantly decreased risk of cognitive impairment/decline and all cognitive outcomes across higher levels of fish intake up to 30% for 150 g/d (RR = 0.70, 95% CI: 0.52, 0.95). The results of this relation based on APOE ε4 allele status was mixed based on the outcome investigated.

CONCLUSIONS

Current findings suggest fish consumption is associated with a lower risk of cognitive impairment/decline in a dose-response manner, while for dementia and Alzheimer's disease there is a need for further studies to improve the strength of evidence.

Metabolic profiling of Alzheimer's disease: Untargeted metabolomics analysis of plasma samples

Alzheimer's disease (AD) is often not recognized or is diagnosed very late, which significantly reduces the effectiveness of available pharmacological treatments. Metabolomic analyzes have great potential for improving existing knowledge about the pathogenesis and etiology of AD and represent a novel approach towards discovering biomarkers that could be used for diagnosis, prognosis, and therapy monitoring. In this study, we applied the untargeted metabolomic approach to investigate the changes in biochemical pathways related to AD pathology. We used gas chromatography and liquid chromatography coupled to mass spectrometry (GC-MS and LC-MS, respectively) to identify metabolites whose levels have changed in subjects with AD diagnosis (N = 40) compared to healthy controls (N = 40) and individuals with mild cognitive impairment (MCI, N = 40). The GC-MS identified significant differences between groups in levels of metabolites belonging to the classes of benzene and substituted derivatives, carboxylic acids and derivatives, fatty acyls, hydroxy acids and derivatives, keto acids and derivatives, and organooxygen compounds. Most of the compounds identified by the LC-MS were various fatty acyls, glycerolipids and glycerophospholipids. All of these compounds were decreased in AD patients and in subjects with MCI compared to healthy controls. The results of the study indicate disturbed metabolism of lipids and amino acids and an imbalance of metabolites involved in energy metabolism in individuals diagnosed with AD, compared to healthy controls and MCI subjects.

Omega-3 long-chain polyunsaturated fatty acids: Metabolism and health implications

Recently, omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) have gained substantial interest due to their specific structure and biological functions. Humans cannot naturally produce these fatty acids (FAs), making it crucial to obtain them from our diet. This comprehensive review details n-3 LC-PUFAs and their role in promoting and maintaining optimal health. The article thoroughly analyses several sources of n-3 LC-PUFAs and their respective bioavailability, covering marine, microbial and plant-based sources. Furthermore, we provide an in-depth analysis of the biological impacts of n-3 LC-PUFAs on health conditions, with particular emphasis on cardiovascular disease (CVD), gastrointestinal (GI) cancer, diabetes, depression, arthritis, and cognition. In addition, we highlight the significance of fortification and supplementation of n-3 LC-PUFAs in both functional foods and dietary supplements. Additionally, we conducted a detailed analysis of the several kinds of n-3 LC-PUFAs supplements currently available in the market, including an assessment of their recommended intake, safety, and effectiveness. The dietary guidelines associated with n-3 LC-PUFAs are also highlighted, focusing on the significance of maintaining a well-balanced intake of n-3 PUFAs to enhance health benefits. Lastly, we highlight future directions for further research in this area and their potential implications for public health.

Association between animal protein sources and risk of neurodegenerative diseases: a systematic review and dose-response meta-analysis

CONTEXT

Current findings about the differential effects of various sources of dietary animal protein on the risk of neurodegenerative diseases are contradictory.

OBJECTIVE

The current meta-analysis was conducted to investigate the associations between intake of dietary animal protein sources and the risk of neurodegenerative diseases.

DATA SOURCES

PubMed, Scopus, Web of Science, and Google Scholar databases were searched systematically until October 2021.

DATA EXTRACTION

Prospective cohort studies exploring the association between consumption of animal protein sources and risk of neurodegenerative diseases in the general population were included. Among 10 571 identified studies, 33 prospective cohort studies met the eligibility criteria.

DATA ANALYSIS

Dietary fish consumption was associated with a reduced risk of Alzheimer's disease (RR = 0.75; 95%CI, 0.57-0.97), dementia (RR = 0.84; 95%CI, 0.75-0.93), and cognitive impairment (RR = 0.85; 95%CI, 0.81-0.95). The risk of developing Parkinson's disease was significantly higher among those in the highest vs the lowest intake categories of total dairy (RR = 1.49; 95%CI, 1.06-2.10) and milk (RR = 1.40; 95%CI, 1.13-1.73). Moreover, dietary intake of total dairy (RR = 0.89; 95%CI, 0.80-0.99), total meat (RR = 0.72; 95%CI, 0.57-0.90), and poultry (RR = 0.82; 95%CI, 0.68-0.99) was significantly associated with a lower risk of cognitive impairment. A linear dose-response meta-analysis revealed that each 200-g increase in total daily dairy intake was associated with an 11% higher risk of Parkinson's disease and a 12% lower risk of cognitive impairment. Furthermore, there was a strong linear association between fish consumption and reduced risk of dementia.

CONCLUSION

Dairy consumption is associated with an increased risk of Parkinson's disease, but a higher intake of fish may be associated with lower risk of neurodegenerative disease. Future well-controlled, randomized clinical trials are essential to validate the present findings.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021281887.

Omega-3 fatty acids and cognitive function

PURPOSE OF REVIEW

The aim is to provide an update on omega-3 polyunsaturated fatty acids (n-3 PUFA) in preventing cognitive decline and dementia.

RECENT FINDINGS

Prospective studies and three new meta-analyses suggest that fish or n-3 PUFA intake are associated with a reduction in development of mild cognitive decline and Alzheimer's disease. Supplementation with docosahexaenoic acid (DHA) in randomized controlled trials (RCTs) in those with mild cognitive impairment showed benefit on cognitive decline, whereas there was no benefit in Alzheimer's disease. In cognitively healthy individuals with clinical coronary artery disease (CAD), 3.36 g EPA and DHA daily slowed cognitive ageing by 2.5 years. Of 15 RCTs in cognitively healthy individuals age more than 55 years, seven reported benefit, whereas eight did not. Potential mechanisms for differences in outcomes include dose, trial duration, apolipoproteinE genotype, sex, stage and rate of cognitive decline, cognitive testing employed and individual characteristics. The downstream product of DHA, neuroprotectin D1, may be involved in beneficial effects.

SUMMARY

Patients with early memory complaints or a family history of dementia and those with CAD should be counselled on the potential benefits of fish intake and supplementation with n-3 PUFA. ApolipoproteinE4 carriers may especially benefit from DHA supplementation prior to development of cognitive decline.

Fish consumption and the risk of dementia: Systematic review and meta-analysis of prospective studies

Accumulating evidence supports some health benefits of nutrients in fish, but evidence from comprehensive investigation of fish consumption and the risk of dementia is limited. We performed a systematic review and meta-analysis of prospective cohort studies to investigate this association. Papers relevant to our study published by 2021 were searched using PubMed, Embase, Cochrane library, and Web of Science databases. Pooled relative risks (RRs) of the association between fish consumption and dementia risk were calculated using a random-effects model. Seven prospective cohort studies with a total of 30,638 subjects were included in the meta-analysis. Overall, people with high fish consumption had a significantly lower risk of dementia compared to those with low fish consumption. In addition, the dose-response meta-analysis also supported the inverse association. The inverse association tended to be stronger in studies conducted in Asia. The findings of the meta-analysis of prospective cohort studies provide quantitative evidence for an inverse association between fish consumption and the risk of dementia. Further research on consumption of specific types of fish with respect to the risk of dementia are needed to provide more informative recommendations to the public.

Associations of fish oil supplementation with incident dementia: Evidence from the UK Biobank cohort study

Background

Although numerous studies have investigated the association of dietary intake of omega-3 fatty acids with cognitive function and the risks of dementia, the relationship between fish oil supplementation and incident dementia in a large population-based cohort study has not yet well studied.

Materials and methods

A total of 211,094 community-dwelling older persons over 60 years from the UK Biobank cohorts enrolled between 2006 and 2010 that reported regularly taking fish oil and had no dementia at baseline, was included in the present study. All participants completed an electronic questionnaire regarding habitual use of supplements including fish oil.

Results

Overall, 83,283 (39.5%) participants reported regularly taking fish oil at baseline. Of 211,094 participants with the median age was 64.1 years, 5,274 participants developed dementia events during a median follow-up of 11.7 years, with 3,290 individuals derived from fish oil non-users. In the multivariable adjusted models, the adjusted hazard ratios (HRs) associated with fish oil supplementation for all-cause dementia, vascular dementia, frontotemporal dementia, and other dementia were 0.91 [CI = 0.84-0.97], 0.83 [CI = 0.71-0.97], 0.43 [CI = 0.26-0.72], 0.90 [CI = 0.82-0.98], respectively (all P < 0.05). However, no significant association between fish oil supplementation and Alzheimer's disease was found (HR = 1.00 [CI = 0.89-1.12], P = 0.977). In the subgroup analyses, the associations between use of fish oil and the risk of all-cause dementia (P for interaction = 0.007) and vascular dementia were stronger among men (P for interaction = 0.026).

Conclusion

Among older adults, regular fish oil supplementation was significantly associated with a lower risks of incident all-cause dementia, as well as vascular dementia, frontotemporal dementia and other dementia but not Alzheimer's disease. These findings support that habitual use of fish oils may be beneficial for the prevention of dementia in clinical practice.

A Review of Oxylipins in Alzheimer's Disease and Related Dementias (ADRD): Potential Therapeutic Targets for the Modulation of Vascular Tone and Inflammation

There is now a convincing body of evidence from observational studies that the majority of modifiable Alzheimer's disease and related dementia (ADRD) risk factors are vascular in nature. In addition, the co-existence of cerebrovascular disease with AD is more common than AD alone, and conditions resulting in brain ischemia likely promote detrimental effects of AD pathology. Oxylipins are a class of bioactive lipid mediators derived from the oxidation of long-chain polyunsaturated fatty acids (PUFAs) which act as modulators of both vascular tone and inflammation. In vascular cognitive impairment (VCI), there is emerging evidence that oxylipins may have both protective and detrimental effects on brain structure, cognitive performance, and disease progression. In this review, we focus on oxylipin relationships with vascular and inflammatory risk factors in human studies and animal models pertinent to ADRD. In addition, we discuss future research directions with the potential to impact the trajectory of ADRD risk and disease progression.

Dietary Regulation of Gut-Brain Axis in Alzheimer's Disease: Importance of Microbiota Metabolites

Alzheimer's disease (AD) is a neurodegenerative disease that impacts 45 million people worldwide and is ranked as the 6th top cause of death among all adults by the Centers for Disease Control and Prevention. While genetics is an important risk factor for the development of AD, environment and lifestyle are also contributing risk factors. One such environmental factor is diet, which has emerged as a key influencer of AD development/progression as well as cognition. Diets containing large quantities of saturated/trans-fats, refined carbohydrates, limited intake of fiber, and alcohol are associated with cognitive dysfunction while conversely diets low in saturated/trans-fats (i.e., bad fats), high mono/polyunsaturated fats (i.e., good fats), high in fiber and polyphenols are associated with better cognitive function and memory in both humans and animal models. Mechanistically, this could be the direct consequence of dietary components (lipids, vitamins, polyphenols) on the brain, but other mechanisms are also likely to be important. Diet is considered to be the single greatest factor influencing the intestinal microbiome. Diet robustly influences the types and function of micro-organisms (called microbiota) that reside in the gastrointestinal tract. Availability of different types of nutrients (from the diet) will favor or disfavor the abundance and function of certain groups of microbiota. Microbiota are highly metabolically active and produce many metabolites and other factors that can affect the brain including cognition and the development and clinical progression of AD. This review summarizes data to support a model in which microbiota metabolites influence brain function and AD.

A gene-environment interplay between omega-3 supplementation and APOE ε4 provides insights for Alzheimer's disease precise prevention amongst high-genetic-risk population

BACKGROUND AND PURPOSE

The present study aimed to explore whether and how omega-3 (ω-3) supplementation could interact with genetic factors to modulate cognitive functions, amyloid pathologies, and Alzheimer's disease (AD) risk.

METHODS

A total of 1,670 non-demented participants (mean age 73 years, 47% females, 41% APOE ε4 carriers) were followed up for 10 years. Hierarchical regressions, linear mixed-effects models, and Cox proportional hazards models were used to examine the interaction effects of ω-3 supplementation with APOE ε4 and polygenic hazard scores, after adjusting for age, gender, education, cognitive diagnosis, insomnia, depression, anxiety, and cardiovascular risk score.

RESULTS

Individuals who progress to AD during the follow-up tend to take a shorter duration of ω-3 at baseline than those stable, for whom the difference remained significant only amongst APOE ε4 carriers (p < 0.01). The interaction term (APOE ε4 × ω-3) accounted for a significant amount of variance in cognition and cerebral amyloid burden. Long-term ω-3 use protected cognition (especially memory function) and lowered amyloid burden and AD risk only amongst APOE ε4 carriers. Mediation analysis suggested that amyloid pathologies, brain reserve capacities, and brain metabolism mediated the relationships of ω-3 use with memory and global cognition for APOE ε4 (+) carriers. Similar interaction and mediation effects were also indicated amongst high-risk subjects defined by polygenic hazard scores.

CONCLUSIONS

Long-term ω-3 intake may have a role in AD prevention in genetically at-risk populations.

Fish, n-3 fatty acids, cognition and dementia risk: not just a fishy tale

With growing and ageing populations, the incidence of dementia is expected to triple globally by 2050. In the absence of effective drugs to treat or reverse the syndrome, dietary approaches which prevent or delay disease onset have considerable population health potential. Prospective epidemiological studies and mechanistic insight from experimental models strongly support a positive effect of a high fish and long chain n-3 fatty acid (EPA and DHA) intake on a range of cognitive outcomes and dementia risk, with effect sizes equivalent to several years of ageing between the highest and lowest consumers. As reviewed here, an effect of EPA and DHA on neuroinflammation and oxylipin production is likely to in part mediate the neurophysiological benefits. However, randomised controlled trials (RCTs) with EPA and DHA supplementation have produced mixed findings. Insight into the likely modulators of response to intervention and factors which should be considered for future RCTs are given. Furthermore, the impact of APOE genotype on disease risk and response to EPA and DHA supplementation is summarised. The prevalence of dementia is several-fold higher in APOE4 females (about 13% Caucasian populations) relative to the general population, who are emerging as a subgroup who may particularly benefit from DHA intervention, prior to the development of significant pathology.

Fish intake, n-3 fatty acid body status, and risk of cognitive decline: a systematic review and a dose-response meta-analysis of observational and experimental studies

CONTEXT

Randomized controlled trials (RCTs) testing supplementation with eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids have failed to provide evidence supporting a suggested inverse association between fish intake and dementia risk.

OBJECTIVE

Dose-response analyses were conducted to evaluate associations between fish intake, all-cause dementia or Alzheimer's Disease (AD), and the effect of EPA/DHA supplementation on cognitive performance.

DATA SOURCES

PubMed, Scopus and Web of Science databases were searched for original research evaluating either associations between fish intake and dementia or AD, or the impact of EPA and/or DHA supplementation on the risk of cognitive decline.

DATA EXTRACTION

Data were collected on study characteristics and methods; number of cases/deaths (for observational studies); categories of exposure; model covariates; risk estimates from the most-adjusted model; type and dosage of supplementation (from RCTs); fatty acid levels in blood; and differences in cognition test results before and after supplementation. Risk of bias was assessed through the ROBINS-E and RoB2.0 tools for observational and experimental studies, respectively.

DATA ANALYSIS

Weighted mixed-effects models were applied, allowing for the inclusion of studies with 2 levels of exposure. Based on findings with low/moderate risk of bias, fish intake of up to 2 portions (250 g) per week was associated with a 10% reduction (95% confidence interval [CI]: 0.79, 1.02, Ν = 5) in all-cause dementia and a 30% reduction (95% CI: 0.54, 0.89, Ν = 3) in AD risk. Changes in EPA and DHA body status had a positive impact on participants' executive functions, but not on their overall cognitive performance.

CONCLUSION

The protection offered by fish intake against cognitive decline levels off at intakes higher than 2 portions/week and likely relates to the impact of EPA and DHA on the individual's executive functions, although there remain questions about the mechanisms linking the short- and long-term effects.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42019139528.

The relationship between plasma free fatty acids, cognitive function and structural integrity of the brain in middle-aged healthy humans

Background: The cerebral composition of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) is believed to influence cognitive function and structural damage of the aging brain. However, existing data is inconsistent.

Materials and Methods: This retrospective study explored the association between free plasma PUFA concentrations, cognitive function and brain structure atrophy in a well-characterized community-dwelling cohort of elderly individuals without stroke and dementia. Ten different fatty acids were analyzed in stored plasma samples from 391 non-demented elderly individuals by gas chromatography mass spectrometry. Neuropsychiatric tests capturing memory, executive function and visuopractical skills were performed in all participants. Brain atrophy was assessed by MRI in a subset of 167 individuals.

Results: Higher plasma concentrations of free ω-6 PUFAs (p = 0.042), and, in particular, linoleic acid (p = 0.01), were significantly associated with lower executive function. No significant association existed between ω-3 PUFA concentrations and cognitive functioning. The volume of the frontal lobes was inversely associated with ω-6 PUFAs, whereas ω-3 PUFAs were positively related with temporal lobe volumes. All associations did not withstand correction for multiple comparisons.

Conclusions: Our study suggests subtle effects of PUFA imbalances on cognition and brain structure. Yet the observed associations are weak and unlikely to be of clinical relevance. The brain regions that seem to be most sensitive to imbalances of ω-3 and ω-6 PUFAs are the frontal and temporal lobes.

Dietary and supplemental long-chain omega-3 fatty acids as moderators of cognitive impairment and Alzheimer's disease

Purpose

There is an ever-growing body of literature examining the relationship between dietary omega-3 polyunsaturated fatty acids (ω3 PUFAs) and cerebral structure and function throughout life. In light of this, the use of ω3 PUFAs, namely, long-chain (LC) ω3 PUFAs (i.e., eicosapentaenoic acid and docosahexaenoic acid), as a therapeutic strategy to mitigate cognitive impairment, and progression to Alzheimer’s disease is an attractive prospect. This review aims to summarise evidence reported by observational studies and clinical trials that investigated the role of LC ω3 PUFAs against cognition impairment and future risk of Alzheimer’s disease.

Methods

Studies were identified in PubMed and Scopus using the search terms “omega-3 fatty acids”, “Alzheimer’s disease” and “cognition”, along with common variants. Inclusion criteria included observational or randomised controlled trials (RCTs) with all participants aged ≥ 50 years that reported on the association between LC ω3 PUFAs and cognitive function or biological markers indicative of cognitive function linked to Alzheimer’s disease.

Results

Evidence from 33 studies suggests that dietary and supplemental LC ω3 PUFAs have a protective effect against cognitive impairment. Synaptic plasticity, neuronal membrane fluidity, neuroinflammation, and changes in expression of genes linked to cognitive decline have been identified as potential targets of LC ω3 PUFAs. The protective effects LC ω3 PUFAs on cognitive function and reduced risk of Alzheimer’s disease were supported by both observational studies and RCTs, with RCTs suggesting a more pronounced effect in individuals with early and mild cognitive impairment.

Conclusion

The findings of this review suggest that individuals consuming higher amounts of LC ω3 PUFAs are less likely to develop cognitive impairment and that, as a preventative strategy against Alzheimer’s disease, it is most effective when dietary LC ω3 PUFAs are consumed prior to or in the early stages of cognitive decline.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02655-4.

Case-cohort study of plasma phospholipid fatty acid profiles, cognitive function, and risk of dementia: a secondary analysis in the Ginkgo Evaluation of Memory Study

BACKGROUND

Phospholipids are biomarkers of dietary fat intake and metabolism, linked to several cardiometabolic disorders. Few prospective studies have assessed plasma phospholipids in relation to dementia risk and cognitive function.

OBJECTIVES

We aimed to evaluate the association between a decrease in linoleic acid accompanied with an increase in other fatty acids and cognitive function and dementia risk.

METHODS

We conducted a case-cohort study nested within the Ginkgo Evaluation of Memory Study. We included 1252 participants, 498 of whom who developed dementia during a mean of 5 y of follow-up. We measured 45 individual plasma phospholipids (as a percentage of total plasma phospholipid fatty acids) by GC and related these to Modified Mini-Mental State Examination (3MSE) scores at baseline and neurologist-adjudicated incidence of all-cause dementia and Alzheimer disease (AD), adjusting for sociodemographic and clinical characteristics.

RESULTS

Substitution of 1% of SFAs for 1% of linoleic acid, the predominant polyunsaturated n-6 (ɷ-6) fatty acid, was associated with higher risk of dementia (HR per 1% of SFAs instead of linoleic acid = 1.03; 95% CI: 1.00, 1.07) and a 0.08 point lower 3MSE score at baseline (95% CI: -0.12, -0.03), signifying worse cognitive function. When compared with linoleic acid, we found no associations of total monounsaturated, n-3 polyunsaturated, or trans fatty acids with risk of dementia or AD. However, the substitution of 1% of the marine n-3 PUFA DHA for linoleic acid was associated with lower risk of dementia (HR = 0.86 per 1% of DHA instead of linoleic acid; 95% CI: 0.76, 0.96). These associations were not modified by apolipoprotein E genotype, mild cognitive impairment at baseline, age, or sex.

CONCLUSIONS

Specific elements of diet may be associated with late-life dementia, a hypothesis that requires formal testing in randomized controlled trials and that represents a possible preventive intervention.

Dietary fatty acids and risk for Alzheimer's disease, dementia, and mild cognitive impairment: A prospective cohort meta-analysis

The association between dietary fatty acid intake and Alzheimer's disease (AD), dementia, and mild cognitive impairment (MCI) risk is inconsistent. This meta-analysis examined the effect of dietary fatty acid intake in prospective cohort studies including patients with AD, dementia, and MCI. PubMed, China Biology Medicine (CBM), China National Knowledge Infrastructure (CNKI), Wanfang Data, and VIP Database were systematically searched through September 2020. The random-effects model was used to combine the highest and lowest categories of multivariable adjusted relative risk (RR). Prospective cohort studies that included associations between dietary fatty acid intake and the risk for AD, dementia, or MCI were included. Fourteen studies were included, comprising 54 177 participants: 1696 patients with AD, 1118 patients with dementia, and 2889 with MCI. The pooled RR showed a significant association only between ω-3 polyunsaturated fatty acid (PUFA) intake and MCI risk (RR, 0.86; 95% CI, 0.75-0.98), with no heterogeneity between studies (I² = 0%). The intake of total fatty acids, saturated fatty acids (SFAs), cholesterol, monounsaturated fatty acids (MUFAs), PUFAs, ω-3 PUFAs, ω-6 PUFAs, docosahexaenoic acids (DHAs), and eicosapentaenoic acids (EPAs) was not significantly associated with AD risk. The intake of total fatty acids, SFAs, MUFAs, PUFAs, and ω-3 PUFAs was not significantly associated with dementia risk. This meta-analysis provided evidence that ω-3 PUFA intake may be negatively associated with MCI risk.

APOE ε4 alters associations between docosahexaenoic acid and preclinical markers of Alzheimer's disease

Docosahexaenoic acid is the main long-chain omega-3 polyunsaturated fatty acids in the brain and accounts for 30−40% of fatty acids in the grey matter of the human cortex. Although the influence of docosahexaenoic acid on memory function is widely researched, its association with brain volumes is under investigated and its association with spatial navigation is virtually unknown. This is despite the fact that spatial navigation deficits are a new cognitive fingerprint for symptomatic and asymptomatic Alzheimer’s disease. We investigated the cross-sectional relationship between docosahexaenoic acid levels and the major structural and cognitive markers of preclinical Alzheimer’s disease, namely hippocampal volume, entorhinal volume and spatial navigation ability. Fifty-three cognitively normal adults underwent volumetric magnetic resonance imaging, measurements of serum docosahexaenoic acid (DHA, including lysophosphatidylcholine DHA) and APOE ε4 genotyping. Relative regional brain volumes were calculated and linear regression models were fitted to examine DHA associations with brain volume. APOE genotype modulated serum DHA associations with entorhinal cortex volume and hippocampal volume. Linear models showed that greater serum DHA was associated with increased entorhinal cortex volume, but not hippocampal volume, in non APOΕ ε4 carriers. APOE also interacted with serum lysophosphatidylcholine DHA to predict hippocampal volume. After testing interactions between DHA and APOE on brain volume, we investigated whether DHA and APOE interact to predict spatial navigation performance on a novel virtual reality diagnostic test for Alzheimer’s disease in an independent population of APOE genotyped adults (n = 46). APOE genotype modulated DHA associations with spatial navigation performance, showing that DHA was inversely associated with path integration in APOE ε4 carriers only. This exploratory analysis suggests that interventions aiming to increase DHA blood levels to protect against cognitive decline should consider APOE ε4 carrier status. Future work should focus on replicating our initial findings and establishing whether a specific dose of supplementary DHA, at a particular time in the preclinical disease course can have a positive impact on Alzheimer’s disease progression in APOE ε4 carriers.

Diet-Cognition Associations Differ in Mild Cognitive Impairment Subtypes

Cognitive function is not generally associated with diet, and there is debate over that association. Moreover, little is known about such associations with the specific cognitive domains and subtypes of mild cognitive impairment (MCI). We analyzed data of 4309 Chinese adults aged 55 and over from the Community-based Cohort Study on Nervous System Diseases from 2018–2019. Dietary habits were assessed at inclusion using a validated semi-quantitative food frequency questionnaire. Cognitive function of the participants was measured by using the Montreal Cognitive Assessment. Analyses were performed using multiple logistic regression and quantile regression with adjustment for socio-demographic, lifestyle, and health-related factors. Compared with normal cognition participants, those with a worse cognition state were characterized as being an older age and lower economic level. After adjustment for potential factors, participants with higher consumption of rice, legumes, fresh vegetables, fresh fruit, pork, poultry, fish, and nuts tended to have higher scores of global cognitive function and domains, and to have lower odds of MCI, while those with higher consumption levels of wheat and eggs had worse cognition, compared with the corresponding bottom consumption level of each food. Participants with a medium consumption level of beef or mutton had 57% (OR: 1.57, 95%CI: 1.07–2.32) higher odds of aMCI-SD, whereas they had 50% (OR: 0.50, 95%CI: 0.34–0.73) lower odds of naMCI-MD. Similarly, the highest consumption level of dairy was positively associated with the odds of aMCI-SD (OR:1.51, 95%CI:1.00–2.29), but inversely linked to the odds of naMCI-SD (OR: 0.60, 95%CI: 0.38–0.93) and naMCI-MD (OR: 0.49, 95%CI: 0.29–0.82). Most diet global cognitive benefits were observed to be associated with the preexisting higher consumption of rice, legumes, fresh vegetables, fresh fruit, meat, and nuts. In addition, the heterogeneity of associations between the consumption of certain foods and MCI subtypes was observed among Chinese adults aged over 55 years. These cross-sectional observations require validation in prospective studies.

Association Between Dietary Fish and PUFA Intake in Midlife and Dementia in Later Life: The JPHC Saku Mental Health Study

BACKGROUND

The relationship between midlife dietary habits and risk of dementia remains unclear.

OBJECTIVE

To investigate the association between dietary fish and n-3 polyunsaturated fatty acid (PUFA) consumption in midlife and risk of dementia in later life.

METHODS

This population-based cohort study assessed food frequency (average intake in 1995 and 2000) and cognition (2014-2015) in 1,127 participants (aged 45-64 in 1995). We used logistic regression analyses to calculate odds ratios (ORs) for dementia and mild cognitive impairment (MCI) diagnoses for consumption quartiles of fish, PUFA-rich fish, total n-3 PUFAs, total n-6 PUFAs, types of PUFAs, and n-3/n-6 PUFA ratio. Estimated ORs were adjusted for age; sex; education; smoking status; alcohol consumption frequency; physical activity; histories of cancer, myocardial infarction, and diabetes mellitus; and depression.

RESULTS

Significantly reduced risks of dementia over non-dementia (MCI plus cognitively normal) were observed in the second (OR = 0.43 (95% CI = 0.20-0.93)), third (OR = 0.22 (95% CI = 0.09-0.54)), and highest quartiles (OR = 0.39 (95% CI = 0.18-0.86)) for fish; the third (OR = 0.39 (95% CI = 0.16-0.92)) and highest quartiles (OR = 0.44 (95% CI = 0.19-0.98)) for eicosapentaenoic acid (EPA); the second (OR = 0.39 (95% CI = 0.18-0.84)), third (OR = 0.30 (95% CI = 0.13-0.70)), and highest quartiles (OR = 0.28 (95% CI = 0.12-0.66)) for docosahexaenoic acid (DHA); and the third (OR = 0.36 (95% CI = 0.16-0.85)) and highest quartiles (OR = 0.42 (95% CI = 0.19-0.95)) for docosapentaenoic acid (DPA).

CONCLUSION

High intake of fish in midlife might aid in preventing dementia.

Association Between Oral Health and the Medical Costs of Dementia: A Longitudinal Study of Older Japanese

OBJECTIVE

Oral health status may be associated with dementia, which in turn results in higher medical costs among older people.

METHODS

This STUDY enrolled 4,275 older individuals. Generalized linear models were constructed with the medical costs of dementia as the dependent variable, and number of teeth, Community Periodontal Index (CPI), and other factors as independent variables.

RESULTS

Individuals with fewer teeth or with poor periodontal condition had significantly higher medical costs ratios for dementia independent of other confounding variables. The adjusted medical costs ratios of dementia were 4.13 (95% CI [confidence interval]; 1.79-9.56) for those with ≤9 teeth compared with those with ≥20 teeth and 3.48 (95% CI; 1.71-7.08) for those with personal CPI code 4 compared with those with personal CPI code 0-2.

CONCLUSIONS

Oral health status was associated with the medical costs of dementia. Preventing tooth loss and maintaining periodontal health may contribute to controlling dementia costs.

Dietary fish hydrolysate supplementation containing n-3 LC-PUFAs and peptides prevents short-term memory and stress response deficits in aged mice

Brain aging is characterized by a decline in cognitive functions, which can lead to the development of neurodegenerative pathologies. Age-related spatial learning and memory deficits are associated with a chronic low-grade inflammation. Anxiety disorders and stress response alterations, occurring for a part of the elderly, have also been linked to an increased neuroinflammation and thus, an accelerated cognitive decline. Nutrition is an innovative strategy to prevent age-related cognitive impairments. Among the nutrients, n-3 long chain polyunsaturated fatty acids (LC-PUFAs) and low molecular weight peptides from proteins, especially those from marine resources, are good candidates for their immunomodulatory, anxiolytic and neuroprotective properties. The aim of this study is to determine the combined effect of n-3 LC-PUFAs and low molecular weight peptides on cognitive functions, and their mechanism of action. We are the first to show that a dietary supplementation with a fish hydrolysate containing n-3 LC-PUFAs and low molecular weight peptides prevented the age-related spatial short-term memory deficits and modulated navigation strategies adopted during spatial learning. In addition, the fish hydrolysate displayed anxiolytic activities with the reduction of anxiety-like behaviour in aged mice, restored the plasmatic corticosterone levels similar to adult animals following an acute stress and modulated the hypothalamic stress response. These effects on behaviour can be explained by the immunomodulatory and neuroprotective properties of the fish hydrolysate that limited microgliosis in vivo, decreased LPS-induced expression of pro-inflammatory cytokines and increased the expression of growth factors such as BDNF and NGF in vitro. Thus, n-3 LC-PUFAs and low molecular weight peptides contained in the fish hydrolysate can play an important role in the limitation of neuroinflammation and stress response alterations during aging and represent a potential strategy for the prevention of age-related cognitive decline.

Adherence to Healthy Diet Can Delay Alzheimer's Diseases Development: A Systematic Review and Meta-Analysis

A healthy diet has long been indicated to be protective against Alzheimer’s diseases (AD). We carried out a systematic review and meta-analysis of published observational studies to explore the relationship between healthy and unhealthy diets and risk of ADs. We screened PubMed, Scopus, Web of Sciences, Google Scholar, Science Direct, and Embase, and screened manually to identify relevant articles published in English and non-English until Jun 2020. We classified the studied dietary patterns into two groups: healthy and unhealthy diets. The pooled weighted mean difference and 95% confidence interval (95% CI) was used to analyze the data using a random-effects model. The data were extracted manually and the preferred reporting items for systematic review and meta-analysis checklist was used to appraise the risk of bias and quality of data. Of the 1,813 articles identified, 21 met the inclusion criteria and were included in the quantitative analysis. A healthy diet was related to a lower risk of AD [odds ratio (OR): 0.45, 95% CI: 0.23 to 0.86, I²=99.7%; n=17 studies]. Moreover, high adherence to an unhealthy diet was not associated with increased risk of AD (OR: 0.99, 95% CI: 0.98 to 0.99, I²=0.0%; n=6 studies). However, the etiology of AD is uncertain and it is difficult draw conclusions about dietary healthy patterns. We concluded that adherence to a healthy diet is associated with a lower risk of AD, but were unable to find evidence that an unhealthy diet increases the risk of AD.

Dietary fatty acids and risk of Alzheimer's disease and related dementias: Observations from the Washington Heights-Hamilton Heights-Inwood Columbia Aging Project (WHICAP)

INTRODUCTION

High dietary intake of long chain, polyunsaturated fatty acids is associated with lower Alzheimer's disease (AD) risk.

METHODS

Washington Heights-Hamilton Heights-Inwood Columbia Aging Project is a multiethnic, prospective observational study of aging and dementia among elderly (≥ 65 years). Dietary intake was measured using a food frequency questionnaire. Dietary short-, medium-, and long-chain fatty acid intakes were categorized by number of carbons and double bonds. Consensus AD diagnoses were made. Associations between AD risk and dietary fatty acid and cholesterol intakes were estimated using multivariable Cox proportional hazards regression models.

RESULTS

Of 2612 multiethnic women (67%) and men (baseline age 76.3 [6.4] years), 380 developed AD over an average 4.5 years follow-up. Lower risk of AD was associated with increasing intakes of docosahexaenoic acid (DHA; hazard ratio [HR] = 0.73, 95% confidence interval [CI]: 0.57 to 0.95, P = 0.018) and eicosapentaenoic acid (EPA; HR = 0.74, 95% CI: 0.57 to 0.95, P = 0.021), and longer AD-free survival (P < 0.05).

DISCUSSION

Higher intake of DHA and EPA are protective for AD.

Dietary Habits and Risk of Early-Onset Dementia in an Italian Case-Control Study

Risk of early-onset dementia (EOD) might be modified by environmental factors and lifestyles, including diet. The aim of this study is to evaluate the association between dietary habits and EOD risk. We recruited 54 newly-diagnosed EOD patients in Modena (Northern Italy) and 54 caregivers as controls. We investigated dietary habits through a food frequency questionnaire, assessing both food intake and adherence to dietary patterns, namely the Greek-Mediterranean, the Dietary Approaches to Stop Hypertension (DASH), and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets. We modeled the relation between dietary factors and risk using the restricted cubic spline regression analysis. Cereal intake showed a U-shaped relation with EOD, with risk increasing above 350 g/day. A high intake (>400 g/day) of dairy products was also associated with excess risk. Although overall fish and seafood consumption showed no association with EOD risk, we found a U-shaped relation with preserved/tinned fish, and an inverse relation with other fish. Similarly, vegetables (especially leafy) showed a strong inverse association above 100 g/day, as did citrus and dry fruits. Overall, sweet consumption was not associated with EOD risk, while dry cake and ice-cream showed a positive relation and chocolate products an inverse one. For beverages, we found no relation with EOD risk apart from a U-shaped relation for coffee consumption. Concerning dietary patterns, EOD risk linearly decreased with the increasing adherence to the MIND pattern. On the other hand, an inverse association for the Greek-Mediterranean and DASH diets emerged only at very high adherence levels. To the best of our knowledge, this is the first study that explores the association between dietary factors and EOD risk, and suggests that adherence to the MIND dietary pattern may decrease such risk.

The Challenge by Multiple Environmental and Biological Factors Induce Inflammation in Aging: Their Role in the Promotion of Chronic Disease

The aging process is driven by multiple mechanisms that lead to changes in energy production, oxidative stress, homeostatic dysregulation and eventually to loss of functionality and increased disease susceptibility. Most aged individuals develop chronic low-grade inflammation, which is an important risk factor for morbidity, physical and cognitive impairment, frailty, and death. At any age, chronic inflammatory diseases are major causes of morbimortality, affecting up to 5-8% of the population of industrialized countries. Several environmental factors can play an important role for modifying the inflammatory state. Genetics accounts for only a small fraction of chronic-inflammatory diseases, whereas environmental factors appear to participate, either with a causative or a promotional role in 50% to 75% of patients. Several of those changes depend on epigenetic changes that will further modify the individual response to additional stimuli. The interaction between inflammation and the environment offers important insights on aging and health. These conditions, often depending on the individual's sex, appear to lead to decreased longevity and physical and cognitive decline. In addition to biological factors, the environment is also involved in the generation of psychological and social context leading to stress. Poor psychological environments and other sources of stress also result in increased inflammation. However, the mechanisms underlying the role of environmental and psychosocial factors and nutrition on the regulation of inflammation, and how the response elicited for those factors interact among them, are poorly understood. Whereas certain deleterious environmental factors result in the generation of oxidative stress driven by an increased production of reactive oxygen and nitrogen species, endoplasmic reticulum stress, and inflammation, other factors, including nutrition (polyunsaturated fatty acids) and behavioral factors (exercise) confer protection against inflammation, oxidative and endoplasmic reticulum stress, and thus ameliorate their deleterious effect. Here, we discuss processes and mechanisms of inflammation associated with environmental factors and behavior, their links to sex and gender, and their overall impact on aging.

DO-HEALTH: Vitamin D3 - Omega-3 - Home exercise - Healthy aging and longevity trial - Design of a multinational clinical trial on healthy aging among European seniors

DO-HEALTH is a multi-center clinical trial among 2157 community-dwelling European men and women age 70 and older. The 2x2x2 randomized-control factorial design trial tested the individual and additive benefit, as well as the cost-effectiveness, of 3 interventions: vitamin D 2000 IU/day, omega-3 fatty acids 1000 mg/day (EPA + DHA, ratio 1:2), and a 30-minute 3 times/week home exercise (strength versus flexibility). Each treatment tested has shown considerable prior promise from mechanistic studies, small clinical trials, or large cohort studies, in the prevention of common age-related chronic diseases, but definitive data are missing. DO-HEALTH will test these interventions in relation to 6 primary endpoints (systolic and diastolic blood pressure, non-vertebral fractures, Short Physical Performance Battery score, the Montreal Cognitive Assessment, and risk of infections), plus several secondary endpoints explored in ancillary studies (i.e. rate of any falls and injurious falls, joint pain, oral health, quality of life, and incident frailty). As the 3 interventions have distinct mechanisms of action for each of the 6 primary endpoints, a maximum benefit is expected for their additive benefit as a "multi-modal" intervention. The trial duration is 3 years with in-person contacts with all participants at 4 clinical visits and by quarterly phone calls. Baseline and follow-up blood samples were collected in all participants to measure changes in 25-hydroxyvitamin D and poly-unsaturated fatty acid concentrations. Our objective was to test interventions that are expected to promote healthy aging and longer life expectancy and that can be easily and safely implemented by older community-dwelling adults.

Expert Opinion on Benefits of Long-Chain Omega-3 Fatty Acids (DHA and EPA) in Aging and Clinical Nutrition

Life expectancy is increasing and so is the prevalence of age-related non-communicable diseases (NCDs). Consequently, older people and patients present with multi-morbidities and more complex needs, putting significant pressure on healthcare systems. Effective nutrition interventions could be an important tool to address patient needs, improve clinical outcomes and reduce healthcare costs. Inflammation plays a central role in NCDs, so targeting it is relevant to disease prevention and treatment. The long-chain omega-3 polyunsaturated fatty acids (omega-3 LCPUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are known to reduce inflammation and promote its resolution, suggesting a beneficial role in various therapeutic areas. An expert group reviewed the data on omega-3 LCPUFAs in specific patient populations and medical conditions. Evidence for benefits in cognitive health, age- and disease-related decline in muscle mass, cancer treatment, surgical patients and critical illness was identified. Use of DHA and EPA in some conditions is already included in some relevant guidelines. However, it is important to note that data on the effects of omega-3 LCPUFAs are still inconsistent in many areas (e.g., cognitive decline) due to a range of factors that vary amongst the trials performed to date; these factors include dose, timing and duration; baseline omega-3 LCPUFA status; and intake of other nutrients. Well-designed intervention studies are required to optimize the effects of DHA and EPA in specific patient populations and to develop more personalized strategies for their use.

Intake of Meat, Fish, Fruits, and Vegetables and Long-Term Risk of Dementia and Alzheimer's Disease

BACKGROUND

The links between diet and the risk of dementia have never been studied considering the possibility of protopathic bias (i.e., reverse causation).

OBJECTIVE

We aimed to examine the relationship between consumption frequency of meat, fish, fruits, and vegetables and long-term risk of dementia and Alzheimer's disease (AD), by taking into account this possibility.

METHODS

We analyzed data of 5,934 volunteers aged 65 and over from the Three-city study who were followed every 2 to 4 years for 12 years. Dietary habits were assessed at inclusion using a brief food frequency questionnaire. The presence of symptoms of dementia was investigated at each follow-up visit. To limit the risk of protopathic bias, a 4-year lag window between exposure and disease assessment was implemented by excluding from the analyses all dementia cases that occurred during the first four years after inclusion. Analyses were performed using a Cox proportional hazard model and were adjusted for socio-demographic, lifestyle, and health factors.

RESULTS

The average follow-up time was 9.8 years. During this period, 662 cases of dementia, including 466 of AD, were identified. After adjustment, only low meat consumption (≤1 time/week) was associated with an increased risk of dementia and AD compared with regular consumption (≥4 times/week) (HR = 1.58 95% CI = [1.17-2.14], HR = 1.67 95% CI = [1.18-2.37], respectively). No association was found between the consumption of fish, raw fruits, or cooked fruits and vegetables and the risk of dementia or AD.

CONCLUSION

These findings suggest very low meat consumption increases the long-term risk of dementia and AD, and that a protopathic bias could have impacted finding from previous studies.

Midlife Dietary Intakes of Monounsaturated Acids, n-6 Polyunsaturated Acids, and Plant-Based Fat Are Inversely Associated with Risk of Cognitive Impairment in Older Singapore Chinese Adults

BACKGROUND

Previous studies have shown inconsistent results for the relation between dietary fat intake and cognitive function in the elderly. Furthermore, prospective studies on this topic among the Chinese population are scarce.

OBJECTIVES

We aimed to examine the association between midlife dietary fat intake and risk of cognitive impairment in the elderly.

METHODS

Prospective cohort analysis was conducted among 16,736 participants from the Singapore Chinese Health Study. Dietary information was assessed by a validated FFQ at baseline (1993-1998) when participants aged 45-74 y (mean: 53.5; SD: 6.22). Cognitive impairment was identified using the Singapore modified Mini-Mental State Examination at the third follow-up visit (2014-2016) when participants aged 61-96 y (mean: 73.2; SD: 6.41). Multivariable logistic regression models were used to calculate ORs and 95% CIs.

RESULTS

Cognitive impairment was presented in 2397 participants. When substituted for total carbohydrate, dietary fat intake was inversely related to cognitive impairment (OR comparing extreme quartiles: 0.80; 95% CI: 0.67, 0.94; P-trend = 0.003). The OR (95% CI) comparing extreme quartiles of specific dietary fats was 1.08 (0.89, 1.31; P-trend = 0.51) for SFAs, 0.80 (0.64, 0.99; P-trend = 0.02) for MUFAs, 0.84 (0.72, 0.99; P-trend = 0.02) for PUFAs, 0.92 (0.77, 1.09; P-trend = 0.49) for n-3 PUFAs, and 0.83 (0.70, 0.98; P-trend = 0.01) for n-6 PUFAs. An inverse association was found for plant-based fat (OR: 0.84; 95% CI: 0.72, 0.98; P-trend = 0.02), but not for animal-based fat (OR: 0.96; 95% CI: 0.81, 1.15; P-trend = 0.76). When substituted for SFAs, the OR (95% CI) was 0.77 (0.61, 0.97; P-trend = 0.02) for MUFAs and 0.82 (0.70, 0.95; P-trend = 0.003) for PUFAs.

CONCLUSIONS

We found that substitution of total carbohydrate or SFAs with MUFAs and PUFAs, particularly n-6 PUFAs, was related to a lower risk of cognitive impairment in elderly Chinese participants. In addition, an inverse association with cognitive impairment was found for plant-based fat.

Fish Intake May Affect Brain Structure and Improve Cognitive Ability in Healthy People

As the population ages worldwide, the prevalence of cognitive disorders including mild cognitive impairment (MCI) is increasing. MCI appears in 10–20% of adults aged 65 years and older and is generally referred to as an intermediate stage between normal cognitive aging and dementia. To develop timely prevention and early treatment strategies by identifying biological factors, we investigated the relationship between dietary consumption of fish, brain structure, and MCI in cognitively normal subjects. The brain structure was assessed using neuroimaging-derived measures including the “gray-matter brain healthcare quotient (GM-BHQ)” and “fractional-anisotropy brain healthcare quotient (FA-BHQ),” which are approved as the international standard (H.861.1) by the International Telecommunication Union Telecommunication Standardization Sector. Dietary consumption of fish was calculated using the brief self-administered diet history questionnaire (BDHQ), and MCI was assessed using the Memory Performance Index (MPI) of MCI screening method (MCI Screen). This study showed that fish intake was positively associated with both FA-BHQ and MPI, and FA-BHQ was more strongly associated with MPI than fish intake. Our findings are in line with those in previous studies, but our study further indicates that the condition of the whole brain integrity measured by the FA-BHQ may mediate the relationship between fish intake and MCI prevention in healthy people. In other words, FA-BHQ may be used to identify people at high risk of MCI to provide the appropriate intervention.

n-3 Polyunsaturated Fatty Acids and Their Derivates Reduce Neuroinflammation during Aging

: Aging is associated to cognitive decline, which can lead to loss of life quality, personal suffering, and ultimately neurodegenerative diseases. Neuroinflammation is one of the mechanisms explaining the loss of cognitive functions. Indeed, aging is associated to the activation of inflammatory signaling pathways, which can be targeted by specific nutrients with anti-inflammatory effects. Dietary n-3 polyunsaturated fatty acids (PUFAs) are particularly attractive as they are present in the brain, possess immunomodulatory properties, and are precursors of lipid derivates named specialized pro-resolving mediators (SPM). SPMs are crucially involved in the resolution of inflammation that is modified during aging, resulting in chronic inflammation. In this review, we first examine the effect of aging on neuroinflammation and then evaluate the potential beneficial effect of n-3 PUFA as precursors of bioactive derivates, particularly during aging, on the resolution of inflammation. Lastly, we highlight evidence supporting a role of n-3 PUFA during aging.

Effect of High-Fat Diets on Oxidative Stress, Cellular Inflammatory Response and Cognitive Function

Cognitive dysfunction is linked to chronic low-grade inflammatory stress that contributes to cell-mediated immunity in creating an oxidative environment. Food is a vitally important energy source; it affects brain function and provides direct energy. Several studies have indicated that high-fat consumption causes overproduction of circulating free fatty acids and systemic inflammation. Immune cells, free fatty acids, and circulating cytokines reach the hypothalamus and initiate local inflammation through processes such as microglial proliferation. Therefore, the role of high-fat diet (HFD) in promoting oxidative stress and neurodegeneration is worthy of further discussion. Of particular interest in this article, we highlight the associations and molecular mechanisms of HFD in the modulation of inflammation and cognitive deficits. Taken together, a better understanding of the role of oxidative stress in cognitive impairment following HFD consumption would provide a useful approach for the prevention of cognitive dysfunction.

Ginsenoside Rg3 Prevents Cognitive Impairment by Improving Mitochondrial Dysfunction in the Rat Model of Alzheimer's Disease

Ginseng, the roots and rhizomes of Panax ginseng C. A. Meyer, is used not only as a herbal medicine but also as a functional food to support body functions. Ginsenoside Rg3 (GRg3) is a major bioactive component in ginseng. In this study, the beneficial effects of GRg3 on rats with Alzheimer's disease (AD) were evaluated via the behavioral experiment and antioxidant capacity. Moreover, metabolomic analysis based on UPLC-QTOF-MS/MS and apoptosis analysis was used to obtain the change between AD and GRg3-administrated rats to assess the underlying mechanisms on improving mitochondrial dysfunction. Results showed that GRg3 could prevent the cognitive impairment of AD rats by improving the mitochondrial dysfunction. The potential mechanisms were related to regulate the abnormality of energy metabolism, electron transport chain, amino acid metabolism, purine metabolism, and antiapoptosis. These findings support the exploitation of GRg3 as an effective complementary and functional food to prevent and delay AD.

Omega-3 Fatty Acids and Neurodegenerative Diseases: New Evidence in Clinical Trials

A nutritional approach could be a promising strategy to prevent or slow the progression of neurodegenerative diseases such as Parkinson's and Alzheimer's disease, since there is no effective therapy for these diseases so far. The beneficial effects of omega-3 fatty acids are now well established by a plethora of studies through their involvement in multiple biochemical functions, including synthesis of anti-inflammatory mediators, cell membrane fluidity, intracellular signaling, and gene expression. This systematic review will consider epidemiological studies and clinical trials that assessed the impact of supplementation or dietary intake of omega-3 polyunsaturated fatty acids on neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. Indeed, treatment with omega-3 fatty acids, being safe and well tolerated, represents a valuable and biologically plausible tool in the management of neurodegenerative diseases in their early stages.

Environmentally Optimal, Nutritionally Sound, Protein and Energy Conserving Plant Based Alternatives to U.S. Meat

Because meat is more resource intensive than vegetal protein sources, replacing it with efficient plant alternatives is potentially desirable, provided these alternatives prove nutritionally sound. We show that protein conserving plant alternatives to meat that rigorously satisfy key nutritional constraints while minimizing cropland, nitrogen fertilizer (Nr) and water use and greenhouse gas (GHG) emissions exist, and could improve public health. We develop a new methodology for identifying nutritional constraints whose satisfaction by plant eaters is challenging, disproportionately shaping the optimal diets, singling out energy, mass, monounsaturated fatty acids, vitamins B_3,6,12 and D, choline, zinc, and selenium. By replacing meat with the devised plant alternatives—dominated by tofu, soybeans, peanuts, and lentils—Americans can collectively eliminate pastureland use while saving 35–50% of their diet related needs for cropland, Nr, and GHG emission, but increase their diet related irrigation needs by 15%. While widely replacing meat with plants is logistically and culturally challenging, few competing options offer comparable multidimensional resource use reduction.

The Role of Nutrition for the Aging Population: Implications for Cognition and Alzheimer's Disease

Improved life expectancy worldwide has resulted in a significant increase in age-related diseases. Dementia is one of the fastest growing age-related diseases, with 75 million adults globally projected to develop the condition by 2030. Alzheimer's disease (AD) is the most common form of dementia and represents the most significant stage of cognitive decline. With no cure identified to date for AD, focus is being placed on preventative strategies to slow progression, minimize the burden of neurological disease, and promote healthy aging. Accumulating evidence suggests that nutrition (e.g., via fruit, vegetables, fish) is important for optimizing cognition and reducing risk of AD. This review examines the role of nutrition on cognition and AD, with specific emphasis on the Mediterranean diet (MeDi) and key nutritional components of the MeDi, namely xanthophyll carotenoids and omega-3 fatty acids. Given their selective presence in the brain and their ability to attenuate proposed mechanisms involved in AD pathogenesis (namely oxidative damage and inflammation), these nutritional compounds offer potential for optimizing cognition and reducing the risk of AD.

Nutrients in Alzheimer’s Disease: The Interaction of Diet, Drugs and Disease

In recent decades, clinical trials in Alzheimer’s disease (AD) have failed at an unprecedented rate. The etiology of AD has since come under renewed scrutiny, both to elucidate the underlying pathologies and to identify novel therapeutic strategies. Here, diet has emerged as a potential causative/protective agent. A variety of nutrients, including lipids, minerals, vitamins, antioxidants and sugars as well as broader dietary patterns and microbiotal interactions have demonstrated associations with AD. Although clinical trials have yet to definitively implicate any singular dietary element as therapeutic or causative, it is apparent that dietary preferences, likely in complex synergies, may influence the risk, onset and course of AD. This review catalogs the impact of major dietary elements on AD. It further examines an unexplored reciprocal association where AD may modulate diet, as well as how potential therapeutics may complicate these interactions. In doing so, we observe diet may have profound effects on the outcome of a clinical trial, either as a confounder of a drug/disease interaction or as a generally disruptive covariate. We therefore conclude that future clinical trials in AD should endeavor to control for diet, either in study design or subsequent analyses.

An exploration of the role of a fish-oriented diet in cognitive decline: a systematic review of the literature

Epidemiological studies have presented inconsistent evidence of the correlation between a fish-oriented dietary intake (FDI) and the risk of cognitive decline. To address these controversies, we performed this systematic review of prospective studies published in December 2016 and earlier using PubMed, Embase, and Web of Science. Two independent researchers conducted the eligibility assessment and data extraction; all discrepancies were solved by discussion with a third researcher. The pooled relative risks (RRs) focused on the incidence of events were estimated with 95% confidence intervals (CIs). Overall, nine studies containing 28,754 subjects were analyzed. When the highest and lowest categories of fish consumption were compared, the summary RR for dementia of Alzheimer type (DAT) was 0.80 (95%CI = 0.65–0.97); i.e., people with a higher intake of fish had a 20% (95%CI = 3–35%) decreased risk of DAT. Additionally, the dose-response synthesized data indicated that a 100-g/week increase in fish intake reduced the risk of DAT by an additional 12% (RR = 0.88, 95%CI = 0.79–0.99). Non-significant results were observed for the risk of dementia of all causes (DAC) and mild cognitive impairment (MCI). Limited evidence involving heterogeneity was found within subgroups or across studies. In conclusion, this review confirmed that a higher intake of fish could be correlated with a reduced risk of DAT. Further research, especially prospective studies that specifically quantify FDI, will help find a more accurate assessment of the different levels of dietary intake.

Association between fish consumption and risk of dementia: a new study from China and a systematic literature review and meta-analysis

Objective

To assess the association of fish consumption with risk of dementia and its dose–response relationship, and investigate variations in the association among low-, middle- and high-income countries.

Design

A new community-based cross-sectional study and a systematic literature review.

Settings

Urban and rural communities in China; population-based studies systematically searched from worldwide literature.

Subjects

Chinese adults aged ≥60 years in six provinces (n 6981) took part in a household health survey of dementia prevalence and risk factors. In addition, 33 964 participants from eleven published and eligible studies were included in the systematic review and meta-analysis.

Results

In the new study in China, 326 participants were diagnosed with dementia (4·7 %); those who consumed any amount of fish in the past two years v. those who consumed no fish had reduced risk of dementia (adjusted OR=0·73, 95 % CI 0·64, 0·99), but the dose–response relationship was not statistically significant. The meta-analysis of available data from the literature and the new study showed relative risk (RR) of dementia of 0·80 (95 % CI 0·74, 0·87) for people with fish consumption; the impact was similar among countries with different levels of income. Pooled dose–response data revealed RR (95 % CI) of 0·84 (0·72, 0·98), 0·78 (0·68, 0·90) and 0·77 (0·61, 0·98) in people with low, middle and high consumption of fish, respectively. Corresponding figures for Alzheimer’s disease were 0·88 (0·74, 1·04), 0·79 (0·65, 0·96) and 0·67 (0·58, 0·78), respectively.

Conclusions

Greater consumption of fish is associated with a lower risk of dementia. Increasing fish consumption may help prevent dementia worldwide regardless of income level.

Interplay Between the Gut-Brain Axis, Obesity and Cognitive Function

Obesity continues to be one of the major public health problems due to its high prevalence and co-morbidities. Common co-morbidities not only include cardiometabolic disorders but also mood and cognitive disorders. Obese subjects often show deficits in memory, learning and executive functions compared to normal weight subjects. Epidemiological studies also indicate that obesity is associated with a higher risk of developing depression and anxiety, and vice versa. These associations between pathologies that presumably have different etiologies suggest shared pathological mechanisms. Gut microbiota is a mediating factor between the environmental pressures (e.g., diet, lifestyle) and host physiology, and its alteration could partly explain the cross-link between those pathologies. Westernized dietary patterns are known to be a major cause of the obesity epidemic, which also promotes a dysbiotic drift in the gut microbiota; this, in turn, seems to contribute to obesity-related complications. Experimental studies in animal models and, to a lesser extent, in humans suggest that the obesity-associated microbiota may contribute to the endocrine, neurochemical and inflammatory alterations underlying obesity and its comorbidities. These include dysregulation of the HPA-axis with overproduction of glucocorticoids, alterations in levels of neuroactive metabolites (e.g., neurotransmitters, short-chain fatty acids) and activation of a pro-inflammatory milieu that can cause neuro-inflammation. This review updates current knowledge about the role and mode of action of the gut microbiota in the cross-link between energy metabolism, mood and cognitive function.

Effect of Chlorogenic Acid Intake on Cognitive Function in the Elderly: A Pilot Study

Objective

To evaluate the effect of chlorogenic acids (CGAs) intake on cognitive function.

Methods

In this pilot study, the Cogstate and CNS Vital Signs test batteries were used to evaluate cognitive function in 8 healthy elderly men and women complaining of subjective memory loss after a 6-month intake of a test beverage containing 330 mg of CGAs just before bedtime.

Results

After a 6-month CGA intake period, significant improvement was observed in the One Back Test of the Cogstate, the Shifting Attention Test, and Finger Tapping Test as well as in the composite memory, verbal memory, complex attention, cognitive flexibility, executive function, and motor speed domains of the CNS Vital Signs test battery.

Conclusion

A 6-month intake of CGAs may improve attentional, executive, and memory functions in the elderly with complaints of subjective memory loss.

Markers of neuroprotection of combined EPA and DHA provided by fish oil are higher than those of EPA (Nannochloropsis) and DHA (Schizochytrium) from microalgae oils in Wistar rats

Background

To overcome the current overexploitation of fish rich in n-3 long chain polyunsaturated fatty acids (LCPUFA), microalgae have become a promising marine lipid source. The purpose of this study was to assess eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), isolated or combined from distinct marine origins, on the promotion of neuroprotective effects.

Methods

The experiment lasted for 10 weeks and involved 32 Wistar rats, divided into 4 diets (n = 8): a diet rich in milk fat was taken as control (Milk Fat) and compared to n-3 LCPUFA enriched diets, either in EPA + DHA form through fish oil (Fish Oil), or EPA through Nannochloropsis oil (Nanno), or DHA through Schizochytrium oil (Schyzo), while maintaining Milk Fat incorporation.

Results

Plasma lipid profile and dopamine levels were more beneficial in Fish Oil diet. In addition, n-3 LCPUFA incorporation was found increased in liver and erythrocytes from Fish Oil fed rats, suggesting that fish oil is a better dietary source for fatty acids deposition in the organism than microalgae. The Forced Swimming Test revealed a positive behavioural action of EPA + DHA, in opposition to Milk Fat and Nanno diets, which had higher immobile times. mRNA levels of serotonin receptors, HT1A and HT2A along with CREB, the transmission factor for learning and memory, were higher in the hippocampus of rats fed n-3 LCPUFA diets comparative to Milk Fat.

Conclusion

Taken together, the combination of EPA and DHA from fish oil can counteract the undesirable health effects of saturated fat based diets and benefit, in the long run, neurological function.

Horseradish and radish peroxidases eaten with fish could help explain observed associations between fish consumption and protection from age-related dementia

A juxtaposition of regional cuisines and recent prospective studies of fish consumption in China and Japan points to fresh horseradish and/or radish (HRR) as possible contributors to delaying age-related dementia. The hypothesis is that the inverse association found sometimes between fish intake and cognitive decline is partially due to exposure of the oral cavity to active peroxidases from HRR served in conjunction with fish. This hypothesis can be tested by specifically looking at whether HRR is consumed with fish and whether such HRR is prepared in a way that preserves activity of HRR peroxidases. It is possible that by putting active HRR peroxidases in their mouths, elderly people supplement their age-diminished salivary antioxidant capacity and break down additional hydrogen peroxide (H₂O₂) in the oral cavity before it can migrate into the brain, thus decreasing the incidence of brain cell death induction by chronically-elevated H₂O₂. Intentional exposure of the oral cavity to active HRR peroxidases could be a prophylactic for delaying dementia. Because vegetable peroxidases are inactivated by gastric juices, it will be difficult to obtain benefit from HRR peroxidases' antioxidant effect via ingestion in encapsulated dietary supplements.

Effects of N-3 Polyunsaturated Fatty Acids on Dementia

N-3 polyunsaturated fatty acids (PUFAs) including α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have anti-inflammatory effects and neuronal protective functions and may benefit prevention of dementia; however, the epidemiological evidence is very limited. Therefore, the literature about the association between n-3 PUFA and dementia was searched, by using Pubmed. In the analyses of observational studies, n-3 PUFA has been reported to be beneficially associated with dementia in 17 studies; however, the beneficial association between n-3 PUFA and dementia was denied by three studies. In the analyses of intervention studies, n-3 PUFA supplementation was beneficially associated with dementia in eight studies; however, five studies reported the negligible effect of n-3 PUFA for dementia. N-3 PUFA may improve Alzheimer’s disease by increasing clearance of amyloid-β peptide, neurotrophic and neuroprotective factors, and by anti-inflammatory effects. In conclusion, patients with mild memory and/or cognitive impairment can be treated by a long-term and higher intake of n-3 PUFA.