Fish Intake, Genetic Predisposition to Alzheimer Disease, and Decline in Global Cognition and Memory in 5 Cohorts of Older Persons

Association of serum n-3 and n-6 docosapentaenoic acids with cognitive performance in elderly adults: National Health and Nutrition Examination Survey 2011-2014

Limited information exists on the influence of docosapentaenoic acid (DPA) on cognitive function. We investigated the association between serum n-3 and n-6 DPAs and cognitive performance in an elderly population from the National Health and Nutrition Examination Survey, 2011-2014. Restricted cubic spline and logistic regression analyses were utilized. A total of 1,366 older participants were included. Elevated proportions of DPA(n3) in total serum fatty acids were slightly associated with higher DSST scores (OR 0.61, 95% CI (0.38-0.97)), and higher proportions of DPA(n6) in total serum fatty acids were significantly associated with lower scores on different cognitive tests (CERAD (1.64, 1.02-2.65), AFT (2.31, 1.43- 3.75), DSST (3.21, 1.98-5.22) and global cognition (2.85, 1.74-4.66)). After multivariable adjustment, DPA(n3) exhibited no association with cognitive performance, whereas DPA(n6) remained correlated with AFT (1.98, 1.13-3.48), DSST (2.63, 1.43-4.82) and global cognition (2.15, 1.19-3.90). In stratified analyses, higher levels of DPA(n3) were associated with better performance in CERAD among participants aged ≥70, in DSST among those without diabetes and in global cognition among people with lower incomes. Increased DPA(n6) levels were associated with worse performance in AFT and DSST among those aged 60-70 and in all cognitive tests among those with better incomes. In conclusions, elevated levels of serum DPA(n3) may be beneficial for cognitive performance among elderly adults, especially in those over 70 years, with lower incomes and without diabetes. Serum n-6 DPA might be negatively associated with cognitive function, and this association is more pronounced among those who aged 60-70 with higher incomes.

Contrasting Effects of an Atherogenic Diet and High-Protein/Unsaturated Fatty Acids Diet on the Accelerated Aging Mouse Model SAMP8 Phenotype

Background/Objectives: Aging has been extensively studied, with a growing interest in memory impairment by a neurobiological approach. Mitochondrial dysfunction is a hallmark of aging, contributing to the aging phenotype; therefore, mitochondrial interventions seem fundamental. The diet is a physiological approximation for modifying mitochondria, which could impact the age-related phenotype. Methods: We studied two diets with low-carbohydrate and high-fat compositions, differing in the amount of protein and the fat type disposable-the atherogenic diet Cocoa (high protein/high saturated fat/high cholesterol) and the South Beach diet (very high-protein/high-unsaturated fat)-on oxidative stress, mitochondrial state, and hippocampus-dependent memory in 3-month-old Senescence-Accelerated Mouse Model (SAMP8) seed over 3 months to determine their pro- or anti-aging effects. Results: Despite its bad reputation, the Cocoa diet reduces the reactive oxygen species (ROS) content without impacting the energy state and hippocampus-dependent spatial acuity. In contrast to the beneficial impact proposed for the South Beach diet, it induced a pro-aging phenotype, increasing oxidative damage and the levels of NR2B subunit of the NMDA, impairing energy and spatial acuity. Surprisingly, despite the negative changes observed with both diets, this led to subtle memory impairment, suggesting the activation of compensatory mechanisms preventing more severe cognitive decline. Conclusions: Our results demonstrated that diets usually considered good could be detrimental to the onset of aging. Also, probably due to the brain plasticity of non-aged animals, they compensate for the damage, preventing a more aggravated phenotype. Nevertheless, these silent changes could predispose or increase the risk of suffering pathologies at advanced age.

The Association between Individual Food Groups, Limbic System White Matter Tracts, and Episodic Memory: Initial Data from the Aiginition Longitudinal Biomarker Investigation of Neurodegeneration (ALBION) Study

(1) Background: Many studies link food intake with clinical cognitive outcomes, but evidence for brain biomarkers, such as memory-related limbic white matter (WM) tracts, is limited. We examined the association between food groups, limbic WM tracts integrity, and memory performance in community-dwelling individuals. (2) Methods: We included 117 non-demented individuals (ALBION study). Verbal and visual episodic memory tests were administered, and a composite z-score was calculated. Diffusion tensor imaging tractography was applied for limbic WM tracts (fornix-FX, cingulum bundle-CB, uncinate fasciculus-UF, hippocampal perforant pathway zone-hPPZ). Food intake was evaluated through four 24-h recalls. We applied linear regression models adjusted for demographics and energy intake. (3) Results: We found significant associations between (a) higher low-to-moderate alcohol intake and higher FX fractional anisotropy (FA), (b) higher full-fat dairy intake and lower hPPZ FA, and (c) higher red meat and cold cuts intake and lower hPPZ FA. None of the food groups was associated with memory performance. (4) Conclusions: Despite non-significant associations between food groups and memory, possibly due to participants' cognitive profile and/or compensatory mechanisms, the study documented a possible beneficial role of low-to-moderate alcohol and a harmful role of full-fat dairy and red meat and cold cuts on limbic WM tracts.

High-Fat Diets in Animal Models of Alzheimer's Disease: How Can Eating Too Much Fat Increase Alzheimer's Disease Risk?

High dietary intake of saturated fatty acids is a suspected risk factor for neurodegenerative diseases, including Alzheimer's disease (AD). To decipher the causal link behind these associations, high-fat diets (HFD) have been repeatedly investigated in animal models. Preclinical studies allow full control over dietary composition, avoiding ethical concerns in clinical trials. The goal of the present article is to provide a narrative review of reports on HFD in animal models of AD. Eligibility criteria included mouse models of AD fed a HFD defined as > 35% of fat/weight and western diets containing > 1% cholesterol or > 15% sugar. MEDLINE and Embase databases were searched from 1946 to August 2022, and 32 preclinical studies were included in the review. HFD-induced obesity and metabolic disturbances such as insulin resistance and glucose intolerance have been replicated in most studies, but with methodological variability. Most studies have found an aggravating effect of HFD on brain Aβ pathology, whereas tau pathology has been much less studied, and results are more equivocal. While most reports show HFD-induced impairment on cognitive behavior, confounding factors may blur their interpretation. In summary, despite conflicting results, exposing rodents to diets highly enriched in saturated fat induces not only metabolic defects, but also cognitive impairment often accompanied by aggravated neuropathological markers, most notably Aβ burden. Although there are important variations between methods, particularly the lack of diet characterization, these studies collectively suggest that excessive intake of saturated fat should be avoided in order to lower the incidence of AD.

Dietary pattern, food, and nutritional supplement effects on cognitive outcomes in mild cognitive impairment: a systematic review of previous reviews

CONTEXT

Nutritional interventions may benefit cognition in people with mild cognitive impairment (MCI). However, evidence is yet to be synthesized in a way that can inform recommendations for clinical and public health settings.

OBJECTIVE

To systematically review evidence on the effect of dietary patterns, foods, and nutritional supplements on cognitive decline in individuals with MCI.

DATA SOURCES

Guided by the Preferred Reporting items for Systematic Review and Meta-Analysis Protocols 2015 statement, the Medline, EMBASE, and CINAHL databases, the JBI Database of Systematic Reviews and Implementation Reports, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects were searched (publication years 2005 to 2020). Included studies were English-language systematic reviews and meta-analyses of randomized controlled trials and cohort studies reporting on the effectiveness of nutritional interventions on cognition of individuals with MCI.

DATA EXTRACTION

Two reviewers independently selected studies and extracted data on cognitive outcomes and adverse events. Review quality was assessed using AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews-2). Primary study overlap was managed following Cochrane Handbook guidelines.

DATA ANALYSIS

Of the 6677 records retrieved, 20 reviews were included, which, in turn, reported on 43 randomized controlled trials and 1 cohort study that, together, addressed 18 nutritional interventions. Most reviews were limited by quality and the small number of primary studies with small sample sizes. Reviews were mostly positive for B vitamins, omega-3 fatty acids, and probiotics (including 12, 11 and 4 primary studies, respectively). Souvenaid and the Mediterranean diet reduced cognitive decline or Alzheimer's disease progression in single trials with <500 participants. Findings from studies with a small number of participants suggest vitamin D, a low-carbohydrate diet, medium-chain triglycerides, blueberries, grape juice, cocoa flavanols, and Brazil nuts may improve individual cognitive subdomains, but more studies are needed.

CONCLUSIONS

Few nutritional interventions were found to convincingly improve cognition of individuals with MCI. More high-quality research in MCI populations is required to determine if nutritional treatments improve cognition and/or reduce progression to dementia.

SYSTEMATIC REVIEW REGISTRATION

Open Science Framework protocol identifier DOI:10.17605/OSF.IO/BEP2S.

A combined DHA-rich fish oil and cocoa flavanols intervention does not improve cognition or brain structure in older adults with memory complaints: results from the CANN randomized, controlled parallel-design study

BACKGROUND

There is evidence that both omega-3 long-chain polyunsaturated fatty acids (PUFAs) (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) and cocoa flavanols can improve cognitive performance in both healthy individuals and in those with memory complaints. However, their combined effect is unknown.

OBJECTIVES

To investigate the combined effect of EPA/DHA and cocoa flavanols (OM3FLAV) on cognitive performance and brain structures in older adults with memory complaints.

METHODS

A randomized placebo-controlled trial of DHA-rich fish oil (providing 1.1 g/d DHA and 0.4 g/d EPA) and a flavanol-rich dark chocolate (providing 500 mg/d flavan-3-ols) was conducted in 259 older adults with either subjective cognitive impairment or mild cognitive impairment. Participants underwent assessment at baseline, 3 mo, and 12 mo. The primary outcome was the number of false-positives on a picture recognition task from the Cognitive Drug Research computerized assessment battery. Secondary outcomes included other cognition and mood outcomes, plasma lipids, brain-derived neurotrophic factor (BDNF), and glucose levels. A subset of 110 participants underwent structural neuroimaging at baseline and at 12 mo.

RESULTS

197 participants completed the study. The combined intervention had no significant effect on any cognitive outcomes, with the exception of reaction time variability (P = 0.007), alertness (P < 0.001), and executive function (P < 0.001), with a decline in function observed in the OM3FLAV group (118.6 [SD 25.3] at baseline versus 113.3 [SD 25.4] at 12 mo for executive function) relative to the control, and an associated decrease in cortical volume (P = 0.039). Compared with the control group, OM3FLAV increased plasma HDL, total cholesterol ratio (P < 0.001), and glucose (P = 0.008) and reduced TG concentrations (P < 0.001) by 3 mo, which were sustained to 12 mo, with no effect on BDNF. Changes in plasma EPA and DHA and urinary flavonoid metabolite concentrations confirmed compliance to the intervention.

CONCLUSIONS

These results suggest that cosupplementation with ω-3 PUFAs and cocoa flavanols for 12 mo does not improve cognitive outcomes in those with cognitive impairment. This trial was registered at clinicaltrials.gov as NCT02525198.

Diet and lifestyle impact the development and progression of Alzheimer's dementia

Dementia is a growing public health concern, with an estimated prevalence of 57 million adults worldwide. Alzheimer's disease (AD) accounts for 60-80% of the cases. Clinical trials testing potential drugs and neuroprotective agents have proven futile, and currently approved drugs only provide symptomatic benefits. Emerging epidemiological and clinical studies suggest that lifestyle changes, including diet and physical activity, offer an alternative therapeutic route for slowing and preventing cognitive decline and dementia. Age is the single most common risk factor for dementia, and it is associated with slowing cellular bioenergetics and metabolic processes. Therefore, a nutrient-rich diet is critical for optimal brain health. Furthermore, type 2 diabetes (T2D) is a risk factor for AD, and diets that reduce the risk of T2D may confer neuroprotection. Foods predominant in Mediterranean, MIND, and DASH diets, including fruits, leafy green vegetables, fish, nuts, and olive oil, may prevent or slow cognitive decline. The mechanisms by which these nutrients promote brain health, however, are not yet completely understood. Other dietary approaches and eating regimes, including ketogenic and intermittent fasting, are also emerging as beneficial for brain health. This review summarizes the pathophysiology, associated risk factors, and the potential neuroprotective pathways activated by several diets and eating regimes that have shown promising results in promoting brain health and preventing dementia.

Dietary folate intake and its association with longitudinal changes in cognition function

BACKGROUND & AIMS

Folate (vitamin B9) is an essential co-factor for one-carbon metabolism. Controversial evidence has emerged regarding the association between folate and cognitive performance. The aim of the study was to investigate the association between baseline dietary folate intake and cognitive decline in a population exposed to mandatory fortification during a median follow-up of 8 years.

METHODS

Multicenter, prospective cohort study involving 15,105 public servants aged 35-74 years old, both sexes, from The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Baseline dietary intake was assessed by a Food Frequency Questionnaire (FFQ). Six cognitive tests were performed in the three waves to assess memory, executive function and global cognition. Linear mixed-effects models were used to assess the association between dietary folate intake at baseline and changes in cognition over time.

RESULTS

Data from 11,276 participants were analyzed. The mean (SD) age was 51.7 (9) years, 50% were women, 63% were overweight/obese, and 56% had graduated from college or more. Overall dietary folate intake was not associated with cognitive decline; neither vitamin B12 intake was a modifier of this association. General dietary supplements and specifically multivitamins use did not affect these findings. Natural food folate group was associated with a slower rate of global cognitive decline (β (95% CI): 0.001 (0.000; 0.002), P = 0.015). There was no association between fortified food group and cognition scores.

CONCLUSION

Overall dietary folate intake was not associated with cognitive function in this Brazilian population. However, folate naturally occurring in food sources may slow global cognitive decline.

Association of Mediterranean-DASH Intervention for Neurodegenerative Delay and Mediterranean Diets With Alzheimer Disease Pathology

BACKGROUND AND OBJECTIVES

Diet may reduce Alzheimer dementia risk and slow cognitive decline, but the understanding of the relevant neuropathologic mechanisms remains limited. The association of dietary patterns with Alzheimer disease (AD) pathology has been suggested using neuroimaging biomarkers. This study examined the association of Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) and Mediterranean dietary patterns with β-amyloid load, phosphorylated tau tangles, and global AD pathology in postmortem brain tissue of older adults.

METHODS

Autopsied participants of the Rush Memory and Aging Project with complete dietary information (collected through a validated food frequency questionnaire) and AD pathology data (β-amyloid load, phosphorylated tau tangles, and global AD pathology [summarized neurofibrillary tangles and neuritic and diffuse plaques]) were included in this study. Linear regression models controlled for age at death, sex, education, APOE-ε4 status, and total calories were used to investigate the dietary patterns (MIND and Mediterranean diets) and dietary components associated with AD pathology. Further effect modification was tested for APOE-ε4 status and sex.

RESULTS

Among our study participants (N = 581, age at death: 91.0 ± 6.3 years; mean age at first dietary assessment: 84.2 ± 5.8 years; 73% female; 6.8 ± 3.9 years of follow-up), dietary patterns were associated with lower global AD pathology (MIND: β = -0.022, p = 0.034, standardized β = -2.0; Mediterranean: β = -0.007, p = 0.039, standardized β = -2.3) and specifically less β-amyloid load (MIND: β = -0.068, p = 0.050, standardized β = -2.0; Mediterranean: β = -0.040, p = 0.004, standardized β = -2.9). The findings persisted when further adjusted for physical activity, smoking, and vascular disease burden. The associations were also retained when participants with mild cognitive impairment or dementia at the baseline dietary assessment were excluded. Those in the highest tertile of green leafy vegetables intake had less global AD pathology when compared with those in the lowest tertile (tertile 3 vs tertile 1: β = -0.115, p = 0.0038).

DISCUSSION

The MIND and Mediterranean diets are associated with less postmortem AD pathology, primarily β-amyloid load. Among dietary components, higher green leafy vegetable intake was associated with less AD pathology.

Effect of nutrition in Alzheimer's disease: A systematic review

Background and objective

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by declining cognitive ability. Currently, there are no effective treatments for this condition. However, certain measures, such as nutritional interventions, can slow disease progression. Therefore, the objective of this systematic review was to identify and map the updates of the last 5 years regarding the nutritional status and nutritional interventions associated with AD patients.

Study design

A systematic review.

Methods

A search was conducted for randomized clinical trials, systematic reviews, and meta-analyses investigating the association between nutritional interventions and AD published between 2018 and 2022 in the PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 38 studies were identified, of which 17 were randomized clinical trials, and 21 were systematic reviews and/or meta-analyses.

Results

The results show that the western diet pattern is a risk factor for developing AD. In contrast, the Mediterranean diet, ketogenic diet, and supplementation with omega-3 fatty acids and probiotics are protective factors. This effect is significant only in cases of mild-to-moderate AD.

Conclusion

Certain nutritional interventions may slow the progression of AD and improve cognitive function and quality of life. Further research is required to draw more definitive conclusions.

Supplementation with Flaxseed Oil Rich in Alpha-Linolenic Acid Improves Verbal Fluency in Healthy Older Adults

The effects of docosahexaenoic acid supplements on cognitive function have long been demonstrated, but the effects of alpha-linolenic acid, a precursor of docosahexaenoic acid, have not been fully tested. The search for functional foods that delay cognitive decline in the older adults is considered a very important area from a preventive perspective. The aim of this study was to conduct an exploratory evaluation of alpha-linolenic acid on various cognitive functions in healthy older subjects. Sixty healthy older adults aged 65 to 80 years, living in Miyagi prefecture, without cognitive impairment or depression, were included in the randomized, double-blinded, placebo-controlled clinical trial. Study subjects were randomly divided into two groups and received either 3.7 g/day of flaxseed oil containing 2.2 g of alpha-linolenic acid, or an isocaloric placebo (corn oil) containing 0.04 g of alpha-linolenic acid for 12 weeks. The primary endpoints were six cognitive functions closely related to everyday life: attention and concentration, executive function, perceptual reasoning, working memory, processing speed and memory function. After 12 weeks of intake, changes in verbal fluency scores on the frontal assessment battery at bedside, a neuropsychological test assessing executive function, in which participants are asked to answer as many words as possible in Japanese, were significantly greater in the intervention group (0.30 ± 0.53) than in the control group (0.03 ± 0.49, p < 0.05). All other cognitive test scores were not significantly different between the groups. In conclusion, daily consumption of flaxseed oil containing 2.2 g alpha-linolenic acid improved cognitive function, specifically verbal fluency, despite the age-related decline, in healthy individuals with no cognitive abnormalities. Further validation studies focusing on the effects of alpha-linolenic acid on verbal fluency and executive function in older adults are needed, as verbal fluency is a predictor of Alzheimer's disease development, important for cognitive health.

The association between adherence to a plant-based diet and cognitive ageing

PURPOSE

While the benefits of adopting a more plant-based diet for sustainability and animal welfare are clear, its long-term health impacts, including the impact on cognitive ageing, are limited studied. Therefore, we investigated the associations between plant-based diet adherence and cognitive ageing.

METHODS

Data from a previous intervention study involving community-dwelling adults aged ≥ 65 years were analysed at baseline (n = 658) and after 2-year follow-up (n = 314). Global and domain-specific cognitive functioning were assessed at both timepoints. Overall, healthful and unhealthful plant-based dietary indices were calculated from a 190-item food frequency questionnaire. Multivariate-adjusted linear regression models were applied to test for associations.

RESULTS

After full-adjustment, higher overall adherence to a plant-based diet was not associated with global cognitive function (difference in Z-score, tertile 1 versus 3 [95% CI]: 0.04 [- 0.05, 0.13] p = 0.40) or cognitive change (- 0.04 [- 0.11, 0.04], p = 0.35). Similarly, healthful and unhealthful plant-based diet indices were not associated with cognitive functioning (respectively p = 0.48; p = 0.87) or change (respectively p = 0.21, p = 0.33). Interestingly, we observed fish consumption to influence the association between plant-based diet adherence and cognitive functioning (p-interaction = 0.01), with only individuals with a fish consumption of ≥ 0.93 portion/week benefitting from better overall plant-based diet adherence (β per 10-point increment [95% CI]: 0.12 [0.03, 0.21] p = 0.01).

CONCLUSION

We did not demonstrate associations of a more plant-based diet with cognitive ageing. However, possibly such association exists in a subpopulation with higher fish intake. This would be in line with earlier observations that diets rich in plant foods and fish, such as the Mediterranean diet, may be beneficial for cognitive ageing.

TRIAL REGISTRATION

Registered at clinicaltrials.gov (NCT00696514) on June 12, 2008.

Analysis of associations between dietary patterns, genetic disposition, and cognitive function in data from UK Biobank

PURPOSE

Research suggests that diet influences cognitive function and the risk for neurodegenerative disease. The present study aimed to determine whether a recently developed diet score, based on recommendations for dietary priorities for cardio metabolic health, was associated with fluid intelligence, and whether these associations were modified by individual genetic disposition.

METHODS

This research has been conducted using the UK Biobank Resource. Analyses were performed using self-report data on diet and the results for the verbal-numerical reasoning test of fluid intelligence of 104,895 individuals (46% male: mean age at recruitment 57.1 years (range 40-70)). For each participant, a diet score and a polygenic score (PGS) were constructed, which evaluated predefined cut-offs for the intake of fruit, vegetables, fish, processed meat, unprocessed meat, whole grain, and refined grain, and ranged from 0 (unfavorable) to 7 (favorable). To investigate whether the diet score was associated with fluid intelligence, and whether the association was modified by PGS, linear regression analyses were performed.

RESULTS

The average diet score was 3.9 (SD 1.4). After adjustment for selected confounders, a positive association was found between baseline fluid intelligence and PGS (P < 0.001). No association was found between baseline fluid intelligence and diet score (P = 0.601), even after stratification for PGS, or in participants with longitudinal data available (n = 9,482).

CONCLUSION

In this middle-aged cohort, no evidence was found for an association between the investigated diet score and either baseline or longitudinal fluid intelligence. However, as in previous reports, fluid intelligence was strongly associated with a PGS for general cognitive function.

Which components of the Mediterranean diet are associated with dementia? A UK Biobank cohort study

Cohort studies suggest that the Mediterranean diet is associated with better global cognition in older adults, slower cognitive decline and lower risk of dementia. However, little is known about the relative contribution of each component of the Mediterranean diet to dementia risk or whether the diet's effects are due to one or more specific food components. We aimed to examine whether Mediterranean diet components are associated with all-cause dementia risk in the UK BioBank cohort. Participants joined the UK Biobank study from 2006 to 2010 and were followed until December 2020. 249,511 participants, who were at least 55 years old, without dementia at baseline were included. We used self-reported consumption of food groups, considered part of the Mediterranean diet including fruit, vegetables, processed meat, unprocessed red meat and unprocessed poultry, fish, cheese, wholegrains. Incident dementia was ascertained through electronic linkage to primary care records, hospital and mortality records or self-report. In this study with a total follow-up of 2,868,824 person-years (median 11.4), after adjusting for all covariates and other food groups, moderate fish consumption of between 2.0 and 3.9 times a week was associated with decreased risk of dementia (HR 0.84, 95%CI 0.71-0.98) compared to no consumption. Additionally, fruit consumption of between 1.0 and 1.9 servings a day was associated with reduced dementia risk (HR 0.85, 95%CI 0.74-0.99) compared to no consumption. No other Mediterranean diet components were associated with dementia risk suggesting that fish consumption may drive the beneficial effects seen from the Mediterranean diet. Further study of potential mechanisms and diet-based intervention trials are needed to establish this.

The EAT-Lancet reference diet and cognitive function across the life course

The EAT-Lancet Commission devised a sustainable reference diet with the aim of reducing the incidence of non-communicable diseases and mortality globally while improving food system sustainability. The extent to which the reference diet supports cognitive function across the life course, however, has not yet been evaluated. This Review assesses the evidence for diet supporting cognitive function from childhood into old age. A comprehensive but non-exhaustive literature search was done, synthesising studies that investigated the effect of whole foods on cognition in healthy, community-dwelling human participants. We found that the current evidence base is weak with mixed conclusions and multiple methodological caveats, which precludes strong conclusions pertaining to the suitability of dietary recommendations for each food group per age group. Long-term intervention and prospective cohort studies are needed to reduce this knowledge deficit. Revising dietary recommendations with the aim of maintaining an adequate nutrient intake to sustain healthy cognitive function across the life course could be worthwhile. This Review outlines recommendations for future work to help improve the current knowledge deficit regarding dietary intake and cognitive function across the life course and its implications for dietary guidelines such as the EAT-Lancet Commission.

Nutrients and Bioactive Compounds in Seafood: Quantitative Literature Research Analysis

This perspective presents current and updated advances in research on nutrients and bioactive compounds in seafood. It is based on a literature quantitative research analysis approach. The main features of seafood components are introduced. This perspective aims at providing a current framework that relates nutrients, bioactive compounds, and seafood in a novel integrated and multidisciplinary manner, highlighting the current knowledge, the main research lines, and emerging strategies. The literature search was carried out by means of the Scopus database, and 22,542 documents were retrieved in the period from 1932 to 2024. Particularly, from the perspective of nutrition and health outputs, the main terms correlated with research on the relationship between seafood and nutritional and bioactive components, and the main existing research lines focused on this topic, were identified. The top recurring keywords were human/s, female, diet, nutrition, fish, male, adult, food intake.

Higher Dietary Intake of Advanced Glycation End Products Is Associated with Faster Cognitive Decline in Community-Dwelling Older Adults

OBJECTIVE

Dietary-derived advanced glycation end products (AGEs) vary for different food types and the methods employed during their preparation may contribute to diverse chronic health conditions. The goal of this study was to investigate the associations of dietary AGEs (dAGEs) with cognitive decline in older adults.

METHODS

Non-demented older adults (n = 684) underwent annual testing with 19 cognitive tests summarized as a global cognitive score based on five cognitive domains. We modified a previously validated food frequency questionnaire designed to assess dAGE. The modified questionnaire assessed portion size and frequency of consumption of six food groups (meat, poultry, fish, cheese, spreads, and processed foods), as well as the method of their preparation (e.g., grilling, boiling). dAGE was the sum of the scores of the six food groups. Linear mixed-effect models were used to examine the association of baseline dAGE with cognitive decline. All models controlled for age, sex, education, race, and body mass index (BMI).

RESULTS

Average follow-up was 3.0 years. Higher baseline dAGEs was associated with a faster rate of global cognitive decline (Estimate = -0.003 (standard error = 0.001, p-value = 0.015). This association was driven by declines in episodic memory (-0.004 (0.002, 0.013)) and perceptual speed (-0.003 (0.001, 0.049)) but not by semantic memory, working memory, and visuospatial domains. These associations were not attenuated by controlling for cardiovascular risk factors and diseases, including diabetes. Levels of dAGE of the specific food groups were not associated with cognitive decline.

CONCLUSIONS

Higher levels of dietary AGE levels in older adults are associated with faster cognitive decline. These data lend further support for the importance of diet and that its modification may slow or prevent late-life cognitive impairment. Further clinical studies will be needed and the molecular mechanisms underlying these associations will need to be identified.

Subjective cognitive decline and total energy intake: Talk too much?

The increasing longevity of the population has resulted in dementia becoming a leading cause of both death and disability. Dementia is not a single disease. Studies of rare Mendelian disorders have documented that Alzheimer's disease, the most common cause of dementia, is associated with a long incubation period from amyloid deposition to neurodegeneration to mild cognitive impairment and dementia. There are three broad hypotheses related to the causes of Alzheimer's dementia: (1) an aging process; (2) brain vascular disease; and (3) metabolic abnormalities associated with either increased production of amyloid-β or decreased clearance from the brain. Therefore, research on the early stages of the dementia process are of high priority. This paper reports that higher energy intake in both the Nurses' Health Study and Health Professionals Follow-up Study is associated with very early symptoms that lead to mild cognitive impairment and dementia. The results are very interesting but hard to interpret because they also show that higher energy intake is not related to body mass index, a very unusual observation. A likely hypothesis is that there is an association between reporting of dietary intake and subjective symptoms, i.e. reporting bias, accounting for their results.

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.

Pelargonidin and Berry Intake Association with Alzheimer's Disease Neuropathology: A Community-Based Study

BACKGROUND

An anthocyanidin, pelargonidin, primarily found in berries, has antioxidant and anti-inflammatory properties, and is associated with better cognition and reduced Alzheimer's dementia risk.

OBJECTIVE

This study investigated if pelargonidin or berry intake is associated with Alzheimer's disease (AD) neuropathology in human brains.

METHODS

The study was conducted among 575 deceased participants (age at death = 91.3±6.1 years; 70% females) of the Rush Memory and Aging Project, with dietary data (assessed using a food frequency questionnaire) and neuropathological evaluations. Calorie-adjusted pelargonidin intake was modeled in quartiles and berry intake as continuous (servings/week). Mean amyloid-beta load and phosphorylated tau neuronal neurofibrillary tangle density across multiple cortical regions were assessed using immunohistochemistry. Global AD pathology burden, a quantitative summary score of neurofibrillary tangles, and diffuse and neuritic plaques using Bielschowsky silver stains in multiple brain regions, was also assessed.

RESULTS

In a linear regression model adjusted for age at death, sex, education, APOE ɛ4 status, vitamin E, and vitamin C, participants in the highest quartile of pelargonidin intake when compared to those in the lowest quartile, had less amyloid-β load (β (SE) = -0.293 (0.14), p = 0.038), and fewer phosphorylated tau tangles (β (SE) = -0.310, p = 0.051). Among APOE ɛ4 non-carriers, higher strawberry (β (SE) = -0.227 (0.11), p = 0.037) and pelargonidin (Q4 versus Q1: β (SE) = -0.401 (0.16), p = 0.011; p trend = 0.010) intake was associated with less phosphorylated tau tangles, no association was observed in APOE ɛ4 carriers. Berry intake was not associated with AD pathology. However, excluding participants with dementia or mild cognitive impairment at baseline, strawberry (p = 0.004) and pelargonidin (ptrend = 0.007) intake were associated with fewer phosphorylated tau tangles.

CONCLUSION

Higher intake of pelargonidin, a bioactive present in strawberries, is associated with less AD neuropathology, primarily phosphorylated tau tangles.

Connecting Cohorts to Diminish Alzheimer's Disease (CONCORD-AD): A Report of an International Research Collaboration Network

Longitudinal observational cohort studies are being conducted worldwide to understand cognition, biomarkers, and the health of the aging population better. Cross-cohort comparisons and networks of registries in Alzheimer's disease (AD) foster scientific exchange, generate insights, and contribute to the evolving clinical science in AD. A scientific working group was convened with invited investigators from established cohort studies in AD, in order to form a research collaboration network as a resource to address important research questions. The Connecting Cohorts to Diminish Alzheimer's Disease (CONCORD-AD) collaboration network was created to bring together global resources and expertise, to generate insights and improve understanding of the natural history of AD, to inform design of clinical trials in all disease stages, and to plan for optimal patient access to disease-modifying therapies once they become available. The network brings together expertise and data insights from 7 cohorts across Australia, Europe, and North America. Notably, the network includes populations recruited through memory clinics as well as population-based cohorts, representing observations from individuals across the AD spectrum. This report aims to introduce the CONCORD-AD network, providing an overview of the cohorts involved, reporting the common assessments used, and describing the key characteristics of the cohort populations. Cohort study designs and baseline population characteristics are compared, and available cognitive, functional, and neuropsychiatric symptom data, as well as the frequency of biomarker assessments, are summarized. Finally, the challenges and opportunities of cross-cohort studies in AD are discussed.

Fish Intake and MRI Burden of Cerebrovascular Disease in Older Adults

BACKGROUND AND OBJECTIVES

Fish intake may prevent cerebrovascular disease (CVD), yet the mechanisms are unclear, especially regarding its impact on subclinical damage. Assuming that fish may have pleiotropic effect on cerebrovascular health, we investigated the association of fish intake with global CVD burden based on brain MRI markers.

METHODS

This cross-sectional analysis included participants from the Three-City Dijon population-based cohort (age ≥65 years) without dementia, stroke, or history of hospitalized cardiovascular disease who underwent brain MRI with automated assessment of white matter hyperintensities, visual detection of covert infarcts, and grading of dilated perivascular spaces. Fish intake was assessed through a frequency questionnaire, and the primary outcome measure was defined as the first component of a factor analysis of mixed data applied to MRI markers. The association of fish intake with the CVD burden indicator was studied with linear regressions.

RESULTS

In total, 1,623 participants (mean age 72.3 years, 63% women) were included. The first component of factor analysis (32.4% of explained variance) was associated with higher levels of all 3 MRI markers. Higher fish intake was associated with lower CVD burden. In a model adjusted for total intracranial volume, compared to participants consuming fish <1 time per week, those consuming fish 2 to 3 and ≥4 times per week had a β = -0.19 (95% confidence interval -0.37 to -0.01) and β = -0.30 (-0.57 to -0.03) lower indicator of CVD burden, respectively (p trend < 0.001). We found evidence of effect modification by age such that the association of fish to CVD was stronger in younger participants (65-69 years) and not significant in participants ≥75 years of age. For comparison, in the younger age group, consuming fish 2 to 3 times a week was roughly equivalent (in the opposite direction) to the effect of hypertension.

DISCUSSION

In this large population-based study, higher frequency of fish intake was associated with lower CVD burden, especially among participants <75 years of age, suggesting a beneficial effect on brain vascular health before manifestation of overt brain disease.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in individuals without stroke or dementia, higher fish intake is associated with lower subclinical CVD on MRI.

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.

Interactions between dietary patterns and genetic factors in relation to incident dementia among 70-year-olds

PURPOSE

To investigate potential interactions between dietary patterns and genetic factors modulating risk for Alzheimer's disease (AD) in relation to incident dementia.

METHODS

Data were derived from the population-based Gothenburg H70 Birth Cohort Studies in Sweden, including 602 dementia-free 70-year-olds (examined 1992-93, or 2000-02; 64% women) followed for incident dementia until 2016. Two factors from a reduced rank regression analysis were translated into dietary patterns, one healthy (e.g., vegetables, fruit, and fish) and one western (e.g., red meat, refined cereals, and full-fat dairy products). Genetic risk was determined by APOE ε4 status and non-APOE AD-polygenic risk scores (AD-PRSs). Gene-diet interactions in relation to incident dementia were analysed with Cox regression models. The interaction p value threshold was < 0.1.

RESULTS

There were interactions between the dietary patterns and APOE ε4 status in relation to incident dementia (interaction p value threshold of < 0.1), while no evidence of interactions were found between the dietary patterns and the AD-PRSs. Those with higher adherence to a healthy dietary pattern had a reduced risk of dementia among ε4 non-carriers (HR: 0.77; 95% CI: 0.61; 0.98), but not among ε4 carriers (HR: 0.86; CI: 0.63; 1.18). Those with a higher adherence to the western dietary pattern had an increased risk of dementia among ε4 carriers (HR: 1.37; 95% CI: 1.05; 1.78), while no association was observed among ε4 non-carriers (HR: 0.99; CI: 0.81; 1.21).

CONCLUSIONS

The results of this study suggest that there is an interplay between dietary patterns and APOE ε4 status in relation to incident dementia.

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.

Seafood Intake as a Method of Non-Communicable Diseases (NCD) Prevention in Adults

Seafood (fish in particular) is one of the main food groups in nutrition models with proven health benefits. Seafood has long been considered a very valuable dietary component, mainly due to presence of n-3 polyunsaturated fatty acids (n-3 PUFA) but it is also an important source of protein (including collagen), anserine, taurine, iodine, selenium, vitamin A, vitamin K, vitamin D, tocopherols, B vitamins and astaxanthin. Considering the beneficial effects of these ingredients on blood pressure, lipid profile and the inflammatory process, seafood should be an essential component of the diet. Non-communicable diseases (NCD) such as cardiovascular diseases, cancer, diabetes and mental disorder, chronic respiratory diseases are common diseases associated with advanced age. Promotion of a healthy lifestyle (including proper nutritional behavior) and prevention of diseases are the most effective and efficient ways to decrease premature mortality from NCD and to maintain mental health and well-being. This review article shows the potential preventive and therapeutic effects of seafood with an emphasis on fish. Our narrative review presents the results of systematic reviews and meta-analysis.

Can Natural Products Exert Neuroprotection without Crossing the Blood-Brain Barrier?

The scope of evidence on the neuroprotective impact of natural products has been greatly extended in recent years. However, a key question that remains to be answered is whether natural products act directly on targets located in the central nervous system (CNS), or whether they act indirectly through other mechanisms in the periphery. While molecules utilized for brain diseases are typically bestowed with a capacity to cross the blood–brain barrier, it has been recently uncovered that peripheral metabolism impacts brain functions, including cognition. The gut–microbiota–brain axis is receiving increasing attention as another indirect pathway for orally administered compounds to act on the CNS. In this review, we will briefly explore these possibilities focusing on two classes of natural products: omega-3 polyunsaturated fatty acids (n-3 PUFAs) from marine sources and polyphenols from plants. The former will be used as an example of a natural product with relatively high brain bioavailability but with tightly regulated transport and metabolism, and the latter as an example of natural compounds with low brain bioavailability, yet with a growing amount of preclinical and clinical evidence of efficacy. In conclusion, it is proposed that bioavailability data should be sought early in the development of natural products to help identifying relevant mechanisms and potential impact on prevalent CNS disorders, such as Alzheimer’s disease.

Dietary Reference Intakes based on chronic disease endpoints: outcomes from a case study workshop for omega 3's EPA and DHA

Given the focus on developing Dietary Reference Intakes (DRIs) based on chronic disease risk reduction and recent research for omega-3 long chain PUFA since the last DRI review, the Canadian Nutrition Society convened a panel of stakeholders for a 1-day workshop in late 2019. Attendees discussed the new NASEM guidelines for establishing DRI values based on chronic disease risk endpoints and the strength of current evidence for EPA and DHA as it relates to the new guidelines. Novelty: Summarizes evidence and expert opinions regarding the potential for reviewing DRI values for EPA and DHA and cardiovascular disease risk and early development.

Eicosapentaenoic Acid Is Associated with Decreased Incidence of Alzheimer's Dementia in the Oldest Old

BACKGROUND

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) may have different effects on cognitive health due to their anti- or pro-inflammatory properties.

METHODS

We aimed to prospectively examine the relationships between n-3 and n-6 PUFA contents in serum phospholipids with incident all-cause dementia and Alzheimer's disease dementia (AD). We included 1264 non-demented participants aged 84 ± 3 years from the German Study on Ageing, Cognition, and Dementia in Primary Care Patients (AgeCoDe) multicenter-cohort study. We investigated whether fatty acid concentrations in serum phospholipids, especially eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), alpha-linolenic acid (ALA), linoleic acid (LA), dihomo-γ-linolenic acid (DGLA), and arachidonic acid (AA), were associated with risk of incident all-cause dementia and AD.

RESULTS

During the follow-up window of seven years, 233 participants developed dementia. Higher concentrations of EPA were associated with a lower incidence of AD (hazard ratio (HR) 0.76 (95% CI 0.63; 0.93)). We also observed that higher concentrations of EPA were associated with a decreased risk for all-cause dementia (HR 0.76 (95% CI 0.61; 0.94)) and AD (HR 0.66 (95% CI 0.51; 0.85)) among apolipoprotein E ε4 (APOE ε4) non-carriers but not among APOE ε4 carriers. No other fatty acids were significantly associated with AD or dementia.

CONCLUSIONS

Higher concentrations of EPA were associated with a lower risk of incident AD. This further supports a beneficial role of n-3 PUFAs for cognitive health in old age.

A Scoping Review of Dietary Factors Conferring Risk or Protection for Cognitive Decline in APOE ε4 Carriers

Alzheimer's disease (AD) is a progressive and fatal neurodegenerative disease. The strongest genetic risk factor for sporadic AD is carriage of the ε4 allele of the Apolipoprotein E (APOE) gene. Strategies to slow the progression of AD, including dietary interventions, may be modified by the pathogenic effect of this polymorphism. Our objective in this review was to determine the extent and quality of the literature investigating how dietary factors and interventions interact with the APOE ε4 genotype to impact cognitive decline in AD. To that end, we performed a systematic scoping review of published English-language articles involving human subjects. We found evidence suggesting that adherence to a Mediterranean diet may reduce cognitive decline among APOE ε4 carriers, whereas ketogenic agents appear to be ineffective. Diets high in saturated fats may be particularly harmful for APOE ε4 carriers. We identified several topics, including the use of ω-3 fatty acid and antioxidant supplements, for which additional high level evidence is needed.

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.

Behavioral, neuromorphological, and neurobiochemical effects induced by omega-3 fatty acids following basal forebrain cholinergic depletion in aged mice

Background

In recent years, mechanistic, epidemiologic, and interventional studies have indicated beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFA) against brain aging and age-related cognitive decline, with the most consistent effects against Alzheimer’s disease (AD) confined especially in the early or prodromal stages of the pathology.

In the present study, we investigated the action of n-3 PUFA supplementation on behavioral performances and hippocampal neurogenesis, volume, and astrogliosis in aged mice subjected to a selective depletion of basal forebrain cholinergic neurons. Such a lesion represents a valuable model to mimic one of the most reliable hallmarks of early AD neuropathology.

Methods

Aged mice first underwent mu-p75-saporin immunotoxin intraventricular lesions to obtain a massive cholinergic depletion and then were orally supplemented with n-3 PUFA or olive oil (as isocaloric control) for 8 weeks. Four weeks after the beginning of the dietary supplementation, anxiety levels as well as mnesic, social, and depressive-like behaviors were evaluated. Subsequently, hippocampal morphological and biochemical analyses and n-3 PUFA brain quantification were carried out.

Results

The n-3 PUFA treatment regulated the anxiety alterations and reverted the novelty recognition memory impairment induced by the cholinergic depletion in aged mice. Moreover, n-3 PUFA preserved hippocampal volume, enhanced neurogenesis in the dentate gyrus, and reduced astrogliosis in the hippocampus. Brain levels of n-3 PUFA were positively related to mnesic abilities.

Conclusions

The demonstration that n-3 PUFA are able to counteract behavioral deficits and hippocampal neurodegeneration in cholinergically depleted aged mice promotes their use as a low-cost, safe nutraceutical tool to improve life quality at old age, even in the presence of first stages of AD.

To Keto or Not to Keto? A Systematic Review of Randomized Controlled Trials Assessing the Effects of Ketogenic Therapy on Alzheimer Disease

Alzheimer disease (AD) is a global health concern with the majority of pharmacotherapy choices consisting of symptomatic treatment. Recently, ketogenic therapies have been tested in randomized controlled trials (RCTs), focusing on delaying disease progression and ameliorating cognitive function. The present systematic review aimed to aggregate the results of trials examining the effects of ketogenic therapy on patients with AD/mild cognitive impairment (MCI). A systematic search was conducted on PubMed, CENTRAL, clinicaltrials.gov, and gray literature for RCTs performed on adults, published in English until 1 April, 2019, assessing the effects of ketogenic therapy on MCI and/or AD compared against placebo, usual diet, or meals lacking ketogenic agents. Two researchers independently extracted data and assessed risk of bias with the Cochrane tool. A total of 10 RCTs were identified, fulfilling the inclusion criteria. Interventions were heterogeneous, acute or long term (45-180 d), including adherence to a ketogenic diet, intake of ready-to-consume drinks, medium-chain triglyceride (MCT) powder for drinks preparation, yoghurt enriched with MCTs, MCT capsules, and ketogenic formulas/meals. The use of ketoneurotherapeutics proved effective in improving general cognition using the Alzheimer's Disease Assessment Scale-Cognitive, in interventions of either duration. In addition, long-term ketogenic therapy improved episodic and secondary memory. Psychological health, executive ability, and attention were not improved. Increases in blood ketone concentrations were unanimous and correlated to the neurocognitive battery based on various tests. Cerebral ketone uptake and utilization were improved, as indicated by the global brain cerebral metabolic rate for ketones and [11C] acetoacetate. Ketone concentrations and cognitive performance differed between APOE ε4(+) and APOE ε4(-) participants, indicating a delayed response among the former and an improved response among the latter. Although research on the subject is still in the early stages and highly heterogeneous in terms of study design, interventions, and outcome measures, ketogenic therapy appears promising in improving both acute and long-term cognition among patients with AD/MCI. This systematic review was registered at www.crd.york.ac.uk/prospero as CRD42019128311.

Genetic and non-genetic factors associated with the phenotype of exceptional longevity & normal cognition

In this study, we split 2156 individuals from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) data into two groups, establishing a phenotype of exceptional longevity & normal cognition versus cognitive impairment. We conducted a genome-wide association study (GWAS) to identify significant genetic variants and biological pathways that are associated with cognitive impairment and used these results to construct polygenic risk scores. We elucidated the important and robust factors, both genetic and non-genetic, in predicting the phenotype, using several machine learning models. The GWAS identified 28 significant SNPs at p-value [Formula: see text] significance level and we pinpointed four genes, ESR1, PHB, RYR3, GRIK2, that are associated with the phenotype though immunological systems, brain function, metabolic pathways, inflammation and diet in the CLHLS cohort. Using both genetic and non-genetic factors, four machine learning models have close prediction results for the phenotype measured in Area Under the Curve: random forest (0.782), XGBoost (0.781), support vector machine with linear kernel (0.780), and [Formula: see text] penalized logistic regression (0.780). The top four important and congruent features in predicting the phenotype identified by these four models are: polygenic risk score, sex, age, and education.

Racial Differences in Dietary Relations to Cognitive Decline and Alzheimer's Disease Risk: Do We Know Enough?

The elderly population in the US is increasing and projected to be 44% minority by 2060. African Americans and Hispanics are at increased risk of cognitive impairment and Alzheimer’s disease compared to non-Hispanic whites. These conditions are associated with many other adverse health outcomes, lower quality of life, and substantial economic burden. In the past few decades, diet has been identified as an important modifiable risk factor for cognitive decline and Alzheimer’s disease. Some studies report poor diet quality among African American and Hispanic older adult populations compared to their white counterparts. We have a limited understanding of how diet affects brain health in different racial-ethnic groups. One primary reason for our lack of knowledge is that most cohort studies are of majority non-Hispanic white participants. Moreover, those that do include minority participants do not publish their findings stratified by racial-ethnic groups, and likely have a less accurate measurement of dietary intake among minority groups. In this review, we summarize the current, albeit limited, literature on racial/ethnic differences in dietary relations to dementia outcomes. We will also discuss methodological issues in conducting nutrition studies in diverse cultures, and suggestions for future research directions. Overcoming the gaps will make it possible to make dietary recommendations for Alzheimer’s prevention that are more relevant for different racial/ethnic groups and set us on a faster track to reduce health disparities.

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.

Perspective: The Potential Role of Circulating Lysophosphatidylcholine in Neuroprotection against Alzheimer Disease

Alzheimer disease (AD), the most common cause of dementia, is a progressive disorder involving cognitive impairment, loss of learning and memory, and neurodegeneration affecting wide areas of the cerebral cortex and hippocampus. AD is characterized by altered lipid metabolism in the brain. Lower concentrations of long-chain PUFAs have been described in the frontal cortex, entorhinal cortex, and hippocampus in the brain in AD. The brain can synthesize only a few fatty acids; thus, most fatty acids must enter the brain from the blood. Recent studies show that PUFAs such as DHA (22:6) are transported across the blood-brain barrier (BBB) in the form of lysophosphatidylcholine (LPC) via a specific LPC receptor at the BBB known as the sodium-dependent LPC symporter 1 (MFSD2A). Higher dietary PUFA intake is associated with decreased risk of cognitive decline and dementia in observational studies; however, PUFA supplementation, with fatty acids esterified in triacylglycerols did not prevent cognitive decline in clinical trials. Recent studies show that LPC is the preferred carrier of PUFAs across the BBB into the brain. An insufficient pool of circulating LPC containing long-chain fatty acids could potentially limit the supply of long-chain fatty acids to the brain, including PUFAs such as DHA, and play a role in the pathobiology of AD. Whether adults with low serum LPC concentrations are at greater risk of developing cognitive decline and AD remains a major gap in knowledge. Preventing and treating cognitive decline and the development of AD remain a major challenge. The LPC pathway is a promising area for future investigators to identify modifiable risk factors for AD.

Adherence to a Mediterranean diet and cognitive function in the Age-Related Eye Disease Studies 1 & 2

INTRODUCTION

The objective was to determine whether closer adherence to the alternative Mediterranean Diet (aMED) was associated with altered cognitive function.

METHODS

Observational analyses of participants (n = 7,756) enrolled in two randomized trials of nutritional supplements for age-related macular degeneration: Age-Related Eye Disease Study (AREDS) and AREDS2.

RESULTS

Odds ratios for cognitive impairment, in aMED tertile 3 (vs 1), were 0.36 (P = .0001) for Modified Mini-Mental State (<80) and 0.56 (P = .001) for composite score in AREDS, and 0.56 for Telephone Interview Cognitive Status-Modified (<30) and 0.48 for composite score (each P < .0001) in AREDS2. Fish intake was associated with higher cognitive function. In AREDS2, rate of cognitive decline over 5 to 10 years was not significantly different by aMED but was significantly slower (P = .019) with higher fish intake.

DISCUSSION

Closer Mediterranean diet adherence was associated with lower risk of cognitive impairment but not slower decline in cognitive function. Apolipoprotein E (APOE) haplotype did not influence these relationships.

Neuroprotective Role of Dietary Supplementation with Omega-3 Fatty Acids in the Presence of Basal Forebrain Cholinergic Neurons Degeneration in Aged Mice

As major components of neuronal membranes, omega-3 polyunsaturated fatty acids (n-3 PUFA) exhibit a wide range of regulatory functions. Recent human and animal studies indicate that n-3 PUFA may exert beneficial effects on aging processes. Here we analyzed the neuroprotective influence of n-3 PUFA supplementation on behavioral deficits, hippocampal neurogenesis, volume loss, and astrogliosis in aged mice that underwent a selective depletion of basal forebrain cholinergic neurons. Such a lesion represents a valid model to mimic a key component of the cognitive deficits associated with dementia. Aged mice were supplemented with n-3 PUFA or olive oil (as isocaloric control) for 8 weeks and then cholinergically depleted with mu-p75-saporin immunotoxin. Two weeks after lesioning, mice were behaviorally tested to assess anxious, motivational, social, mnesic, and depressive-like behaviors. Subsequently, morphological and biochemical analyses were performed. In lesioned aged mice the n-3 PUFA pre-treatment preserved explorative skills and associative retention memory, enhanced neurogenesis in the dentate gyrus, and reduced volume and VAChT levels loss as well as astrogliosis in hippocampus. The present findings demonstrating that n-3 PUFA supplementation before cholinergic depletion can counteract behavioral deficits and hippocampal neurodegeneration in aged mice advance a low-cost, non-invasive preventive tool to enhance life quality during aging.

Inflammation and cardiovascular disease: are marine phospholipids the answer?

This review presents the latest research on the cardioprotective effects of n-3 fatty acids (FA) and n-3 FA bound to polar lipids (PL). Overall, n-3 PL may have enhanced bioavailability and potentially bioactivityversusfree FA and ester forms of n-3 FA.

Diet-Related Metabolites Associated with Cognitive Decline Revealed by Untargeted Metabolomics in a Prospective Cohort

SCOPE

Untargeted metabolomics may reveal preventive targets in cognitive aging, including within the food metabolome.

METHODS AND RESULTS

A case-control study nested in the prospective Three-City study includes participants aged ≥65 years and initially free of dementia. A total of 209 cases of cognitive decline and 209 controls (matched for age, gender, education) with slower cognitive decline over up to 12 years are contrasted. Using untargeted metabolomics and bootstrap-enhanced penalized regression, a baseline serum signature of 22 metabolites associated with subsequent cognitive decline is identified. The signature includes three coffee metabolites, a biomarker of citrus intake, a cocoa metabolite, two metabolites putatively derived from fish and wine, three medium-chain acylcarnitines, glycodeoxycholic acid, lysoPC(18:3), trimethyllysine, glucose, cortisol, creatinine, and arginine. Adding the 22 metabolites to a reference predictive model for cognitive decline (conditioned on age, gender, education and including ApoE-ε4, diabetes, BMI, and number of medications) substantially increases the predictive performance: cross-validated Area Under the Receiver Operating Curve = 75% [95% CI 70-80%] compared to 62% [95% CI 56-67%].

CONCLUSIONS

The untargeted metabolomics study supports a protective role of specific foods (e.g., coffee, cocoa, fish) and various alterations in the endogenous metabolism responsive to diet in cognitive aging.

Social Determinants of Racial Disparities in Cognitive Functioning in Later Life in Canada

Objective: The objectives of this study were (a) to assess the nature and extent of racial disparities in cognitive functioning among older adults in Canada, and (b) to assess the role of socioeconomic factors and patterned health behaviors as social determinants of racial disparities in cognitive functioning. Method: Data were drawn from the 2009-2010 Canadian Community Health Survey. The study sample included 20,646 people aged 60 years or older. Ordered logistic regression analyses were carried out to test hypotheses linking race, socioeconomic factors, and patterned health behaviors, and cognitive functioning. Results: Our findings revealed a racial gap in cognitive functioning among older adults in Canada. This gap was, in part, mediated by socioeconomic inequalities (in income and food security) and socially patterned behaviors (i.e., drinking, physical activity levels). However, socioeconomic status (SES) and behavioral factors appeared to operate independently of one another. Discussion: The findings suggest a need to focus on the direct effects of race as well as its indirect effects, through socioeconomic factors and patterned health behaviors, for an understanding of racial disparities in cognitive functioning.

Effects of seafood consumption and toenail mercury and selenium levels on cognitive function among American adults: 25 y of follow up

OBJECTIVES

The aim of this study was to examine the longitudinal association between seafood and intake of long-chain ω-3 polyunsaturated fatty acids (LCω-3 PUFA) and cognitive function and to explore the possible effect modifications owing to mercury (Hg) and selenium (Se) levels.

METHODS

Participants (N = 3231) from the CARDIA (Coronary Artery Risk Development in Young Adults) study underwent baseline examination and were reexamined in eight follow-up visits. Diet was assessed at baseline and in exam years 7 and 20. Toenail Hg and Se were measured at exam year 2. Cognitive function was measured at exam year 25 using three tests: Rey Auditory Verbal Learning Test (RAVLT), Digit Symbol Substitution Test (DSST), and the Stroop test. The general linear regression model was used to examine cumulative average intakes of LCω-3 PUFA and seafood in relation to the cognitive test scores; and to explore the possible effect modifications caused by Hg and Se.

RESULTS

LCω-3 PUFA intake was significantly associated with better performance in the DSST test (quintile 5 versus quintile 1; mean difference = 1.74; 95% confidence interval, 0.19-3.29; Ptrend, 0.048]), but not in the RAVLT and Stroop tests. Similar results were observed for intakes of eicosapentaenoic acid, docosahexaenoic acid, and non-fried seafood. The observed associations were more pronounced in participants with body mass index ≥25 kg/m2, but not significantly modified by toenail Hg or Se.

CONCLUSION

This longitudinal study supported the hypothesis that LCω-3 PUFA or non-fried seafood intake is associated with better cognitive performance in psychomotor speed among US adults, especially those who are overweight or obese.

Insulin Peptides as Mediators of the Impact of Life Style in Alzheimer's disease

The search for the cause of Alzheimer's disease (AD), that affects millions of people worldwide, is currently one of the most important scientific endeavors from a clinical perspective. There are so many mechanisms proposed, and so disparate changes observed, that it is becoming a challenging task to provide a comprehensive view of possible pathogenic processes in AD. Tauopathy (intracellular neurofibrillary tangles) and amyloidosis (extracellular amyloid plaques) are the anatomical hallmarks of the disease, and the formation of these proteinaceous aggregates in specific brain areas is widely held as the ultimate pathogenic mechanism. However, the triggers of this dysproteostasis process remain unknown. Further, neurofibrillary tangles and plaques may only constitute the last stages of a process of still uncertain origin. Thus, without an established knowledge of its etiology, and no cure in the horizon, prevention - or merely delaying its development, has become a last-resort goal in AD research. As with other success stories in preventive medicine, epidemiological studies have provided basic knowledge of risk factors in AD that may contribute to understand its etiology. Disregarding old age, gender, and ApoE4 genotype as non preventable risk factors, there are diverse life-style traits - many of them closely related to cardiovascular health, that have been associated to AD risk. Most prominent among them are diet, physical and mental activity, exposure to stress, and sleep/wake patterns. We argue that all these life-style factors engage insulinergic pathways that affect brain function, providing a potentially unifying thread for life-style and AD risk. Although further studies are needed to firmly establish a link between faulty insulinergic function and AD, we herein summarize the evidence that this link should be thoroughly considered.