Erythrocyte omega-3 fatty acids are inversely associated with incident dementia: Secondary analyses of longitudinal data from the Women's Health Initiative Memory Study (WHIMS)

Omega-3 world map: 2024 update

In 2016, the first worldwide n3 PUFA status map was published using the Omega-3 Index (O3I) as standard biomarker. The O3I is defined as the percentage of EPA + DHA in red blood cell (RBC) membrane FAs. The purpose of the present study was to update the 2016 map with new data. In order to be included, studies had to report O3I and/or blood EPA + DHA levels in metrics convertible into an estimated O3I, in samples drawn after 1999. To convert the non-RBC-based EPA + DHA metrics into RBC we used newly developed equations. Baseline data from clinical trials and observational studies were acceptable. A literature search identified 328 studies meeting inclusion criteria encompassing 342,864 subjects from 48 countries/regions. Weighted mean country O3I levels were categorized into very low ≤4%, low >4-6%, moderate >6-8%, and desirable >8%. We found that the O3I in most countries was low to very low. Notable differences between the current and 2016 map were 1) USA, Canada, Italy, Turkey, UK, Ireland and Greece (moving from the very low to low category); 2) France, Spain and New Zealand (low to moderate); and 3) Finland and Iceland (moderate to desirable). Countries such as Iran, Egypt, and India exhibited particularly poor O3I levels.

ω-3 Polyunsaturated Fatty Acid Status Testing in Humans: A Narrative Review of Commercially Available Options

There is an increasing body of evidence supporting a link between low intakes of ω-3 long-chain polyunsaturated fatty acids (LCPUFA) and numerous diseases and health conditions. However, few people are achieving the levels of fish/seafood or eicosapentaenoic acid and docosahexaenoic acid intake recommended in national and international guidelines. Knowledge of a person's ω-3 LCPUFA status will benefit the interpretation of research results and could be expected to lead to an increased effort to increase intake. Dietary intake survey methods are often used as a surrogate for measuring ω-3 PUFA tissue status and its impact on health and functional outcomes. However, because individuals vary widely in their ability to digest and absorb ω-3 PUFA, analytical testing of biological samples is desirable to accurately evaluate ω-3 PUFA status. Adipose tissue is the reference biospecimen for measuring tissue fatty acids, but less-invasive methods, such as measurements in whole blood or its components (e.g., plasma, serum, red blood cell membranes) or breast milk are often used. Numerous commercial laboratories provide fatty acid testing of blood and breast milk samples by different methods and present their results in a variety of reports such as a full fatty acid profile, ω-3 and ω-6 fatty acid profiles, fatty acid ratios, as well as the Omega-3 Index, the Holman Omega-3 Test, OmegaScore, and OmegaCheck, among others. This narrative review provides information about the different ways to measure ω-3 LCPUFA status (including both dietary assessments and selected commercially available analytical tests of blood and breast milk samples) and discusses evidence linking increased ω-3 LCPUFA intake or status to improved health, focusing on cardiovascular, neurological, pregnancy, and eye health, in support of recommendations to increase ω-3 LCPUFA intake and testing.

Plasma Omega-3 Fatty Acids and Risk for Incident Dementia in the UK Biobank Study: A Closer Look

Dietary omega-3 fatty acids are promising nutrients in dementia. Several prospective cohort studies have examined the relationships between circulating omega-3 (an objective biomarker of dietary intake) and incident dementia, the largest to date being a report from the UK Biobank (n = 102,722). Given the recent release of new metabolomics data from baseline samples from the UK Biobank, we re-examined the association in a much larger sample (n = 267,312) and also focused on associations with total omega-3, docosahexaenoic acid (DHA), and non-DHA omega-3. Using Cox regression models, we observed that the total omega-3 status was inversely related to the risk of Alzheimer's (Q5 vs. Q1, hazard ratio [95% confidence interval] = 0.87 [0.76; 1.00]) and all-cause dementia (Q5 vs. Q1, 0.79 [0.72; 0.87]). The strongest associations were observed for total omega-3 (and non-DHA omega-3) and all-cause dementia. In prespecified strata, we found stronger associations in men, and in those aged ≥60 years at baseline (vs. those aged 50-59). Thus, in the largest study to date on this topic, we confirmed the favorable relationships between DHA and risk for dementia, and we also found evidence that non-DHA omega-3 may be beneficial. Finally, we have better defined the populations most likely to benefit from omega-3-based interventions.

Omega-3 index, cardiorespiratory fitness, and cognitive function in mid-age and older adults

Higher levels of omega-3 fatty acids in red blood cell membranes (omega-3 index or O3I) and cardiorespiratory fitness (CRF) are each associated with reduced cognitive impairment, but little research has examined the relationship between O3I and cognitive function while accounting for CRF. We analyzed cross-sectional data from 5,464 healthy men and women aged 55-85 years who had preventive medical examinations between 2009 and 2023. Primary exposures included O3I (<4.0%, 4.0-7.9%, or ≥ 8.0%) and age- and sex-based CRF quintile (1 = low, 2-3 = moderate, 4-5 = high). Cognitive impairment was defined as a Montreal Cognitive Assessment score of ≤ 25. We used Poisson regression to estimate relative risks (RR) of cognitive impairment, controlling for covariates. O3I < 4% was associated with increased cognitive impairment relative to ≥ 8.0% (RR, 1.21; 95% CI, 1.01-1.44) in a partially adjusted model. This association did not remain statistically significant in the fully adjusted model which included CRF. Low versus high CRF was associated with cognitive impairment (RR, 1.28; 95% CI, 1.07-1.53), independent of O3I and clinical biomarkers. The interaction between CRF and O3I was not significant (P = 0.8). In joint association analysis, risk of cognitive impairment was elevated with lower omega-3 index or CRF or both. Additional research is needed to fully understand the association between O3I and cognitive function at varying CRF levels.

Red Blood Cell Fatty Acid Profiles Are Significantly Altered in South Australian Mild Cognitive Impairment and Alzheimer's Disease Cases Compared to Matched Controls

Nutritional imbalances have been associated with a higher risk for cognitive impairment. This study determined the red blood cell (RBC) fatty acid profile of newly diagnosed mild cognitive impairment (MCI) and Alzheimer's disease (AD) patients compared to age and gender-matched controls. There was a significant increase in palmitic acid (p < 0.00001) for both MCI and AD groups. Saturated fatty acids were significantly elevated in the MCI group, including stearic acid (p = 0.0001), arachidic acid (p = 0.003), behenic acid (p = 0.0002), tricosanoic acid (p = 0.007) and lignoceric acid (p = 0.001). n-6 polyunsaturated fatty acids (PUFAs) were significantly reduced in MCI, including linoleic acid (p = 0.001), γ-linolenic acid (p = 0.03), eicosatrienoic acid (p = 0.009) and arachidonic acid (p < 0.00004). The n-3 PUFAs, α-linolenic acid and docosahexaenoic acid, were both significantly reduced in MCI and AD (p = 0.0005 and p = 0.00003). A positive correlation was evident between the Mini-Mental State Examination score and nervonic acid in MCI (r = 0.54, p = 0.01) and a negative correlation with γ-linolenic acid in AD (r = -0.43, p = 0.05). Differences in fatty acid profiles may prove useful as potential biomarkers reflecting increased risk for dementia.

Omega-3 index as risk factor in psychiatric diseases: a narrative review

Numerous studies have described associations between the omega-3 index (defined as the RBC percentage of EPA and DHA) and mental conditions, but no risk stratification or target value has gathered consensus so far. This narrative review aims to summarize the published data on the association between omega-3 index and mental illness and to contribute to the concept of an omega-3 index in the field of mental health. The bibliographic searches have been carried out in PubMed, Scopus and Web of Science databases to find relevant English language original research studies related to that association. The study search and selection process were registered in a PRISMA flow. Thirty-six studies were included in this review examining the links between omega-3 index and postpartum depression (3), major depression (15), major depression and bipolar disorder (1), bipolar disorder (4), schizophrenia and major depression (1), schizophrenia and other psychosis (5) and dementia (7). Thirty of these studies found either significant differences in omega-3 index between patients and controls or inverse relationships between omega-3 index and disease severity. The published evidence is compelling enough to suggest omega-3 index as a risk factor for some psychiatric diseases, specifically, major depression, postpartum depression, psychosis, and dementia. In occidental populations, we propose a risk threshold of (a) 4-5% in major depression and dementia, (b) 5% in postpartum depression, and (c) 4% for psychosis transition.

Genome-wide association study of Red Blood Cell fatty acids in the Women's Health Initiative Memory Study

Despite their widespread associations with a wide variety of disease phenotypes, the genetics of red blood cell fatty acids remains understudied. We present one of the first genome-wide association studies of red blood cell fatty acid levels, using the Women's Health Initiative Memory study - a prospective cohort of N = 7,479 women aged 65-79. Approximately 9 million SNPs were measured directly or imputed and, in separate linear models adjusted for age and genetic principal components of ethnicity, SNPs were used to predict 28 different fatty acids. SNPs were considered genome-wide significant using a standard genome-wide significance level of p < 1 × 10-8. Twelve separate loci were identified, seven of which replicated results of a prior RBC-FA GWAS. Of the five novel loci, two have functional annotations directly related to fatty acids (ELOVL6 and ACSL6). While overall explained variation is low, the twelve loci identified provide strong evidence of direct relationships between these genes and fatty acid levels. Further studies are needed to establish and confirm the biological mechanisms by which these genes may directly contribute to fatty acid levels.

Circulating polyunsaturated fatty acids, fish oil supplementation, and risk of incident dementia: a prospective cohort study of 440,750 participants

Cohort studies report inconsistent associations between omega-3 polyunsaturated fatty acids (n-3 PUFA) or fish oil and dementia risk. Furthermore, evidence relating omega-6 polyunsaturated fatty acids (n-6 PUFA) with dementia is scarce. Here, we included 440,750 dementia-free participants from UK Biobank to comprehensively investigate the associations between plasma levels of different types of PUFA, fish oil supplementation, and dementia risk. During a median follow-up of 9.25 years, 7768 incident dementia events occurred. Higher plasma levels of five PUFA measures showed consistent associations with lower dementia risk (hazard ratios [95% confidence intervals] for per standard deviation increment of plasma concentrations 0.85 [0.81-0.89] for total PUFAs; 0.90 [0.86-0.95] for omega-3 PUFAs; 0.92 [0.87-0.96] for docosahexaenoic acid (DHA); 0.86 [0.82-0.90] for omega-6 PUFAs; 0.86 [0.82-0.90] for linoleic acid (LA); all p < 0.001). Compared with non-users, fish oil supplement users had a 7% decreased risk of developing all-cause dementia (0.93 [0.89-0.97], p = 0.002), and the relationship was partially mediated by plasma n-3 PUFA levels (omega-3 PUFAs: proportion of mediation = 57.99%; DHA: proportion of mediation = 56.95%). Furthermore, we observed significant associations of plasma n-3 PUFA levels and fish oil supplementation with peripheral immune markers that were related to dementia risk, as well as the positive associations of plasma PUFA levels with brain gray matter volumes and white matter microstructural integrity, suggesting they may affect dementia risk by affecting peripheral immunity and brain structure. Taken together, higher plasma PUFA levels and fish oil supplementation were associated with lower risk of incident dementia. This study may support the value of interventions to target PUFAs (specifically n-3 PUFAs) to prevent dementia.

Association between blood N-3 fatty acid levels and the risk of coronavirus disease 2019 in the UK Biobank

BACKGROUND

The role of nutritional status and the risk of contracting and/or experiencing adverse outcomes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are unclear. Preliminary studies suggest that higher n-3 PUFA intakes are protective.

OBJECTIVES

This study aimed to compare the risk of 3 coronavirus disease 2019 (COVID-19) outcomes (testing positive for SARS-CoV-2, hospitalization, and death) as a function of the baseline plasma DHA levels.

METHODS

The DHA levels (% of total fatty acids [FAs]) were measured by nuclear magnetic resonance. The 3 outcomes and relevant covariates were available for 110,584 subjects (hospitalization and death) and for 26,595 ever-tested subjects (positive for SARS-CoV-2) in the UK Biobank prospective cohort study. Outcome data between 1 January, 2020, and 23 March, 2021, were included. The Omega-3 Index (O3I) (RBC EPA + DHA%) values across DHA% quintiles were estimated. The multivariable Cox proportional hazards models were constructed, and linear (per 1 SD) relations with the risk of each outcome were computed as HRs.

RESULTS

In the fully adjusted models, comparing the fifth to the first DHA% quintiles, the HRs (95% confidence intervals) for testing positive, being hospitalized, and dying with COVID-19 were 0.79 (0.71, 0.89, P < 0.001), 0.74 (0.58, 0.94, P < 0.05), and 1.04 (0.69-1.57, not significant), respectively. On a per 1-SD increase in DHA% basis, the HRs for testing positive, hospitalization, and death, were 0.92 (0.89, 0.96, P < 0.001), 0.89 (0.83, 0.97, P < 0.01), and 0.95 (0.83, 1.09), respectively. The estimated O3I values across DHA quintiles ranged from 3.5% (quintile 1) to 8% (quintile 5).

CONCLUSIONS

These findings suggest that nutritional strategies to increase the circulating n-3 PUFA levels, such as increased consumption of oily fish and/or use of n-3 FA supplements, may reduce the risk of adverse COVID-19 outcomes.

Derivation of the Omega-3 Index from EPA and DHA Analysis of Dried Blood Spots from Dogs and Cats

The Omega-3 Index (O3I) is the red blood cell (RBC) eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) content expressed as a percentage of total RBC fatty acids. Although a validated biomarker of omega-3 status in humans, little is known about the O3I status of dogs and cats; species in which omega-3 fatty acids have known health benefits. The purpose of this study was to develop equations to predict the O3I in these species from a dried blood spot (DBS) analysis. Random blood samples from 33 dogs and 10 cats were obtained from a community veterinary clinic. DBS and RBC samples were analyzed for fatty acid composition. For both species, the R2 between the DBS EPA + DHA value and the O3I was >0.96 (p < 0.001). The O3I was roughly 75% lower in dogs and cats than in humans. We conclude that the O3I can be estimated from a DBS sample, and the convenience of DBS collection should facilitate omega-3 research in these companion animals.

Dietary fish oil increases catalase activity in patients with probable Alzheimer's disease

Background: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the presence of neuritic plaques and neurofibrillary tangles that finally result in synaptic and neuronal loss. Oxidative stress accompanies pathological changes in AD. Objective: to assess the efficacy of dietary omega 3 polyunsaturated fatty acids supplementation on the levels of proteins oxidation, hydroperoxides and enzymatic activities of catalase and superoxide dismutase in AD patients. Methods: clinical, controlled, randomized, double-blind trial. Patients consumed fish oil or placebo for one year. Oxidative stress markers were assessed in plasma using spectrophotometric methods. Results: carbonyl groups in proteins and hydroperoxides in plasma have similar values in both treatment groups at the beginning of the study. At six and 12 months of treatment, these values decreased significantly in the fish oil group, while in the placebo group no changes were observed in both oxidative stress markers. Catalase activity increased significantly at six and twelve months after treatment in patients treated with fish oil. While the superoxide dismutase activity was not modified in both study groups. Conclusions: patients who consume omega 3 polyunsaturated fatty acids at a stable dose of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) show decreased oxidation of proteins and lipids in plasma. In addition, an increase in catalase activity was detected. Thus, the presented data warrants further studies evaluating the antioxidant effect of omega 3 polyunsaturated fatty acids.

Associations of erythrocyte omega-3 fatty acids with cognition, brain imaging and biomarkers in the Alzheimer's disease neuroimaging initiative: cross-sectional and longitudinal retrospective analyses

BACKGROUND

The association between omega-3 (ω-3) PUFAs and cognition, brain imaging and biomarkers is still not fully established.

OBJECTIVES

The aim was to analyze the cross-sectional and retrospective longitudinal associations between erythrocyte ω-3 index and cognition, brain imaging, and biomarkers among older adults.

METHODS

A total of 832 Alzheimer's Disease Neuroimaging Initiative 3 (ADNI-3) participants, with a mean (SD) age of 74.0 (7.9) y, 50.8% female, 55.9% cognitively normal, 32.7% with mild cognitive impairment, and 11.4% with Alzheimer disease (AD) were included. A low ω-3 index (%EPA + %DHA) was defined as the lowest quartile (≤3.70%). Cognitive tests [composite score, AD Assessment Scale Cognitive (ADAS-Cog), Wechsler Memory Scale (WMS), Trail Making Test, Category Fluency, Mini-Mental State Examination, Montreal Cognitive Assessment] and brain variables [hippocampal volume, white matter hyperintensities (WMHs), positron emission tomography (PET) amyloid-β (Aβ) and tau] were considered as outcomes in regression models.

RESULTS

Low ω-3 index was not associated with cognition, hippocampal, and WMH volume or brain Aβ and tau after adjustment for demographics, ApoEε4, cardiovascular disease, BMI, and total intracranial volume in the cross-sectional analysis. In the retrospective analysis, low ω-3 index was associated with greater Aβ accumulation (adjusted β = 0.02; 95% CI: 0.01, 0.03; P = 0.003). The composite cognitive score did not differ between groups; however, low ω-3 index was significantly associated with greater WMS-delayed recall cognitive decline (adjusted β = -1.18; 95% CI: -2.16, -0.19; P = 0.019), but unexpectedly lower total ADAS-Cog cognitive decline. Low ω-3 index was cross-sectionally associated with lower WMS performance (adjusted β = -1.81, SE = 0.73, P = 0.014) and higher tau accumulation among ApoE ε4 carriers.

CONCLUSIONS

Longitudinally, low ω-3 index was associated with greater Aβ accumulation and WMS cognitive decline but unexpectedly with lower total ADAS-Cog cognitive decline. Although no associations were cross-sectionally found in the whole population, low ω-3 index was associated with lower WMS cognition and higher tau accumulation among ApoE ε4 carriers. The Alzheimer's Disease Neuroimaging Initiative (ADNI) is registered at clinicaltrials.gov as NCT00106899.

Nutritional metabolism and cerebral bioenergetics in Alzheimer's disease and related dementias

Disturbances in the brain's capacity to meet its energy demand increase the risk of synaptic loss, neurodegeneration, and cognitive decline. Nutritional and metabolic interventions that target metabolic pathways combined with diagnostics to identify deficits in cerebral bioenergetics may therefore offer novel therapeutic potential for Alzheimer's disease (AD) prevention and management. Many diet-derived natural bioactive components can govern cellular energy metabolism but their effects on brain aging are not clear. This review examines how nutritional metabolism can regulate brain bioenergetics and mitigate AD risk. We focus on leading mechanisms of cerebral bioenergetic breakdown in the aging brain at the cellular level, as well as the putative causes and consequences of disturbed bioenergetics, particularly at the blood-brain barrier with implications for nutrient brain delivery and nutritional interventions. Novel therapeutic nutrition approaches including diet patterns are provided, integrating studies of the gut microbiome, neuroimaging, and other biomarkers to guide future personalized nutritional interventions.

B vitamin intakes modify the association between particulate air pollutants and incidence of all-cause dementia: Findings from the Women's Health Initiative Memory Study

INTRODUCTION

Particulate air pollutants may induce neurotoxicity by increasing homocysteine levels, which can be lowered by high B vitamin intakes. Therefore, we examined whether intakes of three B vitamins (folate, B12 , and B6 ) modified the association between PM2.5 exposure and incidence of all-cause dementia.

METHODS

This study included 7183 women aged 65 to 80 years at baseline. B vitamin intakes from diet and supplements were estimated by food frequency questionnaires at baseline. The 3-year average PM2.5 exposure was estimated using a spatiotemporal model.

RESULTS

During a mean follow-up of 9 years, 342 participants developed all-cause dementia. We found that residing in locations with PM2.5 exposure above the regulatory standard (12 μg/m3 ) was associated with a higher risk of dementia only among participants with lower intakes of these B vitamins.

DISCUSSION

This is the first study suggesting that the putative neurotoxicity of PM2.5 exposure may be attenuated by high B vitamin intakes.

Red Blood Cell DHA Is Inversely Associated with Risk of Incident Alzheimer's Disease and All-Cause Dementia: Framingham Offspring Study

Docosahexaenoic acid (DHA) might help prevent Alzheimer's disease (AD). Red blood cell (RBC) status of DHA is an objective measure of long-term dietary DHA intake. In this prospective observational study conducted within the Framingham Offspring Cohort (1490 dementia-free participants aged ≥65 years old), we examined the association of RBC DHA with incident AD, testing for an interaction with APOE-ε4 carriership. During the follow-up (median, 7.2 years), 131 cases of AD were documented. In fully adjusted models, risk for incident AD in the highest RBC DHA quintile (Q5) was 49% lower compared with the lowest quintile (Q1) (Hazard ratio [HR]: 0.51, 95% confidence interval [CI]: 0.27, 0.96). An increase in RBC DHA from Q1 to Q5 was predicted to provide an estimated 4.7 additional years of life free of AD. We observed an interaction DHA × APOE-ε4 carriership for AD. Borderline statistical significance for a lower risk of AD was observed per standard deviation increase in RBC DHA (HR: 0.71, 95% CI: 0.51, 1.00, p = 0.053) in APOE-ε4 carriers, but not in non-carriers (HR: 0.85, 95% CI: 0.65, 1.11, p = 0.240). These findings add to the increasing body of literature suggesting a robust association worth exploring dietary DHA as one strategy to prevent or delay AD.

Higher Serum DHA and Slower Cognitive Decline in Patients with Alzheimer's Disease: Two-Year Follow-Up

Omega-3 polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with slower rates of cognitive decline. We investigated the association between omega-3 PUFAs and cognitive function in patients with Alzheimer’s disease (AD) receiving acetylcholinesterase inhibitors (AChEIs). This was a prospective cohort study using registered data. Patients with AD receiving AChEIs were recruited from 1 May 2016 to 30 April 2019 and were followed up for two years. Their daily diet record and blood concentration of omega-3 PUFAs were analyzed. Multiple linear and binary logistic regression was used to determine the factors associated with cognitive decline (continuous and dichotomized cognitive change). In the research, 129 patients with AD were identified with a mean age of 76.5 ± 6.6. Patients with AD with lower baseline omega-3 PUFAs levels were associated with a higher risk of cognitive decline than those with higher levels (odds ratio [OR] = 1.067, 95% confidence interval [CI]: 1.012, 1.125; p = 0.016) after adjustment. Patients with AD with a lower baseline DHA (OR = 1.131, 95% CI: 1.020, 1.254; p = 0.020), but not EPA, were associated with a higher risk of cognitive decline. We found that higher Mini-Nutritional Assessment scores (beta = −0.383, 95% CI = −0.182–−0.048, p = 0.001) and total fat (beta = −0.248, 95% CI = −0.067–−0.003, p = 0.031) were independently associated with slow cognitive decline in patients with AD receiving AChEIs. The baseline blood levels of omega-3 PUFAs were associated with cognitive decline in patients with AD receiving AChEIs. Future randomized controlled trials are needed to clarify whether this association is causal.

Red blood cell fatty acids and age-related macular degeneration in postmenopausal women

PURPOSE

To evaluate the relationship between red blood cell (RBC) polyunsaturated fatty acid (PUFA) levels, and dietary PUFA and fish intake, with prevalent and incident age-related macular degeneration (AMD) in a US cohort of postmenopausal women.

METHODS

This analysis included 1456 postmenopausal women from the Women's Health Initiative (WHI) Clinical Trials. RBC PUFAs were measured from fasting serum samples collected at WHI baseline. Dietary PUFAs and fish intake were assessed via food frequency questionnaires at baseline. There were 240 women who had prevalent AMD and 138 who self-reported AMD development over 9.5 years. Adjusted odds ratios and 95% confidence intervals were estimated for prevalent AMD by RBC PUFA levels, dietary PUFA intake, and frequency of fish consumption. Adjusted hazard ratios and 95% confidence intervals were estimated for incident AMD. A p-for-trend was estimated for continuous measures of dietary PUFA and fish intake.

RESULTS

No significant association was found between prevalent or incident AMD and RBC docosahexaenoic acid (DHA) + eicosapentaenoic acid (EPA), EPA, DHA, alpha-linolenic acid (ALA), linoleic acid (LA), or arachidonic acid (AA). A positive association was found between dietary intake of AA and odds of prevalent AMD (p-for-trend for continuous AA intake = 0.02) and between intake of LA/ALA and incident AMD (p-for-trend for continuous ratio of LA/ALA intake = 0.03). No statistically significant associations were found between AMD and dietary intake of PUFAs or fish.

CONCLUSIONS

RBC PUFAs were not associated with AMD in this cohort. Overall, dietary analyses of PUFAs supported this, excepting dietary AA intake and intake of LA in proportion to ALA of which there were trends of increased risk.

Omega-3 fatty acids and blood-based biomarkers in Alzheimer's disease and mild cognitive impairment: A randomized placebo-controlled trial

BACKGROUND

Increased serum levels of pro-inflammatory biomarkers are consistently associated with cognitive decline. The omega-3 unsaturated fatty acids (n-3 PUFAs) had been linked to slowing cognitive decline due to their potential anti-inflammatory effects. To our knowledge, the different regiments of pure DHA, pure EPA, and their combination on various associated symptoms of dementia, including a mild form of cognitive impairment (MCI) and Alzheimer's disease (AD), have never been studied.

METHODS

This multisite, randomized, double-blind, placebo-controlled trial was conducted at two veteran's retirement centers and one medical center in central Taiwan between 2013 and 2015. 163 MCI or AD patients were randomly assigned to placebo (n = 40), docosahexaenoic acid (DHA, 0.7 g/day, n = 41), eicosapentaenoic acid (EPA, 1.6 g/day, n = 40), or EPA (0.8 g/day) + DHA (0.35 g/day) (n = 42) group for 24 months. The results were measured as the cognitive and functional abilities, biochemical, and inflammatory cytokines profiles. Chi-square tests, two-sample t-test, ANOVA, and linear mixedeffects models were conducted with p < 0.05.

RESULTS

131 (80%) participants had completed the trial with all cognitive, functional, and mood status assessments. The statistically significant difference between the placebo and treatment groups was not determined, concerning the changes in cognitive, functional, and mood status scores, the biochemical profiles, and inflammatory cytokines levels. However, EPA was found to reduce the C-C motif ligands 4 (CCL4) level (p < 0.001). Additionally, EPA could reduce the constructional praxis (p < 0.05) and spoken language ability scores (p < 0.01), and DHA also reduced the spoken language ability score (p < 0.05).

CONCLUSION

Overall, n-3 PUFAs supplements did not reduce cognitive, functional, and depressive symptom outcomes, but spoken language ability and constructional praxis subitems of ADAS-cog. These findings show that attention to clinical heterogeneity in dementia is crucial when studying nutrients interventions, such as n-3 PUFAs. In addition, with small effect size CCL4 is a better indicator than other inflammatory cytokines for EPA treatment response.

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.

Circulating Plasma Metabolites and Cognitive Function in a Puerto Rican Cohort

BACKGROUND

Minorities, including mainland Puerto Ricans, are impacted disproportionally by Alzheimer's disease (AD), dementia, and cognitive decline. Studying blood metabolomics in this population has the potential to probe the biological underpinnings of this health disparity.

OBJECTIVE

We performed a comprehensive analysis of circulating plasma metabolites in relation to cognitive function in 736 participants from the Boston Puerto Rican Health Study (BPRHS) who underwent untargeted mass-spectrometry based metabolomics analysis and had undergone a battery of in-person cognitive testing at baseline.

METHODS

After relevant exclusions, 621 metabolites were examined. We used multivariable regression, adjusted for age, sex, education, apolipoprotein E genotype, smoking, and Mediterranean dietary pattern, to identify metabolites related to global cognitive function in our cohort. LASSO machine learning was used in a complementary analysis to identify metabolites that could discriminate good from poor extremes of cognition. We also conducted sensitivity analyses: restricted to participants without diabetes, and to participants with good adherence to Mediterranean diet.

RESULTS

Of 621 metabolites, FDR corrected (p < 0.05) multivariable linear regression identified 3 metabolites positively, and 10 negatively, associated with cognitive function in the BPRHS. In a combination of FDR-corrected linear regression, logistic regression regularized via LASSO, and sensitivity analyses restricted to participants without diabetes, and with good adherence to the Mediterranean diet, β-cryptoxanthin plasma concentration was consistently associated with better cognitive function and N-acetylisoleucine and tyramine O-sulfate concentrations were consistently associated with worse cognitive function.

CONCLUSION

This untargeted metabolomics study identified potential biomarkers for cognitive function in a cohort of Puerto Rican older adults.

The role of docosahexaenoic acid (DHA) in the prevention of cognitive impairment in the elderly

Aging is an inevitable and progressive biological process that leads to irreversible physiological and functional changes, also in the nervous system. Cognitive decline occurring with age can significantly affect the quality of life of older people. Docosahexaenoic acid (DHA) is necessary for the proper functioning of the nervous system; it can affect its action directly through its impact on neurogenesis and neuroplasticity, but also indirectly by affecting the functioning of the cardiovascular system or anti-inflammatory effect. Literature analysis shows that good nutritional status of n-3 fatty acids, determined on the basis of their level in blood plasma or erythrocytes, is associated with a lower risk of cognitive decline in selected cognitive domains, as well as a lower risk of dementia or Alzheimer’s disease, although studies are also available where the above relationship has not been confirmed. Apart from this, studies on DHA and EPA diet intake, as well as in the form of dietary supplements, show their beneficial effects in the context of cognitive functioning and the risk of dementia. Also, the results of intervention studies, although not explicit, suggest that high doses of DHA and EPA in the form of dietary supplements may slow down the process of deteriorating the cognitive functioning of the elderly within selected domains. Based on the review of the literature, it can be concluded that DHA and EPA play an essential role in the prevention of cognitive impairment.

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.

Importance of EPA and DHA Blood Levels in Brain Structure and Function

Brain structure and function depend on a constant and sufficient supply with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by blood. Blood levels of EPA and DHA reflect dietary intake and other variables and are preferably assessed as percentage in erythrocytes with a well-documented and standardized analytical method (HS-Omega-3 Index^®). Every human being has an Omega-3 Index between 2 and 20%, with an optimum of 8–11%. Compared to an optimal Omega-3 Index, a lower Omega-3 Index was associated with increased risk for total mortality and ischemic stroke, reduced brain volume, impaired cognition, accelerated progression to dementia, psychiatric diseases, compromises of complex brain functions, and other brain issues in epidemiologic studies. Most intervention trials, and their meta-analyses considered EPA and DHA as drugs with good bioavailability, a design tending to produce meaningful results in populations characterized by low baseline blood levels (e.g., in major depression), but otherwise responsible for many neutral results and substantial confusion. When trial results were evaluated using blood levels of EPA and DHA measured, effects were larger than comparing EPA and DHA to placebo groups, and paralleled epidemiologic findings. This indicates future trial design, and suggests a targeted use EPA and DHA, based on the Omega-3 Index.

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.

Blood polyunsaturated omega-3 fatty acids, brain atrophy, cognitive decline, and dementia risk

INTRODUCTION

We searched for consistent associations of an omega-3 index in plasma (sum of eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) with several dementia-related outcomes in a large cohort of older adults.

METHODS

We included 1279 participants from the Three-City study, non-demented at the time of blood measurements at baseline, with face-to-face neuropsychological assessment and systematic detection of incident dementia over a 17-year follow-up. An ancillary study included 467 participants with up to three repeated brain imaging exams over 10 years.

RESULTS

In multivariable models, higher levels of plasma EPA+DHA were consistently associated with a lower risk of dementia (hazard ratio for 1 standard deviation = 0.87 [95% confidence interval, 0.76-0.98]), and a lower decline in global cognition (P = .04 for change over time), memory (P = .06), and medial temporal lobe volume (P = .02).

DISCUSSION

This prospective study provides compelling evidence for a relationship between long-chain omega-3 fatty acids levels and lower risks for dementia and related outcomes.

Erythrocyte ω-3 polyunsaturated fatty acids are inversely associated with the risk of oral cancer: a case-control study

OBJECTIVES

Evidence about ω-3 polyunsaturated fatty acids (ω-3 PUFAs) and oral cancer risk were limited. We aimed to evaluate the association of erythrocyte ω-3 PUFAs with the risk of oral cancer in a population from China.

METHODS

Erythrocyte ω-3 PUFAs of 236 oral cancer patients and 300 controls were determined by gas chromatography. Restricted cubic spline and logistic regression were used to analyze the association between erythrocyte ω-3 PUFAs and oral cancer risk. The crude and adjusted OR with 95% CI was calculated. Stratification analysis was performed to explore the potential interaction between ω-3 PUFAs and other traditional risk factors such as smoking and drinking.

RESULTS

Eicosapentaenoic acids (EPA), docosahexaenoic acids (DHA) and ω-3 index were negatively but non-linearly related to risk of oral cancer as observed by restricted cubic spline. The adjusted OR of EPA, DHA, and ω-3 index were 0.52 (95% CI: 0.35-0.76), 0.19 (95% CI: 0.08-0.44), 0.20 (95% CI: 0.09-0.44), respectively. Stratification analysis showed that the adverse correlation between EPA and oral cancer was only significant in the non-smoking group, while the adverse correlation of ɑ-linolenic acid (ALA), EPA, and DHA were only significant in the non-drinking group. General multiplicative interactions were observed between ω-3 PUFAs and smoking or drinking.

CONCLUSIONS

Adverse but non-linear associations were observed between erythrocyte EPA, DHA, ω-3 index, and oral cancer risk. Additionally, there were multiplicative interactions between ω-3 PUFAs and other behavior factors such as smoking and drinking. The protective effect of ω-3 PUFAs maybe more significant in the non-smoking or non-drinking population.

Docosahexaenoic acid supplementation in age-related cognitive decline: a systematic review and meta-analysis

PURPOSE

To investigate the role of DHA supplementation in preventing age-related cognitive decline (ARCD) in individual cognitive domains by conducting systematic review and meta-analysis.

METHODS

Relevant clinical trials were systematically searched at Medline, PubMed, Scopus, Cochrane, ProQuest, and Embase databases since inception to June 2018. The PRISMA guidelines were adhered for data abstraction, quality assessment, and validation of included studies. Study details such as participant characteristics, DHA supplementation, and cognitive function outcome measures, i.e., memory, attention, working memory, and executive function, were extracted to perform meta-analysis according to the Cochrane guidelines. Additional meta-regression and subgroup analyses were performed to detect confounding variables and sensitivity of results, respectively.

RESULTS

Ten studies including 2327 elderly individuals were part of the final results. Study exhibited minimal or no pooled incremental effects on memory (0.22, 95%CI = - 0.17 to 0.61, I² = 94.36%), attention (0.1, 95%CI = - 0.04 to 0.25, I² = 32.25%), working memory (0.01, 95%CI = - 0.10 to 0.12, I² = 0%), and executive function (0.03, 95%CI = - 0.05 to 0.11, I² = 78.48%) among the DHA-supplemented group. The results from standard mean difference between the groups, on memory (0.08, 95%CI = - 0.12 to 0.28, I² = 76.82%), attention (0.04, 95%CI = - 0.09 to 0.23, I² = 42.63%), working memory (- 0.08, 95%CI = - 0.26 to 0.10, I² = 37.57%), and executive function (0.17, 95%CI = - 0.01 to 0.36, I² = 78.48%) were similar to the results of pooled incremental analysis. Lastly, results remained unaffected by sensitivity and sub-group analyses.

CONCLUSIONS

Current pieces of evidence do not support the role of DHA supplementation, in preventing/retarding ARCD of memory, executive function, attention, and working memory. Protocol registered at PROSPERO (ID: PROSPERO 2018 CRD42018099401).

Relations of magnesium intake to cognitive impairment and dementia among participants in the Women's Health Initiative Memory Study: a prospective cohort study

OBJECTIVE

To examine the associations of dietary and supplemental magnesium (Mg) as assessed by a semi-quantitative food frequency questionnaire with cognitive outcomes among ageing women.

DESIGN

This work conducts a prospective cohort study of participants enrolled in the Women's Health Initiative Memory Study (WHIMS), which was subsequently extended and named WHIMS-Epidemiology of Cognitive Health.

SETTING

Forty clinical centres in the USA.

PARTICIPANTS

Postmenopausal women aged 65-79 years without dementia on enrolment.

MAIN OUTCOME MEASURES

Physician-adjudicated mild cognitive impairment (MCI) and/or probable dementia (PD).

RESULTS

Participants were excluded (n=1006) if they had extreme values of dietary energy intake, had missing or extreme body mass index values, with prevalent MCI/PD at baseline, received only one cognitive assessment or had been followed up for <1 year. During >20 years of follow-up, 765 (11.8%) out of 6473 participants developed MCI/PD. For MCI/PD and MCI, the risks tended to be lower among participants in quintiles Q2-Q5 of Mg consumption compared with those in the lowest quintile. Participants in Q3 had a significantly lower risk of MCI/PD (HR 0.69, 95% CI 0.53 to 0.91) and MCI (HR 0.63, 95% CI 0.45 to 0.87) after multivariate adjustments. No significant association was observed between total Mg intake and PD. The association between total Mg intake, MCI/PD and MCI was non-linear as suggested by the likelihood test.

CONCLUSIONS

Total Mg intake between the estimated average requirement and the recommended dietary allowances may associate with a lower risk of MCI/PD and MCI.

TRIAL REGISTRATION NUMBER

NCT00685009.

Polyunsaturated fatty acids and risk of Alzheimer's disease: a Mendelian randomization study

Purpose

Observational studies have suggested that polyunsaturated fatty acids (PUFAs) may decrease Alzheimer’s disease (AD) risk. In the present study, we examined this hypothesis using a Mendelian randomization analysis.

Methods

We used summary statistics data for single-nucleotide polymorphisms associated with plasma levels of n-6 PUFAs (linoleic acid, arachidonic acid) and n-3 PUFAs (alpha-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid), and the corresponding data for AD from a genome-wide association meta-analysis of 63,926 individuals (21,982 diagnosed AD cases, 41,944 controls).

Results

None of the genetically predicted PUFAs was significantly associated with AD risk; odds ratios (95% confidence interval) per 1 SD increase in PUFA levels were 0.98 (0.93, 1.03) for linoleic acid, 1.01 (0.98, 1.05) for arachidonic acid, 0.96 (0.88, 1.06) for alpha-linolenic acid, 1.03 (0.93, 1.13) for eicosapentaenoic acid, 1.03 (0.97, 1.09) for docosapentaenoic acid, and 1.01 (0.81, 1.25) for docosahexaenoic acid.

Conclusions

This study did not support the hypothesis that PUFAs decrease AD risk.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-02126-x) contains supplementary material, which is available to authorized users.

Nutritional Intervention to Prevent Alzheimer's Disease: Potential Benefits of Xanthophyll Carotenoids and Omega-3 Fatty Acids Combined

BACKGROUND

A growing body of scientific evidence suggests that enrichment of certain nutritional compounds in the brain may reduce the risk of Alzheimer's disease (AD).

OBJECTIVE

To investigate the impact of supplemental xanthophyll carotenoids plus omega-3 fatty acids on disease progression in patients with AD.

METHODS

Three trial experiments were performed. In Trials 1 and 2 (performed on patients with AD over an 18-month period), 12 patients (AD status at baseline: 4 mild and 8 moderate) were supplemented with a xanthophyll carotenoid only formulation (Formulation 1; lutein:meso-zeaxanthin:zeaxanthin 10:10:2 mg/day) and 13 patients (AD status at baseline: 2 mild, 10 moderate, and 1 severe) were supplemented with a xanthophyll carotenoid and fish oil combination (Formulation 2; lutein:meso-zeaxanthin:zeaxanthin 10:10:2 mg/day plus 1 g/day of fish oil containing 430 mg docohexaenoic acid [DHA] and 90 mg eicopentaenoic acid [EPA]), respectively. In Trial 3, 15 subjects free of AD (the control group) were supplemented for 6 months with Formulation 1. Blood xanthophyll carotenoid response was measured in all trials by HPLC. Omega-3 fatty acids were profiled by direct infusion mass spectrometry.

RESULTS

Xanthophyll carotenoid concentration increases were significantly greater for Formulation 2 compared to Formulation 1 (p < 0.05), and progression of AD was less for this group (p = 0.003), with carers reporting functional benefits in memory, sight, and mood.

CONCLUSION

This preliminary report suggests positive outcomes for patients with AD who consumed a combination of xanthophyll carotenoids plus fish oil, but further study is required to confirm this important observation.

Dietary supplement intake among the elderly: hazards and benefits

PURPOSE OF REVIEW

A large percentage of older adults do not receive recommended amounts of many nutrients from food alone. Accordingly, the routine use of dietary supplements has become common among older persons. Although supplement use provides potential benefits by increasing nutrient intakes, there are potential drawbacks.

RECENT FINDINGS

Clinical studies have pointed to potential reductions in the risk to develop age-related diseases among older people who reported long-term use of multivitamin supplements. Higher plasma levels of omega-3 polyunsaturated fatty acids were also associated with fewer cardiovascular deaths in older people consuming omega-3 supplements. Dietary protein supplementation combined with exercise had a strong effect in preventing age-related muscle mass attenuation and leg strength loss in older people. Finally, beneficial effects of purified flavonoids on cognitive functions have been reported in some studies, whereas in a significant number of other studies, no such effect could be observed.

SUMMARY

The use of dietary supplements among older people has increased over the years due to the expectation of reducing the risk of developing chronic diseases. Although some dietary supplements may indeed fulfill some of these expectations, it would be unwise to assume that they are all efficacious and safe to use.

Serial circulating omega 3 polyunsaturated fatty acids and healthy ageing among older adults in the Cardiovascular Health Study: prospective cohort study

OBJECTIVE

To determine the longitudinal association between serial biomarker measures of circulating omega 3 polyunsaturated fatty acid (n3-PUFA) levels and healthy ageing.

DESIGN

Prospective cohort study.

SETTING

Four communities in the United States (Cardiovascular Health Study) from 1992 to 2015.

PARTICIPANTS

2622 adults with a mean (SD) age of 74.4 (4.8) and with successful healthy ageing at baseline in 1992-93.

EXPOSURE

Cumulative levels of plasma phospholipid n3-PUFAs were measured using gas chromatography in 1992-93, 1998-99, and 2005-06, expressed as percentage of total fatty acids, including α-linolenic acid from plants and eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid from seafoood.

MAIN OUTCOME MEASURE

Healthy ageing defined as survival without chronic diseases (ie, cardiovascular disease, cancer, lung disease, and severe chronic kidney disease), the absence of cognitive and physical dysfunction, or death from other causes not part of the healthy ageing outcome after age 65. Events were centrally adjudicated or determined from medical records and diagnostic tests.

RESULTS

Higher levels of long chain n3-PUFAs were associated with an 18% lower risk (95% confidence interval 7% to 28%) of unhealthy ageing per interquintile range after multivariable adjustments with time-varying exposure and covariates. Individually, higher eicosapentaenoic acid and docosapentaenoic acid (but not docosahexaenoic acid) levels were associated with a lower risk: 15% (6% to 23%) and 16% (6% to 25%), respectively. α-linolenic acid from plants was not noticeably associated with unhealthy ageing (hazard ratio 0.92, 95% confidence interval 0.83 to 1.02).

CONCLUSIONS

In older adults, a higher cumulative level of serially measured circulating n3-PUFAs from seafood (eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid), eicosapentaenoic acid, and docosapentaenoic acid (but not docosahexaenoic acid from seafood or α-linolenic acid from plants) was associated with a higher likelihood of healthy ageing. These findings support guidelines for increased dietary consumption of n3-PUFAs in older adults.

Poor cognitive ageing: Vulnerabilities, mechanisms and the impact of nutritional interventions

BACKGROUND

Ageing is a highly complex process marked by a temporal cascade of events, which promote alterations in the normal functioning of an individual organism. The triggers of normal brain ageing are not well understood, even less so the factors which initiate and steer the neuronal degeneration, which underpin disorders such as dementia. A wealth of data on how nutrients and diets may support cognitive function and preserve brain health are available, yet the molecular mechanisms underlying their biological action in both normal ageing, age-related cognitive decline, and in the development of neurodegenerative disorders have not been clearly elucidated.

OBJECTIVES

This review aims to summarise the current state of knowledge of vulnerabilities that predispose towards dysfunctional brain ageing, highlight potential protective mechanisms, and discuss dietary interventions that may be used as therapies. A special focus of this paper is on the impact of nutrition on neuroprotection and the underlying molecular mechanisms, and this focus reflects the discussions held during the 2nd workshop 'Nutrition for the Ageing Brain: Functional Aspects and Mechanisms' in Copenhagen in June 2016. The present review is the most recent in a series produced by the Nutrition and Mental Performance Task Force under the auspice of the International Life Sciences Institute Europe (ILSI Europe).

CONCLUSION

Coupling studies of cognitive ageing with studies investigating the effect of nutrition and dietary interventions as strategies targeting specific mechanisms, such as neurogenesis, protein clearance, inflammation, and non-coding and microRNAs is of high value. Future research on the impact of nutrition on cognitive ageing will need to adopt a longitudinal approach and multimodal nutritional interventions will likely need to be imposed in early-life to observe significant impact in older age.