The association of dietary patterns with cognition through the lens of neuroimaging—a systematic review

Despite the reported benefits of diet on cognition in older adults, randomized controlled trials (RCT) testing the impact of dietary interventions on cognitive scores have yielded less promising results when cognition was assessed via neuropsychological tests. More recently, neuroimaging has been used to identify more subtle brain-related changes associated to cognition. Hence, employing a combination of neuroimaging techniques with neuropsychological tests could clarify this controversy. To determine the effect of diet on cognitive performance, we conducted a systematic review of PubMed and Scopus databases for all studies, on middle-aged and older adults, combining neuroimaging, neuropsychological tests, and data on dietary patterns. The inclusion criteria were met by 14 observational studies and no RCTs. The range of brain measures assessed varied from volumes to white matter integrity, functional connectivity, brain glucose metabolism and beta-amyloid deposition. Given the variability of methods used in assessing cognitive performance, diet and brain correlates, conducting a meta-analysis was not possible. Here the evidence suggests that, in observational studies, dietary patterns may be associated with brain correlates that have been shown to precede cognitive decline. As such, neuroimaging should be included in future RCTs to identify any benefits of diet on brain measures linked with cognitive health

Nutrition as a Modifiable Risk Factor for Cognitive Decline: Associated Cognitive and Physical Health Changes

Dementia is defined as gradual, progressive loss of cognitive functioning, greater than what is expected of normal aging, resulting in functional impairment. There are several types of dementia clinical syndromes that are accompanied by unique patterns of cognitive dysfunction and neuropathological changes. Alzheimer’s disease (AD) is the most common type of clinical dementia syndrome, accounting for approximately 60-70% of cases. Neuropathological mechanisms associated with AD include the disruption of the cholinergic system, accumulation of amyloid-beta plaques and hyperphosphorylated tau, as well as vascular pathology. Vascular pathology complicates the characterization of clinical and neuropathic changes in AD, as there becomes significant overlap with vascular dementia clinical presentation and pathology. Furthermore, many people with dementia have “mixed dementia,” or brain changes associated with more than one cause of dementia. This may contribute to the difficulty establishing effective pharmacological interventions to reverse or prevent future neurodegeneration. As a result, research examining modifiable risk factors to prevent neuropathological changes associated with dementia, including AD, has become of interest. Modifiable risk factors include physical activity, sleep, alcohol and tobacco use, and nutrition. Diet has been proposed to reduce risk of AD via neuroinflammatory mechanisms, oxidative stress, and by reducing risk for other comorbid medical conditions (e.g., vascular disease, diabetes, hypertension). There is limited research in the examination of the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet and cognition, longitudinally, in a middle-aged sample, as well as the potential moderating effect of APOE genotype, of which the e4 allele confers increased risk for AD. The current proposal provides a literature review of AD, including cognitive and neuropathological changes, as well as AD vascular factors, and diet as a modifiable risk factor. The proposed study aimed to examine the longitudinal effects of nonmodifiable risk factors (age, gender, APOE genetic status) and modifiable risk factors (MIND diet adherence and physical health) on cognition; furthermore, to determine if APOE genetic status modifies the relationship between MIND diet and cognition, longitudinally. Participants included middle-aged adults with a family history of AD enrolled in the Wisconsin Register for Alzheimer’s Prevention (WRAP) study. Latent Growth Curve (LGC) modeling was conducted to examine aims, assessing change across three visits (Visit 4 through Visit 6). Cognitive outcomes included previously established WRAP cognitive composite and factor scores. Upon examination of initial hypothesized models, empirical cognitive factor scores had significantly poorer model fit, and therefore, theoretically derived composite outcomes were used for structural modeling. Regarding physical health, waist-to-hip ratio (WHR) significantly reduced structural model fit across all cognitive outcomes, and therefore, WHR as a predictor of cognition was removed from analyses. Nonparametric correlations revealed, as expected, that WHR was negatively correlated with all cognitive outcomes (theoretical and empirical cognitive outcomes). Regarding diet, MIND diet adherence had unexpected significant negative effects on Theoretical Executive Functioning (TEF) growth over time; however, APOE risk scores did not significantly moderate this relationship. Improving the understanding of causative relationships among underlying hypothesized mechanisms of dietary benefits on cognition and AD risk is crucial to reduce the burden of AD. The null findings highlighted important gaps in the literature that warrant additional investigation, including further examination of these relationships in cognitively and demographically diverse individuals and exploration of cognitive phenotypes associated with APOE risk

Nutrition for the ageing brain: towards evidence for an optimal diet

As people age they become increasingly susceptible to chronic and extremely debilitating brain diseases. The precise cause of the neuronal degeneration underlying these disorders, and indeed normal brain ageing remains however elusive. Considering the limits of existing preventive methods, there is a desire to develop effective and safe strategies. Growing preclinical and clinical research in healthy individuals or at the early stage of cognitive decline has demonstrated the beneficial impact of nutrition on cognitive functions. 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). The latest scientific advances specific to how dietary nutrients and non-nutrient may affect cognitive ageing are presented. Furthermore, several key points related to mechanisms contributing to brain ageing, pathological conditions affecting brain function, and brain biomarkers are also discussed. Overall, findings are inconsistent and fragmented and more research is warranted to determine the underlying mechanisms and to establish dose-response relationships for optimal brain maintenance in different population subgroups. Such approaches are likely to provide the necessary evidence to develop research portfolios that will inform about new dietary recommendations on how to prevent cognitive decline

Effects of Nutrition on Cognitive Function in Adults with or without Cognitive Impairment: A Systematic Review of Randomized Controlled Clinical Trials

New dietary approaches for the prevention of cognitive impairment are being investigated. However, evidence from dietary interventions is mainly from food and nutrient supplement interventions, with inconsistent results and high heterogeneity between trials. We conducted a comprehensive systematic search of randomized controlled trials (RCTs) published in MEDLINE-PubMed, from January 2018 to July 2021, investigating the impact of dietary counseling, as well as food-based and dietary supplement interventions on cognitive function in adults with or without cognitive impairment. Based on the search strategy, 197 eligible publications were used for data abstraction. Finally, 61 articles were included in the analysis. There was reasonable evidence that dietary patterns, as well as food and dietary supplements improved cognitive domains or measures of brain integrity. The Mediterranean diet showed promising results, whereas the role of the DASH diet was not clear. Healthy food consumption improved cognitive function, although the quality of these studies was relatively low. The role of dietary supplements was mixed, with strong evidence of the benefits of polyphenols and combinations of nutrients, but with low evidence for PUFAs, vitamin D, specific protein, amino acids, and other types of supplements. Further well-designed RCTs are needed to guide the development of dietary approaches for the prevention of cognitive impairment

Age-related changes in blood-brain barrier integrity in C57BL/6J mice

The blood-brain barrier (BBB) is formed by the endothelial cells of the brain microvasculature, which control the molecular traffic between the blood and brain to maintain the neural microenvironment

Nutrients in the Prevention of Alzheimer's Disease

open6noAlzheimer's disease (AD) is a disease caused by the complex interaction of multiple mechanisms, some of which are still not fully understood. To date, pharmacological treatments and supplementation of individual nutrients have been poorly effective in terms of the prevention and treatment of AD, while alternative strategies based on multimodal approaches (diet, exercise, and cognitive training) seem to be more promising. In this context, the focus on dietary patterns rather than on single food components could be more useful in preventing or counteracting the pathological processes typical of AD, thanks to the potential synergistic effects of various nutrients (neuronutrients). The aim of this narrative review is to summarize the currently existing preclinical and clinical evidence regarding the Mediterranean diet (MeDi), the Dietary Approaches to Stop Hypertension (DASH) diet, and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, which are three dietary patterns with well-known anti-inflammatory and antioxidant properties. Recently, they have been related to brain protection and AD prevention, perhaps thanks to their high content of neuroprotective bioactive compounds. Similarly, intermittent fasting (IF) or calorie restriction (CR) is emerging as interesting approaches that seem to promote hippocampal neurogenesis, activate adaptive stress response systems, and enhance neuronal plasticity, thus leading to motor and cognitive improvements in animal models of AD and hopefully also in human beings.openCremonini A.L.; Caffa I.; Cea M.; Nencioni A.; Odetti P.; Monacelli F.Cremonini, A. L.; Caffa, I.; Cea, M.; Nencioni, A.; Odetti, P.; Monacelli, F