The longer-term impacts of Western diet on human cognition and the brain
Since there is already evidence that a Western diet [containing high saturated fat and refined carbohydrates (HFS diet)] can impair animal brain systems, this review aims to use the converging lines of evidence (from neuropsychological, epidemiological, neuroimaging data) and inspect the evidence for use in humans. The animal research analysed were for dietary induced impairments in frontal, limbic and hippocampal systems, and their associated functions in cognition, learning, memory and hedonics, as well as the relationship between the HFS diet and attention deficit disorder and different neurodegenerative conditions. While data on human research was lacking at the time of publishing, Francis & Stevenson (2013) are convinced there is an association between HFS diet and impaired cognitive function. Furthermore, it is suggested there is a causal link between HFS diet and impaired brain function in humans, and an association with the development of degenerative conditions.
Adverse effects of consuming high fat-sugar diets on cognition: implications for understanding obesity
Based on the evidence that those overweight and obese perform worse in terms of cognitive ability, an aspect that has been shown to have a role in short term decision making in eating, this 2017 review investigates the association between obesity and poorer cognitive function, and the responsibility that may lie with overconsumption of the Western-style high fat (HF) high sugar diets. Past animal and human studies have shown repeated HF or HF and sugar (HFS) diets lead to impairment in hippocampal function, which Yeomans links to the vicious cycle model (VCM), specifically referring to the association between hippocampal function and impaired appetite control, and the resulting knock-on negative effects on subsequent appetite control. There is consistent evidence in animal studies supporting the VCM model, while evidence from human studies are increasing but needs backed up with further research specifically on the precise nature in which HFS diets exerts its effects on cognition.
Intake of fruit and vegetables and the incident risk of cognitive disorders: A systematic review and meta-analysis of cohort studies
This 2017 review explored the role of consuming fruits and vegetables in predisposing cognitive disorders. 6 cohorts were analysed with an assimilated total of 21175 subjects reporting intake of fruits and vegetables and the risk of developing Alzheimer’s disease/dementia/cognitive decline/impairment. Pooled analysis data indicated an inverse relationship between fruit and vegetable consumption with incident risk of cognitive disorders (RR = 0.74, 95% CI 0.62-0.88), with evidence of significant heterogeneity (I2 = 68%) possibly attributed to the diversity in ethnicities. The researchers encouraged supplementary studies on testing fruits and vegetables separately on cognitive disorders and also exploring the potential dose-response effect of fruit and vegetable intake.
Nutrition strategies that improve cognitive function
This Spanish review article from 2018 lists the associations various components of the diet have with cognitive function including vitamins (B1, B6, B12, B9/folic acid, D), choline, iron and iodine and their neuroprotective and intellectual performance enhancing effects, the defensive roles of vitamins C, E, A, zinc, selenium, lutein and zeaxanthin against oxidative stress. The study suggests diets with an adequate ratio of 5:1 of omega 6:3 fatty acids, namely the Mediterranean Diet, should be consumed due to its link with enhanced memory and decreased risk of cognitive deterioration. It states high saturated fat’s strong link with cognitive deterioration while polyunsaturated fatty acids can play a positive role in its prevention. Garcia et al (2018) reveal the negative effects of the currently common diet full of highly saturated fats and refined sugars and low levels of fruits, vegetables and water, and recommend consumption of a better quality diet to optimise brain function and prevent cognitive decline.
Western diet consumption and cognitive impairment: links to hippocampal dysfunction and obesity
This 2011 review provides a summary of research on how the Western diet, containing saturated fats and simple carbohydrates, relates to cognitive impairment, focusing on the hippocampus-dependent memory and learning functions. Kanoski and Davidson (2011) look into how this Western diet may cause neurobiological alterations in the hippocampus, leading to the associated cognitive decline. Another proposal was the influence of the Western diet in the development of excessive eating and obesity. The suggestion was that the diet interferes with hippocampal-dependent memory inhibition found to be important in animals in order to respond to food-related environmental cues, thus resulting in excessive food and calorie intake.
Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet
Stevenson et. al (2020) randomly assorted a sample of 110 healthy lean adults to either a one week western-style (WS) diet intervention or a habitual-diet control group, to examine if the rapid impairments in hippocampal function and poorer appetite control seen when animals were fed with a WS diet can be replicated in humans. Measures of hippocampal-dependent learning and memory (HDLM) and of appetitive control were obtained pre- and post-intervention, as well as at the 3-week follow up for HDLM. HDLM performance and appetite control were lower in the WS-diet group compared to the control but HDLM was indifferent at the follow up and the appetite control was found to be strongly correlated with the HDLM decline. The findings from this study indicate a WS-diet can rapidly impair appetite control which could ultimately promote overeating, and also suggests a functional role of the hippocampus in appetite control in addition to providing new evidence for the adverse neurocognitive effects of a Western-Style Diet.
Intake of vegetables and fruits through young adulthood is associated with better cognitive function in midlife in the US general population
This 2019 study examined the long-term relationship between vegetable and fruit (VF) consumption in young adulthood (including breakdown of subgroups) and cognitive function later in midlife. Both men and women (n=3231) were included in the cohort with ages ranging from 18 to 30 at baseline (in 1985-86). Diet information was taken at baseline, and at the 7 year and 20 year mark, while cognitive function was assessed after 25 years using the Rey Auditory Verbal Learning Test (RAVLT), the Digit Symbol Substitution Test (DSST), and the Stroop test. In all three cognitive tests, consuming whole vegetables (with the exception of potatoes) were significantly associated with an improvement in cognitive performance at midlife. Increase in cognitive ability could be significantly connected to the intake of fruits (except fruit juices). The findings suggest consumption of fruits and vegetables, except low fibre content foods such as fruit juices and potatoes, promote an increase in cognitive performance in this middle-aged US population.
Diet-induced cognitive deficits: the role of fat and sugar, potential mechanisms and nutritional interventions
This 2015 review explores the short- and long-term effects of high-energy diets on cognition and analyses the possible role saturated and polyunsaturated fats and sugar may play in its impairment. Rapid deficits in the hippocampal-dependent memory can occur due to the high-energy diets and leads to weight gain while chronic exposure to the diet can impair additional sorts of memory. Beilharz and colleagues (2015) discuss the many possible mechanisms in which decrease in cognitive ability is achieved, focusing mainly on inflammation and the brain-derived neurotrophic factor (BRNF). Moreover, the supplements that may attenuate cognitive decline are discussed, namely the evidence-backed omega-3 and curcumin that have been observed to show promising signs in enhancing cognition in healthy ageing populations and in disease states. This review intends to provide important and useful data on the causes of diet-induced cognitive deficits and spread awareness of current developments in therapeutics to counteract and minimise cognitive impairment.
Editorial: impact of diet on learning, memory and cognition
This editorial published in 2017 explores the effects of diets and diet-induced obesity on learning, memory and cognition in both experimental and epidemiological settings. The western diet rich in saturated fat and refined carbohydrates has been associated with development of obesity as well as reduced global cognitive function, decline, and dementia. The contents of this editorial offer new and valuable insights into the psychological processes and neural mechanisms underpinning the pervasive influence of diet and food-associated environments. Reichelt, Westbrook & Morris (2017) believe the findings reported will form the basis for novel theoretical ideas and applications to this public health issue.
Beneficial effects of walnuts on cognition and brain Health
This 2020 article analyses the current evidence for the positive effects of walnuts on cognition and brain health. Chauhan & Chauhan (2020) have conducted animal and human studies that suggest both improvement of cognition and reduction in risk and/or progression of mild cognitive impairment (MCI) and Alzheimer’s Disease (AD) after supplementation with walnuts. In addition, the Chauhans have reported the beneficial effects of a diet with walnuts on memory, learning, motor coordination, anxiety, and locomotor activity while other human clinical trials have implied the association between walnut consumption with better cognitive performance and enhanced memory compared to baseline among adults. Furthermore, the findings from Chauhans’ recent study on mice demonstrated a walnut-enriched diet significantly improves antioxidant defense and decreases free radicals’ levels compared to a control diet without walnuts, suggesting walnuts can reduce oxidative stress and thus less oxidative damage to lipids and proteins. Due to the additive or synergistic effects of walnut components for protection against oxidative stress and inflammation, walnuts have been implicated to decrease the risk or progression of other brain disorders such as Parkinson’s disease, stroke, and depression, as well as of cardiovascular disease and type 2 diabetes. But since it takes many years for cognitive impairment and dementia to develop, the writers recommended early and long-term supplementation with walnuts as it may help to maintain cognitive function and may reduce the risk of developing, or delay the onset and/or slow the progression of, MCI and dementia.
Effects of nutrients (in food) on the structure and function of the nervous system: update on dietary requirements for brain. Part 1: micronutrients
This 2006 review is an updated overview of the effects of dietary nutrients on the structure and certain functions of the brain. This update takes a look at micronutrients such as vitamin B1 (which modulates cognitive performance, especially in the elderly), vitamin B9 which preserves the memory and development of the brain during ageing, vitamin B6 which is associated with exerting positive effects in premenstrual depression, vitamin B12 which delays the onset of signs of dementia and blood abnormalities and improves cerebral and cognitive functions in the elderly. Adolescents who have a borderline level of vitamin B12 appear to develop signs of cognitive changes. Bourre (2006) also mentions vitamin D or its analogues could be of interest in the prevention of various aspects of neurodegenerative or neuroimmune diseases and that iron deficiency is found in children with attention-deficit/hyperactivity disorder. Furthermore, iron concentrations in the umbilical artery are critical during the development of the foetus, and in relation with the IQ in the child; infantile anaemia with its associated iron deficiency is linked to perturbation of the development of cognitive functions. The author states iron deficiency anaemia is common especially in women and is associated with apathy (lack of feeling, emotion or interest) and rapid fatigue when exercising. Bourre (2006) adds the details of the crucial roles of other nutrients in the body, such as magnesium (important in all major metabolisms), zinc (involved in the perception of taste), iodine (regularly ensures energy metabolism of the cerebral cells and is critical in pregnancy: lower levels can induce severe cerebral dysfunction), manganese, copper and zinc (all of which participate in enzymatic mechanisms that protect against free radicals, toxic derivatives of oxygen). An unbalanced copper metabolism homeostasis could actually be linked to Alzheimer’s Disease according to the writer. This review explains how deficiency of micronutrients can compromise the full genetic potential of the child for physical growth and mental development: children and adolescents with poor nutritional status are exposed to alterations of mental and behavioural functions but they can be corrected by dietary measures such as nutrient composition and meal pattern. Brain diseases during ageing can also be due to failure for protective mechanisms (due to dietary deficiencies) for instance in antioxidants and nutrients (trace elements, vitamins, non-essential micronutrients such as polyphenols) related with protection against free radicals.
Intake of niacin, folate, vitamin B-6, and vitamin B-12 through young adulthood and cognitive function in midlife: the coronary artery risk development in young adults (CARDIA) study
Qin et. al (2017) based this multicentre study on the hypothesis that higher intake of vitamins such as niacin, folate, vitamin B-6 and vitamin B-12 in young adulthood will reward those individuals with better cognition later in life. Firstly, data from the Coronary Artery Risk Development in Young Adults (CARDIA) study including 3136 participants (black and white men and women aged 18-30). Dietary intake from years 0,7 and 20 were examined, and at year 25 cognitive function was measured through the use of the Rey Auditory Verbal Learning Test (RAVLT) for verbal memory, the Digit Symbol Substitution Test (DSST) for psychomotor speed, and a modified Stroop interference test for executive function. The higher RAVLT and DSST scores indicated enhanced cognitive function later in life. When the highest quintile was compared to the lowest, it was revealed that cumulative total intake of niacin was significantly associated with 3.92 more digits on the DSST (p < 0.01) and 1.89 points lower interference score on the Stroop test (p = 0.05). Also total folate was associated with 2.56 more digits on the DSST (p = 0.01), higher intakes of vitamin B-6 and vitamin B-12 resulted in improved psychomotor speed (comparing quintile 5 with quintile 1). The researchers conclude that greater inclusion of B vitamins throughout young adulthood correlated to higher cognitive function in midlife.
Western diet is associated with a smaller hippocampus: a longitudinal investigation
This 2015 study investigated whether diet is associated with differential rates of hippocampal atrophy (decline) and examined the link between dietary patterns and hippocampal volume in humans. Data was drawn from a subsample (n = 255) from the Personality and Total Health Through Life Study, specifically those aged 60-64 years at baseline and had completed a food frequency questionnaire and underwent MRI scans roughly 4 years apart. Every one standard deviation increase in healthy "prudent" dietary pattern was associated with a 45.7 mm³ larger left hippocampal volume, while higher consumption of an unhealthy "Western" dietary pattern was independently associated with a 52.6 mm³ smaller left hippocampal volume. These relationships were independent of covariates including age, gender, education, labour-force status, depressive symptoms and medication, physical activity, smoking, hypertension and diabetes. However, no relationships were observed between dietary patterns and right hippocampal volume, and no evidence was found to suggest dietary patterns influenced a decline in hippocampal volume over time. Jacka and others (2015) summarise their findings as: lower intakes of nutrient-dense foods and greater consumption of unhealthy foods are each independently associated with smaller hippocampal volume.
The relationships between vitamin K and cognition: a review of current evidence
This 2019 review analysed the evidence of direct correlations between vitamin K intake and cognitive performances, and as well as this, looked at the involvement of vitamin K antagonists (VKAs) in declining cognitive performances. In vitro and animal studies have highlighted vitamin K’s involvement in brain cells development and survival, and have alluded to its anti-apoptotic (apoptosis is cell death) and anti-inflammatory effect. Vitamin K is also involved in sphingolipid metabolism, which is a class of lipids that may be related to neuroinflammation and neurodegeneration if expression in its profile changes. Some studies have pointed at vitamin K antagonists possessing negative influence on cognitive domains such as visual memory, verbal fluency and brain volume. This review examined vitamin k, VKAs and cognitive function in view of an expected increase in prevalence of Alzheimer’s disease and other forms of dementia.
Dietary patterns during adulthood and cognitive performance in midlife: the CARDIA study
This 2019 study retrieved data from the Coronary Artery Risk Development in Young Adults (CARDIA) study (2621 participants; mean age 25 ± 3.5 years at baseline) to find out whether dietary patterns (Mediterranean diet [MedDiet], Dietary Approaches to Stop Hypertension [DASH], and A Priori Diet Quality Score [APDQS]) during adulthood are associated with midlife cognitive performance. Mean diet scores were calculated from diet history at baseline, year 7 and year 20 while cognitive function was assessed at years 25 and 30. Although DASH was not associated with affecting cognitive performance, less decline in cognitive function and Stroop Interference was found to be linked to higher MedDiet and APDQS scores. When comparing the highest to lowest tertiles of the diet scores, odds ratios for poor cognitive function was 0.54 for MedDiet, 0.48 for APDQS and 0.89 for DASH. It was concluded that greater adherence to these dietary patterns (MedDiet and APDQS) during adulthood was associated with greater midlife cognitive performance. McEvoy et. al (2019) does state the need for additional studies in order to determine the food and nutrient combination for optimal brain health across the life course.
Prefrontal cortex inflammation and liver pathologies accompany cognitive and motor deficits following Western diet consumption in non-obese female mice (animal study)
This 2020 mouse study investigated the effect of the Western Diet (WD) on motor coordination, novelty recognition and affective behavior and also molecular and cellular endpoints in brain and peripheral tissues. The female C57BL/6 J mice were checked for glucose tolerance, insulin resistance, liver steatosis (increased build-up of fat in the liver) after being fed the WD for 3 weeks. They were also monitored for changes in motor coordination, object recognition, and despair behavior in the swim test, blood measurements for lipids and liver injury markers, and also brain checks such as serotonin transporter (SERT) expression, density of Iba1-positive cells and concentration of malondialdehyde. The mice exhibited impaired glucose tolerance and insulin resistance, a loss of motor coordination, deficits in novel object exploration and recognition, increased helplessness, dyslipidemia, as well as signs of fatty liver disease and increased liver injury markers. In addition, the researchers found decreased SERT expression, elevated numbers of microglia cells and malondialdehyde levels in the prefrontal cortex, which led Veniaminova and her team (2020) to state that the consumption of a WD not only induces behavior reminiscent of ADHD and ASD like impairment of impulsivity and sociability than previously recognised, the WD might exacerbate motor dysfunction also known to be associated with adult ADHD and ASD.
The cognitive control of eating and body weight: it's more than what you "think"
This 2019 review identifies a few of the important cognitive processes in the control of energy intake and body weight, summarise evidence demonstrating the possibly harmful effects excess consumption of the Western Diet (WD) have on these cognitive processes, and also review the association between the WD and the emergence of pathophysiologies in the hippocampus (important for learning, cognition and memory). Davidson and his colleagues describe the findings from human and non-human animal models and explore the possibility that the changes in cognitive processes induced by the WD may be manifested as early-life deficits in cognitive functioning or could be associated with the emergence of serious late-life cognitive impairment. Evidence from mostly rodent models imply that eating a WD could impair hippocampal function, producing cognitive deficits that promote increased WD intake and body weight gain, which could contribute to further hippocampal dysfunction, cognitive decline, and excess eating and weight gain, thereby creating this “vicious cycle”.
The Western diet regulates hippocampal microvascular gene expression: an integrated genomic analyses in female mice (animal study)
This 2019 study investigated the pathways by which the Western Diet (WD) regulates gene expression in hippocampal brain microvessels of female mice since it is poorly understand how microvasular disease in the memory centre of the brain develops (while consumption of the WD is associated with cognitive impairment and hyperlipidaemia (high levels of fat in the blood) has been identified as a risk factor for dementia). Five-week-old female low-density lipoprotein receptor deficient (LDL-R-/-) and C57BL/6J wild type (WT) mice were fed a chow (Nestle dog food) or WD for 8 weeks, before having their metabolics for lipids, glucose and insulin determined. Differential gene expression, gene networks and pathways, transcription factors, and non-protein coding RNAs were evaluated. The Western Diet resulted in differential expression of 2412 genes, with most of them attributable to differential regulation of cell signaling proteins and their transcription factors, about 7% said to be differential expression of microRNAs (miRNAs) and a less proportion due to other protein coding RNAs (some of which not previously described to be modified by the WD in females). Nuthikattu et. al (2019) found evidence for regular WD consumption resulting in integrated multilevel molecular regulation of the hippocampal microvasculature of female mice, and may have discovered one of the mechanisms underlying vascular dementia.
The effect of high fat, high sugar, and combined high fat-high sugar diets on spatial learning and memory in rodents: a meta-analysis
This 2019 meta-analysis was conducted based on rodent studies firstly assessing the impact of different diets (high in fat, high in sugar, or high in both fat and sugar) on cognitive function and secondly, various hippocampal-dependent tasks such as water maze, place recognition, radial arm maze, and spontaneous alternation were used to assess hippocampal-dependent spatial learning and memory. The meta-analysis restricted the included studies to those examining relatively short-term dietary manipulations (2 months or less of the intervention diet). The findings were that each type of diet and task adversely affected performance, with the largest effect produced by exposure to a combined high fat-high sugar diet and the use of the radial arm maze to assess the effect of such diets on cognition.
Improvement in cognition following double-blind randomized micronutrient interventions in the general population
Denniss, Barker & Day (2019) recruited 60 healthy adults (age 21-59) and randomly assigned the individuals into 3 groups (vitamin D supplement, multivitamin administration, or taking vitamin C), with all supplements to be taken for 8 weeks in order to determine its effect on cognitive function. A 14-day food diary was taken to gather data on micronutrient intake, while the cognitive test battery included measures from the Wechsler Adult Intelligence Scale-III (WAIS-III), Wechsler Memory Scale-IV (WMS-IV), Delis-Kaplan Executive Function System (D-KEFS), the Doors and People, and a serial reaction time task. The results showed improvements in performance in some tasks for all the groups following the intervention period, notably on measures of verbal and visual memory and visuomotor processing speed. The multivitamin group showed significantly greater results than before the supplementation on tasks of visual strategy generation (along with the Vitamin C group), motor planning, explicit and implicit learning, and working memory. Denniss, Barker & Day (2019) claim their findings suggest that sub-optimal micronutrient intake may have a negative effect on cognition across the lifespan.
The longer-term impacts of Western diet on human cognition and the brain
Francis & Stevenson (2013) analysed whether a Western Diet (one high in saturated fat and refined carbohydrates [HFS diet]) can damage brain systems using converging lines of evidence from neuropsychological, epidemiological and neuroimaging data. The review focused on proof of diet induced impairments in frontal, limbic and hippocampal systems, of their associated functions with learning, memory, cognition and hedonics, as well as of HFS diet’s role in attention deficit disorder and neurodegenerative conditions. This 2013 review found human research data to be still at an early stage although demonstrating an association between HFS diet and cognitive impairment, but ultimately Francis & Stevenson (2013) further suggest there is a causal link running from HFS diet to impaired brain function in humans, and that HFS diets also contribute to the development of neurodegenerative conditions.
A four-day Western-style dietary intervention causes reductions in hippocampal-dependent learning and memory and interoceptive sensitivity
This study published in 2017 investigated the impacts of briefly consuming a high fat with high sucrose (HFS) diet over 4 days relative to one lower in saturated fat and added sugar, on hippocampal-dependent learning and memory (HDLM) and perception of internal bodily state (interoception). A group of healthy individuals were randomly assigned to either the Experiment condition (HFS breakfast) or the control condition, and were assessed before and after breakfast on day one and four on HDLM, interoception and biological measures. Food diaries were also completed before and during the study. The results showed significant reductions in HDLM and reduced interoceptive sensitivity to hunger and fullness among the Experimental condition group, in comparison with the control group. The greater reductions in HDLM was associated with the larger changes in blood glucose across breakfast. Those assigned to the experimental condition exhibited markedly different blood glucose and triglyceride responses to their breakfast relative to the control group. The Experimental condition compensated for their energy-dense breakfast by reducing carbohydrate intake, while saturated fat intake remained consistently higher than Controls. Attuquayefio et. al (2017) claims to have replicated the results of animal studies in humans in the way a Western-style diet impacts HDLM, and concludes that the link between diet-induced HDLM changes and blood glucose suggests one pathway by which diet impacts HDLM in humans.
Sugar-sweetened and artificially-sweetened beverages and changes in cognitive function in the SUN project
This 2019 study focused on sugar-sweetened beverages (SSBs) and artificially-sweetened beverages (ASBs), which are often seen as the “healthy” alternatives to SSB, and longitudinally assessed the association between the consumption of the two with cognitive function. A subsample of the 'Seguimiento Universidad de Navarra' (SUN) cohort of university graduates aged over 55 years old was evaluated using the Spanish Telephone Interview for Cognitive Status (STICS-m) at two-time points, separated by 6 years. Consumption of SSB and ASB was appraised using a validated food-frequency questionnaire, which resulted in a significant association being identified between the consumption of SSB and alterations in cognitive function, with a -0.43 difference (p = 0.04) in those that consumed >1 beverage a month compared to never/seldom consumers. Although the association was not found to be significant for the consumption of ASBs, declines in cognition were suggested. The researchers also call for further exploration into the potential mechanisms in which these beverages can be harmful in addition to supplementation in longitudinal studies on relationships between the SSBs and ASBs and cognitive function.
Executive functioning and dietary intake: neurocognitive correlates of fruit, vegetable, and saturated fat intake in adults with obesity
The current 2017 study examined the link between executive function and intake of saturated fats, fruits, and vegetables in an overweight/obese sample (n = 190) using behavioral measures of executive function and dietary recall. The subjects completed neuropsychological assessments measuring intelligence, planning ability, and inhibitory control followed by three dietary recall assessments within a month prior to beginning a behavioral weight loss treatment program. Inhibitory control and two of the three indices of planning each independently significantly predicted fruit and vegetable consumption such that those with better inhibition and planning ability consumed more fruits and vegetables. Despite not finding a correlation between executive function and saturated fat intake, these findings stacked the level of understanding of how executive functioning influences eating behaviors in overweight and obese adults, and suggested it may be crucial to include executive functioning training components in dietary interventions for those with obesity. Causality needs to be determined since diet and executive functioning may bidirectionally influence each other.
Mediterranean diet improves cognition: the PREDIMED-NAVARRA randomised trial
This 2013 randomised controlled trial assessed the effect of a nutritional intervention using Mediterranean Diets (MedDiets) on cognition, compared to with a low-fat control diet. The 522 participants of this present trial (44.6% men, age 74.6 at cognitive evaluation) were at high vascular risk and had enrolled in a multicentre, randomised, primary prevention trial (PREDIMED), after a nutritional intervention comparing two MedDiets (supplemented with either extra-virgin olive oil (EVOO) or mixed nuts) versus a low-fat control diet. The results demonstrated that after adjustments were made for numerous variables including sex, age and education, those assigned to the Mediterranean Diet with EVOO supplement scored higher in mean Mini-Mental State Examination (MMSE) and Clock Drawing Test (CDT), the two examination methods for global cognitive performance, versus control. The adjusted means of MMSE and CDT scores were also higher for participants who took mixed nuts supplements compared to control. These results did not differ after controlling for incident depression. Martínez-Lapiscina and her team decided to conclude that an intervention with MedDiets enhanced with either extra-virgin olive oil or nuts appears to improve cognition relative to a low-fat diet.
Interactions between metabolic, reward and cognitive processes in appetite control: Implications for novel weight management therapies
This article published in 2017 reviewed the emerging evidence that high level cognitive functions such as learning, memory and attention play an important role in everyday appetite control and that homeostatic signals also play a role in cognition. In addition, the writers present a comprehensive model of the control of appetite that integrates cognitive, homeostatic and reward mechanisms, and also discusses the implications of this model for understanding the factors that may contribute to disordered patterns of eating and suggest opportunities for developing more effective treatment approaches for eating disorders and weight management.
Higher heart-rate variability is associated with ventromedial prefrontal cortex activity and increased resistance to temptation in dietary self-control challenges
Maier & Hare (2017) tested the hypothesis that greater heart-rate variability (HRV), which is a marker of physiological flexibility, would be associated with better dietary self-control in humans, since reports have suggested a positive association between self-control with physical health (and psychosocial). The study hoped to find out whether total HRV at sedentary rest (calculated as the standard deviation of normal-to-normal intervals) can act as a biomarker for neurophysiological adaptability, which is generally considered to underlie self-controlled behavior. The authors found that HRV explained a significant portion of the individual variability in dietary self-control, with individuals having higher HRV being better able to downregulate their cravings in the face of taste temptations. Moreover, HRV was associated with activity patterns in the ventromedial prefrontal cortex (vmPFC), a key node in the brain's valuation and decision circuitry. This meant higher HRV scores correlated to greater overall vmPFC blood-oxygen-level-dependent activity and attenuated taste representations when presented with a dietary self-control challenge. Maier & Hare (2017) also revealed consistent behavioral and neural associations with HRV across both the stress induction and control experimental conditions, suggesting HRV may serve as a robust and available biomarker for self-control ability across environmental contexts.