NuBrain: UK consortium for optimal nutrition for healthy brain ageing

Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: findings from the UK Biobank prospective cohort study

BACKGROUND

The identification of effective dementia prevention strategies is a major public health priority, due to the enormous and growing societal cost of this condition. Consumption of a Mediterranean diet (MedDiet) has been proposed to reduce dementia risk. However, current evidence is inconclusive and is typically derived from small cohorts with limited dementia cases. Additionally, few studies have explored the interaction between diet and genetic risk of dementia.

METHODS

We used Cox proportional hazard regression models to explore the associations between MedDiet adherence, defined using two different scores (Mediterranean Diet Adherence Screener [MEDAS] continuous and Mediterranean diet Pyramid [PYRAMID] scores), and incident all-cause dementia risk in 60,298 participants from UK Biobank, followed for an average 9.1 years. The interaction between diet and polygenic risk for dementia was also tested.

RESULTS

Higher MedDiet adherence was associated with lower dementia risk (MEDAS continuous: HR = 0.77, 95% CI = 0.65-0.91; PYRAMID: HR = 0.86, 95% CI = 0.73-1.02 for highest versus lowest tertiles). There was no significant interaction between MedDiet adherence defined by the MEDAS continuous and PYRAMID scores and polygenic risk for dementia.

CONCLUSIONS

Higher adherence to a MedDiet was associated with lower dementia risk, independent of genetic risk, underlining the importance of diet in dementia prevention interventions.

Influence of the Mediterranean Diet on Healthy Aging

The life expectancy of the global population has increased. Aging is a natural physiological process that poses major challenges in an increasingly long-lived and frail population. Several molecular mechanisms are involved in aging. Likewise, the gut microbiota, which is influenced by environmental factors such as diet, plays a crucial role in the modulation of these mechanisms. The Mediterranean diet, as well as the components present in it, offer some proof of this. Achieving healthy aging should be focused on the promotion of healthy lifestyle habits that reduce the development of pathologies that are associated with aging, in order to increase the quality of life of the aging population. In this review we analyze the influence of the Mediterranean diet on the molecular pathways and the microbiota associated with more favorable aging patterns, as well as its possible role as an anti-aging treatment.

Dietary nitrate, aging and brain health: the latest evidence

PURPOSE OF REVIEW

With an increasing population age, cognitive decline and age-associated neurodegenerative diseases are becoming increasingly prevalent and burdensome in society. Dietary supplementation with inorganic nitrate, which serves as a nitric oxide precursor, has been suggested as a potential nutritional strategy to improve brain health in older adults. In this review, we discuss recent findings in this area.

RECENT FINDINGS

A number of studies have emerged in the past 12-18 months exploring the effects of dietary nitrate supplementation on cognitive function, with typically (although not exclusively) null findings emerging. This research is characterized by small, acute/short-term studies, although observational studies and longer-duration randomised controlled trials are beginning to emerge. From the limited research reporting benefits of nitrate supplementation on cognitive function, one important discovery has been the identification of a potential pathway through which nitrate could impact cognitive health, involving modulation of the oral microbiome, which warrants further investigation.

SUMMARY

Despite some promising early findings, there is currently insufficient evidence to recommend increased dietary nitrate intake for the purpose of improving brain health. However, longer-term, larger-scale trials in potentially responsive groups are warranted to provide definitive evidence in this area.

Dietary nitrate and brain health. Too much ado about nothing or a solution for dementia prevention?

Dementia is a significant public health priority with approximately 55 million cases worldwide, and this number is predicted to quadruple by 2050. Adherence to a healthy diet and achieving optimal nutritional status are vital strategies to improve brain health. The importance of this area of research has been consolidated into the new term ‘nutritional psychiatry’. Dietary nitrate, closely associated with the intake of fruits and vegetables, is a compound that is increased in dietary patterns such as the Mediterranean and MIND diets and has protective effects on cognition and brain health. Nitrate is characterised by a complex metabolism and is the precursor of the nitrate–nitrite–nitric oxide (NO) pathway contributing to systemic NO generation. A higher intake of dietary nitrate has been linked to protective effects on vascular outcomes including blood pressure and endothelial function. However, the current evidence supporting the protective effects of dietary nitrate on brain health is less convincing. This article aims to provide a critical appraisal of the current evidence for dietary nitrate supplementation for improving brain health and provide suggestions for future research.

Mediterranean diet and the hallmarks of ageing

Ageing is a multifactorial process associated with reduced function and increased risk of morbidity and mortality. Recently, nine cellular and molecular hallmarks of ageing have been identified, which characterise the ageing process, and collectively, may be key determinants of the ageing trajectory. These include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion and altered intercellular communication. Healthier dietary patterns reduce the risk of age-related diseases and increase longevity and may influence positively one or more of these hallmarks. The Mediterranean dietary pattern (MedDiet) is a plant-based eating pattern that was typical of countries such as Greece, Spain, and Italy pre-globalisation of the food system and which is associated with better health during ageing. Here we review the potential effects of a MedDiet on each of the nine hallmarks of ageing, and provide evidence that the MedDiet as a whole, or individual elements of this dietary pattern, may influence each hallmark positively-effects which may contribute to the beneficial effects of this dietary pattern on age-related disease risk and longevity. We also highlight potential avenues for future research.

Dietary nitrate and population health: a narrative review of the translational potential of existing laboratory studies

BACKGROUND

Dietary inorganic nitrate (NO3-) is a polyatomic ion, which is present in large quantities in green leafy vegetables and beetroot, and has attracted considerable attention in recent years as a potential health-promoting dietary compound. Numerous small, well-controlled laboratory studies have reported beneficial health effects of inorganic NO3- consumption on blood pressure, endothelial function, cerebrovascular blood flow, cognitive function, and exercise performance. Translating the findings from small laboratory studies into 'real-world' applications requires careful consideration.

MAIN BODY

This article provides a brief overview of the existing empirical evidence basis for the purported health-promoting effects of dietary NO3- consumption. Key areas for future research are then proposed to evaluate whether promising findings observed in small animal and human laboratory studies can effectively translate into clinically relevant improvements in population health. These proposals include: 1) conducting large-scale, longer duration trials with hard clinical endpoints (e.g. cardiovascular disease incidence); 2) exploring the feasibility and acceptability of different strategies to facilitate a prolonged increase in dietary NO3- intake; 3) exploitation of existing cohort studies to explore associations between NO3- intake and health outcomes, a research approach allowing larger samples sizes and longer duration follow up than is feasible in randomised controlled trials; 4) identifying factors which might account for individual differences in the response to inorganic NO3- (e.g. sex, genetics, habitual diet) and could assist with targeted/personalised nutritional interventions; 5) exploring the influence of oral health and medication on the therapeutic potential of NO3- supplementation; and 6) examining potential risk of adverse events with long term high- NO3- diets.

CONCLUSION

The salutary effects of dietary NO3- are well established in small, well-controlled laboratory studies. Much less is known about the feasibility and efficacy of long-term dietary NO3- enrichment for promoting health, and the factors which might explain the variable responsiveness to dietary NO3- supplementation between individuals. Future research focussing on the translation of laboratory data will provide valuable insight into the potential applications of dietary NO3- supplementation to improve population health.

Feasibility and acceptability of a multi-domain intervention to increase Mediterranean diet adherence and physical activity in older UK adults at risk of dementia: protocol for the MedEx-UK randomised controlled trial

INTRODUCTION

Dementia prevalence continues to increase, and effective interventions are needed to prevent, delay or slow its progression. Higher adherence to the Mediterranean diet (MedDiet) and increased physical activity (PA) have been proposed as strategies to facilitate healthy brain ageing and reduce dementia risk. However, to date, there have been no dementia prevention trials in the UK focussed on combined dietary and PA interventions. This study aims to: (1) assess feasibility and acceptability of a theory-underpinned digital and group-based intervention for dementia risk reduction in an 'at risk' UK cohort; (2) evaluate behaviour change responses to the intervention; and, (3) provide information on cognitive, neurological, vascular and physiological outcomes to inform the design of a follow-on, full-scale efficacy trial.

METHODS

One hundred and eight participants aged 55 to 74 years with a QRISK2 score of ≥10% will be recruited to take part in this 24-week multi-site study. Participants will be randomised into three parallel arms: (1) Control; (2) MedDiet; and, (3) MedDiet+PA. The study will evaluate a personalised website, group session and food delivery intervention to increase MedDiet adherence and PA in older adults at risk of dementia. Diet and PA will be monitored prior to, during and following the intervention. Feasibility, acceptability and hypothesised mediators will be assessed in addition to measures of cognitive function, brain structure/perfusion (MRI), vascular function and metabolic markers (blood, urine and faecal) prior to, and following, the intervention.

DISCUSSION

This trial will provide insights into the feasibility, acceptability and mechanism of effect of a multi-domain intervention focussed on the MedDiet alone and PA for dementia risk reduction in an 'at risk' UK cohort.

ETHICS AND DISSEMINATION

The study has received NHS REC and HRA approval (18/NI/0191). Findings will be disseminated via conference presentations, public lectures, and peer-reviewed publications.

TRIAL REGISTRATION DETAILS

ClinicalTrials.gov NCT03673722.