Vegetable rich diets contain natural inorganic nitrate. These diets are linked to good heart and brain health. Human cells cannot 'activate' nitrate. Humans must rely on specific bacteria living in the mouth to digest nitrate to an active form called 'nitric oxide' that we can use in the body. We have found that nitrate makes the oral microbiome healthier and improves nitric oxide production. This study will investigate whether changes in oral bacteria caused by dietary nitrate are linked to any changes in brain performance.We will ask 60 healthy men and women of over 50 years of age to take part. We will ask them to drink either nitrate-rich beetroot juice or placebo juice daily for 12 weeks. We will do this investigation entirely remotely by using online tools and by posting of supplements and samples. We will sample the volunteers' oral microbiome and assess their cognitive performance before and after dietary supplementation. We will analyse the nitric oxide content in the samples that the volunteers post us. We will try to findgroups of bacteria linked with goodbrainfunction.The results will help us better understand how oral bacteria may influence cognitive function in older age.

Oral dysbiosis and poor dental health have been associated with impaired cardiovascular and cognitive health, but it is not known which characteristics of bacterial communities specifically might mediate such relationships. One mechanism by which the oral microbiota may influence health is its contribution to production of the signalling molecule, nitric oxide (NO), which, among many other functions, regulates vascular tone and neurotransmission . The capacity for endogenous NO production via the enzymatic NOS synthase pathway declines in older age, contributing to development of arterial hypertension, reduced physical and cognitive functional capacity, and increased morbidity. Therefore, the composition of the oral microbiota may be particularly important to enable older people to benefit from a nitrate-rich diets, such as the Mediterranean diet, which has been associated with reduced risk of developing dementia in older age. A key genetic risk factor for dementia is a form of apolipoprotein E gene called APOE4, which may also modulate responsiveness to dietary interventions.The purpose of this research is to investigate whether specific groups of oral bacteria, that are sensitive to change with dietary nitrate supplementation, are correlated with indices of cognitive function (primary objective) as well as APOE genotype, diet, physical activity, and markers of vascular health (secondary objectives), in people over 50 years of age.

Inclusion Criteria:

• Participant is willing and able to give informed consent.
• Male or Female.
• Over 50 years of age.
• Access to a postal service (Royal Mail)
• Access to the Internet.
• Mainland UK resident.
• APOE genotype available in PROTECT database.

Exclusion Criteria:

• Diagnosis of dementia, because the participant may be unable to provide informed consent.
• Current or previous smoker (within the last year).
• Regular drinkers of alcoholic beverages which are over 14% ABV undiluted.
• Current or recent use of antibiotics (within the past 3 months).
• Self-reported substantial use of mouthwash or tongue scrapers within the past month.
• Self-reported periodontitis, gingivitis or other oral disease.
• No available APOE genotyping in PROTECT database.

Double-blind study where both the Participant and Investigator are blind to the supplement given.