Beetroot juice may boost aging brain blood flow

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age 50-79 years * Cognitively healthy, having mild cognitive impairment * Able to undergo cardiovascular testing procedures including fasting overnight and holding selected morning medication doses. * Ability to understand and willingness to sign a written informed consent document. * Ability to lie comfortably for up to 90 minutes * Women only: Post-menopausal Exclusion Criteria: * Current or history of cardiovascular disease disease (heart attack, stroke, heart failure, cardiomyopathy or peripheral artery disease, heart angioplasty/stent or bypass surgery, valve replacement, carotid endarterectomy, heart transplant. * Medical history of stroke or other neurological disorder or systemic illness that could potentially affect cognition or brain function (outside of a diagnosis of Mild Cognitive impairment, Alzheimer's Disease) or could affect their safety or comfort while undergoing the imaging or cardiovascular studies. * Subjects with evidence of cardiovascular disease at baseline or during the exercise test (evidence of myocardial infarction, abnormal cardiac arrhythmia, myocardial ischemia, conduction delays, \>1mm S-T segment depression or elevation; \>3 beat ventricular tachycardia; atrial fibrillation) will be excluded from the study. * Wilson's disease, hemochromatosis * Individuals taking clonidine or other short-acting beta blocker * Resting blood pressure \> 200/ 110 mmHg or systolic \<90 mmHg * Medical history of chronic major psychiatric or current diagnosis of major psychiatric disease (other than dementia). * Systemic illness or neurological disorder potentially affecting cognition or cerebral blood flow other than mild cognitive impairment * Unable to provide informed consent due to cognitive impairment * Currently taking medications that may affect cerebral blood flow (e.g. papaverine, indomethacin, acetazolamide, etc) or efficacy of beetroot juice (proton pump inhibitors) * Current clinically abnormal thyroid function not adequately regulated by thyroid hormone supplementation or medication. * Allergic to beets * Current tobacco user or history of tobacco use within the past 3 months (cigarettes, cigars, chewing tobacco, hookah, electronic cigarettes) or living with someone who smokes/has smoked in the past 3 months. * Current diagnosis of insulin-dependent diabetes (Type I or insulin dependent Type II) * Current diagnosis of chronic obstructive lung disease, cystic fibrosis, emphysema, chronic bronchitis * History of renal failure, dialysis or kidney transplant * Current diagnosis or history of liver disease or HIV/AIDS, or cancer (other than non-melanoma skin cancers). * Current diagnosis or history of rheumatoid arthritis, systemic lupus erythematosus, Wegener's granulomatosis * Vulnerable populations (prisoners, etc) will not be eligible. * Unwillingness to wash out from a vitamin or dietary supplement regime prior to enrollment and maintain throughout the duration of the study. * Inability to comply with experimental instructions. * Uncontrolled intercurrent illness that would limit compliance with study requirements per investigator. * Inability to fast or hold morning medications doses until after testing is complete. * Hormone replacement use within the past 6 months * Currently enrolled in another study using an study medication, supplement, device or intervention.