Inorganic Nitrate Supplementation on Cerebrovascular Aging and Arterial Stiffness Study

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 o…