Drinking beetroot juice once doesn't fully fix the blood vessel function in people with Alzheimer's, even though it works better in healthy older adults or young people.

In individuals diagnosed with Alzheimer's Disease, compare vascular responsiveness (measured by flow-mediated dilation and nitric oxide bioavailability) after acute ingestion of beetroot juice (standardized for 500 mg dietary nitrate) versus a placebo (nitrate-free control juice), with measurements taken at baseline and 2–3 hours post-ingestion, and compare results to matched healthy elderly and young control groups undergoing identical testing.

Recruit three distinct cohorts: individuals with Alzheimer's Disease, healthy elderly, and healthy young adults. Administer identical acute beetroot juice supplementation (500 mg nitrate) to all participants and measure vascular responsiveness (via brachial artery ultrasound and plasma nitrite/nitrate levels) at baseline and 2–3 hours post-ingestion to determine if the magnitude of improvement differs significantly between groups.

Compare vascular responsiveness before and after acute beetroot juice intake in individuals with Alzheimer's Disease versus age- and sex-matched healthy elderly and young controls, ensuring all receive identical supplementation and measurement protocols to determine if the Alzheimer's group shows significantly less improvement.

Test whether acute beetroot juice or sodium nitrate administration improves vascular reactivity (measured by aortic ring vasodilation or cerebral blood flow) in transgenic Alzheimer's mice (e.g., 5xFAD) compared to wild-type controls, to determine if the deficit observed in humans is replicable in a controlled model.

Determine whether nitrate-derived nitric oxide metabolites (e.g., nitrite, NO) can restore endothelial function in cultured endothelial cells derived from Alzheimer's patients versus healthy donors, by measuring nitric oxide production and eNOS activity.