The BEET PAD Trial is a multi-centered double-blind randomized clinical trial designed to determine whether beetroot juice, compared to placebo, improves six-minute walk distance at four month follow-up in people with lower extremity peripheral artery disease (PAD). Investigators hypothesize that by simultaneously increasing lower extremity perfusion, gastrocnemius muscle mitochondrial activity, and myofiber health and regeneration, beetroot juice will significantly improve walking performance in people with PAD. The primary aim is to determine whether beetroot juice significantly improves six-minute walk distance at 4-month follow-up in people with PAD, compared to placebo. Preliminary evidence suggests that beetroot juice has both acute and chronic effects on walking performance in PAD. The primary outcome will measure the combined acute and chronic effect of beetroot juice (i.e. the maximal effect) on change in 6-minute walk at 4-month follow-up. In secondary aims, investigators will distinguish between acute and chronic effects of beetroot juice on six-minute walk and delineate biologic pathways by which beetroot juice improves walking performance in PAD, by measuring change in gastrocnemius muscle perfusion (MRI arterial spin labeling) and gastrocnemius muscle health. The trial will assess the durability of beetroot juice effects on six-minute walk. Nitrate in beetroot juice is metabolized to nitrite and subsequently to NO, attaining peak nitrite levels 2.5 hours after ingestion. The trial will determine whether a higher peak or a greater increase in plasma nitrite at 2.5 hours after beetroot juice consumption at baseline has a greater effect on six-minute walk at 4-month follow-up, compared to a lower peak or a smaller increase, respectively.