Beetroot's dietary nitrate is converted to nitric oxide in the body, which promotes vasodilation and supports oxygen delivery to cells.

Caffeine blocks adenosine receptors, supporting alertness while causing mild vasoconstriction. These two mechanisms are complementary: one widens, the other narrows, and together the cardiovascular system finds equilibrium.

Dietary nitrate is shown in meta-analyses to modestly reduce systolic blood pressure (~3 mmHg). — Lidder & Webb 2013, BJCP