It is postulated that the high nitrate content in beetroot is responsible for its ability to reduce the blood pressure. Circulation. 2012 June 12; 125(23): 2922–2932, Hypertension. 2008 March; 51(3): 784–790.
The benefit of beetroot juice in reducing the blood pressure is worth cosidering. About 17.6 ounce of juice (3 parts of beetroot and 1 part of apple juice) reduced the blood pressure by 4-5 points, on an average. Reduced endogenous nitric oxide (NO) is associated with hypertension. Dietary inorganic nitrate (NO3–) is absorbed rapidly and completely in the proximal small intestine with 100% bioavailability. Approximately 25% of the nitrate circulating in the plasma is then concentrated in the salivary glands and secreted into the mouth where around 20% (or ≈ 5 – 8% of intake) is converted to nitrite (NO2–) by commensal bacteria on the tongue and subsequently swallowed. Upon reaching the stomach the NO2– is either absorbed directly or reduced to NO as a result of the acidic environment of the stomach. Endogenously produced NO and NO2– are vasoprotective agents and therefore can increase vasodilation, decrease blood pressure and improve cardiovascular function.
There are other pathways that control blood pressure but it is possible that modulating one arm of the pathway may also be effective.