 What could possibly be in beet juice to so revolutionize the field of sports physiology? First, a quick biochemistry breather. Our body uses oxygen to create ATP, the energy currency of our bodies. Every time we think, every time we blink, every time we flex a muscle, we use up ATP, which has to be replenished by breathing more oxygen or we die. The enzyme that makes ATP, ATP synthase, deep inside our cells, is literally a microscopic rotary mechanical motor. Oxygen causes the flow of protons, and like a water wheel in that flow, the enzyme turns and makes ATP. Like any motor, it's not perfectly efficient. There's some slippage of the gears, there's proton leakage out the edges, but it's an extraordinary mechanism. Okay, so where do beets come in? Well, beets offer one of the most concentrated sources of dietary nitrate, which is absorbed in our stomach and then actively concentrated and pumped back into our mouth through our salivary glands, because our body knows that there are special commensal bacteria that live on our tongue. Our tongue bacteria take these nitrates and convert them into nitrites, which are then re-swallowed, absorbed again, and then make their way to our cells, and then convert it into a third compound, nitric oxide, which then acts on the proton pump to either reduce the slippage or plug up the leaks, or even take the place of oxygen in the whole contraption. We're still not sure, but this is why they think beets are able to reduce the oxygen cost of exercise while improving athletic performance.