These results indicate that the positive effects of 6 days of BR supplementation on the physiological responses to exercise can be ascribed to the high NO3− content per se. -J of Applied Physiology, May, 2011
MY COMMENT: These UK researchers were testing the theory that nitrate is indeed the component in beetroot juice responsible for enhancing performance (see Beetroot Juice Improves Performance). It does appear that beetroot juice does increase nitrate levels - Relative to PL (placebo), BR elevated plasma NO2− concentration (183 ± 119 vs. 373 ± 211 nM, P < 0.05) and reduced systolic blood pressure (129 ± 9 vs. 124 ± 10 mmHg, P < 0.01).
Need more evidence?
In a double-blind, placebo-controlled crossover study, nine healthy young well trained men performed sub-maximal and maximal work tests on a cycle ergometer after two separate three-day periods of dietary supplementation. For one of these three-day periods, they received sodium nitrate at a dose of 0.1 millimoles per kilo of bodyweight per day (equating to about 500mgs of actual nitrate – an amount that can be consumed when consuming a high-vegetable diet). For the other period, they received an equal amount of sodium chloride (table salt – placebo).
What the scientists found amazed them. The oxygen cost at sub-maximal levels of exercise was significantly reduced after nitrate supplementation compared with placebo – in other words, they became more efficient at using oxygen. Over the four lowest work rates, their oxygen efficiency jumped from 19.7 to 21.1%. Or to put it another way, the same work output required less oxygen after nitrate supplementation compared to when nitrate wasn’t taken. Moreover, this oxygen-saving effect occurred without any increase in lactate production, indicating that energy production had become more efficient -Sports nutrition: is dietary nitrate the key to enhanced endurance performance?