There is a fundamental truth of exercise and that is that during submaximal aerobic exercise for every “x” amount of oxygen you consume you can do “x” amount of work.  There are standard equations to calculate oxygen consumption and caloric expenditure based on how much work is being performed.  For example, if I am putting out 100 watts of work on the bike then I am consuming a fixed amount of oxygen in order to produce 100 watts.  There isn’t too much I can do to change this relationship.

That is until recently.

In a recent study, scientists had subjects drink 2 cups of beet juice daily a few days prior to doing a cycling test.  When doped up on the beet juice, subjects used 19% less oxygen for the same workload compared to when they were on the placebo juice.  Additionally, in a test to exhaustion, when on the beet juice, they were able to go 16% longer (635 sec vs. 583 sec).  This was ground breaking because prior to this there was no known substance or intervention that could do this.  Using less oxygen for the same workload means that an athlete can now increase the workload (i.e. go faster) for the same oxygen usage.  This represents a significant improvement in the ability to perform work, i.e. performance.  

What is in the beet juice that would account for this?  After numerous studies (for the full story check out this and related videos) it was concluded that it was the nitrates acting to improve ATP production (the energy currency of the body) at the mitochondrial level.

(Note: this is not to be confused with the nitrites that are used in processed meats.  These nitrites are converted to nitrosamines, a potent class of carcinogens.  This is why feeding kids hotdogs can increase their risk of leukemia ten fold).  

The performance enhancing results of beet juice have been confirmed in other studies, both in the lab and on the road.  In one double-blind, placebo, crossover study, ALL subjects improved their 4 and 16.1km time trial cycling performance when on the beet juice compared to when they weren’t.  

But beets aren’t the only sources of nitrates. In fact, vegetable consumption accounts for  up to 80% of our daily intake of nitrates. Thus, eating a vegetable based diet, and in particular one rich in leafy greens, naturally results in higher doses of these nitrates.

The best sources of nitrates though, in order form lowest to highest, are:  beets, oak leaf lettuce, beet greens, basil, spring greens, butter leaf lettuce, cilantro, rhubarb and arugula.  Arugula, incidentally, has about twice the levels of rhubarb (rhubarb and beet juice have similar levels).  

So if you want to improve your performance, eat your greens (and beets and rhubarb).  Although training helps as well.