You've probably heard Olympic runners and professional cyclists credit their super-human achievments to training in low-oxygen conditions—that training in "hypoxia" conditions, like in the mountains and high-altitude terrains of, say Colorado, gives them an edge. Their bodies adapt to lower levels of oxygen by producing extra blood cells so when they head to lower elevations, their blood is teaming with oxygen-rich blood cells that can slower their rate to fatigue. Think of it as natual (or, legal) blood doping. 

Well, to maximize these effects, researchers from the University of Leuven in Belgium say nitrate supplementation used in tandem with sprint interval training in low-oxygen conditions may boost sport performance. 

So: why nitrates? The compound is common in veggie-rich diets and foods like leafy greens; it's known to reduce blood pressure and lower the oxygen cost of all-out exercise, meaning it can help you tolerate intense workouts more and maybe even enhance your performance.  

In the study, published in Frontiers in Physiology, 27 moderately-trained cyclists (who'd never competed in sports at any level or completed a training program before) took a placebo or nitrate supplement (containing ~400 mg molecular NO−3) three hours before training, in which they completed short, intense cycling interval sessions three times a week. Cyclists did intermittent 30-second all-out sprints, interspersed by 4.5 minutes of active recovery intervals at 50 Watts on the bike. The number of sprints was increased from four in weeks 1–2, to five in weeks 3–4, and six in the final week. Including a 5-min warmup and cool-down @50 Watt, the training sessions lasted 30 min in week 1, increasing to 40 min in week 5.

To assess differences in performance in varying conditions, participants worked out in normal oxygen conditions and in low-oxygen conditions that were controlled by "normobaric hypoxic" chambers in a facility. After five weeks of exercise, the researchers noticed those taking the nitrate supplements experienced muscle fiber composition changes, primarily in fast-twitch fibers, when training in low-oxygen conditions.

This is good news because when training in low-oxygen conditions, intense workouts are incredibly taxing on fast-oxidative muscle fibers that are typically fast to fatigue. Enhancing these muscle fiber types through nutritional intake has the possibility to boost performance by enhancing mitochondrial efficiency and reducing the energy cost of muscle contractions (that tire you out); what's more, research has also found nitrate intake increases blood flow to a greater extent in fast-twitch muscle fibers.

But: "Whether this increase in fast-oxidative muscle fibers eventually can also enhance exercise performance remains to be established; [and] consistent nitrate intake in conjunction with training must not be recommended until the safety of chronic high-dose nitrate intake in humans has been clearly demonstrated," lead study author Peter Hespel said in a press release

However, he adds: "it would now be interesting to investigate whether addition of nitrate-rich vegetables to the normal daily sports diet of athletes could facilitate training-induced muscle fiber type transitions and maybe in the long term also exercise performance."

So, we rounded up the ones highest in nitrates so you can start supplementing your diet with some superfoods. Chown down.

Consult with your physician before starting a high-nitrate diet; it may interact with certain medications.