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.
Not only an amazing health food for weight loss, celery is also loaded with nitrates: it's among a very high class of veggies that have greater than or equal to 250mg nitrate/100g, according to research published in the American Journal of Clinical Nutrition.
Different varieties of lettuce boast different levels of nitrates. Oak leaf lettuce has 155mg/100g and butter leaf yields 200mg/100g, per research published in the European Food Safety Authority Journal.
Spinach will pretty much always be a health food staple because of its nutrient profile and ability to bolster your diet and workouts; it contains well over 250mg (according to data published in Sport Medicine). On the high end it can boast 380mg nitrates/100g.
You might not be familiar with Chinese cabbage, but you can use the leaves to make lettuce wraps. The hearty leaves contain 161mg nitrates per 100g serving, per research published in the American Journal of Clinical Nutrition.
Bok choy can yield anywhere from 102–309mg nitrates per 100g serving, per research published in the American Journal of Clinical Nutrition. The texture is in between cabbage and lettuce and is best steamed or cooked to remove its bitterness.
Rhubarb is another standout at 281mg nitrate per 100mg serving, the European Food Safety Authority Journalshows. Never had rhubarb before? Make sure to remove all the leaves (they can make you seriously sick) before trying. If you eat it raw, note that it’s tart (like cranberries), so it’s often sweetened. You can also toss it in smoothies, add it to salads, roast it, or make your own sauce and salsa.
Swiss Chard has about 147-270mg nitrates per 100g serving, according to research published in Food Additives & Contaminants. The leaves are tender and similar in taste to spinach—but with a slightly bitter aftertaste.