They come in so many forms – kale, spinach, Swiss chard, turnip greens, mustard greens, romaine lettuce, watercress, and more, but they all have one thing in common. They’re yummy! But leafy greens are also low in calories and nutrient dense. In fact, leafy vegetables top the list in terms of nutrient density per calorie.
We know that greens pack lots of nutrition and that’s reason enough to eat them. But do they have other health benefits? Believe it or not, there’s some evidence that eating greens can help you perform better during certain types of exercise. Surprised?
Greens Contain Compounds Called Nitrates
Along with the abundance of vitamins and minerals that greens offer, dark, leafy greens are rich in compounds called nitrates. It’s the nitrate content of greens that is the key to enhancing sports performance. In fact, a recent study looked at the potential ergogenic effects of green, leafy vegetables.
As part of the study, researchers at the Athletic Performance Center at the University of Leuven asked athletes to exercise under normal conditions. In another session, they asked them to exercise under conditions where oxygen availability was lower, known as hypoxic training. The purpose of hypoxic training is to help the body to adapt to low oxygen conditions by producing more oxygen-carrying red blood cells, thereby making performance easier during conditions when oxygen is plentiful.
When the athletes received a nitrate supplement before training, an interesting thing happened. The participants developed more fast-twitch muscle fibers, specifically type 2A fibers) when they trained under low-oxygen conditions. In the study, the participants sprinted, so they used mostly fast-twitch muscle fibers. These are muscle fibers that help to sustain the power needed for short, bursts of exercise, such as a sprint. You also call type 2A fibers into play during short periods of vigorous activity, such as high-intensity interval training.
Developing more fast-twitch muscle fibers with the nitrate supplement should improve performance during short-term exercise like sprinting. This isn’t the first study to show the ergogenic benefits of greens. Other research shows that nitrate, in supplement form or from food, can enhance exercise performance for short-term exercise ranging from 5 to 30 minutes. However, there’s no evidence that nitrates have substantial benefits for long duration exercise, such as running a half-marathon. In the study, the participants took a nitrate supplement, but greens are an abundant source of natural nitrates too.
Nitrate Causes Blood Vessels to Produce More Nitric Oxide
How do nitrates boost performance during short-term, high-intensity exercise, like sprinting? When you consume nitrate, your body initially converts it to nitrite. The conversion is carried out by bacteria in the gut. Under low oxygen conditions and when acidity in the blood rises, your blood vessels have the ability to convert nitrates, such as those in greens, to nitric oxide, a volatile gas. When nitric oxide is produced by the inner walls of blood vessels, it causes the vessel to open wider or dilate. When blood vessels dilate, they carry more blood, oxygen, and nutrients to working muscles. It’s not hard to see how this can enhance muscle performance. It also leads to a drop in blood pressure. That can be beneficial for people who suffer from hypertension.
What’s more nitric oxide may aid in muscle recovery as well by increasing blood flow to the fatigued muscles and promoting clearance of waste products and lactic acid. Furthermore, there’s some evidence that nitric oxide reduces inflammation, another mechanism by which it may aid in muscle recovery. Another way some researchers believe nitrates enhance exercise performance is by making the energy powerhouses inside cells, called mitochondria, more efficient. Since mitochondria produce the energy that muscles use to contract, greater mitochondrial efficiency can boost exercise performance.
Can You Get Enough Nitrate by Eating Leafy Greens?
In the study, the participants consumed a supplement that contained 400 milligrams of nitrates. How does that compare to leafy, greens in their whole food state? The quantity of nitrate in leafy greens varies with the type and also when the season during which the green is harvested. Interestingly, the amount is higher in greens harvested in the autumn than the spring. By far, arugula contains the highest quantity of nitrates. Here are is a chart, based on a study, showing the number of nitrates in various greens harvested in the autumn:
Swiss chard 1024.7 mg/kg
Kale 1181.4 mg/kg
Lettuce 1284.8 mg/kg
Spinach 2013.1 mg/kg
Arugula 4354.9 mg/ kg
A serving of raw, leafy greens weighs around 16 ounces or 0.45 kilograms. So, eating two servings of arugula would give you over 4,000 milligrams of nitrates. So, it doesn’t take a lot of leafy greens to get the potential ergogenic benefits of leafy greens.
Are There Downsides to Consuming Nitrate?
One concern about nitrates is the digestive tract can convert nitrates to nitrosamines, known carcinogens. However, this is most pronounced when you consume nitrates from sources like processed meats. Manufacturers add nitrates to cure and preserve packaged meat. But, the nitrates in greens are packaged differently. Researchers believe the antioxidants in leafy greens likely protect against the harmful effects of nitrosamines. More research is needed, but we know that green, leafy vegetables contain chemicals that may protect against cancer, and, therefore, are unlikely to have the harmful effects that consuming nitrates from processed meat could have. Some athletes and bodybuilders use nitrate supplements but it’s safest to get nitrates from natural, plant-based sources, like green, leafy vegetables.
The Bottom Line
Eating your greens could modestly boost your performance when you do short bursts of exercise, like sprinting or even high-intensity interval training. Now, you have another reason to eat your greens. But, there were already so many! So, enjoy adding greens to salads, sandwiches, soups, and as a side dish. They’re too nutrient-rich to pass up.
References:
Science Daily. “Eating your greens could enhance sports performance”|
Afr J Tradit Complement Altern Med. 2017; 14(3): 31–41.
Sports Med. 2014; 44(Suppl 1): 35–45.
Journal of Sport and Health Science. Volume 4, Issue 4, December 2015, Pages 325-332.
PLoS One. 2015; 10(3): e0119712.
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Can Nitrates in Green, Leafy Vegetables Enhance Exercise Performance?
