The One Muscle-Building Nutrient Your Diet Is Probably Missing

When you want to build muscle, you're probably focused on protein. Give you all the grilled chicken breast, salmon and pea protein shakes you can get your hands on.

But you may be missing out on something else that can power up your workouts: leafy greens. These veggies, and others like beets, are packed with chemicals called nitrates, which may help enhance muscular strength and function.

A March 2021 study in ​The​ ​Journal of Nutrition​ looked at the eating habits of more than 3,700 adults over a 12-year period culled from food frequency questionnaires. From there, researchers determined how much nitrates they got and looked at a muscle function test these adults had taken.

To determine muscle function, study authors looked at two tests: knee extension strength and a timed "up-and-go" test, which has participants sit in a chair and then get up and speed walk for eight feet, turn around, and then walk back to sit down.

On average, people in the study consumed 65 milligrams per day of nitrates, most of which came from vegetables. Those who had the highest intake — 91 milligrams per day, the equivalent of 1 cup of green leafy vegetables — had about six pounds stronger (or 11 percent better) knee extension and were 0.24 seconds faster on the timed "up-and-go" test compared to those who ate the least amount of total nitrates, which was, on average 47 milligrams per day.

These are a few green leafies from the study that deliver the nitrates you need:

• Arugula: 196 milligrams nitrates per cup
• Lettuce: 85 milligrams nitrates per cup
• Spinach: 81 milligrams nitrates per cup

It would be easy to assume, perhaps, that these adults who performed better were also fitter and exercised more. But, researchers point out that the benefit of nitrate consumption with muscle strength and speed was independent of physical activity levels.

When you eat dietary sources of nitrate, such as leafy green veggies or beets, the body converts nitrates into nitrites, which then convert into nitric oxide (NO), Amy Goodson, RD, CSSD, who specializes in sports nutrition in Dallas-Fort Worth, tells LIVESTRONG.COM.

"Nitric oxide is positive for your body for exercise performance and overall health. The compound acts as a vasodilator, which means it helps blood vessels relax and expand, making it easier for blood to flow," she explains.

When more blood flows to muscles, you get a surge of nutrients and oxygen that enhances muscle power and performance.

It was already well-known that nitric oxide is a performance enhancer — many athletes use it. But they use it in supplement form. "In the sports world, at supplement stores, there's nitric oxide on every single shelf," Goodson says. But some beet supplements contain as much as 12 times the amount of nitrates as a typical adult consumes daily, ​The Journal of Nutrition​ points out. It's not practical to eat that much.

So, this study was particularly important because it showed that people can enhance their muscle function by eating modest amounts of nitrates readily found in everyday vegetables — and with a serving of just 1 cup of these greens, they're easy to incorporate into a morning smoothie, lunchtime salad or alongside a small piece of lean meat for dinner.

It's also important to keep the results in perspective. The average exerciser won't likely see large differences in performance — you're not going to be able to double your deadlift weight tomorrow (and eating spinach won't cause you to go all Popeye anyway, as you still need to progressively overload muscles to build that type of strength) — but improving blood flow and oxygen to muscles can help you feel better in the gym.

"Consuming nitrate-rich foods can help lower the cost of energy to do the exercise, which means that hard exercise can feel a bit easier. At the end of the day, you might be able to work a little harder for a little bit longer," Goodson says.

That said, you'll likely see your health improve over time — and that's worth it, too. "Consistent nitrate intake from eating a variety of fruits and vegetables has the ability to help regulate your blood pressure," Goodson says. That's critical because, as she points out, about half of the American population has high blood pressure, according to the Centers for Disease Control and Prevention.

Absolutely eat more leafy green vegetables, including spinach, arugula and lettuce. Eat more beets, too.

But consuming a variety of vegetables is important more so than focusing squarely on nitrate-rich ones.

Other vegetables contain nitrates in smaller amounts, but also deliver other important nutrients, like antioxidants needed to repair cells post-workout, Goodson says. Because only one in 10 people eat 3 to 5 servings of veggies and 2 to 4 servings of fruit per day, per the CDC, start to up your intake by adding one extra piece of produce to your next meal or snack.