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  • Dietary nitrates are naturally occurring compounds that the body converts into nitric oxide.
  • They are found in a variety of foods including beet juice and spinach and arugula
  • Research has previously linked higher blood nitrate levels to improved physical performance.
  • New study findings suggest nitrate levels in the muscle actually have a greater influence on force.
  • Dietary nitrates can be obtained through foods including beetroot and dark leafy greens.

Gym-goers and athletes alike use many different compounds to help boost physical performance — from proteins to branched-chain amino acids.

Another one that’s long been associated with improved exercise performance is dietary nitrate, a natural chemical that the body converts to nitric oxide. Research has shown it can improve muscle and cardiovascular function.

Scientists previously thought that dietary nitrate supplementation aided physical performance by influencing blood vessels — helping them dilate so more blood and oxygen could flow through.

However, a new study led by researchers at the University of Exeter in the UK and the US National Institutes of Health, published this month in the journal Acta Physiologica, indicates that nitrates also impact another critical part of the body to enhance function.

The researchers wanted to learn more about how our cells use nitric oxide for exercise.

During the study 10 participants were given either a supplement of potassium nitrate or a placebo. An hour later, they performed 60 contractions of the quads (aka thigh muscles) using an exercise machine.

The researchers found that, compared to a placebo, taking nitrate before exercise increased muscle force in the quads by 7%.

“Previous studies have shown that, when plasma nitrate and nitric oxide levels are increased following nitrate intake, exercise performance is improved — and the same thing was true in this study,” revealed Andy Jones, PhD, professor of applied physiology at the University of Exeter and co-author of the study.

However, whereas previous research primarily linked nitrate levels in the blood to improved physical exertion, this study noted something different.

“A novel finding was that it was the muscle (rather than blood) nitrate levels that were most closely related to the improved muscle force production,” Jones shared with Healthline.

To measure nitrate content in the muscle cells, researchers took small biopsies of the muscle immediately after the initial exercise session and again at the three-hour mark.

Jones revealed that these biopsies showed that “nitrate levels in muscle (and blood) peak at 1-3 hours following ingestion, and the levels remain high for another few hours before declining.”

While muscle force wasn’t re-tested via exercise after three hours, “we’d expect to see the same pattern,” he added.

Furthermore, while the study focused on the quad muscles, Jones said he would expect the benefits of nitrate supplementation to extend to other muscles, too.

“We chose the legs because we wanted to collect muscle samples, and it’s easier to take a biopsy from the thigh than from elsewhere,” he shared.

When dietary nitrate enters the body, it doesn’t always remain in its original form.

“When we consume dietary nitrates, bacteria in the mouth convert some nitrates into nitrites,” Steve Grant, a nutritionist specializing in athletic performance based in London, UK, revealed to Healthline.

“Then, in the stomach, nitrites are converted into nitric acid,” he continued. “Leftover nitrates and nitrites are absorbed in the small intestine, and these too can be converted into nitric oxide.”

Nitric oxide is believed to be particularly important when it comes to exercise and physical performance.

“Nitric oxide can influence blood flow and dilation of blood vessels and improves blood flow to skeletal muscle,” Grant noted. “Due to this function, it has also been linked with improving muscular endurance.”

This study affirmed that dietary nitrate could have notable benefits in enhancing muscle force when taken before exercise. But how does it take effect?

“Nitrates, via nitric oxide, can help to improve the efficiency of muscle contraction by reducing the amount of oxygen used during exercise,” shared Grant.

“It is also said that nitrates — through the work of nitric acid — improve how the muscle contracts by increasing intracellular calcium (a trigger of muscle contraction),” he added.

The role of calcium in muscle performance is important, explained Samantha Coogan, MS, RDN, CSSD, LD, FAND, program director/lecturer in nutrition sciences of the School of Integrated Health Sciences at the University of Nevada, Las Vegas.

“More free-flowing calcium within the cells increases skeletal muscle myosin light chain kinase (MLCK) activation,” she told Healthline. MLCK is a key process involved in the contraction of smooth muscles.

“This then increases myosin regulatory light chain phosphorylation,” Coogan continued — “with phosphorylation being a necessary process for cellular storage and energy transfer.”

The result?

“Greater calcium-related contractile sensitivity, which results in greater output of twitch force, rate force development, maximal shortening velocity, and maximal power output of muscle,” she stated.

Dietary nitrates can also aid muscle development through their influence on protein, stated Holly Roser, a sports nutritionist and personal trainer.

“Nitrogen is found in amino acids, which are considered the building blocks of protein,” she told Healthline. “Protein is necessary for muscle growth and repair, which will help increase performance in your workouts.”

However, previous research found this compound can improve other areas of physical performance, too.

“Nitrates increase blood flow, allowing for improved oxygen and nutrient delivery,” shared Roser. “The increased oxygenation can lead to better endurance, power output, and overall physical performance,” she explained.

For instance, a 2021 meta-analysis of 78 studies saw that taking dietary nitrate supplements before exercise increased the time it took participants to reach exhaustion and allowed them to cover greater distances.

Coogan revealed that nitric oxide can also have a beneficial effect on the heart — which is crucial for cardiovascular-related performance.

“Nitric oxide is also a key component in heart health and cardiovascular responses, such as blood pressure and blood flow,” she said. “The heart itself is a muscle, so we can really maximize muscle potential through adequate nitric oxide intake.”

A 2015 study found that taking beet juice (which is high in nitrates) for three days prior to exercise enabled participants to perform high-intensity aerobic exercises more efficiently.

Two main approaches can help enhance your dietary nitrate and nitric oxide levels.

The first is through diet. According to Grant, some of the best food sources include:

  • Beets
  • Rhubarb
  • Spinach
  • Arugula
  • Turnip greens
  • Dill
  • Swiss chard
  • Celery
  • Radish
  • Watercress
  • Kale
  • Lettuce

However, he adds, “a reasonable amount may need to be consumed” for benefits to occur.

It’s also vital to note that not all food-based nitrates are equal. “You may be familiar with added nitrates to food, such as processed meats, which preserve the color of food,” highlighted Rosner. “These aren’t good for your health and are linked to cancer and problems during pregnancy.”

The other method, Coogan shared, is through beet-based dietary nitrate supplements. These can be found in the form of pre-workout blends, concentrated juice shots, capsules, and gummies.

As Jones noted, “for athletes, it isn’t easy to consume, say, a salad a couple of hours before a competition. Drinking a concentrated beetroot juice shot is more convenient.”

Remember that supplements aren’t regulated by the Food and Drug Administration (FDA), and too high an intake of dietary nitrates can potentially lead to side effects.

“A physician and registered dietitian should always be consulted before starting any type of supplement regimen,” Coogan asserted.

Scientists have long thought that increased levels of dietary nitrate in the blood helped improve athletic performance.

While this remains a factor, new research indicates that the direct uptake and usage of dietary nitrate by the muscle has the biggest impact on enhancing muscle force.

The new findings are significant, said Jones, because “they show for the first time that having a higher muscle nitrate concentration (which can be manipulated via the diet) is associated with the ability to produce more force.”

Ultimately, this knowledge may be beneficial for more than those hitting the gym. “This is important for athletes, but possibly also for older people and those with diseases that cause muscle weakness,” Jones added.