Consuming a plate of fresh spinach or a handful of beets may allow muscles to operate more efficiently, according to research conducted at the Karolinska Institutet in Stockholm, Sweden.

A study published in the journal Cell Metabolism found that participants who took small daily doses of inorganic nitrates experienced an improvement in the function of their mitochondria, the organelles that provide energy for human cells.

This allowed them to use less oxygen with each breath while riding an exercise bicycle.

Nitrate has long been considered of little value to the human body. In large doses it is toxic, and it can be found as an oxidizer in airbag propellants, solid rocket furl and fireworks. However, previous studies have suggested nictric oxide, a compound derived from nitrates, may help blood vessels dilate, which relieves high blood pressure.

Researchers noted that the amount of nitrate needed to produce the mitochondrial effect was no more than may be found in spinach, beets and certain other vegetables.

They concluded that eating spinach may not only help improve heart health but contribute to muscle function as well.

Spinach is also a rich source of iron, calcium, lutein and antioxidants, according to the Centers for Disease Control and Prevention.